Oltipraz

Oltipraz is a drug that was originally used to treat intestinal worms. It was later found to prevent a broad variety of cancers (1). This was attributed to its ability to upregulate cellular detoxification and repair mechanisms.

Researchers eventually discovered that oltipraz acts by activating Nrf2, the same transcription factor activated by ionizing radiation and polyphenols (2, 3, 4). Nrf2 activation mounts a broad cellular protective response that appears to reduce the risk of multiple health problems.

A recent paper in Diabetologia illustrates this (5). Investigators put mice on a long-term refined high-fat diet, with or without oltipraz. These carefully crafted diets are very unhealthy indeed, and when fed to rodents they rapidly induce fat gain and something that looks similar to human metabolic syndrome (insulin resistance, abdominal adiposity, blood lipid disturbances). Adding oltipraz to the diet prevented the fat gain, insulin resistance and inflammatory changes that occurred in the refined high-fat diet group.

The difference in fasting insulin was remarkable. The mice taking oltipraz had 1/7 the fasting insulin of the refined high-fat diet comparison group, and 1/3 the fasting insulin of the low-fat comparison group! Yet their glucose tolerance was normal, indicating that they were not low on insulin due to pancreatic damage. The low-fat diet they used in this study was also refined, which is why the two control groups (high-fat and low-fat) didn't diverge more in body fatness and other parameters. If they had used a group fed unrefined rodent chow as the comparator, the differences between groups would have been larger.

This shows that in addition to preventing cancer, Nrf2 activation can attenuate the metabolic damage caused by an unhealthy diet in rodents. Oltipraz illustrates the power of the cellular hormesis response. We can exploit this pathway naturally using polyphenols and other chemicals found in whole plant foods.

Polyphenols, Hormesis and Disease: Part II

In the last post, I explained that the body treats polyphenols as potentially harmful foreign chemicals, or "xenobiotics". How can we reconcile this with the growing evidence that at least a subset of polyphenols have health benefits?

Clues from Ionizing Radiation

One of the more curious things that has been reported in the scientific literature is that although high-dose ionizing radiation (such as X-rays) is clearly harmful, leading to cancer, premature aging and other problems, under some conditions low-dose ionizing radiation can actually decrease cancer risk and increase resistance to other stressors (1, 2, 3, 4, 5). It does so by triggering a protective cellular response, increasing cellular defenses out of proportion to the minor threat posed by the radiation itself. The ability of mild stressors to increase stress resistance is called "hormesis." Exercise is a common example. I've written about this phenomenon in the past (6).

The Case of Resveratrol

Resveratrol is perhaps the most widely known polyphenol, available in supplement stores nationwide. It's seen a lot of hype, being hailed as a "calorie restriction mimetic" and the reason for the "French paradox."* But there is quite a large body of evidence suggesting that resveratrol functions in the same manner as low-dose ionizing radiation and other bioactive polyphenols: by acting as a mild toxin that triggers a hormetic response (7). Just as in the case of radiation, high doses of resveratrol are harmful rather than helpful. This has obvious implications for the supplementation of resveratrol and other polyphenols. A recent review article on polyphenols stated that while dietary polyphenols may be protective, "high-dose fortified foods or dietary supplements are of unproven efficacy and possibly harmful" (8).

The Cellular Response to Oxidants

Although it may not be obvious, radiation and polyphenols activate a cellular response that is similar in many ways. Both activate the transcription factor Nrf2, which activates genes that are involved in detoxification of chemicals and antioxidant defense**(9, 10, 11, 12). This is thought to be due to the fact that polyphenols, just like radiation, may temporarily increase the level of oxidative stress inside cells. Here's a quote from the polyphenol review article quoted above (13):

We have found that [polyphenols] are potentially far more than 'just antioxidants', but that they are probably insignificant players as 'conventional' antioxidants. They appear, under most circumstances, to be just the opposite, i.e. prooxidants, that nevertheless appear to contribute strongly to protection from oxidative stress by inducing cellular endogenous enzymic protective mechanisms. They appear to be able to regulate not only antioxidant gene transcription but also numerous aspects of intracellular signaling cascades involved in the regulation of cell growth, inflammation and many other processes.

It's worth noting that this is essentially the opposite of what you'll hear on the evening news, that polyphenols are direct antioxidants. The scientific cutting edge has largely discarded that hypothesis, but the mainstream has not yet caught on.

Nrf2 is one of the main pathways by which polyphenols increase stress resistance and antioxidant defenses, including the key cellular antioxidant glutathione (14). Nrf2 activity is correlated with longevity across species (15). Inducing Nrf2 activity via polyphenols or by other means substantially reduces the risk of common lifestyle disorders in animal models, including cardiovascular disease, diabetes and cancer (16, 17, 18), although Nrf2 isn't necessarily the only mechanism. The human evidence is broadly consistent with the studies in animals, although not as well developed.

One of the most interesting effects of hormesis is that exposure to one stressor can increase resistance to other stressors. For example, long-term consumption of high-polyphenol chocolate increases sunburn resistance in humans, implying that it induces a hormetic response in skin (19). Polyphenol-rich foods such as green tea reduce sunburn and skin cancer development in animals (20, 21).

Chris Masterjohn first introduced me to Nrf2 and the idea that polyphenols act through hormesis. Chris studies the effects of green tea on health, which seem to be mediated by polyphenols.

A Second Mechanism

There is a place in the body where polyphenols are concentrated enough to be direct antioxidants: in the digestive tract after consuming polyphenol-rich foods. Digestion is a chemically harsh process that readily oxidizes ingested substances such as polyunsaturated fats (22). Oxidized fat is neither healthy when it's formed in the deep fryer, nor when it's formed in the digestive tract (23, 24). Eating polyphenol-rich foods effectively prevents these fats from being oxidized during digestion (25). One consequence of this appears to be better absorption and assimilation of the exceptionally fragile omega-3 polyunsaturated fatty acids (26).

What does it all Mean?

I think that overall, the evidence suggests that polyphenol-rich foods are healthy in moderation, and eating them on a regular basis is generally a good idea. Certain other plant chemicals, such as suforaphane found in cruciferous vegetables, and allicin found in garlic, exhibit similar effects and may also act by hormesis (27). Some of the best-studied polyphenol-rich foods are tea (particularly green tea), blueberries, extra-virgin olive oil, red wine, citrus fruits, hibiscus tea, soy, dark chocolate, coffee, turmeric and other herbs and spices, and a number of traditional medicinal herbs. A good rule of thumb is to "eat the rainbow", choosing foods with a variety of colors.

Supplementing with polyphenols and other plant chemicals in amounts that would not be achievable by eating food is probably not a good idea.


* The "paradox" whereby the French eat a diet rich in saturated fat, yet have a low heart attack risk compared to other affluent Western nations.

** Genes containing an antioxidant response element (ARE) in the promoter region. ARE is also sometimes called the electrophile response element (EpRE).

Tropical Plant Fats: Coconut Oil, Part II

Heart Disease: Animal Studies

Although humans aren't rats, animal studies are useful because they can be tightly controlled and experiments can last for a significant portion of an animal's lifespan. It's essentially impossible to do a tightly controlled 20-year feeding study in humans.

The first paper I'd like to discuss come from the lab of Dr. Thankappan Rajamohan at the university of Kerala (1). Investigators fed three groups of rats different diets:

1. Sunflower oil plus added cholesterol
2. Copra oil, a coconut oil pressed from dried coconuts, plus added cholesterol
3. Freshly pressed virgin coconut oil, plus added cholesterol

Diets 1 and 2 resulted in similar lipids, while diet 3 resulted in lower LDL and higher HDL. A second study also showed that diet 3 resulted in lower oxidized LDL, a dominant heart disease risk factor (2). Overall, these papers showed that freshly pressed virgin coconut oil, with its full complement of "minor constituents"*, partially protects rats against the harmful effects of cholesterol overfeeding. These are the only papers I could find on the cardiovascular effects of unrefined coconut oil in animals!

Although unrefined coconut oil appears to be superior, even refined coconut oil isn't as bad as it's made out to be. For example, compared to refined olive oil, refined coconut oil protects against atherosclerosis (hardening and thickening of the arteries) in a mouse model of coronary heart disease (LDL receptor knockout). In the same paper, coconut oil caused more atherosclerosis in a different mouse model (ApoE knockout) (3). So the vascular effects of coconut oil depend in part on the animals' genetic background.

In general, I've found that the data are extremely variable from one study to the next, with no consistent trend showing refined coconut oil to be protective or harmful relative to refined monounsaturated fats (like olive oil) (4). In some cases, polyunsaturated oils cause less atherosclerosis than coconut oil in the context of an extreme high-cholesterol diet because they sometimes lead to blood lipid levels that are up to 50% lower. However, even this isn't consistent across experiments. Keep in mind that atherosclerosis is only one factor in heart attack risk.

What happens if you feed coconut oil to animals without adding cholesterol, and without giving them genetic mutations that promote atherosclerosis? Again, the data are contradictory. In rabbits, one investigator showed that serum cholesterol increases transiently, returning to baseline after about 6 months, and atherosclerosis does not ensue (5). A different investigator showed that coconut oil feeding results in lower blood lipid oxidation than sunflower oil (6). Yet a study from the 1980s showed that in the context of a terrible diet composition (40% sugar, isolated casein, fat, vitamins and minerals), refined coconut oil causes elevated blood lipids and atherosclerosis (7). This is almost certainly because overall diet quality influences the response to dietary fats in rabbits, as it does in other mammals.

Heart Disease: Human Studies

It's one of the great tragedies of modern biomedical research that most studies focus on nutrients rather than foods. This phenomenon is called "nutritionism". Consequently, most of the studies on coconut oil used a refined version, because the investigators were most interested in the effect of specific fatty acids. The vitamins, polyphenols and other minor constituents of unrefined oils are eliminated because they are known to alter the biological effects of the fats themselves. Unfortunately, any findings that result from these experiments apply only to refined fats. This is the fallacy of the "X fatty acid does this and that" type statements-- they ignore the biological complexity of whole foods. They would probably be correct if you were drinking purified fatty acids from a beaker.

Generally, the short-term feeding studies using refined coconut oil show that it increases both LDL ("bad cholesterol") and HDL ("good cholesterol"), although there is so much variability between studies that it makes firm conclusions difficult to draw (8, 9). As I've written in the past, the ability of saturated fats to elevate LDL appears to be temporary; both human and certain animal studies show that it disappears on timescales of one year or longer (10, 11). That hasn't been shown specifically for coconut oil that I'm aware of, but it could be one of the reasons why traditional cultures eating high-coconut diets don't have elevated serum cholesterol.

Another marker of cardiovascular disease risk is lipoprotein (a), abbreviated Lp(a). This lipoprotein is a carrier for oxidized lipids in the blood, and it correlates with a higher risk of heart attack. Refined coconut oil appears to lower Lp(a), while refined sunflower oil increases it (12).

Unfortunately, I haven't been able to find any particularly informative studies on unrefined coconut oil in humans. The closest I found was a study from Brazil showing that coconut oil reduced abdominal obesity better than soybean oil in conjunction with a low-calorie diet, without increasing LDL (13). It would be nice to have more evidence in humans confirming what has been shown in rats that there's a big difference between unrefined and refined coconut oil.

Coconut Oil and Body Fat

In addition to the study mentioned above, a number of experiments in animals have shown that "medium-chain triglycerides", the predominant type of fat in coconut oil, lead to a lower body fat percentage than most other fats (14). These findings have been replicated numerous times in humans, although the results have not always been consistent (15). It's interesting to me that these very same medium-chain saturated fats that are being researched as a fat loss tool are also considered by mainstream diet-heart researchers to be among the most deadly fatty acids.

Coconut Oil and Cancer

Refined coconut oil produces less cancer than seed oils in experimental animals, probably because it's much lower in omega-6 polyunsaturated fat (16, 17). I haven't seen any data in humans.

The Bottom Line

There's very little known about the effect of unrefined coconut oil on animal and human health, however what is published appears to be positive, and is broadly consistent with the health of traditional cultures eating unrefined coconut foods. The data on refined coconut oil are conflicting and frustrating to sort through. The effects of refined coconut oil seem to depend highly on dietary context and genetic background. In my opinion, virgin coconut oil can be part of a healthy diet, and may even have health benefits in some contexts.


* Substances other than the fat itself, e.g. vitamin E and polyphenols. These are removed during oil refining.

Tropical Plant Fats: Palm Oil

A Fatal Case of Nutritionism

The concept of 'nutritionism' was developed by Dr. Gyorgy Scrinis and popularized by the food writer Michael Pollan. It states that the health value of a food can be guessed by the sum of the nutrients it contains. Pollan argues, I think rightfully, that nutritionism is a reductionist philosophy that assumes we know more about food composition and the human body than we actually do. You can find varying degrees of this philosophy in most mainstream discussions of diet and health*.

One conspicuous way nutritionism manifests is in the idea that saturated fat is harmful. Any fat rich in saturated fatty acids is typically assumed to be unhealthy, regardless of its other constituents. There is also apparently no need to directly test that assumption, or even to look through the literature to see if the assumption has already been tested. In this manner, 'saturated' tropical plant fats such as palm oil and coconut oil have been labeled unhealthy, despite essentially no direct evidence that they're harmful. As we'll see, there is actually quite a bit of evidence, both indirect and direct, that their unrefined forms are not harmful and perhaps even beneficial.

Palm Oil and Heart Disease

Long-time readers may recall a post I wrote a while back titled Ischemic Heart Attacks: Disease of Civilization (1). I described a study from 1964 in which investigators looked for signs of heart attacks in thousands of consecutive autopsies in the US and Africa, among other places. They found virtually none in hearts from Nigeria and Uganda (3 non-fatal among more than 4,500 hearts), while Americans of the same age had very high rates (up to 1/3 of hearts).

What do they eat in Nigeria? Typical Nigerian food involves home-processed grains, starchy root vegetables, beans, fruit, vegetables, peanuts, red palm oil, and a bit of dairy, fish and meat**. The oil palm Elaeis guineensis originated in West Africa and remains one of the main dietary fats throughout the region.

To extract the oil, palm fruit are steamed, and the oily flesh is removed and pressed. It's similar to olive oil in that it is extracted gently from an oil-rich fruit, rather than harshly from an oil-poor seed (e.g., corn or soy oil). The oil that results is deep red and is perhaps the most nutrient-rich fat on the planet. The red color comes from carotenes, but red palm oil also contains a large amount of vitamin E (mostly tocotrienols), vitamin K1, coenzyme Q10 and assorted other fat-soluble constituents. This adds up to a very high concentration of fat-soluble antioxidants, which are needed to protect the fat from rancidity in hot and sunny West Africa. Some of these make it into the body when it's ingested, where they appear to protect the body's own fats from oxidation.

Mainstream nutrition authorities state that palm oil should be avoided due to the fact that it's approximately half saturated. This is actually one of the main reasons palm oil was replaced by hydrogenated seed oils in the processed food industry. Saturated fat raises blood cholesterol, which increases the risk of heart disease. Doesn't it? Let's see what the studies have to say.

Most of the studies were done using refined palm oil, unfortunately. Besides only being relevant to processed foods, this method also introduces a new variable because palm oil can be refined and oxidized to varying degrees. However, a few studies were done with red palm oil, and one even compared it to refined palm oil. Dr. Suzanna Scholtz and colleagues put 59 volunteers on diets predominating in sunflower oil, refined palm oil or red palm oil for 4 weeks. LDL cholesterol was not different between the sunflower oil and red palm oil groups, however the red palm oil group saw a significant increase in HDL. LDL and HDL both increased in the refined palm oil group relative to the sunflower oil group (2).

Although the evidence is conflicting, most studies have not been able to replicate the finding that refined palm oil increases LDL relative to less saturated oils (3, 4). This is consistent with studies in a variety of species showing that saturated fat generally doesn't raise LDL compared to monounsaturated fat in the long term, unless a large amount of purified cholesterol is added to the diet (5).

Investigators have also explored the ability of palm oil to promote atherosclerosis, or hardening and thickening of the arteries, in animals. Not only does palm oil not promote atherosclerosis relative to monounsaturated fats (e.g., olive oil), but in its unrefined state it actually protects against atherosclerosis (6, 7). A study in humans hinted at a possible explanation: compared to a monounsaturated oil***, palm oil greatly reduced oxidized LDL (8). As a matter of fact, I've never seen a dietary intervention reduce oxLDL to that degree (69%). oxLDL is a major risk factor for cardiovascular disease, and a much better predictor of risk than the typically measured LDL cholesterol (9). The paper didn't state whether or not the palm oil was refined. I suspect it was lightly refined, but still rich in vitamin E and CoQ10.

As I discussed in my recent interview with Jimmy Moore, atherosclerosis is only one factor in heart attack risk (10). Several other factors are also major determinants of risk: clotting tendency, plaque stability, and susceptibility to arrhythmia. Another factor that I haven't discussed is how resistant the heart muscle is to hypoxia, or loss of oxygen. If the coronary arteries are temporarily blocked-- a frequent occurrence in modern people-- the heart muscle can be damaged. Dietary factors determine the degree of damage that results. For example, in rodents, nitrites derived from green vegetables protect the heart from hypoxia damage (11). It turns out that red palm oil is also protective (12, 13). Red palm oil also protects against high blood pressure in rats, an effect attributed to its ability to reduce oxidative stress (14, 15).

Together, the evidence suggests that red palm oil does not contribute to heart disease risk, and in fact is likely to be protective. The benefits of red palm oil probably come mostly from its minor constituents, i.e. the substances besides its fatty acids. Several studies have shown that a red palm oil extract called palmvitee lowers serum lipids in humans (16, 17). The minor constituents are precisely what are removed during the refining process.

Palm Oil and the Immune System

Red palm oil also has beneficial effects on the immune system in rodents. It protects against bacterial infection when compared with soybean oil (18). It also protects against certain cancers, compared to other oils (19, 20). This may be in part due to its lower content of omega-6 linoleic acid (roughly 10%), and minor constituents.

The Verdict

Yet again, nutritionism has gotten itself into trouble by underestimating the biological complexity of a whole food. Rather than being harmful to human health, red palm oil, an ancient and delicious food, is likely to be protective. It's also one of the cheapest oils available worldwide, due to the oil palm's high productivity. It has a good shelf life and does not require refrigeration. Its strong, savory flavor goes well in stews, particularly meat stews. It isn't available in most grocery stores, but you can find it on the internet. Make sure not to confuse it with refined palm oil or palm kernel oil.


* The approach that Pollan and I favor is a simpler, more empirical one: eat foods that have successfully sustained healthy cultures.

** Some Nigerians are also pastoralists that subsist primarily on dairy.

*** High oleic sunflower oil, from a type of sunflower bred to be high in monounsaturated fat and low in linoleic acid. I think it's probably among the least harmful refined oils. I use it sometimes to make mayonnaise. It's often available in grocery stores, just check the label.

Nitrate: a Protective Factor in Leafy Greens

Cancer Link and Food Sources

Nitrate (NO3) is a molecule that has received a lot of bad press over the years. It was initially thought to promote digestive cancers, in part due to its ability to form carcinogens in the digestive tract. As it's used as a preservative in processed meats, and there is a link between processed meats and gastric cancer (1), nitrate was viewed with suspicion and a number of countries imposed strict limits on its use as a food additive.

But what if I told you that by far the greatest source of nitrate in the modern diet isn't processed meat-- but vegetables, particularly leafy greens (2)? And that the evidence specifically linking nitrate consumption to gastric cancer has largely failed to materialize? For example, one study found no difference in the incidence of gastric cancer between nitrate fertilizer plant workers and the general population (3). Most other studies in animals and humans have not supported the hypothesis that nitrate itself is carcinogenic (4, 5, 6). This, combined with recent findings on nitrate biology, has the experts singing a different tune in the last few years.

A New Example of Human Symbiosis

In 2003, Dr. K. Cosby and colleagues showed that nitrite (NO2; not the same as nitrate) dilates blood vessels in humans when infused into the blood (7). Investigators subsequently uncovered an amazing new example of human-bacteria symbiosis: dietary nitrate (NO3) is absorbed from the gut into the bloodstream and picked up by the salivary glands. It's then secreted into saliva, where oral bacteria use it as an energy source, converting it to nitrite (NO2). After swallowing, the nitrite is reabsorbed into the bloodstream (8). Humans and oral bacteria may have co-evolved to take advantage of this process. Antibacterial mouthwash prevents it.

Nitrate Protects the Cardiovascular System

In 2008, Dr. Andrew J. Webb and colleagues showed that nitrate in the form of 1/2 liter of beet juice (equivalent in volume to about 1.5 soda cans) substantially lowers blood pressure in healthy volunteers for over 24 hours. It also preserved blood vessel performance after brief oxygen deprivation, and reduced the tendency of the blood to clot (9). These are all changes that one would expect to protect against cardiovascular disease. Another group showed that in monkeys, the ability of nitrite to lower blood pressure did not diminish after two weeks, showing that the animals did not develop a tolerance to it on this timescale (10).

Subsequent studies showed that dietary nitrite reduces blood vessel dysfunction and inflammation (CRP) in cholesterol-fed mice (11). Low doses of nitrite also dramatically reduce tissue death in the hearts of mice exposed to conditions mimicking a heart attack, as well as protecting other tissues against oxygen deprivation damage (12). The doses used in this study were the equivalent of a human eating a large serving (100 g; roughly 1/4 lb) of lettuce or spinach.

Mechanism

Nitrite is thought to protect the cardiovascular system by serving as a precursor for nitric oxide (NO), one of the most potent anti-inflammatory and blood vessel-dilating compounds in the body (13). A decrease in blood vessel nitric oxide is probably one of the mechanisms of diet-induced atherosclerosis and increased clotting tendency, and it is likely an early consequence of eating a poor diet (14).

The Long View

Leafy greens were one of the "protective foods" emphasized by the nutrition giant Sir Edward Mellanby (15), along with eggs and high-quality full-fat dairy. There are many reasons to believe greens are an excellent contribution to the human diet, and what researchers have recently learned about nitrate biology certainly reinforces that notion. Leafy greens may be particularly useful for the prevention and reversal of cardiovascular disease, but are likely to have positive effects on other organ systems both in health and disease. It's ironic that a molecule suspected to be the harmful factor in processed meats is turning out to be one of the major protective factors in vegetables.

Pastured Dairy may Prevent Heart Attacks

Not all dairy is created equal. Dairy from grain-fed and pasture-fed cows differs in a number of ways. Pastured dairy contains more fat-soluble nutrients such as vitamin K2, vitamin A, vitamin E, carotenes and omega-3 fatty acids. It also contains more conjugated linoleic acid, a fat-soluble molecule that has been under intense study due to its ability to inhibit obesity and cancer in animals. The findings in human supplementation trials have been mixed, some confirming the animal studies and others not. In feeding experiments in cows, Dr. T. R. Dhiman and colleagues found the following (1):

Cows grazing pasture and receiving no supplemental feed had 500% more conjugated linoleic acid in milk fat than cows fed typical dairy diets.

Fat from ruminants such as cows, sheep and goats is the main source of CLA in the human diet. CLA is fat-soluble. Therefore, skim milk doesn't contain any. It's also present in human body fat in proportion to dietary intake. This can come from dairy or flesh.

In a recent article from the AJCN, Dr. Liesbeth Smit and colleagues examined the level of CLA in the body fat of Costa Rican adults who had suffered a heart attack, and compared it to another group who had not (a case-control study, for the aficionados). People with the highest level of CLA in their body fat were 49% less likely to have had a heart attack, compared to those with the lowest level (2).

Since dairy was the main source of CLA in this population, the association between CLA and heart attack risk is inextricable from the other components in pastured dairy fat. In other words, CLA is simply a marker of pastured dairy fat intake in this population, and the (possible) benefit could just as easily have come from vitamin K2 or something else in the fat.

This study isn't the first one to suggest that pastured dairy fat may be uniquely protective. The Rotterdam and EPIC studies found that a higher vitamin K2 intake is associated with a lower risk of heart attack, cancer and overall mortality (3, 4, 5). In the 1940s, Dr. Weston Price estimated that pastured dairy contains up to 50 times more vitamin K2 than grain-fed dairy. He summarized his findings in the classic book Nutrition and Physical Degeneration. This finding has not been repeated in recent times, but I have a little hunch that may change soon...

Vitamin K2
Cardiovascular Disease and Vitamin K2
Can Vitamin K2 Reverse Arterial Calcification?

Corn Oil and Cancer: Reality Strikes Again

The benefits of corn oil keep rolling in. In a new study by Stephen Freedland's group at Duke, feeding mice a diet rich in butter and lard didn't promote the growth of transplanted human prostate cancer cells any more than a low-fat diet (1).

Why do we care? Because other studies, including one from the same investigators, show that corn oil and other industrial seed oils strongly promote prostate cancer cell growth and increase mortality in similar models (2, 3).

From the discussion section:

Current results combined with our prior results suggest that lowering the fat content of a primarily saturated fat diet offers little survival benefit in an intact or castrated LAPC-4 xenograft model. In contrast to the findings when omega-6 fats are used, these results raise the possibility that fat type may be as important as fat amount or perhaps even more important.

The authors seem somewhat surprised and pained by the result. Kudos for publishing it. However, there's nothing to be surprised about. There's a large body of evidence implicating excess omega-6 fat in a number of cancer models. Reducing omega-6 to below 4% of calories has a dramatic effect on cancer incidence and progression*. In fact, there have even been several experiments showing that butter and other animal fats promote cancer growth to a lesser degree than margarine and omega-6-rich seed oils. I discussed that here.

I do have one gripe with the study. They refer to the diet as "saturated fat based". That's inaccurate terminology. I see it constantly in the diet-health literature. If it were coconut oil, then maybe I could excuse it, because coconut fat is 93% saturated. But this diet was made of lard and butter, the combination of which is probably about half saturated. The term "animal fat" or "low-omega-6 fat" would have been more accurate. At least they listed the diet composition. Many studies don't even bother, leaving it to the reader to decide what they mean by "saturated fat".


* The average American eats 7-8% omega-6 by calories. This means it will be difficult to see a relationship between omega-6 intake and cancer (or heart disease, or most things) in observational studies in the US or other industrial nations, because we virtually all eat more than 4% of calories as omega-6. Until the 20th century, omega-6 intake was below 4%, and usually closer to 2%, in most traditional societies. That's where it remains in contemporary traditional societies unaffected by industrial food habits, such as Kitava. Our current omega-6 intake is outside the evolutionary norm.

Skin Texture, Cancer and Dietary Fat

Richard and I exchanged a series of e-mails last week in which he remarked that Thai people generally have nice skin, which is something I've also noticed in Thai immigrants to the U.S. I believe you can often tell what kind of fat a person eats by looking at their face, especially as people age or bear children.

People who eat predominantly traditional fats like butter and coconut oil usually have nice skin. It's smoother, rosier and it ages more gracefully than the skin of a person who eats industrial fats like soy and corn oil. Coconut is the predominant fat in the traditional Thai diet. Coconut fat is about 87% saturated, far more than any animal fat*. Coconut oil and butter are very low in omega-6 linoleic acid, while industrial vegetable oils and margarine contain a lot of it.

I saw a great movie last week called "The Betrayal", about a family of Lao refugees that immigrated to the U.S. in the late 1970s. The director followed the family for 23 years as they tried to carve out a life for themselves in Brooklyn. The main fats in the traditional Lao diet are lard and coconut milk. The mother of the family was a nice looking woman when she left Laos. She was thin and had great skin and teeth, despite having delivered half a dozen children at that point. After 23 years in the U.S., she was overweight and her skin was colorless and pasty. At the end of the movie, they return to Laos to visit their family there. The woman's mother was still alive. She was nearly 100 years old and looked younger than her daughter.

Well that's a pretty story, but let's hit the science. There's a mouse model of skin cancer called the Skh:HR-1 hairless mouse. When exposed to UV rays and/or topical carcinogens, these mice develop skin cancer just like humans (especially fair-skinned humans). Researchers have been studying the factors that determine their susceptibility to skin cancer, and fat is a dominant one. Specifically, their susceptibility to skin cancer is determined by the amount of linoleic acid in the diet.

In 1994, Drs. Cope and Reeve published a study using hairless mice in which they put groups of mice on two different diets (Cope, R. B. & Reeve, V. E. (1994) Photochem. Photobiol. 59: 24 S). The first diet contained 20% margarine; the second was identical but contained 20% butter. Mice eating margarine developed significantly more skin tumors when they were exposed to UV light or a combination of UV and a topical carcinogen. Researchers have known this for a long time. Here's a quote from a review published in 1987:

Nearly 50 years ago the first reports appeared that cast suspicion on lipids, or peroxidative products thereof, as being involved in the expression of actinically induced cancer. Whereas numerous studies have implicated lipids as potentiators of specific chemical-induced carcinogenesis, only recently has the involvement of these dietary constituents in photocarcinogenesis been substantiated. It has now been demonstrated that both level of dietary lipid intake and degree of lipid saturation have pronounced effects on photoinduced skin cancer, with increasing levels of unsaturated fat intake enhancing cancer expression. The level of intake of these lipids is also manifested in the level of epidermal lipid peroxidation.

Here's a quote from a study conducted in 1996:

A series of semi-purified diets containing 20% fat by weight, of increasing proportions (0, 5%, 10%, 15% or 20%) of polyunsaturated sunflower oil mixed with hydrogenated saturated cottonseed oil, was fed to groups of Skh:HR-1 hairless mice during induction and promotion of photocarcinogenesis. The photocarcinogenic response was of increasing severity as the polyunsaturated content of the mixed dietary fat was increased, whether measured as tumour incidence, tumour multiplicity, progression of benign tumours to squamous cell carcinoma, or reduced survival... These results suggest that the enhancement of photocarcinogenesis by the dietary polyunsaturated fat component is mediated by an induced predisposition to persistent immunosuppression caused by the chronic UV irradiation, and supports the evidence for an immunological role in dietary fat modulation of photocarcinogenesis in mice.

In other words, UV-induced cancer increased in proportion to the linoleic acid content of the diet, because linoleic acid suppresses the immune system's cancer-fighting ability!

It doesn't end at skin cancer. In animal models, a number of cancers are highly sensitive to the amount of linoleic acid in the diet, including breast cancer. Once again, butter beats margarine and vegetable oils. Spontaneous breast tumors develop only half as frequently in rats fed butter than in rats fed margarine or safflower oil (Yanagi, S. et al. (1989) Comparative effects of butter, margarine, safflower oil and dextrin on mammary tumorigenesis in mice and rats. In: The Pharmacological Effects of Lipids.). The development of breast tumors in rats fed carcinogens is highly dependent on the linoleic acid content of the diet. The effect plateaus around 4.4% of calories, after which additional linoleic acid has no further effect.

Conversely, omega-3 fish oil protects against skin cancer in the hairless mouse, even in large amounts. In another study, not only did fish oil protect against skin cancer, it doubled the amount of time researchers had to expose the mice to UV light to cause sunburn!

Thus, the amount of linoleic acid in the diet as well as the balance between omega-6 and omega-3 determine the susceptibility of the skin to damage from UV rays. This is a very straightforward explanation for the beautiful skin of people eating traditional fats like butter and coconut oil. It's also a straightforward explanation for the poor skin and sharply rising melanoma incidence of Western nations (source). Melanoma is the most deadly form of skin cancer. If you're dark-skinned, you're off the hook:

I believe the other factor contributing to rising melanoma incidence is sunscreen. Most sunscreens block sunburn-causing UVB rays but not melanoma-causing UVA rays. The fact that they allow you to remain in the sun for longer without burning means they increase your exposure to UVA. I've written about this before. Sunscreen also blocks vitamin D formation in the skin, a process that some researchers believe also promotes cancer. I'll end with a couple more graphs that are self-explanatory (source). "PUFA" stands for polyunsaturated faty acids, and primarily represents linoleic acid:





*Not only do Thais have clear skin, they also have clear arteries. Autopsies performed in the 1960s showed that residents of Bangkok had a low prevalence of atherosclerosis and a rate of heart attack (myocardial infarction) about 1/10 that of Americans living in Los Angeles.

Low Stomach Acid and Nutrient Absorption

As I mentioned here and here, low stomach acid (hypochlorhydria) causes many problems, including bacterial overgrowth in the small intestine, lowered resistance to infection by ingested pathogens, an increase in gastric cancer susceptibility, and reduced nutrient absorption. It has the potential to underlie many other issues, including food sensitivities. The prevalence varies by age, increasing from less than 10% in the young to over 50% in the elderly.

In a previous post, I mentioned a few nutrients I had come across that require full stomach acidity for optimum absorption. I recently found a nice paper from 1989 titled "Hypochlorhydria: a Factor in Nutrition", which broadened my perspective. Here's a revised list of nutrients known to be affected by hypochlorhydria, as of 1989:

• Calcium
• Iron
• Folic acid
• Vitamin B6
• Vitamin B12
• Vitamin A
• Vitamin E
• Niacin
• Protein

That's a hefty list, and it's not even comprehensive!

Sugar, Hydrogen, Bacteria and Maldigestion

There are several ways to cause a nutrient deficiency. The first is to eat too little of a nutrient. Another way is to burn through your body's nutrient stores at an accelerated rate, for example, what omega-6 vegetable oils do to vitamin E, and what wheat bran does to vitamin D. A third way is to eat enough nutrients but fail to absorb them efficiently.

A good way to reduce your absorption of nutrients is to lower your stomach's acidity. This will protect you from those pesky nutrients protein, vitamin B12, and iron (and probably others as well). The stomach is one tough organ. When it receives food, a healthy stomach lowers its pH to roughly 2.0 by secreting hydrochloric acid. That's more acidic than lemon juice and more than 10 times more acidic than vinegar. This begins to break food down, and will kill most bacteria and other pathogens. Stomach acidity is basically the body's way of "cooking" food before further digestion. At the same time, the stomach secretes pepsin, which is an acid-stable enzyme that digests protein.

Insufficient stomach acidity promotes bacterial overgrowth in the small intestine and allows undigested proteins into the intestine. The gastrin knockout mouse, which is incapable of producing stomach acid, suffers from bacterial overgrowth, inflammation, damage and precancerous polyps in its intestines. The same thing happens when you treat mice with a drug that inhibits stomach acidification.

There are a few different ways to reduce your stomach's acidity level. The most straightforward is to take an antacid, or any number of drugs that lower stomach acidity (as in the mouse study above). But can we do it naturally? Sure, all it takes is a little Helicobacter pylori infection! Luckily, most people already have one.

H. pylori is a bacterium that's the main proximal cause of stomach ulcers. Antibiotics are now the standard treatment for ulcers, and they're effective. Treating an asymptomatic H. pylori infection with antibiotics increases stomach acidity, suggesting that H. pylori is capable of suppressing the secretion of stomach acid. In another study, eradicating H. pylori with antibiotics improved nearly all patients suffering from hypochlorhydria (insufficient stomach acid).

Like any organism, H. pylori likes to stay well-fed. Its favorite food is hydrogen gas (H2), and the more it gets, the more it grows. It's not the only bacterium to like H2. Salmonella, of food poisoning fame, requires H2 to become pathogenic. Clostridium bacteria are also associated with elevated H2. H2 is produced by the fermentation of food by bacteria in the digestive tract. It's very small so it diffuses around the body, reaching the stomach lining where it's eagerly gobbled up by H. pylori. It may be equally good food for a number of other parasites around the body.

Now let's stop beating around the bush and get to the meat of this post. It's all summed up in a beautiful title: Fructose Intake at Current Levels in the United States May Cause Gastrointestinal Distress in Normal Adults. Dr. Richard W. McCallum et al. fed doses of isolated fructose to 15 normal adults. Can I say it any better than the abstract?

More than half of the 15 adults tested showed evidence of fructose malabsorption after 25 g fructose and greater than two thirds showed malabsorption after 50 g fructose... Fructose, in amounts commonly consumed, may result in mild gastrointestinal distress in normal people.

Here's where it gets really interesting. One of the measures of malabsorption they used was H2 on the breath. Both the 25g and the 50g doses caused a large increase in H2, especially the 50g dose (5-fold increase). This is the same thing you see in people who are lactose intolerant. Bacterial fermentation is the only significant source of H2 in the human body. That means the fructose was hanging around in the small intestine for long enough to be decomposed by the local bacteria, who took advantage of it to proliferate.

Certain types of fiber also promote H2 production. Resistant starch, as well as certain non-caloric sweeteners, are readily fermented into H2 in some people. Cellulose, the predominant fiber in vegetables and grains, does not increase H2. The large difference in fiber content of rural vs. urban Mexican diets doesn't seem to correlate with H2 production by intestinal bacteria. Interestingly, both white and whole wheat bread increase H2 production.

Let's put those doses of fructose into perspective. One medium banana contains about 7 grams. A 16-ounce bottle of apple juice contains about 30 grams. A slice of cake contains about 12. One "child-size" 12 ounce cup of Coca-Cola from McDonald's contains 17 grams (as long as you don't get a refill!). One large 32 ounce Coca-Cola contains 47 grams. Your H. pylori will be VERY pleased if you drink one of those, especially if you use it to wash down the white flour bun on your hamburger.

I do think it's important to mention that the study described above used isolated fructose. It's not clear that other sources of fructose would behave the same. For example, the presence of glucose enhances fructose absorption. Fruit, table sugar and high-fructose corn syrup all contain glucose. It's also not clear what the effect would be of eating fructose with a meal rather than in isolation. None of this has been studied to my knowledge, so we're left extrapolating from studies that used pure fructose.

Now let's connect the dots. Excessive fructose, certain types of fiber, and wheat cause bacterial overgrowth and H2 production (if you believe the fructose-H2 connection). Elevated H2 causes overgrowth of H. pylori and possibly other pathogenic bacteria in the body. H. pylori lowers stomach acid, causing further overgrowth of bacteria in the small intestine. This causes inflammation and increases the risk for digestive cancers.

Decreased stomach acid also causes malabsorption of protein, B12, iron and perhaps other nutrients. It allows undigested protein to travel into the small intestine. This could potentially be very important. For example, many people are allergic to the casein in milk. It's one of the two most common alleriges, along with gluten. Both casein and gluten are proteins. A normally functioning stomach at the proper pH should completely digest casein. You can't be allergic to casein if there's none around. I don't know if the same applies to gluten.

Robust digestion may explain why many healthy non-industrial groups do very well eating dairy, sometimes to the exclusion of nearly everything else, yet many people in modern societies do better without dairy protein (butter is typically well tolerated). This phenomenon could also go a long way toward explaining the fact that allergies are becoming more and more common in industrial nations as we consume more sugar.

Thanks to Peter and Matt Stone for some of the ideas I incorporated into this post. Thanks to pbo31 for the CC photo.

Vitamin D and Cancer

I'd like to point readers to a couple of posts by Richard Nikoley over at Free the Animal, on the relationship between vitamin D status and various types of cancer. The epidemiology consistently shows an inverse relationship between vitamin D levels and cancer incidence. A few intervention trials also support a protective role of vitamin D against cancer. Increased sunscreen use has not reduced melanoma incidence, to the contrary. I've discussed this before as well. Richard got his graphs from the website GrassrootsHealth.

Vitamin D deficiency and All Cancer

Melanoma, Sun and its Synthetic Defeat (sunscreen)

Vitamin D is not just another vitamin. It's a hormone precursor that plays a fundamental role in the regulation of numerous bodily processes. Sunlight is an essential nutrient for physical and mental health.

Here are the best natural sources of vitamin D:

• Sunlight
• High-vitamin cold liver oil
• Summer blood from animals raised outdoors (for example, blood sausage)
  
• Fatty fish

Vitamin D is one of the few nutrients that may be worth supplementing during wintertime. Make sure to buy D3 and take at least 2,000 IU if you are going to bother.

Book Review: Dangerous Grains

Dangerous Grains is about the health hazards of gluten grains. It's co-written by James Braly, an M.D. who specializes in food allergies, and Ron Hoggan, a celiac patient who has written widely on the subject.

Celiac disease is a degeneration of the intestinal lining caused by exposure to gluten. Gluten sensitivity is a broader term that encompasses any of the numerous symptoms that can occur throughout the body when susceptible people eat gluten. The term gluten sensitivity includes celiac disease. Gluten is a protein found in wheat, its close relatives (kamut, spelt, triticale), barley and rye. Wheat is the most concentrated source.

Dangerous Grains is a good overview of the mountain of data on celiac disease and gluten sensitivity that few people outside the field are familiar with. For example, did you know:

• An estimated one percent of the U.S. population suffers from celiac disease.
• Approximately 12 percent of the US population suffers from gluten sensitivity.
• Gluten can damage nearly any part of the body, including the brain, the digestive tract, the skin and the pancreas. Sometimes gastrointestinal symptoms are absent.
  
• Both celiac and other forms of gluten sensitivity increase the risk of a large number of diseases, such as type 1 diabetes and cancer, often dramatically.
• The majority of people with gluten sensitivity are not diagnosed.
• Most doctors don't realize how common gluten sensitivity is, so they rarely test for it.
  
• Celiac disease and other symptoms of gluten sensitivity are easily reversed by avoiding gluten.

Twelve percent of Americans have gluten sensitivity! That's an enormous disease burden coming from a single type of food. I suspect the true incidence may actually be higher. There are preliminary data suggesting that most people may mount an immune response to gluten that does not require antibodies (through the innate immune system). This type of gluten sensitivity would be overlooked by the typical antibody tests, but could still result in damage.

Dangerous Grains also discusses the opioid-like peptides released from gluten during digestion. Opioids are powerful drugs, such as heroin and morphine, that were originally derived from the poppy seed pod. They are strong suppressors of the immune system and quite addictive. There are no data that conclusively prove the opioid-like peptides in gluten cause immune suppression or addiction to wheat, but there are some interesting coincidences and anecdotes. Celiac patients are at an increased risk of cancer, particularly digestive tract cancer, which suggests that the immune system is compromised. Heroin addicts are also at increased risk of cancer. Furthermore, celiac patients often suffer from abnormal food cravings. From my reading, I believe that wheat causes excessive eating, perhaps through a drug-like mechanism, and many people report withdrawal-like symptoms and cravings after eliminating wheat.

I know several people who have benefited greatly from removing gluten from their diets. Anyone who has digestive problems, from gas to acid reflux, or any other mysterious health problem, owes it to themselves to try a gluten-free diet for a month. Gluten consumption has increased quite a bit in the U.S. in the last 30 years, mostly due to an increase in the consumption of processed wheat snacks. I believe it's partly to blame for our declining health. Wheat has more gluten than any other grain. Avoiding wheat and all its derivatives is a keystone of my health philosophy.

Another notable change that Sally Fallon and others have pointed out is that today's bread isn't made the same way our grandparents made it. Quick-rise yeast allows bread to be fermented for as little as 3 hours, whereas it was formerly fermented for 8 hours or more. This allowed the gluten to be partially broken down by the microorganisms in the dough. Some gluten-sensitive people report that they can eat well-fermented sourdough wheat bread without symptoms. I think these ideas are plausible, but they remain anecdotes to me at this point. Until research shows that gluten-sensitive people can do well eating sourdough wheat bread in the long term, I'll be avoiding it. I have no reason to believe I'm gluten sensitive myself, but through my reading I've been convinced that wheat, at least how we eat it today, is probably not healthy for anyone.

I'm not aware of any truly healthy traditional culture that eats wheat as a staple. As a matter of fact, white wheat flour has left a trail of destruction around the globe wherever it has gone. Polished rice does not have such a destructive effect, so it's not simply the fact that it's a refined carbohydrate. Hundreds, if not thousands of cultures throughout the world have lost their robust good health upon abandoning their traditional foods in favor of white flour and sugar. The medical and anthropological literature are peppered with these stories. I'm aware of one healthy culture that traditionally ate sourdough-fermented whole grain rye bread, the Swiss villagers of the Loetschental valley described in Nutrition and Physical Degeneration.

Overall, the book is well written and accessible to a broad audience. I recommend it to anyone who has health problems or who is healthy and wants to stay that way!

The Inuit: Lessons from the Arctic

The Inuit (also called Eskimo) are a group of hunter-gatherer cultures who inhabit the arctic regions of Alaska, Canada and Greenland. They are a true testament to the toughness, adaptability and ingenuity of the human species. Their unique lifestyle has a lot of information to offer us about the boundaries of the human ecological niche. Weston Price was fascinated by their excellent teeth, good nature and overall robust health. Here's an excerpt from Nutrition and Physical Degeneration:

"In his primitive state he has provided an example of physical excellence and dental perfection such as has seldom been excelled by any race in the past or present...we are also deeply concerned to know the formula of his nutrition in order that we may learn from it the secrets that will not only aid in the unfortunate modern or so-called civilized races, but will also, if possible, provide means for assisting in their preservation."

The Inuit are cold-hardy hunters whose traditional diet consists of a variety of sea mammals, fish, land mammals and birds. They invented some very sophisticated tools, including the kayak, whose basic design has remained essentially unchanged to this day. Most groups ate virtually no plant food. Their calories came primarily from fat, up to 75%, with almost no calories coming from carbohydrate. Children were breast-fed for about three years, and had solid food in their diet almost from birth. As with most hunter-gatherer groups, they were free from chronic disease while living a traditional lifestyle, even in old age. Here's a quote from Observations on the Western Eskimo and the Country they Inhabit; from Notes taken During two Years [1852-54] at Point Barrow, by Dr. John Simpson:

These people [the Inuit] are robust, muscular and active, inclining rather to spareness [leanness] than corpulence [overweight], presenting a markedly healthy appearance. The expression of the countenance is one of habitual good humor. The physical constitution of both sexes is strong. Extreme longevity is probably not unknown among them; but as they take no heed to number the years as they pass they can form no guess of their own ages.

One of the common counterpoints I hear to the idea that high-fat hunter-gatherer diets are healthy, is that exercise protects them from the ravages of fat. The Inuit can help us get to the bottom of this debate. Here's a quote from Cancer, Disease of Civilization (1960, Vilhjalmur Stefansson):

"They are large eaters, some of them, especially the women, eating all the time..." ...during the winter the Barrow women stirred around very little, did little heavy work, and yet "inclined more to be sparse than corpulent" [quotes are the anthropologist Dr. John Murdoch, reproduced by Stefansson].

Another argument I sometimes hear is that the Inuit are genetically adapted to their high-fat diet, and the same food would kill a European. This appears not to be the case. The anthropologist and arctic explorer Vilhjalmur Stefansson spent several years living with the Inuit in the early 20th century. He and his fellow Europeans and Americans thrived on the Inuit diet. American doctors were so incredulous that they defied him and a fellow explorer to live on a diet of fatty meat only for one year, under the supervision of the American Medical Association. To the doctors' dismay, they remained healthy, showing no signs of scurvy or any other deficiency (JAMA 1929;93:20–2).

Yet another amazing thing about the Inuit was their social structure. Here's Dr. John Murdoch again (quoted from Cancer, Disease of Civilization):

The women appear to stand on a footing of perfect equality with the men, both in the family and the community. The wife is the constant and trusted companion of the man in everything except the hunt, and her opinion is sought in every bargain or other important undertaking... The affection of parents for their children is extreme, and the children seem to be thoroughly worthy of it. They show hardly a trace of fretfulness or petulance so common among civilized children, and though indulged to an extreme extent are remarkably obedient. Corporal punishment appears to be absolutely unknown, and children are rarely chided or punished in any way.

Unfortunately, those days are long gone. Since adopting a modern processed-food diet, the health and social structure of the Inuit has deteriorated dramatically. This had already happened to most groups by Weston Price's time, and is virtually complete today. Here's Price:

In the various groups in the lower Kuskokwim seventy-two individuals who were living exclusively on native foods had in their 2,138 teeth only two teeth or 0.09 per cent that had ever been attacked by tooth decay. In this district eighty-one individuals were studied who had been living in part or in considerable part on modern foods, and of their 2, 254 teeth 394 or 13 per cent had been attacked by dental caries. This represents an increase in dental caries of 144 fold.... When these adult Eskimos exchange their foods for our modern foods..., they often have very extensive tooth decay and suffer severely.... Their plight often becomes tragic since there are no dentists in these districts.

Modern Inuit also suffer from very high rates of diabetes and overweight. This has been linked to changes in diet, particularly the use of white flour, sugar and processed oils.

Overall, the unique lifestyle and diet of the Inuit have a lot to teach us. First, that humans are capable of being healthy as carnivores. Second, that we are able to thrive on a high-fat diet. Third, that we are capable of living well in extremely harsh and diverse environments. Fourth, that the shift from natural foods to processed foods, rather than changes in macronutrient composition, is the true cause of the diseases of civilization.

Sunscreen and Melanoma

Melanoma is the most deadly type of skin cancer, accounting for most skin cancer deaths in the US. As Ross pointed out in the comments section of the last post, there is an association between severe sunburn at a young age and later development of melanoma. Darker-skinned people are also more resistant to melanoma. The association isn't complete, however, since melanoma sometimes occurs on the soles of the feet and even in the intestine. This may be due to the fact that there are several types of melanoma, potentially with different causes.

Another thing that associates with melanoma is the use of sunscreen above a latitude of 40 degrees from the equator. In the Northern hemisphere, 40 degrees draws a line between New York city and Beijing. A recent meta-analysis found consistently that sunscreen users above 40 degrees are at a higher risk of melanoma than people who don't use sunscreen, even when differences in skin color are taken into account. Wearing sunscreen decreased melanoma risk in studies closer to the equator. It sounds confusing, but it makes sense once you know a little bit more about UV rays, sunscreen and the biology of melanoma.

The UV light that reaches the Earth's surface is composed of UVA (longer) and UVB (shorter) wavelengths. UVB causes sunburn, while they both cause tanning. Sunscreen blocks UVB, preventing burns, but most brands only weakly block UVA. Sunscreen allows a person to spend more time in the sun than they would otherwise, and attenuates tanning. Tanning is a protective response (among several) by the skin that protects it against both UVA and UVB. Burning is a protective response that tells you to get out of the sun. The result of diminishing both is that sunblock tends to increase a person's exposure to UVA rays.

It turns out that UVA rays are more closely associated with melanoma than UVB rays, and typical sunscreen fails to prevent melanoma in laboratory animals. It's also worth mentioning that sunscreen does prevent more common (and less lethal) types of skin cancer.

Modern tanning beds produce a lot of UVA and not much UVB, in an attempt to deliver the maximum tan without causing a burn. Putting on sunscreen essentially does the same thing: gives you a large dose of UVA without much UVB.

The authors of the meta-analysis suggest an explanation for the fact that the association changes at 40 degrees of latitude: populations further from the equator tend to have lighter skin. Melanin blocks UVA very effectively, and the pre-tan melanin of someone with olive skin is enough to block most of the UVA that sunscreen lets through. The fair-skinned among us don't have that luxury, so our melanocytes get bombarded by UVA, leading to melanoma. This may explain the incredible rise in melanoma incidence in the US in the last 35 years, as people have also increased the use of sunscreen. It may also have to do with tanning beds, since melanoma incidence has risen particularly in women.

In my opinion, the best way to treat your skin is to tan gradually, without burning. Use clothing and a wide-brimmed hat if you think you'll be in the sun past your burn threshold. If you want to use sunscreen, make sure it blocks UVA effectively. Don't rely on the manufacturer's word; look at the ingredients list. It should contain at least one of the following: titanium dioxide, zinc oxide, avobenzone (Parsol 1789), Mexoryl SX (Tinosorb). It's best if it's also paraben-free.

Fortunately, as an external cancer, melanoma is easy to diagnose. If caught early, it can be removed without any trouble. If caught a bit later, surgeons may have to remove lymph nodes, which makes your face look like John McCain's. Later than that and you're probably a goner. If you have any questions about a growth, especially one with irregular borders that's getting larger, ask your doctor about it immediately!

How to Cause a Cancer Epidemic

A report came out recently showing that melanoma incidence has increased dramatically in the US since 1973, particularly among women. The authors suggested the rise could be due to increasing sun exposure, which I am highly skeptical of. The data he cites to support that idea are quite weak. I think the prevalence of vitamin D deficiency in this country suggests otherwise.

Melanoma is the most deadly form of skin cancer, and the only type that is commonly life-threatening. Its link to sun exposure is tenuous at best. For example, it often occurs on the least sun-exposed parts of the body, and its incidence is lower in outdoor workers.

What is the solution to rising melanoma incidence? Sunblock! Slather it on, ladies and gentlemen! No matter that we evolved outdoors! No matter that it may do nothing for melanoma incidence or mortality! No matter that you'll be vitamin D deficient! No matter that it contains known carcinogens! 30+ SPF, the more the better. Don't let one single deadly UV photon through.

The irony of all this is that if you believe the data on vitamin D, avoiding the sun would cause many more cancers than it would prevent, even if all melanoma were due to sun exposure.

Cancer in Other Non-Industrialized Cultures

In Cancer, Disease of Civilization (1960), Wilhjalmur Stefansson mentions a few cultures besides the Inuit in which large-scale searches never turned up cancer. Dr. Albert Schweitzer examined over 10,000 traditionally-living natives in Gabon (West Africa) in 1913 and did not find cancer. Later, it became common in the same population as they began "living more and more after the manner of the whites."

In Cancer, its Nature, Cause and Cure (1957), Dr. Alexander Berglas describes the search for cancer among natives in Brazil and Ecuador by Dr. Eugene Payne. He examined approximately 60,000 people over 25 years and found no evidence of cancer.

Sir Robert McCarrison conducted a seven year medical survey among the Hunza, in what is now Northern Pakistan. Among 11,000 people, he did not find a single case of cancer. Their diet consisted of soaked and sprouted grains and beans, fruit, vegetables, grass-fed dairy and a small amount of meat (including organs of course).

I no longer think of cancer as an inevitable risk of getting old, but as another facet of the disease of civilization.

Mortality and Lifespan of the Inuit

One of the classic counter-arguments that's used to discredit accounts of healthy hunter-gatherers is the fallacy that they were short-lived, and thus did not have time to develop diseases of old age like cancer. While the life expectancy of hunter-gatherers was not as high as ours today, most groups had a significant number of elderly individuals, who sometimes lived to 80 years and beyond. Mortality came mostly from accidents, warfare and infectious disease rather than chronic disease.

I found a a mortality table from the records of a Russian mission in Alaska (compiled by Veniaminov, taken from Cancer, Disease of Civilization), which recorded the ages of death of a traditionally-living Inuit population during the years 1822 to 1836. Here's a plot of the raw data:

Here's the data re-plotted in another way. I changed the "bin size" of the bars to 10 year spans each (rather than the bins above, which vary from 3 to 20 years). This allows us to get a better picture of the number of deaths over time. I took some liberties with the data to do this, breaking up a large bin equally into two smaller bins. I also left out the infant mortality data, which are interesting but not relevant to this post:


Excluding infant mortality, about 25% of their population lived past 60. Based on these data, the approximate life expectancy (excluding infant mortality) of this Inuit population was 43.5 years. It's possible that life expectancy would have been higher before contact with the Russians, since they introduced a number of nasty diseases to which the Inuit were not resistant. Keep in mind that the Westerners who were developing cancer alongside them probably had a similar life expectancy at the time. Here's the data plotted in yet another way, showing the number of individuals surviving at each age, out of the total deaths recorded:


It's remarkably linear. Here's the percent chance of death at each age:


In the next post, I'll briefly summarize cancer data from several traditionally-living cultures other than the Inuit.

Cancer Among the Inuit

I remember coming across a table in the book Eat, Drink and Be Healthy (by Dr. Walter Willett-- you can skip it) a few years back. Included were data taken from Dr. Ancel Keys' "Seven Countries Study". It showed the cancer rates for three industrialized nations: the US, Greece and Japan. Although specific cancers differed, the overall rate was remarkably similar for all three: about 90 cancers per 100,000 people per year. Life expectancy was also similar, with Greece leading the pack by 4 years (the data are from the 60s).

The conclusion I drew at the time was that lifestyle did not affect the likelihood of developing cancer. It was easy to see from the same table that heart disease was largely preventable, since the US had a rate of 189 per 100,000 per year, compared to Japan's 34. Especially since I also knew that Japanese-Americans who eat an American diet get heart disease just like European-Americans.

I fell prey to the same logic that is so pervasive today: the idea that you will eventually die of cancer if no other disease gets you first. It's easy to believe, since the epidemiology seems to tell us that lifestyle doesn't affect overall cancer rates very much. There's only one little glitch... those epidemiological studies compare the sick to the sicker.

Here's the critical fact that modern medicine seems to have forgotten: hunter-gatherers and numerous non-industrial populations throughout the world have vanishingly small cancer rates. This fact was widely accepted in the 19th century and the early 20th, but has somehow managed to fade into obscurity. I know it sounds unbelievable, but allow me to explain.

I recently read Cancer, Disease of Civilization by Vilhjalmur Stefansson (thanks Peter). It really opened my eyes. Stefansson was an anthropologist and arctic explorer who participated in the search for cancer among the Canadian and Alaskan Inuit. Traditionally, most Inuit groups were strictly carnivorous, eating a diet of raw and cooked meat and fish almost exclusively. Their calories came primarily from fat, roughly 80%. They alternated between seasons of low and high physical activity, and typically enjoyed an abundant food supply.

Field physicians in the arctic noted that the Inuit were a remarkably healthy people. While they suffered from a tragic susceptibility to European communicable diseases, they did not develop the chronic diseases we now view as part of being human: tooth decay, overweight, heart attacks, appendicitis, constipation, diabetes and cancer. When word reached American and European physicians that the Inuit did not develop cancer, a number of them decided to mount an active search for it. This search began in the 1850s and tapered off in the 1920s, as traditionally-living Inuit became difficult to find.

One of these physicians was captain George B. Leavitt. He actively searched for cancer among the traditionally-living Inuit from 1885 to 1907. Along with his staff, he performed 50,000 examinations a year for the first 15 years, and 25,000 a year thereafter. He did not find a single case of cancer. At the same time, he was regularly diagnosing cancers among the crews of whaling ships and other Westernized populations. It's important to note two relevant facts about Inuit culture: first, their habit of going shirtless indoors. This would make visual inspection for external cancers very easy. Second, the Inuit generally had great faith in Western doctors and would consult them even for minor problems. Therefore, doctors in the arctic had ample opportunity to inspect them for cancer.

A study was published in 1934 by F.S. Fellows in the U.S Treasury's Public Health Reports entitled "Mortality in the Native Races of the Territory of Alaska, With Special Reference to Tuberculosis". It contained a table of cancer mortality deaths for several Alaskan regions, all of them Westernized to some degree. However, some were more Westernized than others. In descending order of Westernization, the percent of deaths from cancer were as follows:


Keep in mind that all four of the Inuit populations in this table were somewhat Westernized. It's clear that cancer incidence tracks well with Westernization. By "Westernization", what I mean mostly is the adoption of European food habits, including wheat flour, sugar, canned goods and vegetable oil. Later, most groups also adopted Western-style houses, which incidentally were not at all suited to their harsh climate.

In the next post, I'll address the classic counter-argument that hunter-gatherers were free of cancer because they didn't live long enough to develop it.