One of the major dietary changes that has accompanied the downward slide of American health is the replacement of animal fats with industrially processed vegetable oils. Soybean oil, corn oil, cottonseed oil and other industrial creations have replaced milk and meat fat in our diet, while total fat consumption has remained relatively constant. The result is that we're eating a lot more polyunsaturated fat than we were just 30 years ago, most of it linoleic acid (omega-6). Corn oil may taste so bad it inspires you to violence, but its insidiousness goes beyond the flavor. Take a look:
This figure is from a paper that Dr. Joe Hibbeln sent me recently, of which he is the first author. This followed an interesting e-mail conversation with Robert Brown, author of Omega Six: the Devil's Fat. He put me in touch with Dr. Hibbeln and Dr. William Lands (NIH, NIAAA), both of whom warn of the dangers of excessive linoleic acid consumption from modern vegetable oils. Dr. Lands has been researching the relationship between dietary fat and inflammation since the 1970s, and has been a critic of modern vegetable oils for just as long. Both Dr. Hibbeln and Dr. Lands were very generous in sending me a number of their papers. The figure above shows the homicide rate vs. linoleic acid consumption of five countries over the course of 40 years. Each point represents one year in one country. The U.S. has the distinction of being in the upper right.
I asked Dr. Hibbeln how he selected the five countries, and he told me the selection criteria were 1) available homicide and linoleic acid consumption statistics, 2) "first world" countries, and 3) countries representing a diversity of linoleic acid intakes. I'm satisfied that there was probably not a significant selection bias.
What's interesting about the graph is that not only does the homicide rate track with linoleic acid consumption across countries, but it also tracks within countries over time. For example, here is the same graph of the US alone:
And here is the UK, which doesn't suffer as much from the confounding factor of firearm availability:
Epidemiological associations don't get much better than that. In the next few posts, I'll explore the data from intervention trials that support the hypothesis that excessive omega-6 consumption, and insufficient omega-3 consumption, cause serious problems for psychiatric and physical health.