Sunday, January 18, 2009

Insulin, Leptin, Aging and Health

I recently read an article by Dr. Ron Rosedale that I found through commenter Stan's blog. Dr. Rosedale is one of those rare individuals who is capable of taking a truly big-picture view of health and aging, incorporating evolutionary biology, genetics and medicine into a coherent whole. The article discusses the role of the master hormones insulin and leptin in aging, health and disease.

I don't agree with everything he says, but I think it's a great article to read if you want a general orientation on the role of these hormones in health.

If you've read it, here are my main points of disagreement:
  1. Dr. Rosedale says that insulin's ability to regulate blood sugar is a minor role, and that other hormones do the same thing. Tell that to a type 1 diabetic. Excessive blood glucose is Not Good, and that's what you get if there isn't enough insulin around.
  2. I'm not convinced by the theory that organisms balance reproduction and repair, emphasizing one at the expense of the other. The amount of energy it takes to fuel cellular repair processes is negligible compared to the amount it takes to maintain body temperature, fuel the brain and contract skeletal muscles. Why not just have the organism eat an extra half-teaspoon of mashed potatoes to fuel the heat-shock proteins and make a little extra catalase? I think the true reasons behind lifespan extension upon caloric restriction will turn out to be more complex than a balance between reproduction and repair.
  3. I disagree with the idea that carbohydrate itself is behind elevated fasting insulin and leptin. Just look at the Kitavans. They get 69% of their calories from high-glycemic-load carbohydrates, with not much fat (21%) or protein (10%) to slow digestion. Yet, they have low fasting insulin and remarkably low fasting leptin. I believe the fasting levels of these hormones are more responsive to macronutrient quality than quantity. In other words, what matters most is not how much carbohydrate is in the diet, but where the carbohydrate comes from. The modern Western combination of carelessly processed wheat, sugar and linoleic acid-rich vegetable oil seems to be particularly harmful.

1 comment:

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