Tuesday, October 28, 2014

Evolving one's diet

I recently heard an interview of Dr. Steven Gundry over at Jimmy Moore's Livin' La Vida Low Carb site. Gundry said a few things that intrigued me, so I felt I should try and follow up by reading his book, "Dr. Gundry's Diet Evolution" [1].

Gundry's basic premise is that our diet affects which genes are turned on, and which off. That's not earth-shattering, the notion that environment shapes gene expression is pretty old hat. And most of what Gundry introduces in the first chapter is well supported stuff from the literature. But there's one thing that doesn't have any citations, and that's his notion that there is a genetic program designed to kill us off once we've served our purpose: transmitting our genes to the next generation. 

This "killer gene" program got my attention because there's a new hypothesis for the evolution of aging  in the evolutionary literature, and that is called the "programmed death" hypothesis. The basic idea is that our genes articulate a "use by" date, and once we're past it all sorts of things come unglued. In models at least, the advantage appears to be an increase in a lineage's ability to evolve [2]. There are species that do not age, and cell lineages that also don't age. 

Gundry's assertion is that once we've reproduced our genes prefer we get out of our offspring's way. He brings up a few interesting observations, like why do clots in our arteries form in the heart, brain and legs, but not say, in our noses and ears? It's almost as if they're targeting essential survival systems ... Gundry's idea is that our modern western diet, full of refined sugars and starches, is so good at getting us to reproduce quickly that our genes then quickly kill us off to reduce competition for our offspring. 

I'm willing to grant the programmed death idea as a hypothesis, but Gundry takes it to extremes. For example, he asserts that overeating until you are overweight also triggers the killer genes because "your genes percieve [this] as threatening the food supply of others." [page 16] That's just one example of how he has bought into a group selection argument for the existence of these killer genes. And convincing your genes that you're not a threat is the basis for phases 2 and 3 of his diet plan. 

Phase 1 of Gundry's plan is pretty standard -- drop the refined carbohydrates and starchy vegetables. Where he differs from a LCHF plan is by focusing on lean protein as the replacement for carbs, rather than fat. The logic is that you're trying to convince your body that "Winter's here", and animals would be lean in winter. There are a few little inconsistencies though. The key "Gundryism" here is "If it's white, out of sight", like sugar, flour and WHAT MAYONNAISE! There's no rationale for that, but in an earlier chapter he mentions that soybean oil (the main ingredient in commericial mayonnaise) should be avoided because of a high Omega-6 : Omega-3 ratio. OK, but then why is tofu listed as an acceptable protein? It's actually white too, now that I think about it. This "teardown" phase is supposed to last until your weight loss plateaus, and you're not showing signs of illness. 

In Phase 2, "Rebuilding", the main emphasis is on reducing the protein and increasing the green stuff. This is meant to imitate the diet of our pre-agricultural ancestors. He draws on the diet of a silver-back gorilla as inspiration -- lots of calorie sparse leaves*. The biological hypothesis in this section seems to be that eating protein raises metabolism, and a high metabolism is bad. So eat less protein, lower the heat, and you'll be better off for it. He also cites the China Study as support for this perspective. If you're still thinking that's a good idea, you should read the critiques by Denise Minger or Chris Masterjohn. Sorry Gundry, you're loosing me here.

In Phase 3, "Longevity", the goal is to keep those gene's from thinking you're a threat and providing a little bit of stress via plant toxins. Eat raw food, because that preserves those phytochemical toxins. Eat less, because that way you convince your genes you're not competing with your offspring. Calorie restriction is associated with longevity, at least in animal models, from the citations he provides. One thing that is slightly alarming here is that calorie restriction increases cortisol, and that's one mechanism that can increase fasting blood glucose levels. Which might be fine, if you're not insulin resistant.

To wrap up, I'm convinced that our genes matter and that our environment (including what we eat) influences which genes are on or off. But I was convinced of that before. I agree that programmed death is a valid hypothesis, but I don't see any evidence for the "competing with my offspring" as a trigger for killer genes. I agree that lots of low calorie vegies are good, but not sure about being able to get the majority of my protein from them without growing a gorilla sized colon. Eating less, check, as long as I'm not hungry. Back to the library with you, Gundry. 

[1] Steven R. Gundry. 2008. Dr. Gundry's diet evolution: turn off the genes that are killing you -- and your waistline -- and drop the weight for good. Crown Publishers, New York.

[2] Joshua Mittledorf and Andre Martins. 2014. Programmed Life Span in the Context of Evolvability. The American Naturalist, 184:289-302.

*But, but, gorillas have colons more than twice the size of a human which is why they can survive on calorie sparse food!

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