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Saturday, December 29, 2012

Book Review: Wheat Belly is a bestseller, but what's the science behind it?

If a doctor writes a book in the forest...
Wait a minute, that's not right.

If a doctor writes a book about health... is it science?

This is the question I had in mind while reading Wheat Belly. When a physician like William Davis, MD, takes time out of his (no doubt) busy schedule to write a health-related book, ideally he has taken the time to  get familiar with all the scientific literature on the topic. This may be easier for doctors than for some other writers, as Davis may have had the benefit of hearing research summaries at conferences, or having literature reviews arrive on his desk with the daily mail. Add that to years of clinical experience, and you have the potential for a pretty compelling argument on a health issue.

But what if, instead, a doctor seems to have spent years giving a certain piece of unusual clinical advice about a dietary change. And he has had such great success with patients who follow that advice that he goes looking for science to explain why it works. He scraps together a few studies that he thinks are relevant, connects some dots, and writes a book. What then?

Interesting, but not necessarily science.

So here's the heads up: Wheat Belly is an example of the latter. Though Davis, a cardiologist, has written a very interesting book with a timely message, you should know that it is not strictly based on science. Meaning: there is little or no evidence for his claims about the ill health effects of wheat.

Case in point: the glycemic index stats he cites are from an article published in 1981 - and he repeats again and again that the study found a greater blood sugar rise with "whole-meal" bread than with white bread, even though - ahem - a fair amount of glycemic index research has been done since, and a quick visit to almost any diabetes association website will confirm that whole wheat breads (for the most part) have lower glycemic indices than white breads. Davis gives a few nods to how his claims fit in, or don't fit in, with the advice of professional bodies. But he doesn't present a complete picture of why and how science shows that eliminating wheat from one's diet is a good idea, because the scientific evidence doesn't exist at present.

The point of the book is that it's bad to eat things that spike your blood sugar - i.e. things with a high glycemic index (GI). Apparently wheat spikes the blood sugar more than you'd expect - the oft-cited study found whole grain bread had a GI of 72, while a Mars bar had a GI of only 68 - and therefore we should eliminate wheat.

It follows that we should eliminate all things that spike blood sugar. Davis advocates this. So properly, the book should be called "Carb Belly". (Of course, the arguments against carbs have been well-explored in books that promote the Atkins diet, Paleo diet, Specific Carbohydrate diet, etc.) But Davis says the one carbohydrate that people have the most trouble eliminating is wheat. Hence, the name Wheat Belly.

Here's what's in the book:

Part 1:
Davis explains how wheat strains have changed with hybridization and how modern types of wheat affect us in unprecedented ways.

Part 2:
Davis describes wheat's "head-to-toe destruction of health": (1) the addictive properties of wheat that can influence behaviour and mood, (2) the way wheat triggers blood sugar and insulin extremes, which lead to visceral fat accumulation, (3) how intestinal permeability triggered by a protein in gluten may be responsible for the rise of autoimmune disorders and digestive disorders, (4) an argument that wheat may cause type 2 diabetes, (5) an explanation of how wheat affects the body's pH, resulting in an "acid-rich situation" and that promotes osteoporosis, (6) wheat's promotion of AGEs, which signal aging, (7) how wheat leads to heart disease by increasing triglycerides that turn into atherosclerotic plaque, (8) how the immune system's attack on nerve cells results in cerebellar ataxia and brain fog, and (9) how increased levels of insulin, and an immune reaction to gluten, can show up as acne or skin rash.

Note that for most of these claims, Davis's evidence is in the realm of the "theoretically possible." As far as I can tell, the science actually addressing these claims is weak. The studies conducted on humans where all else is equal, except the inclusion of wheat in the diet, are rare. Making his claims premature at best.

Part 3:
He talks about the "how to" of eliminating wheat and other carbohydrates. The book includes menus and recipes for low-carb eating.

So now the question, can we really knock Dr. Davis for proposing a low-risk treatment that seems to work like magic clinically for a host of health problems? Can we truly fault a compelling book that's convinced a lot of people to do something that seems to improve their health? It doesn't escape me that it took a lot of bravery for him to so emphatically convey this message in a world that is very wheat-centred.

So yes, Davis has perhaps inspired many people to initiate a positive change for their health by penning a bestselling book with lots of media coverage. But by putting together a misleading scientific grab-bag for convincing people to make this change, he is ensuring they never fully understand what caused their complex health problems in the first place.


...mainly tell the same story as these: