The science of diets

Following my previous article [1] about how to identify good science, I thought I would put my advice to use to take a closer look at the science behind the claims on which some popular diets are based.

Wheat Belly: Lose the Wheat, Lose the Weight, and Find Your Path Back To Health by William Davis, M.D.

I’ll start by saying that reading Wheat Belly  has affected how I eat: this book motivated me to reduce my overall intake of white flour and grains. Vegetables are now my staple; grains are a treat. However, Wheat Belly does break several of the rules of good science.

First, this book is full of anecdotal evidence. Dr. Davis claims that the wheat of today is a “frankenwheat” and that our modern wheat is not only unhealthy and toxic, but also addictive. However, the “Frankenwheat” notion has never been scientifically proven. Dr. Davis uses a study on rats from 1979 to support his claim that wheat is addictive, and that study is not recent and has not been peer-reviewed or replicated. This CBC article summarizes the shaky science behind Wheat Belly.

In a recent BBC Horizon Episode: Clean Eating, Dr. Giles Yeo spoke with Dr. Davis, who is now extrapolating from Dr. Fasano’s research on Celiac disease to support his claim that “the consumption of grains is harming all of us to some degree.” This claim has not been scientifically proven.

• Dr. Davis uses the documented increase in Celiac Disease to support his position; however, the increase in cases of this disease is mostly attributed to, according to Dr. Fasano, our improved ability to detect and diagnose the disease.

• In addition, Dr. Fasano’s research shows that you need to have some pre-existing conditions (four to be exact: genetic predisposition, a leaky gut, a faulty immune system, and an imbalance in gut microbes) in order for gluten to be a problem.

• Finally, Dr. Fasano disagrees with Dr. Davis’ claim that the Gliadin protein can initiate the process of an autoimmune response leading the body to attack its own organs. Dr. Davis is not only extrapolating to support his philosophy, but is also ignoring good science by cherry picking.

Dr. Bill Davis is particularly dangerous because he portrays himself as someone who, like me, is trying to wade through all the misinformation out there and give people the facts. He is guilty of questionable science. Dr. Giles Yeo summarizes Dr. Davis and his philosophy like this: “Bill Davis has no proof that giving up grains will have all these health effects on this wide range of diseases. Extreme dietary advice requires proof, otherwise all you are doing is stoking fear about a food group that most people shouldn’t have to worry about.” (BBC Horizon: Clean Eating).

The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss, and Long-Term Health

The China Study is known as the “most comprehensive study of nutrition ever conducted,” however, it too has been found to have used questionable research methods.

The main author, Dr. Colin Campbell, asserts that “plant based foods are beneficial and animal based foods are NOT, period.” However, eliminating ALL animal based foods has not been scientifically proven to be a healthier way of eating.

Dr. Giles Yeo asked if Dr. Colin could have been affected by Observational Bias (when a researcher sees what they want to see instead of what the data shows) while researching for the China Study. Dr. Colin does admit that this may have occurred.

In addition, Dr. Colin used Cholesterol as a proxy. In the Proxy Method, a variable (Dr. Colin used increased levels of cholesterol) which correlates with the variable of interest (increased risk of cardiovascular disease) is measured, then used to infer the value of the variable of interest. (Wikipedia).

The Proxy Method is a form of Extrapolation (A= Meat Intake, B= Increased cholesterol levels and C= Increased risk of cardiovascular disease. If you have data linking A to B and B to C, you cannot then conclude that A=C).  Many factors contribute to increased cholesterol, like genetics, not just meat intake.

Dr. Colins went into his research looking to prove that meat consumption increased the risk of CV disease. He cherry picked the data on cardiovascular disease that supported his position instead of considering all of the risk factors for cardiovascular disease.

A simple Litmus test of scientific information

I found some useful tips on how to tell fake news from real news and the tips apply here, especially this one:  How does it make you feel? Is the study/article telling you what you WANT to hear? Is it confirming your bias? 

It is important to be aware of your biases, otherwise it is too easy to fall prey to extreme health claims that ultimately lead to disappointment, frustration, uncertainty about who to trust and what to believe. Reading a study published in a scientific journal can be intimidating, but you can save yourself time by looking for these key words: randomized, peer reviewed, and double blind. I summarized these in a previous article here.

Knowledge is your best weapon against media hype and bad science.