The Science and Pseudoscience of What We Eat

Dr. Joe Schwarcz sets the record straight about food myths and what the research actually shows. 


What should we eat? There’s no lack of experts and celebrities who are eager to advise us about diet, but different experts have different advice and often directly contradict each other. Obviously they can’t all be right. Which “experts” should we listen to? What diet is best? Vegan, organic, Mediterranean, paleo, keto, or…? Is meat good or bad? Should we eat or skip breakfast? How many eggs should we eat? What about multivitamins, omega-3s, probiotics?

Dr. Joe Schwarcz has (another!) new book out that asks those questions and examines the evidence. Science is supposed to be unbiased: the evidence should speak for itself and all observers in all countries, both “Western” and “Eastern” should reach the same conclusions. But Dr. Joe shows that different “experts” can look at the same published data and come to opposite conclusions. He helps the reader understand why that is, and he reviews the various studies the “experts” rely on. Studying nutrition is fiendishly complicated. There are no good, straightforward answers, and everything you read should be taken with a grain of salt, even this book.

The new book’s title is A Grain of Salt: The Science and Pseudoscience of What We Eat. The author is eminently qualified to write such a book. A professor of chemistry at McGill, he is the director of McGill University’s Office for Science and Society. He vigorously combats “chemophobia” (explaining that we shouldn’t be afraid of “chemicals” because everything is chemicals) and he spreads accurate information about science through his books, public presentations, his long-running radio show, media appearances, videos, newspaper columns, and more. His superpower is explaining complicated concepts about chemistry and other areas of science in simple terms for the public.

As with most of his previous books, this one is a compilation of short articles, some new and some updated. The bite-sized 2-4-page chapters are perfect for easy consumption, tasty snacks that can be consumed in waiting rooms or on public transportation.

Research about food is difficult

He explains that

The human body is a staggeringly complex machine, and our food supply is a staggeringly complex mixture of chemicals… Predicting the outcome of blending these complexities is extremely challenging. Factor in the influence of genetics, food intolerances, allergies, biochemical individuality, and age, and you have a practically unsolvable problem.

To add to the confusion, most food studies rely on notoriously unreliable food frequency questionnaires. It’s hard enough to remember what you ate yesterday. Estimates of how many apples or servings of broccoli you ate over the last six months? Pure guesswork. And subjects want to look good, so they tend to overestimate foods they believe are healthy and underestimate foods they believe are unhealthy.

False conclusions about human nutrition are often based on test tube or animal studies that don’t apply to humans. The myth that bananas fight cancer was based on a study where they injected banana extract into the peritoneal cavity of rodents. Why on earth did they do that, and why would anyone think it has implications for human health? Humans are not rats, and they take in bananas by mouth, not by peritoneum.

The book is a smorgasbord of essays on everything about food. He evaluates the evidence for probiotics, GMOs, antioxidants, salt, coconut oil, raw water, brain supplements, wheatgrass, cockroach milk, pesticides, food labels, superfoods, and much, much more. He explains the scientific studies pro and con. It’s a valuable lesson in how to evaluate research studies to separate the good ones from the not-so-trustworthy.

Fun with science and history

Dr. Joe has a knack for ferreting out juicy nuggets of obscure history and trivia facts that would be ideal for stimulating conversations at cocktail parties. Did you know Alfred Hitchcock claimed to have never tasted an egg because he was afraid of them? It’s called oviphobia. Did you know John Harvey Kellogg of cereal company fame never consummated his marriage, believing that sex drained the body’s health?

In the orphanage experiment that identified poor diet as the cause of pellagra, they noticed that the older children were not as likely to develop pellagra as the younger children. It seems they were old enough and resourceful enough to snitch the more nutritious foods that were intended only for the staff.

People once refused to drink white milk because they had become used to milk that was discolored by adulterants; they assumed that to appear so white, milk must contain whitening adulterants.

I learned some interesting facts

  • I learned a new word: turophile means a lover of cheese.
  • Eating 5-10 servings of fruits and vegetables a day has been scientifically shown to reduce the risk of cancer by 50%.
  • Cancer of the stomach is the most common cancer in the world.
  • Chile is the largest per capita soft drink consuming country in the world.
  • Algae produce 50% of the oxygen in the atmosphere.
  • Vitamin C can be effective for colds, but only if taken in large doses on the first day of symptoms, or before extreme physical exertion or exposure to cold stress.
  • Some people have been avoiding gluten because of a totally bogus applied kinesiology test. The patient holds a slice of bread against his stomach with his left hand while the nutritionist pushes down on his outstretched right arm. If he can push it down more easily with bread than without, the patient is gluten intolerant. Dr. Joe politely says applied kinesiology has “no scientific validity”. He could have said much worse.

He provides fascinating explanations of how smoked meats and bagels are produced. He explains the environmental downsides to the production of Greek yogurt.

So what should I do?

He deals with the calories in/calories out dogma of weight loss by saying it is theoretically sound but is of little practical significance, because the effective calories available from a food are not equal to the calories as determined by conventional experimental methods.

At the end of the book, he answers the many people who have asked him what he eats. He describes his personal diet choices, but does not recommend them as general guidelines for everyone. He says to take it with a large grain of salt, preferably iodized.

His conclusion is that there is no conclusion. But the general scientific consensus has not changed much in decades: more complex carbohydrates, less added sugar, less saturated fat, limiting salt, avoiding overweight, exercising. What has been added recently: more plants than animals, 5-7 servings of fruits and vegetables, and minimizing processed foods. The rest is details. He says some details are dumb, some are dumber, superdumb, and hyperdumb. He puts raw water in the category of dumb beyond a suitable qualifier.

Conclusion: A fun-to-read survey of current knowledge about the science and pseudoscience of food

After reading this book, you may not know what you should eat, but you will have a better idea what the evidence actually shows, and you will understand why you can’t really know for sure. And it should dissuade you from following the advice of self-styled experts and celebrities.

The book is a treasure trove. I won’t offer any more spoilers. You can enjoy unearthing its nuggets for yourself. Highly recommended.

This article was originally published in the Science-Based Medicine blog.

Dr. Hall is a contributing editor to both Skeptic magazine and the Skeptical Inquirer. She is a weekly contributor to the Science-Based Medicine Blog and is one of its editors. She has also contributed to Quackwatch and to a number of other respected journals and publications. She is the author of Women Aren’t Supposed to Fly: The Memoirs of a Female Flight Surgeon and co-author of the textbook, Consumer Health: A Guide to Intelligent Decisions.