The Nutrition Proposition: How Much Do Your Food Choices Really Matter?

Book Title: The Nutrition Proposition: How Much Do Your Food Choices Really Matter?

Authors: James McCormack, Marcie Gray

Publication Details: self-published, Amazon, 414 pp., $19.99, paperback

What if the following choices don’t actually make much, if any, difference to your health?...

• Adding salt to food

• Restricting or increasing the amount of carbs, fat, and protein

• Being a meat eater, a vegetarian, or a vegan

• Eating a doughnut, cheesecake, ice cream, or chocolate

• Drinking a glass of milk or a soft drink a day

• Eating an apple a day (p. 7)

So begins McCormack and Gray’s quirky, highly entertaining, evidence-based book on the complex subject of nutrition, with all its entrenched dogma and furious debates. McCormack and Gray step into the fray armed with considerable experience in data analysis, a willingness to abandon preconceived ideas about what is good for us, and an obvious ability to enjoy themselves. Ms Gray is a journalist; Dr McCormack is a pharmacist who teaches at the University of British Columbia.

The writers make an early distinction between studies that report mortality, strokes, and heart attacks and those that report easily measured surrogate markers, like low-density lipoprotein or high-density lipoprotein. This distinction ends up being pivotal because many of the surrogate markers, while compelling, don’t predict mortality as we think they should.

This leads us to the characteristic of this book that makes it so refreshing and intriguing; the principal author is not a nutrition content expert. Dr McCormack is an expert on evidence assessment and data analysis, and his perspective as an outsider gives him the freedom to investigate core questions without being hampered by assumptions (such as the validity of surrogate markers for those outcomes of greatest importance). Sometimes outsiders can generate solutions that are inaccessible to experts within a field, for example, when crowdsourcing solutions to scientific problems.¹

After an introduction to nutrition research and terms, the authors provide the best current evidence for each food group. They cover beverages (ie, water, alcohol, coffee, tea), then macronutrients (ie, carbs, fats, proteins), then fruits and vegetables, and so on. In every chapter, there are surprises, most of them quite encouraging news for those of us who enjoy our food. For example, the best studies find that reducing salt does not reduce mortality, but it does decrease the risk of myocardial infarction (MI) by 1.5%. That means that 98.5% of people see no benefit from reducing their salt intake over 3 through 15 years (p. 195). They report on the best cohort studies on sodium intake, including one analysis of over 130,000 people whose sodium intake was verified by urine samples. It found the lowest mortality and lowest risk of strokes and MI occurred when sodium intake was between 4 and 6 g/d, with the highest risk occuring below 3 g/d. (p. 199). They conclude that their average reader, who takes in about 3 grams of sodium per day, would not need to change their intake.

Similarly, their findings on dairy, which is also often maligned, would be surprising to many readers. It turns out that increasing dairy intake from zero to two or more servings per day is associated with a 2% to3% decrease in mortality, heart attacks, and strokes (p. 208).

An attractive feature of The Nutrition Proposition is the clarity with which McCormack dives into the data to explain controversies. Thus, we learn that the best studies of the impact of meat consumption show increased absolute risks of cardiovascular disease at 0.5% for unprocessed meat and 2% for processed meat. “In other words, if red meat is the causal agent, 98% [to] 99% of people would not experience any impact on mortality or cardiovascular disease by eating an extra serving or two of meat each week over the course of 10 years” (p. 138). He then describes how two well-designed studies that found similar results reached very different conclusions, because one looked only at the health of the individuals, while the other reported results in context of the health of our planet. This led to conflicting reports in the press, although the data were nearly identical. No wonder our patients are confused.

It strikes me that this book might need to be self-published. It is packed with tables of key data from the major studies reviewed, and McCormack walks the reader through those patiently and with humor and clarity. I suspect it would have been difficult to persuade an editor at a publishing house to allow the authors to jam in so much data, but I’m glad this book was born exactly as it is. It’s a great read, both data packed and refreshingly funny in its unorthodoxy. I anticipate it will be extremely useful to physicians helping patients understand conflicting guidance about nutrition.