Sunday, January 16, 2011

Science is About Strength of Evidence: Nutrition

Book review

Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating, by M.D. Walter C. Willett

Eat, Drink and be Healthy discusses a wide range of ways diet affects health. Eat, Drink is remarkable for the amount of respect it hands to issues of strength of evidence. The entire Chapter 2 is dedicated to deepening the reader's intuition of strength evidence. It discusses the different kinds of medical studies people do, and how the confident we should be in each. A study with 20 genetically-modified mice is not the same as a study with 200,000 randomly chosen nurses (which is also not the same as a study of 18 hand-picked children, ran by a fraudulent doctor who gets money from an ambulance-chaser, but I disgress.)

The book is worth reading for its Chapter 2 alone. Reading it grants a heightened standard for the reporting of nutrition news, a standard that most (all?) newspapers will immediately fail. Each recommendation should come with a citation of the primary research, with a discussion of effect sizes for each recommendation, and with a discussion of the strength of evidence. Eat, Drink methodically provides all three for every one of its recommendations.

I found Eat, Drink to be a vastly better than The China Study. Eat, Drink draws from a wider base of studies, and it deploys more care to ensure that each of its recommendation is delivered with a thorough description of the scientific evidence. In contrast, I found The China Study to be too narrowly focused on their own study, and too self congratulatory. I found nothing in the China Study that wasn't covered better in Eat, Drink.

The book chapters starts from the corner with the strongest evidence, then follows the trail down:

Chapter 1: Don't smoke. If you smoke, stop reading. Smoking is going to kill you faster than anything else and nothing in the book can help you.

[Chapter 2: Discussion about strength of evidence.]

Chapter 3: Don't be overweight. If you are, stop reading.

Chapter 4: Avoid all trans-fats like it is a poison. Reduce saturated fat; transition from beef to pork, from pork to chicken, from chicken to fish, and from fish to veggies. Reduce butter and whole-fat milk, prefer olive oil and soy milk instead.

Chapter 5: Minimize refined sugars, including natural white-sugar-equivalents like white rice and potatoes.

Chapter 6: Eat from a wide-variety of protein sources, especially plant-based proteins (since animal protein comes loaded with much saturated fat, c.f. Chapter 4.) The wide variety is a must if your are vegetarian, and it is good for you all the same if you're not.

Chapter 7: Veggies, eat a lot of them, to your heart's content. It is the best food. Eat from a wide-variety of vegetables. Their gifts are spread across all the kinds.

Chapter 8 covers drink (water, juice, alcohol, coffee, tea.)

Chapter 9 debunks the calcium scare.

Chapter 10 debunk the vitamin scare.

Chapter 11 is the conclusion.

Chapter 12 is a quite good recipe book with too few vegetarian recipes.

Along the way, Eat, Drink debunks many diet ideas which are floating in our culture that do not have scientific support. These non-recommendations are as valuable as the rest. They will free a lot of people from pointless anxieties and open a lots of delicious cooking options (c.f. Chapter 12.)


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