Review of The Harvard Medical School Guide to Healthy Eating by Walter Willett and P.J. Skerrett
FOLIC
ACID
If there is one message this book hits hardest, it is the above. Other than the disdain for low-fat diets and potatoes, the above phrase is the most repeated point in the book. This is despite the fact that, as the authors state,
Folic acid deficiency, defined by blood level, has almost disappeared in the United States.
A meta-analysis of thirty randomized controlled trials that included 82,000 participants showed that getting extra folic acid from supplements decreased the risk of stroke by 10 percent and the risk of any kind of cardiovascular disease by 4 percent. The benefit was biggest among participants with low folate levels to start.
Folate’s key role in building DNA means that it plays a role in cell division and so may help prevent cancer as well.
This is the 2017 edition of the book, which also happens to be the best.
The authors questionably claim
This survival adaptation means that complex chemical interactions between body and mind that evolved eons ago in response to routine periods of starvation may drive us to eat whenever possible.
, ignoring the fact the Koreans, Japanese, and Indonesians have not trended toward mass obesity despite skyrocketing opportunities for calorie intake.
Low-fat diets are (presumably due to the ease of purchasing low-quality carbohydrates, though this is usually not explicitly stated) repeatedly condemned, pointing to low-carb diets’ generally superior effect short-term weight loss.
In fact, the area with the lowest rate of heart disease in the study, Crete, had the highest average total fat intake: about 40 percent of calories—mostly due to liberal use of olive oil.
Instead of any of the USDA food guide charts, the authors strongly encourage the “Harvard Healthy Eating Pyramid” and “Harvard Healthy Eating Plate” (click here for differences between the Harvard and USDA plates).
The book claims (correctly) that saturated fat has as much of a “harmful effect on the cardiovascular system” as processed carbs, and that polyunsaturated fatty acids (both Omega-3 and Omega-6) are far more protective than saturated fat/processed carbs and somewhat more protective than high quality carbs (whole grains/fruits/vegetables).
HDL cholesterol is erroneously called “protective”, rather than simply correlated with good health outcomes nearly every time it’s mentioned. This is a grave demerit in the book.
There is no response to many people’s success on the “potato diet”, first brought into prominence more than half a decade before the latest revision of the book. This is a grave omission.
The book also bizarrely claims nuts are linked to “less weight gain”, even though they are very easy to overeat (don’t worry; they -in particular walnuts- are still overall good for your health).
The book is skeptical of dairy, pointing to studies concluding that heavy milk consumption is not related to a lower risk of osteoporosis or fractures. Though the book makes it clear that milk is the food most associated with greater “ultimately attained height”, “greater height is a strong risk factor for hip fracture, probably because of simple physics: a long stick is easier to break than a shorter stick”.
Coffee, on the other hand, is praised-
Coffee drinking has been associated with lower risk of type 2 diabetes with remarkable consistency.
Findings from the Nurses’ Health Study, the Health Professionals Follow-Up Study, and other cohorts have shown that suicide rates are as much as 50 percent lower among coffee drinkers than they are among non–coffee drinkers.
In one of the latest analyses, coffee drinkers were about 25 percent less likely to have developed Parkinson’s disease. The benefit peaked at about three cups of coffee a day.
The book says surprisingly little about dark chocolate, other than it is among “the healthiest foods you can eat”. Interestingly, the %s cacao in its recipes’ “dark” chocolate are laughably low. Eat the 85%, not “64% to 72%”.
Vitamin D is also glorified -
A growing body of research suggests that many Americans could reduce bone loss by getting extra vitamin D.
Two in three Americans between the ages of fifty-one and seventy fall short of what appears to be the optimal level for vitamin D; older people fare even worse, with nine in ten not meeting this level.
The authors are, consistent with my longstanding opinion, strongly against demonizing omega-6 fatty acids, commonly found in seed oils and generally being considered essential fatty acids:
In the Nurses’ Health Study, the ratio of omega-3 to omega-6 fatty acids wasn’t linked with risk of heart disease because both of these were beneficial. In 2016, our group examined consumption of different types of fat in relation to deaths from all causes. We found that omega-6 fatty acids were more strongly linked to lower death rates than omega-3 fats.
Soy is seen skeptically:
One thing we know for certain about soy is that the phytoestrogens it contains are potent biological agents. Whether they trigger, suppress, or have no effect on breast cancer, prostate cancer, or memory is unfortunately an open question. That’s why you should treat concentrated soy supplements or isoflavone pills with the same caution you would a totally untested new drug. These findings don’t mean to steer you completely clear of soy. Instead, eat it now and then rather than several times a day.
The book is pro-egg, claiming straightforwardly “No research has ever shown that people who regularly eat eggs have more heart attacks than people who don’t eat eggs.”, contradicting Michael Greger’s anti-egg stance. Derek (More Plates More Dates) is pretty clear egg whites are not all what they’re cracked up to be.
There is far too much stress in the book on the “glycemic index”, which the weight of the evidence suggests does not matter.
I generally tend to prefer Michael Greger’s books over this one, as Greger’s books go into much more detail and come to what seems to me more logical (and often more restrictive) conclusions.
Rating: four out of five stars