Plant Chat: Walter Willett
Tune into this interview between Sharon Palmer and Walter Willett, a celebrated nutrition expert, as they talk about calcium, omega-3 requirements, and more.
I was in New York last week for the Food For Your Whole Life Conference with a number of amazing speakers, including David Katz, Michael Roizen, and Mehmet Oz. Among the roster of celebrated nutrition experts was Walter Willett, DrPH, MD from Harvard School of Public Health. He has been leading the way in nutrition research for decades, with his landmark studies the Nurses’ Health Studies I and II and the Health Professionals Follow-up Study. In addition, Willett has published hundreds of articles, several books, and is among the five most cited persons in the field of clinical science. I was invited for a one-on-one chat with Dr. Walter Willett, and it went something like this.
Sharon: Do you feel that sugar has a role in obesity other than mere energy balance?
Walter: There are problems with sugar due to adverse metabolic effects, but the idea that fructose is dangerous—the science doesn’t support this. To only focus on sugar as the problem—the science isn’t there. There may be subtle metabolic differences in the body with fructose. Cutting back on sugar is an important part of a healthy diet, along with cutting back on refined starches and fruit juice, which has the same glycemic load as sugar—of course, there are some nutrients there, but it’s much better to eat the whole fruit. It takes three oranges to get a glass of orange juice, without a large effect on satiety. One small glass of fruit juice a day—that amount is ok.
Sharon: Does the advice that 3,500 calories equals a pound still hold true?
Walter: In general, to focus on calories isn’t helpful. We should focus on the type of food. There is some value to talking about calories in foods, such as three glasses of juice a day may provide 400 calories. But in human physiology, it’s complicated. The simple calculation of 3,500 calories per pound doesn’t work; it doesn’t account for metabolic efficiencies when people start to lose weight. There is also a metabolic cost for carrying extra weight that isn’t reflected in this calculation. In the end, calories do count. And it’s the quality of the diet that matters. A high intake of starches and refined carbohydrates is a huge problem for weight.
Sharon: Can you discuss calcium requirements?
Walter: Our calcium requirements are vastly overstated. The research on calcium and bone density is based on short term studies for 9 – 12 days; it’s the basis of our calcium recommendations. The World Health Organization set their recommendations at 500 milligrams per day. [The DRI in the U.S. is currently 1,000 – 1,200 mg for adults].
Sharon: Why does research show risks related to red and processed meat consumption?
Walter: We’re still not sure; there is an increased risk for type 2 diabetes and it could be because of the increase in heme iron, which is not really better absorbed and may be toxic to the pancreatic islet cells. The mix of fatty acids is not optimal and there is a fair amount of cholesterol. Processed meats are high in salt and tend to be high in fat, and there’s the nitrate issue. The evidence is not clear yet.
Sharon: Is it possible for vegetarians to gain adequate omega-3 fatty acids for optimal health?
Walter: We don’t have the final answer on that, but it may be possible. You get conversion from ALA [plant omega-3s] to EPA and DHA, which may be adequate. In pregnant women, the conversion goes way up. We are studying marine algae supplements now.
Sharon: Do you feel that whole grains in their natural form are better than ground whole wheat flour?
Walter: There is a whole grain spectrum, with pure white flour on one side and intact whole grains on the other and whole grain flour in the middle. It’s not a matter of micronutrients, but of glycemic index—the intact grains are lower in glycemic index. The evidence on glycemic index and diabetes is very strong.
Check out some of Sharon’s favorite interviews on a healthy lifestyle:
Eating for IBS on a Plant-based Diet
Enjoying Alcohol in a Healthy Diet
How to Eat a Healthy, Plant-Based Mediterranean Diet