Harvard Health Publications, publisher of the Harvard Health Letter, and the Harvard School of Public Health’s nutrition department developed the Healthy Eating Plate as an alternative to the federal government’s MyPlate eating guide. We conferred with Dr. Walter C. Willett, chair of the nutrition department and a member of the Health Letter‘s Editorial Board, to answer your questions about it. You can find the full version of the plate at www.health.harvard.edu/plate/healthy-eating-plate.
Why aren’t eggs included as a healthy protein on the Healthy Eating Plate?
The omission is more a matter of limited space, and not having the room to list all the healthful sources of protein, than it is nutritional advice. For most people, eggs are a good, healthful — if limited — source of protein. A large egg has a little over 6 grams, which is less than half the amount of protein in a cup of red kidney beans or a 3-ounce serving of salmon.
But going hog wild with egg intake is not a good idea. Averaging one whole egg (the yolk and white) a day is a reasonable upper limit while evidence is still being collected. People with diabetes should limit themselves to two or three whole eggs a week (egg whites are not limited) because the abundant cholesterol in egg yolks does seem to increase their chances of getting heart disease.
Some studies suggest that a diet heavy on eggs might increase the chances of getting diabetes in the first place, but Dr. Willett and his colleagues haven’t seen that association in their large epidemiologic investigations.
What’s so bad about potatoes?
The Healthy Eating Plate makes a point of saying that potatoes and French fries should not be counted as vegetables. Potatoes do contain some healthful nutrients — vitamin C, potassium, B vitamins, some protein if you eat the skin. But they also have a lot of starch that’s digested quickly, so our blood sugar levels shoot up when we eat them. Depending on how it is prepared, a cup of potatoes can have about the same effect on blood sugar levels as a can of Coca-Cola and a handful of jelly beans.
In their epidemiologic studies, Dr. Willett and his colleagues have found an association between potato consumption and weight gain and the development of diabetes, which is consistent with what is known about high-glycemic-index diets.
The Healthy Eating Plate recommends limiting milk and dairy consumption to one or two servings a day. But why don’t you recommend low-fat milk and dairy?
The diet and nutritional advice that has demonized fat and pushed low-fat products (including low-fat dairy products) has been misguided. There are “good” and “bad” fats. Your body needs the former but can be injured by too much of the latter. Much of the fat in dairy products is saturated fat, a relatively bad fat, whereas plant-based foods contain primarily unsaturated fat (good fat). It’s both hard and unnecessary to completely avoid saturated fat. Just go light on it. In fact, compared to the same number of calories from carbohydrate, saturated fat has about the same effect on risk of heart disease.
So if you limit your daily intake of milk or dairy products to one or two servings a day, the fat content makes little, if any, difference in changing your risk for heart disease and probably other conditions, too. Even at higher intakes, the difference between low- and full-fat dairy products is probably small.
Why limit your intake? Because drinking lots of milk does not reduce fracture risk, despite many assertions otherwise, and some studies suggest (yes, more research is needed) an association between higher dairy intake and an increased risk for getting some cancers.
From a public health perspective, the low-fat dairy product accomplishes little. The fat removed to reduce the fat content of particular dairy products doesn’t just disappear. It stays in the food supply and is used to make butter, cream, and ice cream. So even if you’re scrupulous about eating low-fat products, the missing fat ends up in someone else’s diet.
The plate says to limit juice intake to one small glass a day. But juice can be made from pure fruit, so why the limit?
Because ounce for ounce, most fruit juice contains just as much sugar and just as many calories as a sugary soda. And perhaps the last thing the American diet needs is more sugar and calories.
Moreover, drinking juice isn’t the same as eating the whole fruit or vegetable. Even if you drink the pulpy varieties, you are missing out on some of the fiber in the whole fruit or vegetable. And liquids don’t satisfy appetites as well as solid food, so people tend to consume more calories if they drink juice instead of eating the whole foods. The glycemic index, or how much a food or drink increases blood sugar levels, is another consideration. Because fruit sugars are more readily absorbed in the form of juice compared with the whole fruit, they have higher glycemic indexes than whole fruit.
Of course, juice is better for you than the empty calories of soda, and the Healthy Eating Plate advice is to limit juice, not ban it altogether. That glass of juice that many of us like to have at breakfast is perfectly fine.