Everyone knows that vegetables are good for you and French fries are not. But we still can’t wrap our heads around some of the finer nuances of proper nutrition, such as how much protein to eat and whether we really need to cut our carbohydrate intake…and to even understand what a carb is. 

To get a handle on persisting misperceptions about food and healthy eating, we spoke with diet expert and preventive-medicine specialist David L. Katz, MD. 


Misperception #1: You need to eat more protein as you get older. 

Truth: Most adults get more than enough protein to meet their nutritional needs. You would have to have a very unbalanced, quirky diet to be protein-deficient. Government recommendations advise getting 10% to 35% of calories from protein sources—roughly one-half gram per pound of body weight. Currently in the US, women eat, on average, about 90 grams per day and men eat about 100 grams—more than enough. 

It’s true that most people begin to lose muscle starting between ages 50 and 60. And it’s also true that protein helps you maintain muscle. But it’s a myth that eating more protein will help you build muscle. Only exercise enables you to maintain and build muscle. In fact, extra protein above that 35% of daily calories will turn into body fat, just as extra calories from fat or carbs do. Too much protein also can stress the kidneys and liver, leading to disease of those organs, as well as weaken your bones.

Misperception #2: You need to eat animal products to get complete ­nutrition.

Truth: A complete protein source delivers all of the essential amino ­acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) that our bodies can’t make but still need to function optimally. Yes, meat provides these essential amino acids in the ideal proportions all at once, but higher intake of meat is associated with higher overall risk for chronic disease and premature death. 

Plant foods also deliver all of the essential amino acids, just at lower concentrations. The distribution of amino acids in nuts, grains, legumes, vegetables, fungi and seeds is complementary—if you don’t get all the amino acids that your body needs from one type of plant, you’ll get it from another. Your body couldn’t care less if you get these amino acids—so-called “complete protein”—all at once or from animals or plants. There’s no need to worry about food combinations within one meal as long as you get a balance of foods in general.

Misperception #3: Your diet can be healthy only if you limit carbs.

Truth: Carbohydrates actually should be the predominant foods in your diet. Whether you are an omnivore, a vegetarian or a vegan, 40% to 70% of your daily calories should come from complex carbs. Important: Carbs don’t just mean sugar, pasta, bread, grains and other starchy foods. All fruits, vegetables and beans are carbs too. And all of the best diets around the world—“Blue Zone” diets that are associated with health and longevity—are predominantly plant-based and thus carb-based. 

Beware: There are plenty of bad processed carbs out there—chips, pizza, candy, white bread, white pasta, cakes, sugary cereals and sugar-sweetened drinks, etc.—all lacking in nutrition and designed to put your appetite into overdrive. 


Given what we know, then, how exactly should we be eating? It’s actually simple, and it’s boring, as you already know. Consume a variety of wholesome, minimally processed foods, including vegetables, fruits, whole—not refined—grains, beans, seeds and nuts. Drink plain water when you’re thirsty, as well as coffee, tea, seltzer and mineral water. As you prefer, follow a specific diet plan—from vegetarian to vegan, low-fat, low-carb, Mediterranean, Paleo or flexitarian—but optimize that with plant-based foods. 

Best: A vegan diet—no animal products of any kind, including no dairy, eggs or fish—which is good not only for your health but is the kindest diet plan for the environment and animals. 

Avoid: A ketogenic diet, such as the Atkins diet, which is too high in saturated fat and meats and too low in carbs. 

There never has been a better time to think about improving how you eat. A healthy diet is one of the biggest weapons we have against all types of diseases, including COVID-19. COVID-19 is not an equal opportunity threat. It attacks the elderly and people with inflammatory conditions such as diabetes, obesity and high blood pressure the most severely. That means a low-quality diet that doesn’t support your immune health or control your weight will increase your risk for complications if you ­develop COVID-19. 

Can You Cheat?

If you follow a healthy diet plan, does that mean you can never eat unhealthy foods such as processed snack foods? Of course not. If you want ice cream, cake, candy or chips, have them—but only occasionally. 

Caveat: If you feel like you want to eat these kinds of foods frequently, you’re probably not getting your diet right most of the time. Why? Because familiarity with the way a food tastes is a potent determinant of what you’ll want to eat. 

Example: If you eat a lot of snack foods, sweetened cereals, milk chocolate and foods with artificial sweeteners, you’ll crave them. But if you stop eating those foods, your desire for them will decrease within a few weeks. Once you’ve changed your taste buds, you probably won’t want them anymore. They’ll taste like the pseudo foods they really are—sickeningly sweet, oversalted or fatty. Junk food will taste like junk. 

Better cheats: Whole-grain chips with salsa…homemade oatmeal raisin or dark chocolate chip cookies made with whole-grain flour. 

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