Harvard Heart Letter

Say cheese?

Dairy products don’t seem to harm the heart. But plant-based fats are probably a better choice than cheese.

Health-conscious consumers know to steer clear of diets that include lots of meat—especially fatty, salty processed meat. But what’s the deal with dairy? Nutrition experts have long recommended low-fat milk and yogurt as good choices for getting the two to three daily servings of dairy recommended by federal dietary guidelines.

Over the past few decades, Americans have been spooning up more yogurt and drinking much less milk. But the biggest change by far has been in our cheese consumption, which has skyrocketed since the 1970s (see “Trends in dairy intake: Less milk, more cheese and yogurt”).

Dairy products—especially cheese—are a major source of saturated fat in the average American diet. Saturated fats tend to raise harmful LDL cholesterol, which can boost heart disease risk. But research on the role of dairy in heart disease risk has been mixed and has spread some confusion. Are full-fat cheese and yogurt okay, or should you avoid those foods? A report that pooled data from three large, long-term Harvard studies offers some insight and advice.

Dairy fat and heart disease

In a nutshell, researchers found that dairy fat was not associated with a higher risk of cardiovascular disease (defined as nonfatal heart attack, fatal heart disease, and stroke) when compared with the same amount of calories from carbohydrates. However, replacing about 5% of calories from dairy fat with a similar amount of unsaturated fat from vegetables or vegetable oil was linked to a 24% lower risk of cardiovascular disease.

“Overall, the results are consistent with current dietary recommendations to consume mostly unsaturated fats rather than saturated fats,” says Dr. Frank Hu, professor of nutrition at the Harvard T.H. Chan School of Public Health and senior author of the study.

Published in the August 2016 American Journal of Clinical Nutrition, the study looked at more than 220,000 women and men in the Health Professionals Follow-Up Study, the Nurses’ Health Study, and the Nurses’ Health Study II, all of which explore the role of risk factors (especially diet and lifestyle) in major chronic diseases. The participants filled out food questionnaires every four years for up to 26 years. The dairy products they tracked included skim and low-fat milk, whole milk, cream, ice cream, yogurt, cottage and ricotta cheeses, cream cheese, and other cheese.

The analysis also suggested that replacing dairy fat with other animal fat (that is, from meat) would slightly raise the risk for cardiovascular disease. Several earlier studies have suggested that diets that include dairy products—even full-fat dairy—don’t seem to raise heart disease risk and may even help reduce risk for obesity and type 2 diabetes.

More than just the fat

The explanation for these observations isn’t entirely clear, but the other nutrients in dairy products could play a role, says Dr. Hu. Milk is a good source of calcium and potassium (two minerals important for blood pressure control) as well as protein, which can help you feel satisfied and less likely to overeat. Both yogurt and kefir (a tangy dairy drink) also contain live bacteria known as probiotics thought to be beneficial to the digestive system and possibly even the cardiovascular system. But at this point, we know far too little about which types of bacteria might be helpful—or how they function and survive either in foods or in your body—to give any advice about specific brands of yogurt or other products, Dr. Hu notes.

He recommends up to two servings of dairy daily for most adults. “But I wouldn’t choose full-fat milk or eat a lot of cheese,” he says. Pizza, which is probably the biggest cheese vehicle in the American diet, is especially unhealthy because it’s typically made with a refined white-flour crust and often topped with unhealthful meats, such as pepperoni or sausage, he notes. You’re much better off enjoying a small piece of cheese as a snack with fruit or whole-grain crackers, or sprinkled on a salad (see “What’s a serving of dairy?” for serving size guidelines).

As for yogurt, look for plain varieties with no or little added sugar. Some brands add a full tablespoon of sugar—half the amount of sugar the American Heart Association recommends that women consume in an entire day. And for men, it’s about a third of the daily suggested limit. Instead, mix fresh or dried fruit into your yogurt for added sweetness.

Trends in dairy intake: Less milk, more cheese and yogurt

On average, Americans now drink about half as much milk (just over a half-cup per day) as they did in the 1970s. But our yogurt intake has quadrupled, and we now chow down 35 pounds of cheese per person every year—up from just 11 pounds per year in 1970. Much of this rise comes from the popularity of convenience foods like frozen pizza, macaroni and cheese, and prepackaged cheese slices, as well as our love of cheese-rich Italian and Tex-Mex cuisines.

What counts as a serving of dairy?

Per the U.S. Dietary Guidelines, foods in the dairy group include milk and foods made from milk that retain their calcium content, as well as calcium-fortified soy milk. Foods made from milk that have little or no calcium (cream cheese, cream, and butter) are not included.

Food

What counts as one serving?

Milk

1 cup (8 ounces)

Yogurt

1 cup (8 ounces)

(Note: Single-serving yogurt containers range from 4 to 6 ounces.)

Hard cheese

(cheddar, mozzarella, Swiss, Parmesan)

1.5 ounces

(Note: This is about the size of four dice or 1/3 cup if shredded.)

Ricotta cheese

½ cup

Cottage cheese

2 cups

(Note: ½ cup is a typical portion size but only counts as ¼ of a serving of dairy.)

Calcium-fortified

soy milk

1 cup

Source: USDA, ChooseMyPlate.gov.

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