Nutrition Archive

Supplements aren't held to the same standards as FDA-approved drugs. Evidence indicates that few are effective, many are useless, and others may be harmful.

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Dietary supplements—including herbs, vitamins, minerals, and other products—are a $37-billion industry in the United States, and 60% of women are taking them regularly. At the same time, mounting research is suggesting that supplements—even mainstays like calcium—may be harmful at high doses.

The use of supplements and other alternatives to standard treatments is centuries old, but Dr. David Eisenberg, adjunct associate professor at the Harvard T.H. Chan School of Public Health, was the first to document the widespread use of alternative therapies in the United States. In a 1993 article in The New England Journal of Medicine, Dr. Eisenberg and colleagues reported that more than a third of Americans were using unconventional therapies, largely for chronic conditions, and most were doing so without letting their clinicians know. That report covered acupuncture, spinal manipulation, massage, and yoga, but it also focused public attention on all unconventional treatments, including the growing use of herbal remedies and other dietary supplements. In 1998, the Office of Alternative Medicine in the National Institutes of Health (NIH) was revamped as the National Center for Complementary and Alternative Medicine and charged with funding rigorous studies into the safety and effectiveness of alternative physical treatments as well as popular dietary supplements and herbs.

In the January Health Letter, we gave you suggestions for finding healthy frozen food entrees. Because of a typographical error, the text of the article incorrectly stated that you should look for 5 or fewer grams of fiber per serving. In contrast, the table (reproduced below) noted accurately that you should look for entrees with 5 or more grams of fiber per serving. We apologize for the error in the text.

Most Americans don't get the recommended amount of these potentially heart-protecting fats.

Recently, a Harvard Heart Letter subscriber emailed us a question about omega-3 fatty acids, the unique fats abundant in many types of fish that may be linked to a lower risk of cardiovascular disease. Is there a difference, he wondered, between farm-raised and wild-caught salmon in terms of omega-3 fatty acid content?

It's a reasonable question, especially considering that wild salmon is often far more expensive than the farm-raised variety. But how much omega-3 fatty acid do we really need in our diets? And are fish the only source? Here's a brief summary of what you should know about omega-3s.

The longstanding "More Matters" campaign urges Americans to eat more fruits and vegetables (see www.fruitsandveggiesmorematters.org). Evidence to support this healthy habit keeps piling up, with the latest from a study that pooled dietary data from three large, long-term studies that followed more than 187,000 people for an average of over 20 years.

The researchers found that people who ate more whole fruits—especially apples, pears, grapes, and raisins—were less likely to develop high blood pressure than those who rarely ate those foods. As for vegetables, broccoli and carrots appeared to be the best choices for staving off high blood pressure. Fruits and vegetables provide minerals such as potassium and substances called flavonoids, both of which are linked to lower blood pressure. The study was published online in the Dec. 7, 2015, issue of Hypertension.

If someone you know has been diagnosed with type 2 diabetes, you might be wondering about how you can lower your own risk. Fortunately, multiple studies have shown that many of the same healthy eating choices that can help your friend or loved one control their diabetes can also help you prevent it. The exact relationship between eating specific types of foods and the risk of developing diabetes remains somewhat controversial. But the study findings are consistent with what experts consider to be healthy eating habits for most adults.

So, if you're interested in lowering your risk of type 2 diabetes, it can't hurt to try getting more of the foods and nutrients that can lower your risk — and to avoid those that can raise it.

Turmeric, coriander, and cumin may boost your health and breathe new life into tired dishes.

The health benefits of foods such as berries, broccoli, and salmon are well known. But your kitchen's spice rack may also hold some secret weapons against conditions such as inflammation, heart disease, cancer, and more. "Spices are underused, but it would be very easy to take advantage of them and improve health," says Dr. Lipi Roy, an internal medicine physician at Harvard-affiliated Massachusetts General Hospital.

There are few large randomized trials that demonstrate spices' health effects. But many studies in animals suggest that several spices offer benefits. So instead of flavoring your food with salt and butter, which can contribute to high blood pressure and heart disease, consider using the following spices.

Ask the doctors

Q: I just read that we shouldn't be getting more than 10% of our calories from sugar. Should I cut back on fruit?

A: While it's a good idea to limit sugars from processed foods, you can worry less about eating too much fruit. In fact, one small study found no ill effects in people who ate 20 servings of fruit a day for 12 to 24 weeks.

This ancient practice can transform the way you think about food and set the stage for a lifetime of healthy eating.

Like most of us, you've probably eaten something in the past few hours. And, like many of us, you may not be able to recall everything you ate, let alone the sensation of eating it. According to a 2011 report from the U.S. Department of Agriculture, the average American spends two-and-a-half hours a day eating, but more than half the time, we're doing something else, too. Because we're working, driving, reading, watching television, or fiddling with an electronic device, we're not fully aware of what we're eating. And this mindless eating—a lack of awareness of the food we're consuming—may be contributing to the national obesity epidemic and other health issues, says Dr. Lilian Cheung, a nutritionist and lecturer at Harvard T.H. Chan School of Public Health.

Research we're watching

Walnuts are loaded with folate, vitamin E, and lots of good fats. Although they are also high in calories, they don't seem to contribute to weight gain. Researchers at Yale University Prevention Research Center wanted to determine if eating walnuts daily could help people at risk for diabetes control their cholesterol and blood sugar.

The researchers randomly assigned 112 people ages 25 to 75—70% of whom were women—to two groups. People in both groups were given 2 ounces of walnuts to eat daily. They were told to eat whatever else they wanted but to keep a record of what they ate. One group was also told to eat 366 fewer calories from other food to compensate for the calories added by the walnuts. Both groups ate the walnuts for six months, and their customary diet without walnuts for another six months.

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A high-sugar diet may raise heart disease risk. But no-calorie sweeteners aren't ideal alternatives.

If you have a sweet tooth, your heart may be paying the price. Diets high in added sugars have been linked to a host of health woes, including obesity, high blood pressure, high cholesterol, and even a higher risk of dying of heart disease.