Nutrition Archive

Fish is an excellent source of protein, and its healthy oils protect against cardiovascular disease. Because a diet rich in seafood protects the heart and aids neurological development, fish remains an important component of a healthy diet.

However, nearly all fish and shellfish contain traces of mercury, a toxic metal, and some seafood contains other contaminants known as persistent organic pollutants (POPs). As small fish are eaten by larger fish up the food chain, concentrations of mercury and POPs increase, so that large, predatory deep-ocean fish tend to contain the highest levels. That makes it best to avoid eating large fish, such as shark, swordfish, tilefish, and king mackerel. As long as you avoid these higher sources of mercury, the benefits of eating fish far outweigh the risks of mercury in fish.

It's no secret that alcohol affects our brains. Although excessive drinking is linked to an increased risk of dementia, decades of observational studies have indicated that moderate drinking has few ill effects. However, a recent British study seems to have bad news for moderate drinkers.

Research we're watching

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Do you swallow a daily multivitamin, hoping to make up for a less-than-ideal diet? Sorry, but this strategy won't stave off heart disease, according to a study published online April 5, 2017, by JAMA Cardiology.

Previous research has also failed to find convincing evidence that a daily multivitamin lowers the risk of heart disease or cancer. But these studies didn't always account for the participant's dietary habits, which could potentially skew the results. In theory, people with poor diets might reap greater benefits from vitamins than those who eat healthier diets.

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New research may help explain why diets rich in animal-based foods are linked to a higher risk of heart attack.

The average American diet contains about 300 milligrams per day of choline, a nutrient found in meat, eggs, and milk. Earlier research found that when gut bacteria feed on choline, they make a compound called TMA. In the liver, TMA is converted to TMAO — a compound closely tied to heart disease risk.

On call

Q. I have heard that exercising on an empty stomach burns more fat and at a faster rate. Is this true?

A. When the body is in a fasting state, several backup mechanisms ensure your muscles and brain get the necessary sugar for fuel. During exercise, after your body's sugar stores are exhausted, the body then taps into stored fat and turns that into sugar or turns protein from muscle into sugar. This has led to the hypothesis that exercising when the body is already "sugar starved" will lead to more rapid fat burning.

Can curbing your usual daily calorie intake by 10% improve health and longevity?

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There is a saying: "The less you eat, the longer you live." The rising rates of obesity have shown that Americans consume more than necessary, and cutting back on calories may be a smart move.

"People naturally gain about a pound a year, on average, beginning in middle age, so healthy weight needs to be a goal for older men," says Vasanti Malik, a research scientist in the Department of Nutrition at Harvard's T.H. Chan School of Public Health. "That is why being mindful of how many calories you really need — and perhaps cutting back some, an approach called calorie restriction — may help some men stay healthy and maybe even live longer."

Research we're watching

Gluten, a storage protein in wheat, rye, and barley, triggers inflammation and intestinal damage in people with celiac disease. Due to concern that gluten may also increase the risk of obesity, diabetes, and cardiovascular disease among healthy people, the number of people without celiac disease who have adopted a gluten-free diet grew more than threefold from 2009 to 2014.

A team led by researchers from Harvard T.H. Chan School of Public Health used 20 to 30 years of data from the 64,714 women in the Nurses' Health Study and the 45,305 men in the Health Professionals Follow-up Study to examine the relationship of dietary gluten to the risk of chronic conditions such as coronary artery disease in people without celiac disease or heart disease. All the participants had completed questionnaires on their diet and health every four years from 1986 through 2010.