Diet and nutrition Archive

In the journals

Flavanols give fruits and vegetables their bright colors. They are also found in tea and cocoa. Observational studies have shown that eating foods rich in flavanols is linked with less cognitive decline as people age. New research suggests a possible reason why: flavanols appear to improve blood flow to the brain.

Researchers gave cocoa flavanols to 18 healthy adults in two separate trials. In one, the people consumed a cocoa drink with about 681 milligrams (mg) of flavanols. In the other, they had a cocoa drink with about 4 mg of flavanols. About two hours after having the cocoa drink, participants briefly inhaled air with high concentrations of carbon dioxide to raise their blood level above normal. (The brain's normal response to high blood carbon dioxide levels is to increase both blood flow to the brain and its uptake of oxygen.) The researchers then measured the speed of brain oxygenation and administered a set of mental tasks to assess cognitive performance. People had a faster brain oxygenation response after consuming high amounts of flavanols compared with lower amounts. They also scored higher on the cognitive tests and correctly solved problems 11% quicker.

Research we're watching

Widely considered the healthiest diet for your heart, the Mediterranean diet is rich in plant-based foods and features only small amounts of meat and dairy products. But a variation that includes more green plant foods may be even better for you, a small study suggests.

The study included 294 sedentary, moderately obese people whom researchers randomly divided into three groups. Each received different dietary advice: a standard healthy diet, a low-calorie Mediterranean diet, or a "green" Mediterranean diet. Both Mediterranean diet groups included about a quarter-cup of walnuts daily, and poultry and fish replaced beef and lamb.

Losing weight sometimes takes experimentation. If you give a diet your best shot and it doesn't work long term, maybe it wasn't the right one for you, your metabolism, or your situation. Genes, family, your environment — even your friends — influence how, why, what, and how much you eat, so don't get too discouraged or beat yourself up because a diet that "worked for everybody" didn't pay off for you. Try another, keeping in mind that almost any diet will help you shed pounds — at least for a short time.

Here's a look at three common diet approaches.

Stress eating can ruin your weight loss goals – the key is to find ways to relieve stress without overeating

There is much truth behind the phrase "stress eating." Stress, the hormones it unleashes, and the effects of high-fat, sugary "comfort foods" push people toward overeating. Researchers have linked weight gain to stress, and according to an American Psychological Association survey, about one-fourth of Americans rate their stress level as 8 or more on a 10-point scale.

In the short term, stress can shut down appetite. The nervous system sends messages to the adrenal glands atop the kidneys to pump out the hormone epinephrine (also known as adrenaline). Epinephrine helps trigger the body's fight-or-flight response, a revved-up physiological state that temporarily puts eating on hold.

Here's what the research says about diet and depression.

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If you've ever found yourself in front of the TV after a bad day, mindlessly digging ice cream out of the container with a spoon, you know that mood and food are sometimes linked. But while stress eating is a verified phenomenon, the relationship between food and actual mood disorders, such as depression, is less clear. Or, to put it another way: can the things you eat influence your risk for depression — and can dietary changes potentially improve your mental health?

"The research regarding dietary factors and depression is still inconclusive," says Patricia Chocano-Bedoya, a visiting scientist in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. But there have been hints that food may play a role in depression.

The foods you eat (and don't) can determine how well your body fights painful inflammation.

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It's been said that you are what you eat, and that's definitely true when it comes to chronic pain.

"A lot of chronic pain is the result of chronic inflammation, and the evidence is quite strong that your diet can contribute to increased systemic inflammation," says Dr. Fred Tabung, a visiting researcher with the Department of Nutrition at Harvard's T.H. Chan School of Public Health. "But your diet is also one of the best ways to reduce it."

Make sure your diet meets the recommended mineral targets.

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Gold, silver, and platinum get all the attention as the world's most precious metals. But they're more precious for the global economy than for human health. Instead, other metals and minerals (metals are one type of mineral) are more important for our health (see "What essential metals do for us"). Indeed, some of them are so important that we can't live without them. "Each one plays a role in hundreds of body functions. It may take just a very small quantity of a particular mineral, but having too much or too little can upset a delicate balance in the body," says Dr. Bruce Bistrian, chief of clinical nutrition at Beth Israel Deaconess Medical Center.

They're packed with nutrients but high in starchy carbohydrates.

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Root vegetables — like turnips, rutabagas, and parsnips — may not be the sexiest foods on the table. But they're big celebrities in a number of cuisine trends like the "vegetable forward" movement (which elevates vegetables into creative entrees and side dishes) and root-to-stem cooking (which uses every part of a vegetable, including the tops, stems, and skins).

While it's fun to use old standbys in more interesting ways (like roasted parsnips with pistachio and lemon), it's important to eat root vegetables judiciously. "They are so high in carbohydrates that they are more like grains than greens. It makes more sense to put them in the same category as breads, rice, or pasta," says dietitian Teresa Fung, adjunct professor in the nutrition department at the Harvard T.H. Chan School of Public Health.

Most older adults take some kind of over-the-counter dietary supplement. But are these products right for everyone?

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Over-the-counter dietary supplements are big business — more than 90,000 products generate about $30 billion every year in the United States. Older adults make up a big part of these sales, too. A survey of almost 3,500 adults ages 60 and older published Oct. 1, 2017, in The Journal of Nutrition found that 70% use a daily supplement (either a multivitamin or individual vitamin or mineral), 54% take one or two supplements, and 29% take four or more.

But are these pills good medicine, or a waste of money?

Bananas are one of the most popular fruits in the United States, perhaps because they're affordable (about 58 cents per pound, on average) and available year-round.

Among all fruits, bananas are one of best sources of potassium, with about 450 milligrams (mg) per banana. Healthy adults not on certain medications should aim for 4,700 mg of potassium daily, although few Americans meet this goal. A high potassium intake may help reduce high blood pressure and has also been linked to a lower risk of stroke and possibly heart disease.