Probing Question: Are 'superfoods' really nutritional powerhouses?

It’s a little of both, said Penny Kris-Etherton, distinguished professor of nutrition in the Department of Nutritional Sciences at Penn State.

“Nutritionists don’t have a definition for ‘superfood,’ ” she said. What might well deserve the label “super,” though, is “a food that has a high nutrient density or contains bioactive components with proven health benefits.”

In our era of super-sized snack foods with lots of calories and scant nutritional value, Kris-Etherton said nutrient density is vital.

“Research is beginning to show that restricting calories can have health benefits beyond weight loss, such as extending life span. There are a lot of ways to practice caloric restriction. One way is just to cut calories, regardless of whether you’re cutting nutrients. This isn’t good because you won’t meet nutrient recommendations for good health. A better way is to cut calories but not nutrients, and to do that, you really need nutrient-dense foods,” she said.

A bioactive component, on the other hand, is a compound that has known health benefits but that, unlike essential nutrients (the vitamins and minerals our bodies need daily), is not required to achieve a nutritionally adequate diet.

“The key one I can think of is resveratrol, which seems to be an anti-aging compound,” Kris-Etherton said.

Resveratrol is found in grape skins, among other sources, though how much is necessary to obtain a benefit is still under debate. Current research suggests that it is a lot -- much more than we can get in a typical healthy diet. Some of the foods making headlines, such as acai berries, pomegranate juice, green tea, and goji berries, boast high antioxidant content, she noted. Others, such as yogurt and kefir, are thought to promote good digestive health, and still other foods, such as seaweeds and green leafy vegetables, are known for their mineral content and phytochemicals like beta-carotene.

The problem with superfoods, said Kris-Etherton, is that people may overestimate their power.

“There is no one food that provides everything your body needs,” she said. “We have be careful using that term. They’re not magic foods. We must pay attention to the total diet. [However,] the so-called superfoods do have some health benefits, especially when they’re incorporated into a healthy diet.”

Consuming a variety of foods, including lots of fruits and vegetables along with other plant foods such as whole grains, legumes, nuts and seeds, gives a person the best chance of obtaining the full spectrum of nutrients and bioactives, she said. Preparation is important, too.

“Cooking some vegetables makes the nutrients more available,” said Kris-Etherton. “With cooked carrots, for example, you get more of the carotinoids, but on the other hand, if you cook veggies too much you can destroy heat-sensitive nutrients like vitamin C. So you have to balance this with a variety of food preparation techniques.”

Many other factors affect the absorption of nutrients. Some vitamins, for instance, are fat soluble, and in order to get their full benefit a person’s diet must include fat. In a recent study, she said, a tomato-based salsa eaten with fat-laden avocado was shown to be better for vitamin A uptake than salsa alone.

In the end, Kris-Etherton tells us what we should already know: the best way to ensure a long, healthy life is to eat a balanced diet that contains a variety of foods and plenty of fruits and vegetables.

“What I think people should do with all this new information is stay tuned. We’ve got to get to where there is a large evidence base before nutritionists will say, ‘I think you should take this for these reasons.’"

Besides the ubiquitous fruits and vegetables, there are other foods that everyone should be eating, too. She recommended the consumption of two servings of fish per week, touted dark chocolate's effect on cardiovascular health and insulin sensitivity, and other foods.

"That’s just the tip of the iceberg,” she said.

Source: By Alexa Stevenson, Research/Penn State