Superfoods are foods — mostly plant-based but also some fish and dairy — thought to be nutritionally dense and thus good for one's health. Blueberries, salmon, kale and acai are just a few examples of foods that have garnered the "superfood" label.
However, there are no set criteria for determining what is and what is not a superfood, according to the American Heart Association.
"Superfoods don't have their own food group," said Despina Hyde, a registered dietician with the weight management program at New York University's Langone Medical Center. "As a dietician, I think 'superfood' is more of a marketing term for foods that have health benefits."
Consuming foods that are packed with nutrients (as many so-called superfoods are) is certainly a good idea, Hyde told Live Science. But the key to a healthy diet is to consume a variety of nutritious foods in the right quantities, she added.
"Superfoods have extra-large doses of vitamins and minerals that can help us ward off diseases and live a longer, healthier life," said Hyde.
Some of the nutrients that certain superfoods contain include antioxidants, thought to ward off cancer; healthy fats, thought to prevent heart disease; fiber, thought to prevent diabetes and digestive problems; or phytochemicals, the chemicals in plants responsible for deep colors and smells, which can have numerous health benefits.
Blueberries often top many lists of superfoods because they are rich in vitamins, soluble fiber and phytochemicals. But the same nutrients found in blueberries are also found in many other kinds of berries, including strawberries and cranberries. A study published in 2013 in the journal Circulation found that a high intake of phytochemicals known as flavonoids — which are found in blueberries, as well as other kinds of berries — may reduce the risk of certain heart conditions in young women.
Kiwifruit also tops many a list of popular superfoods. Its benefits are similar, for the most part, to berries, melons, citrus fruit, apples and pears, all of which are high in vitamin C and rich in antioxidants. Kiwifruit is labeled a superfood perhaps because it contains a wider range of nutrients compared to some other fruits. A very small study published in 2011 in the Asia Pacific Journal of Clinical Nutrition suggested that consumption of kiwifruit (which also contains serotonin, a hormone that helps induce and maintain sleep) might promote a better night's rest in people with sleep disorders.
Beans and whole grains are standard additions to the superfood lists. Beans are a source of low-fat protein. Beans contain insoluble fiber, which lowers cholesterol; soluble fiber, which provides a longer feeling of fullness; and loads of vitamins and trace minerals largely absent in the typical American diet, such as manganese. Whole grains — named such because, unlike refined grains, they are not stripped of their nutrient-containing bran and germ during processing — have similar benefits to beans, though they don't contain as much protein. Quinoa is not a grain, but it cooks up like one, and this too is a remarkable source of protein, vitamins, minerals, fiber and antioxidants.
Nuts and seeds contain high levels of minerals and healthy fats. Although these are common additions on superfood lists, the downside is that they are high in calories. Portion control is key. Shelled nuts and seeds, in this regard, are ideal because they take time to crack open and slow you down. A quick handful of shelled nuts could contain more than 100 calories, according to Hyde. [Related: Reality Check: 5 Risks of Raw Vegan Diet]
Kale lives up to the hype of a superfood. But so do most dark, leafy greens: Swiss chard, collards, mustards (including radish greens), spinach (and others in the amaranth family), and cabbages. Add broccoli to that list, as well. It's in the cabbage-mustard family; the modern version is merely grown for its floret instead of leaves. These dark vegetables are loaded with vitamins A, C and K, as well as fiber, calcium and other minerals.
Sweet potato and squash also usually make the superfood list, for similar reasons as those listed for leafy greens. Both kinds of food are generally excellent sources of fiber, vitamin A and much more. They are also naturally sweet and don't require the butter, cream or salt typically added to potatoes.
Salmon, sardines, mackerel and certain other fatty fish are rich in omega-3 fatty acids, which are thought to lower the risk of heart disease and stroke. The benefits of eating fish may far outweigh the risk of harming your health from the mercury these fish contain, according to Harvard's T.H. Chan School of Public Health. If you worry about the contaminants your fish dinner may contain, you can try eating lower down on the food chain. Certain fish, such as sharks, swordfish, king mackerel and tilefish, contain higher levels of mercury than smaller fish, like sardines, smelt, and anchovy.
The "exotic fruit of the year" will surely be on any superfood list, too. This might be acai berry, noni fruit, dragon fruit, rambutan or pomegranate. These fruits might be healthful, but scientific studies do not show that they are more healthful than other, less exotic (and therefore less expensive) fruits, such as blueberries. Some of these fruits may be particularly dense in certain kinds of nutrients. Pomegranate, for example, contains ellagitannins (ellagic acid), which have known anti-cancer properties. But red raspberries, which are arguably just as delicious as pomegranate seeds, also contain ellagic acid.
One could just as easily include green tea, coffee, dark chocolate, yogurt, and olives to the superfood list for a variety of reasons mentioned above.
Criticism of the nomenclature
As healthful as superfoods might be, the use of the term is largely a marketing tool. Scientists do not use the term. For example, a search for "superfood" on PubMed, the repository of most peer-reviewed biomedical journal articles, yields fewer than a dozen results. And several of these studies actually warn of dangers of superfoods, such as arsenic and pesticide residue in imported foods. [Infographic: Pesticides Lurk in Fruits & Veggies]
The first general criticism of the use of the term "superfood" is that, while the food itself might be healthful, the processing might not be. For example, green tea has several antioxidants. But green tea sold in the United States is generally cut with inferior teas and brewed with copious amounts of sugar. The Japanese and Chinese generally do not drink green tea with sugar. Many kinds of super-juices — acai berry, noni fruit, pomegranate — can be high in added sugar.
Similarly, many whole grains are processed in a way to be more palatable and less healthful. For example, instant whole-grain oats are as unhealthy as overly processed white bread in that they quickly spike sugar levels in the bloodstream once consumed, promoting insulin-resistance, obesity and diabetes, according to research by David Ludwig at Harvard University.
And even fruits without added sugar still contain calories, noted Hyde, who said she encourages her clients, many of whom are trying to lose weight, to eat everything in moderation.
"When we label these foods as 'super' and 'healthy,' people think they can eat them in unlimited quantities. But you do have to be cautious of the amount you eat, because you can gain weight from eating too much healthy food," Hyde said.
A second criticism is that, because the term "superfood" is not scientific, it can mean very little and prompt some consumers to eat one kind of food over another. Is broccoli really that superior to asparagus?
Research has shown that the ideal diet is one that is largely plant-based with a wide variety of fruits, vegetables, whole grains and healthful animal products. Superfoods might be a good entry into healthy eating, and understanding the nutritional value of the food you eat can be enlightening, but there are lots of healthy foods out there to explore, even if no one is calling them "super."