Superfoods are foods mostly plant-based but also some fish and dairy that are 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, as a dietician, I think 'superfood' is more of a marketing term for foods that have health benefits. Superfoods contain a variety of nutrients, such as antioxidants, which are thought to ward off cancer. They also have healthy fats, thought to prevent heart disease; fiber, thought to prevent diabetes and digestive problems; and phytochemicals - the chemicals in plants responsible for deep colors and smells, which can have numerous health benefits. Consuming foods that are packed with nutrients (as many so-called superfoods are) is certainly a good idea. But the key to a healthy diet is to consume a variety of nutritious foods in the right quantities. 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. But the small, vibrant berry may take the top spot purely because it has been more frequently studied. Kale lives up to the hype it has attracted as 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. Include broccoli on that list as well. It's in the cabbage-mustard family; the modern version is grown for its flower instead of its leaves. These dark vegetables are loaded with vitamins A, C and K, as well as fiber, calcium and other minerals. Sweet potatoes and squash also usually make the superfood list, for reasons similar to 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. Beans and whole grains are also included on superfood lists. Beans are a source of low-fat protein. These nuggets of nutrition 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 as such because, unlike refined grains, they are not stripped of their nutrient-containing bran and germinating part during processing - have benefits similar to those found in beans, though they don't contain as much protein. Quinoa is not a grain, but it cooks up like one, and is also 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. A quick handful of nuts could contain more than 100 calories, according to Hyde. Shelled nuts and seeds, in this regard, are ideal because they take time to crack open, which slows you down. 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. If you worry about the contaminants your fish dinner may contain, avoid eating fish that are high up on the food chain.