The term 'Superfoods' is one without any scientific or regulatory meaning but is used in marketing certain foodstuffs that proponents claim are unusually dense in chemicals needed to stay healthy or fight disease. Blueberries, for example, are said be be high in antioxidants which can inhibit certain cancerous growths and have been shown to prevent and reverse age-related memory decline in rats. Studies on pomegranate juice have suggested that it can lower blood pressure in the short-term and there is evidence that the antioxidant flavonoids in tea and cocoa are beneficial for cardiovascular health.
Lots of social media posts by people marketing sales of these superfoods focus on the claimed health benefits and quote scientific studies which show good evidence for the impact these compounds have on human health. However, the fact that these foods contain these compounds and chemicals does not mean that they have the impact claimed. Often the studies are on animal models, or in vitro cell cultures. Food is not consumed in isolation and the human metabolism is hugely complex and subject to many many variables. Sometimes these superfoods contain other compounds which are equally or even very harmful, especially when consumed in large quantities.
This is not to say that food scientists and dieticians can't say what foods are more or less healthy than any other but it does mean that the picture is very complicated. Labelling certain foods as 'super' is disingenuous and leads people to think there is a magic bullet that can fix their health. As the The European Food Information Council state: 'A diet based on a variety of nutritious foods, including plenty of fruits and vegetables, remains the best way to ensure a balanced nutrient intake for optimal health'