I would add that a "superfood" may have provided some nutritional substance that a person was lacking and had a positive effect, but no everyone is lacking the

I would add that a "superfood" may have provided some nutritional substance that a person was lacking and had a positive effect, but no everyone is lacking the same things and once you have built up an appropriate reserve there should usually be no further beneficial effect to consuming more of the superfood. "Superfoods" are simply classified by being nutritionally dense foods. If you have the nutrition, you won't get any benefit from consuming them.