Unless you’ve been living in a cave, you’ve probably been bombarded with news about “superfoods.” But you’ve probably also wondered which foods are “super” are and what makes them that way.

As it turns out, you might be asking the wrong questions. We spoke with an expert in what can more accurately be described as “functional foods”: Dr. Jeffrey Blumberg, professor at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University and professor of pharmacology and experimental therapeutics at Tufts University School of Medicine.

We wanted to get his views about the word “superfood” itself, the trends, and what savvy consumers need to know. The following is a condensed and lightly edited version of our video interview with him here.

What does the term “superfoods” mean?

There is no scientific or regulatory definition for a superfood. It’s really just a marketing term, and it’s a term I don’t happen to like. I think it’s very misleading. It may lead consumers to think that if I eat one superfood, I don’t have to eat very healthfully otherwise. It detracts from one of the central tenets of healthful nutrition, and that’s to choose a diversity of foods.

Have foods that are marketed as “superfoods” been proven by science?

If you’re going to label your products “superfoods,” to me it suggests that you probably don’t have the evidence, otherwise you would be making statements about the function that your food is really helping. If the food just helps me to meet my requirement for a vitamin or a mineral or for a particular fatty acid, that’s great. But a functional food has to go beyond meeting basic nutritional needs to support some physiologic function or reduce the risk for some known disease.

What are prebiotics and probiotics, and what’s the difference?

One might consider both prebiotics and probiotics to be functional ingredients. A probiotic is live bacteria that’s good for us. Our guts contain lots of bacteria that are important for promoting digestion and lots of other functional benefits of the gastrointestinal system, and indeed our whole body. Prebiotics generally refer to dietary fibers that those bacteria like to eat and thrive on. Or you can create foods that we called “synbiotics,” which is a combination of pre- and probiotics together.

What are the benefits of soy?

All plant foods including soy contain a number of phytochemicals—that is, compounds that are not essential nutrients like vitamins and minerals but in fact are bioactive components of our diet. Soy is particularly rich in compounds we call flavonoids. But the flavonoids that soy contains are different than the flavonoids you’re going to find in an orange or orange juice, for example. This is one of the reasons we like to talk about diversity of foods, so that we can take advantage of the benefits from all of these different phytochemical compounds.

A lot of people have been excited to hear that there may be health benefits in dark chocolate. Is this true?

Dark chocolate, and in particular the cocoa powder from which dark chocolate is made, is rich in flavonoids. Any product that comes from plant foods that are high in flavonoids is going to be high in whatever the final product is. We know from randomized control studies, as well as from big observational studies, that a reasonable amount of dark chocolate can in fact provide a functional benefit in terms of improving vascular health.

What can consumers do to incorporate these foods into their diet?

It’s really a challenge because the labeling that we currently use does not identify particular bioactive ingredients, but you can look for whether there are sources. Does the product mixture, the beverage, or the bar that you’re going to buy have blueberries in it? Does it have cranberries in it? That would suggest that it has some of those bioactives. It becomes incumbent upon consumers to educate themselves a little bit. If you’re looking to promote eye health or reduce your risk for age-related macular degeneration, then you need to know that lutein and zeaxanthin, which are carotenoids, are very powerful in having this functional benefit. But you’re not going to find foods labeled with lutein and zeaxanthin.

What’s the future of functional foods?

I think the future of functional foods is very bright. The more we learn about nutrition science, about how the components in our diets and in our dietary patterns promote health and physiologic function, or reduce our risk for common chronic diseases, we’re going to see more and more functional foods being formulated and more dietary guidelines based on the functionality of foods. As we know now that nutrition and genetics intersect, we’re going to see people being given advice to eat according to their genes, to feed their genes in just the right way. I think it’s probably not too long before we find 3D printers in the kitchen that are going to formulate the perfect food for you.