7 Must-Do's Before You Buy a 'Functional Food'

Probiotic yogurts claim to improve your "digestive health." Energy drinks say they'll give you "more immunity" or "more clarity." A breakfast cereal purports to improve kids' attention span. All of these products belong to the market segment known as functional foods. That phrase means different things to different people, but to keep it simple, let's use the definition used by the Institute of Food Technologists: Functional food refers to foods and food components that provide a health benefit beyond basic nutrition. The beneficial ingredient can occur naturally—say, as with blueberries, whose antioxidants may help protect against some chronic diseases—or it may be added where it doesn't ordinarily belong—such as in a cereal bar spiked with those same antioxidants.

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Functional food can certainly do good. For example, the government mandates that grain products, including flour and bread, be fortified with folic acid in order to prevent birth defects. But claims about the health benefits of these foods can be confusing at best and misleading at worst. Here are seven things to do when you're weighing the purchase of a functional food:

1. Ask yourself why you want to buy this particular food. This isn't meant to cause an existential crisis in the middle of the cookie aisle, but it is an important question. What additional benefit does this item possess that makes you want to toss it in your cart? Does it appear to be a low-calorie food, and you're watching your weight? Does it have a nutrient—say, vitamin D—that you think you should be consuming more of? Do you have a specific health problem, like high cholesterol or constipation, that you're trying to address with diet? Define the benefit you're trying to get.

2. Figure out what health benefit the product is really claiming to provide. This can be tricky to figure out, because the semantic sea regarding health claims is confusing for everyone except a small percentage of nutritionists and lawyers. When a food label makes a specific claim about a disease—say, that an ingredient may cut your risk of cancer—that claim has to be preapproved by the government. But the evidence behind those claims isn't equal. Without getting into the regulatory mumbo jumbo, know that health claims meeting a certain standard of evidence are allowed for a dozen diet-disease relationship categories, including calcium and vitamin D for osteoporosis and soluble fiber for heart disease.

There's a whole other category of functional-food claims, though, that meet a less rigorous standard. Those are called "qualified health claims," which means they can carry a range of disclaimers depending on how strong the supporting evidence is. Included in that list: claims about nuts and heart disease, and tomatoes and prostate cancer. Confused? You're not alone. Until there's a more straightforward system, all you can do is read the label carefully, including all the small print. If it says things like "very limited and preliminary evidence," realize it is just that: very limited and preliminary evidence. Would you make any other kind of purchase based solely on such thin gruel?

3. Take vague language with a big grain of salt. A label can also give you the impression that a food is healthful without actually saying it will cut your risk of disease, often just by naming an ingredient or stating how it affects the body's structure or function. No government preapproval is needed for these claims, which often use vague language about keeping your heart or other body part "healthy" or statements like "contains vitamin B for energy."

Take that latter claim as an example. We all want energy: A study conducted in 2008 by the International Food Information Council found that 91 percent of people surveyed either consumed or would be interested in consuming foods and beverages that they felt could "improve physical energy or stamina." It's certainly true that to break down the foods you eat and convert them to energy, you need B vitamins, says Hope Barkoukis, a nutritionist and dietitian at Case Western Reserve University and chair of the American Dietetic Association's Sports, Cardiovascular, and Wellness Nutrition Practice Group. Someone who is deficient in certain B vitamins will definitely see benefits by getting them, she says. Trouble is, B vitamin deficiency is not generally a problem in the United States. And there is "no data saying that someone who has sufficient B vitamins would have any increased energy subsequently to eating or drinking anything," she says. So a sports drink linking the presence of B vitamins to energy is pretty meaningless in that context.

4. As with everything else, realize that if it sounds too good to be true, it probably is. Would you believe that Frosted Mini-Wheats cereal has been "clinically shown to improve kids' attentiveness by nearly 20 percent"? Kellogg Co. recently agreed to settle Federal Trade Commission charges that those ad claims were false and broke the law. As it turns out, according to the study used to support that claim, only about half the kids who ate the cereal for breakfast showed any improvement in attentiveness, and only about 1 in 9 improved by at least 20 percent, the FTC said. There are plenty of misleading ads out there. Caveat emptor, especially with health claims for food.

5. Be prepared to drop something else from your diet. There is no magic bullet that will compensate for otherwise unhealthy eating habits; simply adding something to your diet isn't necessarily helpful unless you also subtract something. The limited health claims permitted for olive oil, for example, do not mean you can simply add it to your diet on top of everything else you eat; it has to replace a similar amount of saturated fat and not increase the number of calories you eat in a day. So tossing a handful of walnuts on a hot fudge sundae is not going to compensate for the sundae, says Alice Lichtenstein, a nutritional biochemist at Tufts University's Friedman School of Nutrition Science and Policy. (Sorry.)

6. Look at what else is in there. Juicy Juice now has special varieties that are touted as promoting "brain development" (with DHA, from omega-3 fatty acids) and "immunity" (with vitamin C, zinc, and prebiotic fiber) in small kids. Sounds great . . . except that the juice is still more than 75 percent sugar. And the American Academy of Pediatrics has said that instead of juice, children should be encouraged to eat fiber-rich whole fruits and that kids under 6 months shouldn't get juice at all.

The biggest trap in functional-food shopping is buying something that seems healthful but really isn't. Energy and breakfast bars, for example, make all kinds of claims about the added fiber but don't tout the fact that they often get more than half their calories from fat and sugar. That's why New York University nutritionist Marion Nestle calls them "vitamin-supplemented, fiber-supplemented cookie bars." Or what about eating chocolate to help your heart? As the Tufts University Health and Nutrition Letter has pointed out, CocaVia Heart Healthy chocolate bars do contain certain chemicals—cocoa flavanols and canola sterol esters—that may benefit your cardiovascular system. But each small candy bar has 100 calories and gets 60 of those calories from fat and 36 from sugar. Be sure to read the nutrition label on the back of the package, not just the claims on the front. (Here are 8 fixes nutritionists would like to see on food labels.) Bottom line: A functional food should be healthful before extra nutrients are added, says Barkoukis. That doesn't mean you can't enjoy chocolate, but don't think it's been transformed into a health food.

7. Consider your diet and supplements. Many of the nutrients that may attract people to functional foods are prevalent in whole foods that are easy to get and that, in fact, they may already be eating. The omega-3 fatty acids found in fish and plant sources are added to Tropicana Healthy Heart orange juice, for example. "At our house, we eat fish three times a week, so we don't buy it," says Christine Gerbstadt, spokesperson for the American Dietetic Association. On the other hand, someone who hates fish and doesn't eat a lot of plant sources of omega-3s may opt for fortified OJ, she says. And some nutrients are particularly tough to get from food alone (vitamin D is an example). That's why it's added to foods, including milk, some kinds of OJ, and margarine.

Gerbstadt also advises that you take into account supplements you already take; getting both those and functional food may not be necessary. "It's not that you will be getting toxic amounts per se, but it may be toxic to your food budget," she says. "And there are plenty of examples in science that show that more isn't always better."