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

The grocery aisles are filled with functional foods that claim to improve your health. How to choose?

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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.

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.