What you see on the front of the packaging doesn't always reveal what's really inside.

Imagine three items in your grocery cart: Peppercorn Ranch SunChips, Cocoa Krispies and Country Crock margarine.

The first is stamped with a red heart, indicating that it's a good source of whole grains. The second has a banner saying that the vitamin-enriched rice cereal will boost your immunity. The third bears a green label deeming it a "Smart Choice," a green seal of approval on the front of food packaging to indicate healthier fare.

If you are like the typical hurried consumer, chances are you don't spend much time considering how such messages end up there. Here's one way to look at it: The chips have no trans fat and contain 18 grams of whole grains; the cereal boasts one-quarter of one's recommended daily vitamin intake; the margarine has fewer calories and less cholesterol than butter.

Yet, even with this information, it can be hard to understand why a bag of chips with more than 20 ingredients--including corn syrup--and a cereal laced with sugar and semi-sweet chocolate, are purportedly good for one's health.

That confusion can often be traced to inconclusive research and eager marketing claims. While science has given us clues about how to achieve optimal health, researchers don't yet know how the body best absorbs certain nutrients. Meanwhile, the food manufacturers behind the labeling have a lot at stake: The market for so-called functional foods and beverages--or products that offer improved health through supplements or a combination of healthful ingredients--was more than $30 billion last year.

The gray areas in the research mean that creating the ideal diet--beyond eating whole grains, fruits, vegetables and lean protein--remains a bit of a guessing game. It doesn't help that a product can come close to exceeding or just barely offering a vitamin or nutrient and still be sold as good for you. And that's when food labels can sometimes give way to potentially misleading health claims.

Parsing the Claims

Marion Nestle, Ph.D., a professor in the department of Nutrition, Food Studies and Public Health at New York University, has a rule about food products that bear health claims: Don't buy them.

The box of immunity-boosting Cocoa Krispies is a useful example, she says. The Kellogg cereal may be loaded with antioxidants, but current research is inconclusive about the health benefits of these compounds, which are predominantly found in fruits and vegetables. They have been shown to protect cells against deterioration, but it's unclear if consuming them in a supplement form is effective, and some research has shown that consuming excessive amounts of Vitamin E, in particular, can be harmful.

Kellogg spokeswoman Susanne Norwitz said in an e-mail that the claim is based on peer-reviewed research and statements from the Institute of Medicine, a private organization created to advise the federal government and the public on scientific issues.

Kellogg, she said, "is confident that the claim about the antioxidants and nutrients in Rice Krispies cereals helping support the body's immune system is supported by reliable and competent scientific evidence."

Earlier this year, the company was reprimanded when it used the results of a study to advertise Frosted Mini-Wheats cereal as "clinically" shown to improve a child's attentiveness by 20%. The Federal Trade Commission, a government agency that regulates marketing claims, declared its study unsatisfactory and prohibited Kellogg from making similar claims about its breakfast and snack products.

Hard Choices

In addition to claims based on company-funded studies, consumers also have to interpret proprietary labeling systems that brand a product as a good or healthy choice. There are also two major voluntary programs: the American Heart Association's certification system of "heart healthy" foods and Smart Choices, a new labeling initiative that tries to indicate healthier fare in 19 different food and beverage categories. Food companies pay fees to participate in both labeling systems.

The AHA program has operated since 1995 with little controversy, offering its heart-shaped stamp of approval to products like whole-grain breads, low-fat meats and high-fiber canned goods. Yet some of the selections can seem questionable.

General Mills' Oatmeal Crisp Crunchy Almond cereal, for example, is a heart-healthy product according to the AHA. Though it contains whole-grain oats and whole-grain wheat, it also has two types of sugar as some of its highest ingredients and, in addition, has added corn syrup and honey.

Kimberly F. Stitzel, a registered dietitian and director of nutrition and obesity at the AHA, says that the organization chooses products based on the FDA's claims on cardiovascular health.

Currently the FDA does not require products to display the added sugar content--yet another instance of how slowly evolving guidelines can create a gray area in food manufacturing and marketing. (The AHA plans to revise its added sugar policy in accordance with any new guidelines from the FDA.)

Such blind spots in nutrition can open the door for misleading health claims, which can then leave consumers feeling overwhelmed.

Barbara Schneeman, Ph.D. director of the Office of Nutrition, Labeling and Dietary Supplements at the FDA has some straightforward advice: When in doubt check out the nutrition facts and look for the serving size and calories. As a rule of thumb, 5% or less of an ingredient's recommended daily value is low, and 20% is high.

These facts "should resonate with the front-of-the-pack claims," she says.

And when it seems like too hard a puzzle to solve, the best choice might be to just trade the bag of chips or box of cereal in for an apple, which has a much longer track record in promoting human health.