These products include winners and sinners: juices that supply kids with needed calcium, but also candy disguised as granola bars with just a smidgeon of much-ballyhooed nutrients.
The industry calls these products "nutraceuticals" or "functional foods." Critics say they could lead people to consume too much of certain nutrients, plus too many calories and fats.
New York University food scientist Marion Nestle calls them "calorie distractors."
"Functional foods are about marketing, not health," she said. "They delude people into thinking that these things are healthy," and they often eat more than is wise, she said.
Her shame list includes a candy bar pumped with caffeine and B vitamins, marketed as an "energy boost," and fattening ice creams enriched with calcium and helpful bacteria called probiotics.
Other nutrition experts worry about too much of a good thing. The studies are far from definitive, but some suggest that too much of vitamins A, C, E and folic acid can be risky for some people.
Folic acid, for example, is "uncharted territory" because so many foods now are fortified with it, said Tufts University nutrition expert Alice Lichtenstein. "We don't actually know how high you can go" and be safe, she said.
Americans have a big appetite for these products. Functional foods account for more than $27 billion in sales a year - about 5 percent of the U.S. food market, the Pricewaterhouse report says. Estimates of future growth range from 8.5 to 20 percent per year, far more than the 1 to 4 percent forecast for the food industry as a whole.
Fiber, for digestive health, has been a big draw. In 2007, General Mills expanded its Fiber One brand into bars with appealing flavors such as Oat & Caramel and Chocolate Mocha. Sales exceeded $100 million in the first year.
In 2004, the company added whole grain to its entire Big G cereal line - 50 to 60 brands. Kathy Wiemer, a company dietitian, argues that a cereal such as Lucky Charms, made from whole grain oats and containing less sugar than many yogurts, is a healthy breakfast choice.
"There are some misperceptions around foods that contain sugar," she said. "And we know that consumers are far below the recommended intakes" for fibers and whole grains.
Among beverages, vitamin-enhanced versions of Tropicana Pure Premium juices now account for 40 percent of Tropicana sales and the share is growing, said Dave DeCecco, a spokesman for Tropicana's maker, PepsiCo Inc. A kids' version has added vitamins A, C, D and E plus folic acid, potassium and calcium.
Coca-Cola Inc. makes an enhanced Minute Maid orange juice with a host of vitamins plus zinc, and an apple juice marketed for kids with multiple vitamins and calcium. Kraft Foods Inc. sells a version of Capri Sun drinks with added antioxidant vitamins.
Soft drinks, including vitamin waters and sports beverages, now claim a third of the nutraceutical market, according to the Pricewaterhouse report. They have gained as carbonated soft drink sales have declined.
Dairy products, led by yogurts such as Yoplait and Dannon's Activia line, accounted for nearly $7 billion in sales in 2007, just behind the beverage category, the Pricewaterhouse report says.
However, "plus" products can have minuses, such as sweetened "silly beverages that cost $2 and $3 apiece with added ginkgo or caffeine or chromium, a supposed appetite suppressant," said David Schardt, senior nutritionist for the consumer group Center for Science in the Public Interest.
"It's really a junk food dressed up to look prettier than it is," he said. "People are going to be deceived into thinking a lot of these products are especially healthy for them when there's little evidence they are. There's more hype to these products than there is reality."
Some consumers agree.
Ahna Deverey, shopping at a grocery store in suburban Milwaukee, shook her head at milk with added DHA/omega-3 fatty acid. The label said it "helps support a healthy brain."
"I sometimes think it's overkill," she said. "I try to avoid as many additives as possible, and when it says 'doctor-recommended,' you know damned well you don't need it."
The federal Food and Drug Administration is paying more attention to health claims on functional foods. The FDA recently sent General Mills a letter saying that Cheerios was being "promoted for conditions that cause it to be a drug" - lowering cholesterol 4 percent in six weeks.
General Mills says it is working with the FDA, that its fiber health claim "has been FDA-approved for 12 years," and that the cholesterol claim has been on Cheerios boxes for more than two years.
Several nutrition scientists say they hope the agency will go after hyped claims of foods and ingredients that can "boost immunity" - a vague concept with little hard science to back it up, Schardt said.
Omega-3 fatty acids also are drawing more attention. The ones that some studies have linked to heart benefits are derived from marine sources, such as fish oil, but many foods touting omega-3 use plant sources, Lichtenstein said.
The biggest worry is that adding a nutrient will give "a health halo" to foods and lead to overconsumption, she said.
"The biggest problem we have in the United States is overnutrition - too much calories," Lichtenstein said.
Brian Wansink, a food marketing expert at Cornell University, sees another risk. Health benefits come from eating the entire food, not just a single nutrient inside it, he said.
"People are sort of losing the point of why they're eating certain foods," Wansink said. With functional foods, "we end up eating it like it is medicine, so we end up eating too much of it."