Nutritional fortification could be altering our innate, healthy relationship with food. Credit: Photographs by Yasu + Junko

Cheerios with protein. Jif with omega-3s. Tropicana orange juice with "3X the vitamin C." Walk through any supermarket and you'll find hundreds of products packed with added vitamins and minerals, promising a path to better health through engineered food, and appealing to our faith that the more nutrients we get, the healthier we become.

There's just one problem. No one knows if adding nutrients makes people healthier. In fact, many nutrition experts fear that these products may have the exact opposite effect. Nutrient-fortified foods not only dupe consumers into buying calorie-rich, sugar-dense processed junk, they may actually contribute to weight gain more than unfortified products. And, more ominously, some scientists fear that fortified foods could rewire our natural cravings, curbing our desire to eat nutritious whole foods in the first place.

"Throwing nutrients into junk food does not produce good food," says Dr. David L. Katz, director of the Yale University Prevention Research Center. "It produces nutrient-fortified junk."

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Still, Americans love the stuff. Sales of "functional foods" — which include any product with an added component that's clinically proven to provide a health benefit, such as vitamins, minerals, or protein — are expected to reach $54 billion by 2017, according to market analysts Leatherhead Food Research. That's up from $40 billion in 2013.

The U.S. started fortifying its food in the 1920s, when the government began adding iodine to salt to prevent the thyroid condition known as goiter. In the 1940s, B vitamins were added to white flour and corn flour, an effort to correct nutritional deficiencies and to replace some, but not all, of the nutrients lost during processing.

Then, in the early 1980s, food giants such as General Mills and Kraft discovered there was big money in selling products marketed as low-fat and low-cholesterol. (This was stoked by the widespread belief at the time that fats were to blame for weight gain and cardiovascular disease.) For the next three decades, as fortification techniques advanced, the category grew to include products with added fiber, phytochemicals, antioxidants, and, more recently, omega-3s, electrolytes, protein, and vitamins. The sector continues to grow because consumers think these products really work. Nearly two-thirds of Americans believe that functional foods provide added health benefits, according to a 2013 report from the International Food Information Council.

In reality, the nutrients in functional foods do a poor job at best of  balancing our nutritional needs.

Consider omega-3s. During the last decade, research has found an association between these fatty acids and better cardiovascular and brain health, and now you can find hundreds of products fortified with the nutrient. In one much-publicized move in 2010, Colorado-based Horizon Dairy began adding 32 milligrams per serving of the omega-3 lipid DHA to its chocolate milk.

It sounds like a win-win: healthy omega-3s in a drink adults and kids like. But it's not. "Thirty-two milligrams of DHA might sound like a lot, but a serving of salmon has about 1,000 milligrams," says Ameer Taha, a food scientist at UC Davis. "To get as much DHA from Horizon's milk, you'd have to drink two gallons." (Or eat 60 tablespoons of Jif omega-3 peanut butter or drink 20 cups of Tropicana Pure Premium Healthy Heart orange juice.)

This kind of thinking also plays on the assumption — and it's a big one — that a nutrient on its own equals good health. Dr. Richard Bazinet, of the University of Toronto's department of nutrition, points out that numerous clinical trials have failed to support that idea. "We still don't understand what it is about eating fish that confers a health benefit," Bazinet explains. "But we do know that omega-3s are not some kind of magic bullet that makes people healthier."

Worse, we rarely consider what else we're consuming along with all those added nutrients. A Gatorade Chocolate Chip Whey Protein Bar, for example, advertises 20 grams of protein (about a third of the recommended daily amount for a 160-pound man). But the bar also has 350 calories and 28 grams of sugar. That's more than two-thirds of the sugar recommended for men per day.

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However nutritious fortified foods seem, they just don't compare to what you'll get from nature, says Donald Davis, a former research scientist with the University of  Texas's Biochemical Institute. "Whole foods," he says, "have broad ranges of 20 to 30 nutrients in significant amounts relative to the calories they contain." A bottle of Vitaminwater, he points out, has a fraction of those nutrients and, like fortified chocolate milk or a protein-loaded bar, contains a major dose of sugar.

While some fortified foods offer a meager portion of nutrients, others may supply far too much. More than half of American adults take some kind of dietary supplement. According to a 2012 study in the Journal of the Academy of Nutrition and Dietetics, that can increase the likelihood of consuming certain nutrients in excess. Add in functional foods, and the amounts can become megadoses. A 2014 report in the journal Applied Physiology, Nutrition, and Metabolism analyzed 46 functional beverages — waters and sports and energy drinks — and many contained well above the daily requirement of a half-dozen vitamins, including B6, B12, niacin, and riboflavin. "The potential for massive dosing is very real," says study co-author Valerie Tarasuk, a professor of nutritional science at the University of Toronto. "We have no evidence that intakes well in excess of requirements will confer benefit, but harm is an open question."

One of those harms could be weight gain. In a paper published last year in the World Journal of Diabetes, Dr. Shisheng Zhou, a physiology researcher at Dalian University, showed that excess B vitamins can enhance fat synthesis, cause insulin resistance, and create an oxidative stress that cues the body to store fat in fat cells and then prevents the cells from releasing it to be used as energy. Countries that prohibit flour fortification with vitamins — including France, Norway, and Finland — have a lower rate of obesity than those that mandate it, Zhou notes. He goes further still, connecting spikes in U.S. obesity and diabetes rates with each new wave of fortification — first in the early 20th century, then again in the Seventies and Eighties, and most recently over the past decade. "It is necessary and urgent to review and modify the standards of vitamin fortification," he says.

Food manufacturers, not surprisingly, claim they are simply providing customers with more healthful choices. Asked to comment for this story, Coca-Cola — which makes Minute Maid enhanced juices, Fuze Tea, Vitaminwater, and Powerade — gave this statement: "We offer a variety of beverages with added nutrients — for example, juices and juice beverages with added vitamin D and calcium, which help build strong bones — to meet consumer preference and taste."

But Dr. Yoni Freedhoff, professor of medicine at the University of Ottawa and medical director of the Bariatric Medical Institute, argues that fortified food legitimizes what can essentially be junk food. "No one would think Coca-Cola is healthy," he says. "But Vitaminwater, they do." This creates a halo effect. Because we believe fortified foods are good for us, we're likely to eat much more of them.

There may be something deeper and more harmful at play: Nutritional fortification could be altering our innate, healthy relationship with food.

Human beings have a natural ability to seek out the nutrients their bodies need. One of the first studies to illustrate this took place in 1926, when a Chicago pediatrician named Clara Davis allowed 15 babies and toddlers to select what they wanted to eat from a range of whole foods. The kids didn't binge on sugary fruits or ignore their vegetables. They chose a remarkably balanced and healthy diet. One baby with rickets, a vitamin D deficiency, even drank cod-liver oil of his own volition, curing the disease.

Davis' study is not the only example of humans possessing "nutritional wisdom" — the idea that the foods we like and crave correspond to our nutritional needs. According to Jonathan Lamb, a historian at Vanderbilt University, 18th-century sailors stricken by scurvy were often overcome by a desire for fruits and vegetables. In one well-documented case, a scurvy-ravaged crew gorged on watercress, turnips, and radishes upon landfall.

Had it been available, would those sailors have guzzled a 23-ounce bottle of  "vitamin C fortified" Arizona Grapeade instead?

Decades of research on animals suggest that they would have. In a study last year, 23 lambs at the University of Western Australia were intentionally fed a diet low in vitamin E, and then offered orange-flavored feed that had been fortified with vitamin E or a nonfortified feed. After 15 days, the results were clear: The lambs wanted the orange pellets. They preferred a flavor they didn't ordinarily like, orange, because it was paired with a needed nutrient. "Animals have an extraordinary ability to seek out the nutrients that are essential for survival," says Fred Provenza, a behavioral ecologist who has studied the eating habits of animals for more than 40 years.

Viewed another way, however, and the study's outcome is disturbing: The micronutrient manipulated the lambs' dietary preference. "The addition of a single vitamin can induce lambs to eat a food they would normally have no interest in eating," Provenza says.

And adding those nutrients to carbs can fatten animals up. As counterintuitive as that may sound — vitamins contributing to weight gain — it's old news in farming. More than a century ago, farmers knew that corn and barley (carbs, in other words) could make animals put on weight. But if that's all chicken and pigs were fed, they would get sick. They had to be let outdoors to forage or be fed green feed and kitchen scraps. "Back then, livestock needed to eat vegetables to get their vitamins," says Allen Williams, a former professor of animal science at Louisiana State University and livestock consultant.

That changed when we discovered that adding nutrients to feed allowed farm animals to thrive on a sensationally high carb diet. The feed was now nutritionally complete, and instead of making the animals sick, it made them gain weight faster than ever, Williams says. The animals were content to eat it. "If you supplement them with vitamins and minerals," Williams explains, "they get lazy and have no desire to go out and graze. You can actually have an effect on their behavior."

Could something similar be happening to humans? If we get our essential nutrients through white bread, sugary cereals, protein-packed bars, and vitamin-enhanced drinks, does it curtail our desire to eat whole foods? It's a question worth asking, scientists say. "The fact that we no longer need to get micronutrients via a wide range of plants is one of many ways that the current food system in humans no longer fits our evolutionary history," says Gary Beauchamp, the former director of the Monell Center, a hub for research on the science of food taste and smell.

Provenza suggests that we may already have the answer. "If people are on a diet of wholesome foods and they experience cravings," he says, "it is the body guiding a person to select foods that provide nutrients needed at the cellular level." A craving for eggs or steak, for example, leads to consuming a complex amalgam of protein, fat, vitamins, and minerals. Similarly, craving a salad brings the body a blend of vitamins, minerals, fiber, and phytonutrients. But if people are getting their essential nutrients from processed foods, the nutrients may be reinforcing the desire to eat junk foods over whole foods. "People are being conditioned to want to eat them," Provenza says. "And when they do, they wind up overconsuming calories in an attempt to obtain necessary nutrients."

The perverse result is that much of the food we eat resembles the feed that's been engineered to fatten livestock: high in calories and loaded with essential nutrients.

"We never stop to think about it, but if you want an animal or a human to get fat quickly," Provenza says, "you can't do it without vitamins."