The truth about vitamin and mineral diet supplements.

The truth about vitamin and mineral diet supplements.

Danielle Schupp, a registered dietitian who is affiliated with a top fitness club in New York City, works with people who are generally committed to a healthy lifestyle. Her clients eat well, exercise and take the supplements-vitamins and minerals-they think they need. The problem, as Schupp notes, is they often don't really know what they need. "I had a client in her mid-forties who had recently discovered her bone density was low," recalls Schupp. "She had become so obsessed with preventing osteoporosis-her mother had it-that she was supplementing with 2,500 milligrams of calcium a day plus getting dairy and various calcium-fortified foods in her diet. All in all, she was consuming about 5,000 milligrams of calcium a day-well above what she needed to reduce her risk for disease." By the time the client was referred to Schupp, she had developed kidney stones from taking too much calcium.

Though perhaps an extreme case, Schupp's client is one of millions of Americans who are turning to supplements with the belief that they can help make them healthier and stave off diseases. Americans now spend $23 billion a year on supplements-nearly triple the $8.8 billion we spent in 1994. We're also shelling out $36 billion annually on fortified foods, such as vitamin-fortified cereals and juices with calcium added.

The supplement trend began taking off 30 years ago, says John Vanderveen, Ph.D., a retired Food and Drug Administration scientist: "There emerged a philosophy-perpetuated by some scientists and some supplement companies-that vitamins and minerals could be used not only to meet nutrient requirements (and prevent deficiencies), but also to improve health and treat chronic conditions." From the 1970s to the mid-1990s, U.S. supplement use grew steadily; then, the trend exploded. The ignition: the Dietary Supplement Health and Education Act of 1994. This law defined the term "dietary supplement"; it also established a dream regulatory situation for the companies that sell them. DSHEA stipulated that supplements were to be regulated like foods, not drugs, which meant manufacturers would not be required to prove a product safe or effective before selling it. It also allowed manufacturers of supplements and fortified foods to market their products with health-associated claims similar to those used to sell pharmaceutical drugs.

Fast-forward to today. We now have bottles of multivitamins-some, $50 formulas-promising "glucose control" or "stress relief," packets of powder that, with water, morph into fruit-flavored megadoses of vitamin C, and chocolate chews that deliver more calcium than a glass of milk. Orange juices claim to supply nutrients that "support your body's natural defenses" or "build healthy bones." Waters are infused with 250 percent the recommended daily dose of vitamin C. Fortified cereals are old-school. Now, even snack foods are fortified.

"When you add vitamins and minerals to traditional food products, they sell better," says Marion Nestle, Ph.D., professor of food studies and public health at New York University and author of What to Eat (North Point Press, 2006).

And there are good reasons why. Americans can be a nervous bunch when it comes to their health, says Nestle. "Supplements help relieve some of that anxiety-and marketers take advantage of the anxiety to push products." It isn't difficult to imagine how, over a decade, Americans' supplement obsession might have snowballed: bombarded with messages that suggest staying healthy requires eating more of certain nutrients, mothers started urging their adult daughters to consume more calcium; adult daughters began persuading aging fathers to take vitamin E. Health-concerned consumers facing landmark birthdays reflected upon preceding decades ("that was some hard living"), concluding that maybe it wasn't too late ("Might still be time to mop up some free radicals, undo some damage"). And so it goes.

According to the National Institutes of Health (NIH), 52 percent of Americans use dietary supplements, mostly vitamins and minerals. Are they helping? Maybe. Maybe not. Fact is, supplement makers aren't required to prove their products effective. There is little scientific proof-at least in the form of randomized clinical trials, the gold standard of scientific research-that vitamin and mineral supplements actually help prevent chronic diseases. This was what a panel of top nutrition experts reported at a "state of the science" conference held in May 2006 at the NIH headquarters in Bethesda, Maryland.

It goes beyond that. As J. Michael McGinnis, M.D., senior scholar at the Institute of Medicine of the National Academies, notes, "We're concerned that, without stronger oversight of the quality of supplements and the monitoring of adverse effects, we can't tell how many people may be getting too much of certain nutrients."

Too little? Too much? Just right?

At their best, vitamin and mineral supplements help fill nutrient gaps when the diet is lacking. Supplements may be most useful to people who can't afford a variety of healthful foods (a basic multivitamin/mineral supplement taken daily can cost as little as $15 per year). People in age groups that require higher intakes for some nutrients (e.g., calcium for teenagers and postmenopausal women) may also benefit from supplement use, as can people who follow special diets for medical (e.g., lactose intolerance) or ethical (e.g., veganism) reasons. Since federal nutrition surveys suggest that considerable numbers of Americans may be falling short on a handful of specific nutrients (vitamin A, vitamin C, vitamin E, calcium and magnesium), some experts recommend that all adults take a multivitamin/mineral supplement-one that delivers no more than 100 percent of recommended daily doses-as "dietary insurance." Other experts argue that these surveys don't accurately account for nutrients Americans get through fortified foods, and say that taking a supplement may enable poorer food choices ("Oh, I had a multi this morning, so I'll have a cookie, instead of an orange and almonds, for a snack").

Though the NIH panel generally cited "lack of evidence" for supplements' benefits, it emphasized that even for consistently healthy eaters, special circumstances warrant the use of supplements. Women who could become pregnant should take supplemental folic acid, as multiple studies suggest folic acid is better absorbed than food folate and helps reduce the risk of a neural-tube birth defect. Postmenopausal women are encouraged to take calcium and vitamin D supplements: the combination appears to decrease the risk of fractures. People with age-related macular degeneration-a condition in which the center of the retina deteriorates-should consider taking antioxidants. Mounting research suggests that free-radical damage accelerates the condition, and one well-designed clinical trial showed that supplementing with antioxidants, including vitamins C and E, beta carotene and zinc, slowed progression of the disease.

The irony of dietary supplements, however, is that "the people who need supplements most take them least," says Nestle. And the reverse is true: "Most supplements are taken by people whose diets are just fine without them." Indeed, research consistently shows that people who use dietary supplements generally have better diets; they exercise more and smoke less. What's more, emerging research suggests some people taking supplements are getting too much of certain nutrients.

In a study of 2,195 middle-aged people (published last year in the Journal of the American Dietetic Association), some supplement users had intakes of certain nutrients that exceeded tolerable upper intake levels (ULs)-guidelines set by the Institute of Medicine's (IOM) Food and Nutrition Board to help protect consumers from the potential adverse effects associated with high intakes. Eighteen percent surpassed the tolerable upper intake level for niacin (high doses can cause flushed, itchy skin). Nearly 5 percent exceeded the UL for magnesium (too much from supplemental sources may cause diarrhea). Three percent exceeded the upper limit for vitamin C (excessive amounts may bring about gastrointestinal distress).

Whether adverse effects actually occurred, the scientists aren't sure, says Sujata L. Archer, Ph.D., R.D., the study's lead author and a research assistant professor at the Feinberg School of Medicine at Northwestern University in Chicago. "These upper limits were established to help consumers monitor excessive intakes of nutrients. Exceeding them does not always result in adverse effects."

Yet it can-and does. It's been shown that too much vitamin D can harm the kidneys, and high doses of vitamin A may damage the liver and nerves. Excessive iron may increase risk of vascular disease and cancer. In high doses, folic acid, a water-soluble B vitamin, may mask the symptoms of a vitamin B12 deficiency-and too little B12 can cause permanent neurological damage.

But unless you're consuming nutrient doses well beyond the recommended amounts, you're unlikely to hit upper levels, says Maret Traber, Ph.D., a vitamin E expert and professor of nutrition at Oregon State University in Corvallis: "It's when people decide to take handfuls of different things, or consume gobs of one nutrient, that they get into trouble." Indeed, in Archer's 2005 study in the Journal of the American Dietetic Association, subjects who exceeded upper intake levels took single nutrient supplements-often on top of a multivitamin/mineral.

The power of food

One might argue that you could just as easily overdose on nutrients by consuming whole foods. Possible, sure-but highly improbable. Exceeding the upper intake level for vitamin C would require eating 24 oranges in as many hours-for days and days. (For most vitamins and minerals, upper levels are based upon chronic daily intake, not a few days of overshooting.) For calcium, you'd need to guzzle eight cups of milk. Even then, it's unlikely you'd suffer side effects. "There's never been a case of calcium intoxication from food," says Robert P. Heaney, M.D., a calcium expert and professor of medicine at Creighton University in Omaha, Nebraska. "Farm workers in the 1930s could consume a gallon and a half of milk a day without trouble. Most of what we know about calcium toxicity comes from supplements."

Occasionally, eating lots of carrots, sweet potatoes and leafy greens, which are rich in beta carotene, can cause the skin to yellow. Beta carotene is the biological precursor to vitamin A, and when intake is high, less is converted and the rest is stored just under the skin. The effect may be alarming (people often think it's jaundice, a symptom of liver disease), but it's considered harmless, and goes away when you vary your vegetable choices. Plus, it's not all that common: "In the 12 years I've been a nutritionist I've seen two people whose skin turned yellow because they were eating too many carrots," says Schupp.

In food, nutrients interact with each other in ways they don't in a high-dose supplement, often putting the brakes on an "overdose" of a nutrient before it can cause any adverse effects. Calcium and iron compete for absorption; so do copper and zinc. Other food components (including oxalates, compounds in leafy greens) bind nutrients, making them unavailable. Such interactions are factored into the recommended intakes, which assume you get most of your nutrients from food.

Recommended intakes for nutrients, for the most part, have been extrapolated from data that show what foods, in what amounts, have been keeping Americans healthy. That's why it is so important to meet your nutrient needs with food first. Doing so also ensures you reap the benefits of other components (fiber, phytochemicals, healthy fats) and the synergistic effects of nutrients. While some nutrients limit each other's absorption, others combine to offer nutrition gains greater than the sum of their respective benefits. For example, vitamin E is better absorbed with fat, which is why sources of healthy fats like nuts, seeds and cooking oils are good choices for getting vitamin E.

The state of a new science

At present, the state of science on vitamin and mineral supplements may feel unsatisfyingly inconclusive. As the relatively new field of nutrition evolves, confusing claims will keep coming: Calcium may help you to lose weight. (Debatable but, some say, yes.) Vitamin K may help prevent osteoporosis. (Likely, according to recent research.) Newly discovered "utopia-phenol" erases wrinkles, smoothes cellulite and enhances sexual prowess. (Now wouldn't that be nice?) Over time, some preliminary findings will be confirmed in clinical trials and, eventually, get incorporated into nutrition recommendations; others will be disproved and go away. (Expect answers slowly: the NIH's Office of Dietary Supplements is funding good research, but its financial resources pale in comparison to the dollars we spend on supplements.)

Meanwhile, get savvy about supplements. When you read about benefits backed by "scientific studies," don't take that as gospel. But don't become a total cynic, either. "Preliminary" studies aren't bunk; it just takes decades to produce conclusive findings.

Maret Traber, the vitamin E expert from Oregon State, suggests that those who are struggling with whether to take supplemental vitamin E (in light of inconclusive research on its benefits) could take a basic multivitamin/mineral supplement that supplies 100 percent of E as well as other nutrients' daily values. By doing so, one forgoes the potential (unproven) benefits of higher doses, but "right now, we just don't know what is a sufficient dose," says Traber. "A multivitamin/mineral is a smarter approach."

Remember, too: supplements should supplement a healthy diet, not stand in for nutrient-rich foods. Does rinsing with mouthwash give you license to toss your toothbrush? (Run that one by your dentist.) And before adding in pills or fortified foods, assess your diet: you may be doing better than you think, says Schupp. A registered dietitian (find one at can help you evaluate your eating habits and decide upon the best approach for meeting your needs.

Which is exactly what Schupp did for her client. "When she first came in, she said there was no way she could meet her needs without a supplement," says Schupp. To show her a well-planned diet could provide adequate calcium, Schupp outlined options that included a dairy serving at every meal: breakfast might be yogurt and granola, or whole-grain cereal with skim milk; lunch, a slice of pizza or a sandwich with a slice of Swiss cheese. Schupp emphasized that even snacks, such as string cheese and skim lattes, contributed good amounts of calcium to her overall intake. On days she didn't get it all in, she popped a calcium chew. "She used them only when she fell short, which is how they should be used," says Schupp. "People are surprised by how easy it can be."

Senior Editor Nicci Micco has a master's degree in nutrition and food science.

December 2006