Vitamin supplements: Hype, hope or harm?

Consumer enthusiasm for supplements is overwhelming, with sales of all supplements, especially vitamins, enjoying a rapid, robust increase in the last 15-20 years, especially in developed countries. In the US, for example, national nutrition surveys from 2003-2006 showed that 54 percent of adults used one or more dietary supplements. Multivitamins are the most common, used by 40 percent of men and women.

Doctors are on board as well: Of 900 physicians recently surveyed, 51 percent said they regularly took dietary supplements, while 79 percent said they have recommended supplements to patients. Indeed, the rising popularity of dietary supplements fuels a booming business. Nutrition Business Journal reports that Americans spent a staggering $29.9 billion on dietary supplements of all types in 2009.

What's powering its popularity?

How did vitamin supplements take such a strong hold on our hearts and pocketbooks? There are likely several reasons. People are now exposed to more nutrition messages than ever before, thanks to public health campaigns and greater media attention. For industry, the temptation to inflate health claims looms larger. For consumers, the promise of a simple pill solution to health worries is irresistible.

"Supplements are vulnerable to people latching onto the process early on, even before the science has played out," says Howard Sesso, ScD, associate epidemiologist at Brigham and Women's Hospital in Boston. "This presents a unique challenge to research on supplements."

What the science says

Vitamin supplements bask in a health halo. This stems in part from research showing that people who eat a diet high in fruits and vegetables — rich sources of vitamins — have less risk for heart disease and cancer than those who eat less produce. What's troubling is that although observational studies (designed to track trends between supplement use and disease) show promising health effects, when high-dose supplements are tested in controlled trials (designed to study causation between supplements and disease), the apparent benefits disappear.

Why the mismatch? Perhaps the disease-nutrient relationship is simply too complex for one pill to solve. Here's a recap of the research, and an overview of the harm, hype or hope of vitamin supplements for chronic disease.

• Vitamin E and heart disease: Potential harm

Hope was high in the 1980s, after observational studies and small interventional trials showed that this antioxidant vitamin could reduce heart disease risk by protecting LDL cholesterol (the bad cholesterol) from oxidation (the process contributing to heart harm). Optimism deflated after large clinical trials using high-dose supplements reportedly found no benefit. Later, research noted vitamin E doses above 400 IU per day (17 times greater than recommended doses) actually increased mortality.

• Vitamin A/beta-carotene and lung cancer: Harm

In a similar study, initial observation linked high intake of dietary beta-carotene (a precursor to vitamin A), with reduced risk of lung cancer. Then large clinical trials using high-dose supplements found no benefit in lung-cancer prevention — and even increased risk in smokers. Later, scientists at Tufts University's Human Nutrition Research Center on Aging (HNRCA) conducted similar studies in ferrets, and discovered that only low doses of beta-carotene (like amounts naturally found in food) can weakly protect against lung cancer.

• B vitamins and Alzheimer's: Hype

Some adults with Alzheimer's disease have low vitamin B12 levels, a common deficiency in later life due to decreased absorption of the vitamin. Vitamin B12 supplements have been given to people with and without cognitive decline, but with disappointing results. In 2010, the Cochrane Collaboration, an international consortium of scientists, summed up the existing evidence saying "supplementation with vitamin B12 does not prevent or slow progression of the disease among those who already have Alzheimer's."

• Folic acid and heart disease: Hype — for now

Epidemiology in the 1980s indicated that B vitamins such as folic acid could lower homocysteine, an amino acid that when elevated is thought to increase risk of heart disease. But clinical trials using folate supplements showed no effect on heart disease, cancer or mortality. Says nutritional scientist Dr. Paul Jacques, "No one understood the mechanism between homocysteine and heart disease. Also the clinical trials were done in high-risk people who already had the disease, and probably were not designed to truly test the hypothesis. I think this question of B vitamin supplements, homocysteine, and heart disease is still up in the air."

• Vitamin D and heart disease, cancer, diabetes: Hype — for now

Vitamin D is essential to many cellular functions, and vitamin D deficiency has been observed in many chronic-disease states. But it is too early to say if supplements can prevent chronic-disease states. Sesso comments, "We are in an upward trajectory phase; the vitamin D story may be a rehash of vitamin E where initial promise was not corroborated by large clinical trials. With vitamin E, we initially thought, 'How could vitamin E not do good?' Many feel the same way about vitamin D now, but definitive trials have yet to be completed." Sparse intervention trials and disagreement on appropriate dosages make recommendations difficult at this time.

• Vitamin D and osteoporosis: Hope

For those at risk of osteoporosis, and who cannot get enough vitamin D from sun exposure and food, there is encouraging evidence that supplements can increase bone mineral density and decrease fractures. Precise vitamin advice is blurry, however, since vitamin D status differs across individual skin tone and sun exposure. And remember that optimal bone health requires vitamin D and calcium.

• Antioxidant vitamins and age-related macular degeneration: Hope

A 2006 US National Institutes of Health (NIH) report cited the use of antioxidant vitamins C and E, along with beta-carotene and zinc, to prevent age-related macular degeneration (AMD) in those at high risk as one of only three cases in which the scientific evidence strongly supports a protective benefit for supplementation. (The others were folic acid for preventing birth defects and vitamin D and calcium against osteoporosis.) Research continues on the best formulation to fight this leading cause of blindness among older people.

• Multivitamins and chronic disease: Hype

The benefit of multivitamins for chronic disease has been extensively debated. In the 2006 report, the NIH stated, "The present evidence is insufficient to recommend either for or against the use of multivitamins and multiminerals by the public to prevent chronic disease." Supplement advocates in the US, such as Steven Mister, president and CEO of the Council for Responsible Nutrition trade group, argue, "The NIH did not look at contribution to overall well-being. A multivitamin is a good insurance policy; it fills in the nutritional gaps." The bottom line: While multivitamins have not been found to do any harm, the majority of scientific evidence has failed to demonstrate any benefit against heart disease, cancer or overall mortality.

Food or Pills?

Perhaps, future generations can pop, swish, and swallow individualized vitamin prescriptions, tailored for personalized disease prevention. But in 2012, the best advice is to maximize vitamins from whole foods (see table on Page D-1). A varied diet of fruits, vegetables, whole grains, and lean proteins will supply an adequate amount of vitamins for the average healthy person.

Dee Sandquist, MS, RD, spokesperson for the American Dietetic Association, says, "The choice for vitamin supplements depends on a lot of factors, such as the ability to eat a variety of foods, money to buy food, access to a food store." In addition, certain life stages or dietary patterns may warrant specific vitamin supplements. Consult your doctor or nutritionist to discuss your personal dietary needs.

An unfinished story

In the late 1700s, Francois Magendie, a French surgeon and one of the earliest nutrition pioneers, prophesized, "Nutrition has often been the subject of conjectures and ingenious hypothesis — but our actual knowledge is so insufficient that it's only used to try to satisfy our imagination. If we could arrive at some more exact facts, they could well have applications in medicine."

More than 200 years later, our knowledge of nutrition and vitamins remains insufficient, especially for today's most pressing concerns of chronic disease. Fortunately, nutrition scientists aim to avoid mere "conjecture and ingenious hypotheses" through ongoing vitamin research. In return, the media and the public can exercise patience with the research process, never counting on any single vitamin as a "magic bullet" for health.