Vitamins and Supplements: Do They Work?
Health & Wellness - Katherine Hobson
Late in October, 2008, just before his 65th birthday, Robert Marks got a phone call: Stop the pills.
For more than a decade, the retired Lutheran minister from Grapeville, Pennsylvania, had been among more than 35,000 men enrolled in SELECT, a clinical trial designed to see whether taking selenium and vitamin E might help prevent prostate cancer.
But as a letter following up the call explained, not only was the answer "no," but vitamin E apparently increased the chance of prostate cancer, if very slightly, and selenium seemed to raise the risk of diabetes.
The news was another blow in the general battering of vitamin and mineral supplements as weapons in fending off chronic and age-related diseases like cancer and heart disease.
In November, 2008, researchers from the Physicians' Health Study-II reported that neither vitamin E nor vitamin C reduced the odds of major cardiovascular problems. A few days later, researchers said that more data from the study showed those vitamins didn't help stave off cancer, either. And another recent study found that supplemental B vitamins, including folic acid, didn't lower the risk of breast or other cancers.
Americans are amply fed and, for the most part, well nourished.
Because much of our food is fortified with nutrients, once common deficiency diseases such as scurvy and rickets (caused by a lack of vitamin C and D, respectively) have nearly disappeared in this and other developed countries. Researchers generally believe that with a few exceptions, like pregnant women or the elderly, most people don't need supplements.
But if bottles of vitamins and nutritional supplements line your medicine cabinet shelves, hold off before going completely cold turkey.
Some researchers maintain that the diets of many Americans still fall short on several essential nutrients--not enough to cause those debilitating deficiency diseases, but perhaps enough to miss out on their benefits without extra help from supplements. While experts say you should be skeptical of most claims about the disease-preventing power of vitamins and minerals, some evidence does support taking a few as a hedge.
What follows is the current thinking, pro and con, on some key supplements that are both popular and well studied.
Millions of people pop a multivitamin every day with little evidence that it does any good.
The U.S. Preventive Services Task Force neither recommends nor advises against multivitamins (or other supplements) for preventing cancer or cardiovascular disease.
Yet many researchers say a multivitamin has a role as "a very inexpensive insurance policy," says David Schardt, senior nutritionist at the Center for Science in the Public Interest, Washington, D.C.
There's no need for anything fancy that claims "heart health" or "prostate health" benefits, he says; an inexpensive, basic brand is fine. Harvard Men's Health Watch newsletter editor Harvey Simon, who earlier this year recommended against multivitamins, says his concerns have recently eased.
His chief worry was that on top of already fortified foods, the folate in a multi could spur cancer. But a study since then showed that cancer was not increased, at least in a group of women at risk for heart problems who were given folic acid supplements.
CALCIUM AND VITAMIN D
Extra calcium to protect bone health is safe and routinely prescribed for womenwho get too little from food. And consensus is building that Americans get too little vitamin D, which promotes calcium uptake. It is produced by sun-exposed skin and is difficult to get from unfortified foods--fatty fish are the only major food source. Studies suggest vitamin D also may help fend off cancer and ward off infections.
Researchers are hungry for more evidence.
"We really need to do the studies," says Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
The Institute of Medicine has announced it will review the daily recommended dietary allowance of vitamin D, now from 200 to 600 international units depending on age, gender, and race. Experts put the high end anywhere from 800 IU to 2,000 IU a day. The IOM review is due in early 2010. Until then, while the benefits are unproven, adding 1,000 IU of vitamin D won't likely hurt and could help, especially for people who don't get much sun.
The evidence for the worth of the omega-3 fatty acids in fish oil, especially for heart-related conditions, continues to pile up.
In August, a study in the Lancet online found a slightly lower rate of deaths and hospitalizations in heart-failure patients who took a daily 1,000-milligram fish oil supplement.
The American Heart Association recommends fish oil supplements for those at high risk of a heart attack. Simon, no fan of nutrients in pill form, says that, for those with heart risks who don't eat fatty fish like tuna and salmon twice a week, adding 1,000 mg or so is a good idea.
The glowing promise of antioxidants, by contrast, remains elusive.
These substances, among them selenium and vitamins A, C, and E, are believed to help sop up molecules called free radicals. These react with other molecules in the body and promote oxidative damage--another name for cellular wear and tear.
"There's a lot of data supporting the idea that oxidation, over time, has a role in chronic illnesses," says J. Michael Gaziano, a cardiologist with Brigham and Women's Hospital and VA Boston Healthcare System and coauthor of the recent Physicians' Health Study-II papers.
Many observational studies of people who gobble antioxidant-laden fruits and veggies or supplements suggest they lower the risk of some forms of heart disease and cancer. Most clinical trials, however, do not support this. Some research, in fact, has shown that supplemental beta carotene, another antioxidant, may actually increase the risk of lung cancer among smokers. Vitamin E may do the same. And cancer patients shouldn't add more vitamin C than the amount in a multi; research suggests that too much of the vitamin helps cancer cells withstand treatment.
Supplement supporters argue that the observational studies should be taken seriously. But one logical explanation for their results is that people who eat fruits and veggies or take antioxidant supplements may eat better diets overall, have access to better medical care, and get exercise. Or, says Alice Lichtenstein, professor of nutrition science and policy at Tufts University's Friedman School of Nutrition, such people could appear to be healthier because they presumably are eating smaller amounts of meat and processed foods--and therefore are likely to be leaner.
Before making claims about any nutrient, "we need to step back and look at the basic biology and chemistry," says Cynthia Thomson, associate professor in the University of Arizona department of nutritional sciences. As Lichtenstein notes, perhaps we're assuming that a particular nutrient in a carrot, say, is key when really it's one of a thousand substances that are all working together.
Researchers are still studying whether supplemental antioxidants might slow the progression of age-related macular degeneration and perhaps prevent noise-related hearing loss. But "no doctor would recommend them for the prevention of cancer, of cardiovascular disease, or of dementia," says Simon.
WHAT ABOUT YOU?
Nutritional profiles are not all the same.
Recommended intake varies by age, gender, and even race.
And genetic differences mean everyone utilizes or responds to vitamins differently, says K. Simon Yeung, a research pharmacist in the Integrative Medicine Service at Memorial Sloan-Kettering Cancer Center, New York, NY.
Eating preferences, such as a low-fat or vegetarian diet, will alter the mix of nutrients taken in.
Moreover, lab tests that analyze the nutrients in your system and indicate which ones might need boosting or trimming are, with a few exceptions, not readily available and not often performed.
"You can get your cholesterol checked, but not your niacin levels," says Thomson. However, keeping tabs on your dining habits for a few days at MyPyramidTracker, a U.S. Department of Agriculture tool, will give you a sense of whether you're on the right course.
Lichtenstein worries that supplements give Americans license to continue their unhealthful ways so long as they pop a pill after the steak and hot fudge sundae. Diet is still the best source of nutrients. Adding supplements--or fruits and veggies, for that matter--to a high-calorie diet is not going to work magic. Good health begins with physical activity and a balanced diet that is heavy on fruits, veggies, whole grains, "good" fats, and fish and light on red meat, "bad" fats, and processed food--and not too high in calories.
"Nature," says the ACS's Lichtenfeld, "is probably better than our manufacturers."
More Health Watch Articles
(c) 2009 U.S. News and World Report