Last reviewed by Faculty of Harvard Medical School on February 25, 2010
By Harvey B. Simon, M.D.
Harvard Medical School
Dietary supplements, which include vitamin, mineral and herbal products, come under a set of U.S. Food and Drug Administration (FDA) regulations called the Dietary Supplement Health and Education Act of 1994. They're different than the regulations that cover "conventional" foods and prescription and over-the-counter drugs.
Under these regulations the government has little control over the purity, potency, safety, or effectiveness of supplements. Makers of dietary supplements don't have to get FDA approval before selling them. As a result, the supplement industry has been able to hype their products with little need to prove their claims.
Not surprisingly, supplements have become wildly popular. According to recent estimates, about 20% of all American adults take herbal supplements on a regular basis, and over 25% take at least one vitamin.
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Studying What Supplements Can and Can't Do
In most cases, scientific investigations of supplements start with observational studies. Researchers compare the health of folks who take a particular supplement with the health of people who don't take the supplement. It's an important effort, but the results can be misleading because they may not account for subtle but important differences between the groups. And observational studies can never establish cause-and-effect relationships.
A more accurate study is a randomized clinical trial. Volunteers are assigned by chance to take either the supplement or an identical-looking placebo ("dummy pill") while researchers track their health. In the best studies, neither the volunteers nor the researchers know who is getting the real thing until the code is broken at the end of the trial.
Randomized clinical trials have opened our eyes to what supplements can and can't do. Unfortunately, most of what we see is discouraging. Here's a quick scorecard on popular supplements as of 2007.
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Antioxidants
Vitamins E, A, C and beta-carotene were favorite supplements during the 1980s and early 1990s when laboratory, animal, and observational studies suggested they could protect against coronary artery disease. But in careful studies since then, they have not shown any benefit. In fact, vitamin E may boost the risk of respiratory infections; even moderate doses of vitamin A can increase the risk of fractures; and beta-carotene increases the risk of lung cancer in male smokers. Antioxidants are no longer recommended.
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Calcium
All the vitamin D in the world won't protect your bones unless you get enough calcium. Ideally, calcium should come from your diet. Most of us, however, don't eat enough dairy products and other calcium-rich foods. The Recommended Daily Allowance (RDA) for calcium is 1,000 mg for people under age 50 and 1,200 mg for people age 50 and older. If your diet falls short, supplements make sense. Calcium carbonate and calcium citrate are the best forms of calcium to take because they're absorbed the best. Men should limit themselves to the RDA since some evidence suggests very high levels may increase the risk of prostate cancer.
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Chromium
Although this mineral is heavily promoted for weight loss, it won't help you shed pounds. Chromium may help boost HDL ("good") cholesterol levels, but the evidence is mixed and preliminary. It's not recommended for routine use.
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Fiber
Most people think fiber supplements are just for treating constipation. But a high fiber intake has many potential health benefits, ranging from heart disease and obesity to hernias and varicose veins. The Institute of Medicine recommends 38 grams of fiber a day for men younger than age 50 and 30 grams a day for older men. Whole grains, fruits, vegetables, nuts, and seeds are the best sources of fiber, but many people need fiber supplements to meet these goals.
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Fish Oil
For years, doctors have known that eating fish protects people from heart disease and stroke. A major European randomized clinical trial showed that fish oil supplements work, too. As a result of this research, the American Heart Association now recommends 1,000 mg of fish oil a day for people with coronary artery disease. People with major cardiac risk factors such as high blood pressure, abnormal cholesterol levels, and diabetes can also benefit from taking fish oil supplements. People who eat fish regularly may not benefit from extra fish oil. If you decide to take fish oil, don't choose fish liver oil, which has too much vitamin A.
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Folic Acid
Although this B vitamin is clearly important for women who are pregnant or planning to become pregnant, supplements have not lived up to the hope that they might reduce the risk of heart disease, stroke, and memory loss. A good diet can provide what you need, and a suitable multivitamin offers insurance.
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Glucosamine
It may reduce the pain of arthritis for some people, but it’s certainly not an "arthritis cure." With or without condroitin sulfate, glucosamine may be worth a try for some patients with arthritis pain.
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Iron
Iron supplementation is not recommended for healthy men.
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Multivitamins
There is no clear evidence that a daily multivitamin is beneficial. But most provide 400 IU of vitamin D along with B vitamins, which may provide a bit of nutritional insurance. Don't waste your money on "high-potency" or "all natural" multivitamins. While some experts recommend multivitamins that provide extra amounts of certain vitamins, exceeding the RDA for vitamin A can do more harm than good.
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Niacin
In very high doses, niacin improves cholesterol levels, but it can also have major side effects. Even though niacin is available over-the-counter, it's best to use it under a doctor's supervision.
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Selenium
A randomized clinical trial found that 200 micrograms a day appears to reduce a man's risk of prostate cancer. It's a reasonable supplement for men to take, but more research is needed to confirm the prostate-cancer link.
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St. Johns Wort
This herb may improve symptoms of mild to moderate depression, but it's not a substitute for the medical treatment of severe depression.
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Vitamin D
Vitamin D is produced the old-fashioned way, when our skin is exposed to adequate sunshine. But many Americans have become deficient in "the sunshine vitamin" because our workplace has shifted from the farm to the office and, we use sunscreens to reduce the risk of skin cancer and wrinkles. Older adults, patients with chronic illnesses, and people of color are at particular risk because they get less ultraviolet energy from sunlight.
Vitamin D helps our bodies absorb calcium from the intestines. That's why it's so important for healthy bones. There's also preliminary evidence that good levels of vitamin D may help reduce the risk of prostate cancer and other cancers as well as some neuromuscular problems that can cause falls.
Current guidelines call for 200 IU (international units) a day if you're under age 50, 400 IU a day from ages 51 to 70, and 600 IU a day for people over age 70. But many experts recommend 800 IU (or even 1000 IU) a day. Daily doses up to 2,000 IU are considered safe, but more can be toxic.
It's very hard to get the vitamin D you need from your diet. Oily fish and fortified dairy products are the only good food sources. So vitamin D supplements make good sense.
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Save Your Money on These
I don't recommend the following supplements because they have failed careful clinical trials or the evidence behind them is inconclusive:
- Zinc for preventing colds or shortening cold symptoms
- Echinacea for treating respiratory infections
- Saw palmetto for an enlarged prostate gland or prostate cancer
- Ginseng for reducing fatigue and improving concentration
- Ginkgo for improving mental alertness and memory
- Yohimbine for erectile dysfunction
- DHEA for anti-aging, memory loss, sexual potency, bone density and obesity
It's easy to see why supplements are so appealing. But good health doesn't come in a bottle. A few simple supplements may help men stay healthy, but they should never be misused a substitutes for a good diet, regular exercise, and good medical care.
Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.
