The world of dietary supplements is getting more and more complicated.
People aren't just taking vitamins and minerals anymore. Now, things like
glucosamine, saw palmetto, black cohosh and ginkgo biloba are crowding onto
shelves beside old standbys like vitamin C, calcium and iron. How do you
sort through it all?
Dietary supplements include a broad range of vitamins, minerals, herbs and other
substances meant to improve upon your diet. They can come as pills,
The U.S. Food and Drug Administration, which regulates dietary supplements,
treats them more like foods than like drugs. Dr. Paul M. Coates, director
of NIH's Office of Dietary Supplements (ODS), says, "Dietary supplements are
generally regarded as safe based on a long history of human use, unless proven
otherwise. By contrast, drugs are not assumed to be safe until extensive
testing has been done to prove their safety."
Supplements can play an important role in your health. Some doctors advise
patients to take a multivitamin-mineral supplement to make sure they're getting
enough of all the nutrients they need. While this may provide some
insurance, Carol Haggans, a consultant with ODS, cautions, "People shouldn't
feel they can make up for an unhealthy diet by taking a multivitamin-mineral
supplement." A combination of all the vitamins and minerals together in
foods provide the greatest health benefit, she says. "In general, if you
eat a healthy diet, you shouldn't need to supplement it with extra nutrients."
However, some people might need more of certain nutrients. Doctors often
advise women of child-bearing age to take folic acid, for example. Many
people don't get enough calcium. According to some surveys, 44% of boys
and 58% of girls age 6-11 don't get enough-and the numbers get even higher as
people age. It's probably best to eat 2-3 servings per day of
calcium-rich foods like dairy products. But if you have trouble eating
dairy products because they upset your stomach and you don't get enough calcium
in other foods, a supplement might help.
Since some supplements may help you, it's easy to go a step farther and think
that taking more would be even better. This can cost a lot and may not
provide the benefit you expect. It can also be risky.
"Almost all of the nutrients have tolerable upper intake levels-the amount it's
recommended you stay under each day," Haggans says. Amounts above these
levels can be toxic. Too much vitamin A, for instance, can cause birth
defects, liver problems, weak bones and nervous system disorders. Too
much calcium can cause kidney problems and block your ability to use other
minerals in your diet.
NIH has several studies under way to look at whether high doses of certain
supplements can prevent disease. For example, NIH's National Cancer
Institute is funding the Selenium and Vitamin E Cancer Prevention Trial
(SELECT) to see if selenium and vitamin E can help prevent prostate
cancer. But this isn't an area you should experiment in by yourself.
Dr. Coates explains that, for the most part, supplement "megadoses" haven't been
tested. "Absence of evidence of harm isn't the same as evidence of
absence of harm," he says. "In many cases we just don't know."
It's not difficult to get high doses of certain nutrients, either.
Breakfast cereals have long been fortified with vitamins and minerals.
Now, many other fortified products are crowding onto grocery shelves as
consumers buy into the idea that more is better. Look at the foods and
supplements you're eating together to make sure that your total intake of any
one nutrient isn't too high. If you're concerned, talk to a health care
provider such as a doctor, pharmacist or registered dietitian or check the
nutrient recommendation information at the ODS web site.
Dietary supplements beyond traditional vitamins and minerals have also become
popular. In one study, about 19%, or 1 out of every 5 people surveyed,
used natural products such as echinacea, ginseng, glucosamine and ginkgo
biloba. But since they're regulated more like foods than drugs, in a lot
of cases we don't know how or even if these supplements work as their
"Be prepared to ask questions," Dr. Coates advises. "These products are
available on drug store shelves, supermarket shelves and vitamin store shelves
in packaging that makes them look like drugs, but they aren't regulated like
drugs. Consumers have to realize that the drug rules don't apply."
Haggans adds, "People assume if it's on the shelf it must be safe and we must
know a lot about it, but that's not necessarily the case."
The National Center for Complementary and Alternative Medicine (NCCAM) takes the
lead at NIH in funding studies of supplements beyond traditional vitamins and
minerals. They now have dozens of studies under way to test their safety
In the meantime, if you're considering taking a supplement, consult with your
health care provider. Some supplements can interfere with other
medications, so have a list ready of all the medications and supplements you're
taking or considering.
If you decide that a particular dietary supplement is right for you, make sure
you're buying a reliable brand. There are independent laboratories that
test supplement products for quality and purity. "There are companies
whose products are made to very high standards," Dr. Coates says, "but that's
not always the case."