Your mother made you take them. Many doctors agree. Even the Flintstones seem to endorse them.

But do you really need a multivitamin.”In some cases, they are wildly off,” says Paul Coates, director of the National Institute of Health’s Office of Dietary Supplements. An FDA spokeswoman said the agency is considering revisions. 

There is no standard multivitamin formula. The term applies to any combination of vitamins and minerals in any strength, as long as they are listed on the label. The price was no predictor of quality. Some multivitamins selling for less than 10 cents a day performed better on the tests than those selling for 50 cents or more.

Looking at randomized controlled trials, the gold standard for determining cause-and-effect, an NIH panel in 2007 concluded that “the present evidence is insufficient to recommend either for or against the use of [multivitamins and minerals] by the American public to prevent chronic disease.”

A 2003 U.S. Preventive Services Task Force report found insufficient evidence either for or against taking multivitamins to prevent cancer or cardiovascular disease.

The dietary-supplement trade group says observational studies have shown benefits, including a lower risk of cataracts and colon cancer, and fewer colds.

The consumer-advocacy group Center for Science in the Public Interest has asked the FDA to require warning labels on multivitamins and other supplements for some of these conditions.

The answer is … probably not, although much depends on your age, gender, diet, and health. One thing is certain: A one-size-fits-all multivitamin can’t precisely meet everyone’s needs. People over 50 need extra vitamin B-12, but not as much iron as many multivitamins contain.

Children who take adult multivitamins may be getting too much vitamin A. And many women need a separate supplement to get extra calcium since it’s too bulky to fit into a multivitamin.

No wonder the vitamin aisle is so confusing, as manufacturers tailor products for different population segments. The one-A-Day brand alone offers 14 versions, from Men’s 50+ Advantage to Vitacrave Gummies for kids.

Reading labels can lead to even more confusion. Recommended Dietary Allowances (RDA) for vitamins and minerals, which are set by the independent Institute of Medicine, differ by an individual’s age and gender. But for convenience, the Food and Drug Administration requires dietary supplements to list a single Daily Value, usually the highest needed.

For some people, that’s too high: The RDA for iron, for example, is 8 milligrams for men and postmenopausal women. But the Daily Value on supplement labels is 18 milligrams, the amount recommended for women of childbearing age. What’s more, the Daily Values haven’t been updated since 1968, even though the institute’s recommendations for some vitamins and minerals have changed.

The label may not even exactly match what’s in the bottle. ConsumerLab, a supplement-testing company, reported last week that 10 of 38 multivitamin brands tested contained either more or less of some ingredients than the label indicated.

The Council for Responsible Nutrition, a trade group that represents most multivitamins and other supplement makers, says, “It concerns us anytime ConsumerLab says we don’t meet label claims,” says CRN’s chief executive and president. Steven Mister. “But there is nothing in the report that suggests that consumers are getting levels that will do them harm.” Are multivitamins even necessary? The dietary supplement industry likens them to nutritional insurance—filling in gaps when people don’t eat perfectly balanced meals.

That rationale has helped make multivitamins, introduced in the 1940s, the best-selling dietary supplement, with more than $4.8 billion in sales in 2008, according to Nutrition Business Journal. A third of American adults take them regularly. Use is particularly high among women, children, physicians, the elderly, and people with high incomes, low body-mass indexes, and healthy eating habits, according to government surveys.

Given those traits and demographics, people most likely to benefit from multivitamins—due to unhealthy habits—also are least likely to take them. Conversely, because people who take multivitamins tend to have other healthy habits, it’s difficult to prove what effect multivitamins have, if any, in overall health.

Such studies, though, can’t determine cause and effect, only association. And several large observational trials have come to opposite conclusions. A study in the American Journal of Epidemiology this year that followed 182,000 people in Hawaii and California for 11 years found no association between multivitamin use and deaths from cancer, cardiovascular disease, or any cause.

Compared with over-the-counter and prescription drugs, dietary supplements are lightly regulated. Makers don’t need to demonstrate that they are safe or effective. But there are limits to what they can claim. Ads that use terms such as “support” breast health or mental alertness must note that such statements haven’t been evaluated by the FDA and that the product isn’t intended to diagnose, treat, cure or prevent any disease.

Still, a scientific consensus has emerged that some groups of people do require more of certain nutrients than they are likely to get from food. Women who might become pregnant should get an additional 400 micrograms a day of folic acid, to reduce the risk of serious neurological issues in a fetus that may occur even before a woman knows she is pregnant. People over age 50 should get the recommended 2.4 micrograms of vitamin B-12 from supplements or fortified foods because they become less able to absorb it from food as they age. Vegetarians and vegans also need extra B-12.

Infants who are being breastfed should get 400 International Units (IUs) a day of supplement vitamin D until they are weaned. In fact, most Americans need 600 IUs per day, according to a 2010 report from the Institute of Medicine. People who get minimal sun exposure and don’t consume much salmon or milk also should supplement their Vitamin D.

On the other hand, some people may get too much of certain nutrients, depending on their age and health, particularly if they use the current Daily Values listed on labels as a guide. For example, 100% of the current Daily Value for vitamin A is 5,000 IUs—which is over the Institute of Medicine’s safe upper limit of 2,000 IUs for children and far beyond the RDA for children ages 1 through 3 of just 1,000 IUs. Excess vitamin A can cause headaches, hair loss, visual disturbances, and a possibly increased risk of osteoporosis. And smokers should avoid taking extra beta carotene, which has been linked to increased risk of lung cancer.

Officials at the dietary-supplement trade group say evidence of the need for such warnings is scant, and the upper limit for vitamins is still safe. “That’s not to say that if you cross that threshold, you will have a fatal condition,” says Duffy MacKay, a naturopathic doctor, and CRN vice president.

Given all the complexities, it pays to discuss individual needs with a doctor, dietitian, or other health professional. Some people may find the a la carte approach works best. Others may like the extra “insurance” provided by a multivitamin targeted to their age and sex. Dr. Coates, of the NIH, says based on the best evidence, “If you are taking multivitamins, there is no reason to stop, and if you are not taking them, there is no reason to start. You are unlikely to harm yourself, whatever you’re doing.”

Article Source: Figuring Out Daily Values on Multivitamin Labels.