Updated May 22, 2008

Choosing a Multivitamin

by Marie Spano, M.S., R.D.

A good diet can supply most if not all of the vitamins and minerals you need. But maintaining such a diet day in and day out can be a challenge, which is why many people take a daily multivitamin–multimineral supplement as a form of insurance. Taking a daily supplement makes particular sense for people who don't eat much, such as people who are following a weight-loss diet. While a supplement can't supply all of what is present in fruits, vegetables, and whole grains, such as fiber and phytochemicals (healthy plant chemicals that may help fight cancer and other diseases), it can help to fill in some of the holes.

The question then is how to choose a supplement that meets your needs. Which vitamins and minerals should it contain, and how much?

What and how much
Most people should look for a supplement that contains 100% Daily Value (%DV) of each of the following vitamins and minerals:

• Vitamin A (preferably in the form of beta-carotene)
• Folic acid
• Niacin
• Vitamin B1 (thiamine)
• Vitamin B2 (riboflavin)
• Vitamin B6
• Vitamin B12
• Vitamin C
• Vitamin D
• Vitamin E
• Copper
• Zinc

Premenopausal women should additionally look for a supplement that contains 100% DV for iron (18 milligrams), but postmenopausal women and men are generally advised to take no more than 8 milligrams of iron daily, and some people may be advised by their physician to take no supplemental iron.

People with diabetes may additionally want to look for a supplement that contains 100% DV for chromium and at least 25% DV for magnesium. (Multivitamins never contain 100% DV for magnesium because it won't fit into a single pill.)

To quickly find a multivitamin–multimineral supplement that contains at least 100% DV of at least two-thirds of the nutrients it contains, look for the words "high potency" on the label. This label term is regulated by the U.S. Food and Drug Administration.

Is more better? Not necessarily. Taking more can be harmful in some instances or just a waste in others. Though many people take extra vitamins and minerals in the hopes of preventing cancer and other chronic diseases, the research is mixed regarding the use of supplemental vitamins and minerals for this purpose.

Some companies sell special supplement formulas targeted toward seniors, women, men, or other particular groups. However, it is up to the company itself to decide what to put in each of those formulas. There is no standard definition or regulation determining what should go into a specialized formula. And some of these targeted formulas may fall short on certain vitamins and minerals, including those especially necessary for the exact age group or sex they are targeting! Before you buy a supplement that claims to meet the needs of a specific group, read the bottle yourself and evaluate whether it really provides what you need.

What the numbers mean
The %DVs found on supplement labels are based on the Dietary Reference Intakes (DRIs) established by the Food and Nutrition Board of the National Academy of Sciences and Health Canada. The DRIs are a set of recommended intakes of nutrients for individuals according to their age and sex and may be stated as recommended dietary allowance (RDA) or adequate intake (AI).

Marie Spano is a registered dietitian and exercise physiologist. She is a freelance writer, consultant, and speaker in the nutrition, fitness, and health industries. In addition, she is a spokesperson for the International Society of Sports Nutrition.

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