Special Dietary Needs Populations

• All women of childbearing age should take 400 micrograms of folic acid to prevent neural tube birth defects.Jupiterimages/Photos.com/Getty Images
  
  However, the FDA does state multivitamins can benefit population segments with special nutritional requirements. Pregnant and other child bearing-age women need folic acid to prevent birth defects, iron to oxygenate the blood and calcium to support bones. People on restricted diets or those with nutrient-depleting illnesses, such as diabetes, cancer or gastro-intestinal disorders, should take the antioxidants vitamins C and E. Vegetarians should supplement with calcium, vitamin D, iron and vitamin B12 unless they totally understand how to get all these nutrients from foods.
  
  

Recommended Daily Allowances

• The safest source of vitamin A comes from plant sources (beta-carotene).Jupiterimages/Creatas/Getty Images
  
  There are 13 essential vitamins: A, C, D, E, K and the B vitamins (thiamine, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, vitamin B-12 and folate). The Joslin Diabetes Center, a Harvard Medical School affiliate, recommends picking a multivitamin with no more than 100 to 150 percent of the daily value for the listed vitamins and minerals, with at least 20 listed. It should contain 400 mg of folic acid and 400 IU of vitamin D. Look for a maximum of 5,000 international units (IU) of vitamin A, primarily from beta-carotene sources such as carrots. New guidelines for vitamin D and calcium were released in late 2010, so some brands may not yet reflect the new guidelines. Most store-brand vitamins are fine, according to Consumer Reports, but watch out for discount store brands; many have been found to be over-reporting nutrient levels.
  
  

Contraindications

• The FDA recommends you talk to your doctor before taking multivitamins. Some supplements interact badly with pharmaceuticals and can have unwanted effects pre- or post-surgery, such as excess bleeding with vitamin E. Men don't need any iron in their supplements, unlike women. Never give adult multivitamins to children; their nutritional needs are different those of adults. Out-of-date vitamins lose their effectiveness and oils become rancid, so check dates. Adverse effects from vitamins should be reported to the FDA and your doctor as soon as possible.
  
  

Safety and Purity

• Some vitamins have recommended daily limits set by the National Academy of Sciences.Jupiterimages/Photos.com/Getty Images
  
  Just because a multivitamin company claims certain levels for nutrients doesn't make it true, according to Consumer Labs, LLC. The company provides independent test results for more than 350 brands of vitamins to help consumers identify best quality products. It publishes an annual Survey of Vitamin & Supplement Users for its paid membership. Although low-dose vitamins may only waste your money, according to Vasilios Frankos, Ph.D., director of FDA's Division of Dietary Supplement Programs, "Vitamins are not dangerous unless you get too much of them, especially fat-soluble ones." For some vitamins and minerals, the National Academy of Sciences has established upper daily limits of intake (ULs) it recommends not to exceed.