By Shira Hirshberg, M.S.
Brigham and Women's Hospital
More people use multivitamins than any other dietary supplement. Thirty-nine percent of the U.S. population took multivitamins from 2003 to 2006. In the United States alone, we spent $4.5 billion on multivitamins in 2007.
Are they worth it? Unfortunately, the jury is still out.
Back to top
A History of the Research
Here's a brief history of milestones in the scientific study of multivitamins.
2006: The National Institutes of Health reviewed the evidence and could not recommend either for or against the use of multivitamins to prevent chronic disease.
2007: A research study in Hawaii showed that multivitamin supplements can reduce nutrient deficiencies by 8%, especially for vitamins A, E, B6 and zinc. A multivitamin was less likely to help people increase their intakes of key nutrients like calcium, magnesium and potassium to the recommended levels. Taking multivitamins resulted in excessive intakes of iron, zinc, vitamin A and niacin for some people.
2009: The Academy of Nutrition and Dietetics published a position paper on supplements. It concluded that multivitamins, when taken regularly, can be an effective way to increase nutrient intakes to recommended levels. However, the best way to promote health and reduce chronic disease risk is to eat a variety of foods. Data suggest that it's the types and amounts of foods people eat, not amounts of individual nutrients, that have a positive effect on our health.
The Women's Health Initiative studied 160,000 post-menopausal women. About 40% of the women in the study used multivitamins. After 8 years, taking multivitamins did not reduce the risk of cancer, heart disease or death.
2011: An epidemiological study showed that multivitamin use was not associated with a decreased diabetes risk.
2012: A review of the current scientific literature could not find evidence of benefit of taking multivitamins. The authors noted that antioxidant supplements, such as beta-carotene, vitamin E and higher doses of vitamin A, seem to increase mortality. The most vitamin A you should have (called the tolerable upper limit) is 300 micrograms RAE or 1,000 IUs. For vitamin E it is 1,000 milligrams or 1,500 IUs. Thirty milligrams of beta-carotene daily has been associated with increased lung cancer and cardiovascular disease.
2012: The first gold-standard study (large-scale, randomized, placebo-controlled trial) tested the benefit of a multivitamin in middle and older-aged male doctors. Daily multivitamin supplementation (Centrum Silver) reduced the total risk of getting cancer by 8%. Taking the multivitamin did not decrease the risk of dying from cancer. Nor did it reduce heart disease risk or overall risk of death.
Back to top
Who Benefits Most from Taking a Multivitamin?
People who have inadequate nutrient intakes are most likely to benefit from a multivitamin. They include:
- Older adults
- Pregnant women
- People who are dependent on alcohol
- Strict vegetarians and vegans
- People who have trouble affording enough food
- People with certain health conditions (cystic fibrosis, HIV/AIDS)
- People who take certain medicines that increase nutrient needs (blood pressure medications, certain types of steroids)
Other people more likely to benefit from a multivitamin are those who have:
- Difficulty swallowing
- A special diet that eliminates whole food groups
- A poor appetite or who eat fewer than 1,200 calories a day
- Roux-en-Y gastric bypass surgery
- Conditions that affect absorption, such as celiac disease, irritable bowel disease or radiation enteritis (inflammation of the small bowel after radiation therapy)
Back to top
Choosing a Multivitamin?
The U.S. Food and Drug Administration does not regulate makers of vitamins and minerals. Consumers should look for USP on the label. It means the product has been tested for how well it dissolves in your body. This affects absorption. You can also do a home test by checking how well your multivitamin dissolves in water. Or choose a major brand, such as Centrum® or One-A-Day®.
Here are some other guidelines to keep in mind when choosing a multivitamin:
- Iron: Men and post-menopausal women should avoid multivitamins with more than 15 milligrams of iron. Child-bearing women may need additional iron.
- Calcium: Adults need about 1,200 milligrams of calcium every day. Each serving of dairy has about 300 milligrams. Most people get about 200 milligrams from other foods. If you don't get enough calcium from your diet, taking a multivitamin with calcium can help you make up the difference.
- Vitamin D: In the summer you can get vitamin D from the sun, but in the winter you'll need this from foods or supplements. To maintain a good vitamin D level during the winter, you need about 1,000 international units (IUs).
- B12: Adults over the age of 50 should look for this in their multivitamin, as the ability to absorb B12 gets worse as you age.
- Folic acid: Women who are trying to get pregnant should look for a multivitamin with this, as it can help prevent birth defects.
- Iodine: Look for 220 micrograms in a prenatal vitamin and 290 micrograms while you are breastfeeding to reduce risk of impaired mental function in your baby.
Back to top
The Bottom Line
More of a nutrient isn't always better. And some are dangerous when taken in large doses.
If you're concerned that you are not getting the vitamins and minerals you need in your diet, you can schedule an appointment with a health professional, such as a registered dietitian. She can create individualized recommendations based on your health needs and current diet. Find a registered dietitian in your area at www.eatright.org.
Shira Hirshberg, M.S. is a dietetic intern at Brigham and Women's Hospital. She graduated with a B.S. in Public Relations from Syracuse University and a M.S. in Nutrition from the University of Rhode Island. She lives in Providence, RI.
Gahche J, Bailey R, Burt V, et al. Dietary supplement use among U.S. adults has increased since NHANES III (1988-1994). NCHS Data Brief. Apr 2011(61):1-8.
2008 Supplement Business Report. San Diego, CA: New Hope Natural Media, Penton Media Inc 2008. Nutrition Business Journal.
NIH State-of-the-Science Conference Statement on Multivitamin/Mineral Supplements and Chronic Disease Prevention. Ann Intern Med. 2006;145:364–371.
Murphy, Suzanne P., et al. Multivitamin-multimineral supplements' effect on total nutrient intake. The American journal of clinical nutrition 2007; 85.1:280S-284S.
Marra, MV and Boyar, AP. Position of the American Dietetic Association: nutrient supplementation. Journal of the American Dietetic Association. 2009; 109.12: 2073.
Neuhouser ML, Wassertheil-Smoller S, Thomson C, et al. Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women's Health Initiative Cohorts. Arch Intern Med. 2009;169(3):294-304. doi:10.1001/archinternmed.2008.540.
Song, Yiqing, et al. Multivitamins, individual vitamin and mineral supplements, and risk of diabetes among older US adults. Diabetes care. 2011; 34.1: 108-114.
Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2102; CD007176.
Dietary Supplements Fact Sheet. http://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/. Accessed June 6, 2013.
Gaziano JM, Sesso HD, Christen WG, et al. Multivitamins in the prevention of cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA. Nov 2012;308(18):1871-1880.
Lonn, Eva M. Multivitamins in Prevention of Cardiovascular Disease: Multivitamins in Cardiovascular Disease Prevention. JAMA: the journal of the American Medical Association. 2012;308.17: 1802-1803.
Puig-Domingo, M., and L. Vila. "The Implications of Iodine and its supplementation during pregnancy in fetal brain development." Current clinical pharmacology. 2012.
Back to top