More than one-third of Americans take vitamin and mineral supplements daily. Vitamin-mineral supplements fall under the category of a dietary supplement. In addition to vitamins and minerals, a dietary supplement may contain:

• a vitamin, a mineral, an herb or other botanical, or an amino acid
• a dietary substance for use in supplementing the diet by increasing total dietary intake
• a concentrate, metabolite, or constituent extract
• a combination of any of the above ingredients mentioned.

According to the Office of Dietary Supplements of the National Institutes of Health, multivitamin and mineral (MVM) supplements account for about 20% of dietary supplement purchases. In 2009, U.S. sales of all dietary supplements totaled an estimated $26.9 billion. This includes $11.3 billion for all vitamin- and mineral-containing supplements, with $4.8 billion spent on MVM supplements. Among single vitamin or mineral supplements, vitamins D and E are popular, as are the minerals calcium and iron. Vitamin C is one of the most commonly used supplements, although the amount needed to prevent scurvy is quite small (10 mg/day).

Despite the large sums of money consumers spend on dietary supplements, many don’t know much about these products. Typically, these supplements are self-prescribed. What’s more, their use remains largely unregulated, underscoring the need for better consumer education.

In 1994, Congress passed the Dietary Health and Education Act to help consumers make informed decisions about nutritional supplements. The supplement industry spends a great deal of money trying to influence both regulators and consumers. Manufacturers don’t need to prove their supplements are safe or effective; nor do they need approval from the Food and Drug Administration (FDA) to put their products on the market. FDA investigates (and subsequently may decide to pull a supplement off the market) only when it receives enough reports of ill effects.

Who takes MVM supplements?

An analysis by the National Health and Nutrition Examination Survey (NHANES) of data collected from 2003 to 2006 found 33% of the U.S. population ages 1 year and older took an MVM supplement in a given month. Females (36%) were more likely to take one than males (31%). By age 71 or older, 48% of women and 43% of men were taking supplements. (See the box below.)

Why do people take supplements?

People take supplements for varying reasons—to reduce disease risk, to make up for suboptimal nutrient intakes from food, and inability to eat enough food (especially among the elderly). Vegetarians who restrict some important food groups entirely, as well as habitual dieters or people consuming fewer than 1,200 calories/day, also may take supplements.

Today, few Americans suffer classic nutritional deficiencies, such as scurvy, beriberi, or pellagra. For overt deficiencies, a physician may prescribe a therapeutic dose of a particular vitamin or mineral.

Disease risk reduction

Research strongly supports the role of folic acid supplementation in reducing the risk of neural tube defects, such as spina bifida. A pregnant female who previously delivered an infant with a neural tube defect may be prescribed a therapeutic folic acid dose that’s 10 times the normal requirement to reduce the chance of recurrence. To help prevent such defects, females of childbearing age capable of getting pregnant should get least 400 mcg of folic acid daily, either in supplement form or through fortified foods or other foods rich in this nutrient.

Some people also take supplements to reduce other disease risks. For instance, a person with documented coronary artery disease may decide to take fish oil supplements providing 1 g of the omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid. Larger doses (2 g to 4 g) should be monitored by the patient’s physician because they can cause bleeding and other adverse effects.

For persons at risk for osteoporosis, calcium and vitamin D supplements may be indicated. Recommendations for these nutrients are based on age, life stage, or both. The Dietary Reference Intakes Committee of the Institute for Medicine has set a tolerable upper intake (UI) level for these nutrients.

• • For calcium, the UI level is 2,500 mg/day for adults ages 19 to 50.
  • For vitamin D, the UI level is 4,000/day for adults aged 19 to 70.

For vegans (vegetarians who eat an all-plant-based diet), persons with atrophic gastritis, and those who’ve had gastrectomy surgery, vitamin B₁₂ supplementation may be recommended. No UI level for vitamin B₁₂ has been set.

Possible risks of taking MVM supplements

Taking too much of any nutrient can cause toxicity, so be sure to teach patients about the risks of excessive supplementation. For instance, too much vitamin A (in retinol, its preformed form) has been linked to bone defects, including the risk of fractures and osteoporosis. During pregnancy, excessive vitamin A has contributed to birth defects.

In children, toxic vitamin and mineral overdoses are fairly common. Children’s chewable vitamins in multiple colors and flavors and gummy supplements that taste like candy may entice a child to consume unsafe amounts. Ingesting iron-containing supplements is a leading cause of accidental death in young children; as few as five iron tablets containing 200 mg of iron have been known to cause death.

Excess iron supplementation also may harm persons with hemochromatosis, an iron overload disorder that can lead to liver damage, heart disease, and arthritis. Excess iron acts as a pro-oxidant, which can damage tissues and organs.

Also, zinc may interfere with copper metabolism; the UI level is 40 mg/day. In animal studies, copper deficiency has increased blood cholesterol levels and damaged blood vessels.

Be aware that whole foods provide naturally occurring vitamins and minerals, and many food products are fortified with additional nutrients. With the addition of fortified foods comes the risk of getting too much of a nutrient. On its website, the National Institutes of Health’s Office of Dietary Supplements lists UI levels for selected nutrients, as well as dietary reference intakes for all vitamins and minerals according to age, gender, and life stage. (Visit http://ods.od.nih.gov/HealthInformation/nutrientrecommendations.sec.aspx.)

What should nurses teach patients about supplements?

Many nurses are in an excellent position to give patients sound advice about vitamin and mineral supplements. But before you can teach patients, make sure you’re well educated yourself. The Journal of the American Dietetic Association has published a practice paper on dietary supplements that lists reliable resources for evaluating dietary supplement use by patients.

The Internet can be a good resource, too—but only if you use reputable websites. Some websites contain misinformation, possibly leading some people to self-prescribe vitamin and mineral supplements in the belief these may prevent, treat, or cure a disease.

When obtaining the history, ask if the patient takes supplements. If so, find out the types, amounts, and reason for using them. Gather information about the ingredient list on these supplements and look for contraindications to their use. Direct patients to reputable websites for information on drug-nutrient interactions and other contraindications to supplement use. (See the box below.)

Having a collaborative relationship with allied healthcare professionals, such as registered dietitians, provides an evidence-based approach to patient education. If you have limited time or resources to teach patients about vitamin and mineral supplements, consider referring them to a registered dietitian who can conduct a complete nutritional assessment. This assessment may include a comprehensive review of micronutrient requirements.

Catherine R. Heinlein is an assistant professor in the School of Nursing at Azusa Pacific University in Azusa, California.

Selected references

Bailey RL, Gahche JJ, Lentino CV, Dwyer JT, Engel JS, Thomas PR, et al. Dietary supplement use in the United States, 2003-2006. J Nutr. 2011;141(1):261-6.

National Institutes of Health State-of-the-Science Panel. NIH State-of-the-Science Conference Statement: multivitamin/mineral supplements and chronic disease prevention. Am J Clin Nutr. 2007;85(1):257S-64S.

Practice Paper of the American Dietetic Association: dietary supplements. J Am Diet Assoc. 2005;105:3:460-70.

Rolfes SR, Pinna K, Whitney E. Understanding Normal and Clinical Nutrition. 9th ed. Wadsworth Cengage Learning: Belmont, CA; 2011.

Sarubin Fragakis A, Thomson C. The Health Professional’s Guide to Popular Dietary Supplements. 3rd ed. Chicago, IL: American Dietetic Association; 2006.

Wildish, DE. An evidence-based approach for dietitian prescription of multiple vitamins with minerals. J Am Diet Assoc. 2004;104(5):779-86.