Vitamins and Minerals
Vitamins and minerals are essential substances that our bodies need to develop and function normally. There are 14 known vitamins: vitamins A, C, D, E, and K, choline, and the vitamins (thiamin, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, vitamin B12, and folate/folic acid). Fifteen minerals are essential for health: calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, zinc, iodine, chromium, copper, fluoride, molybdenum, manganese, and selenium. According to the Dietary Guidelines for Americans 2010, it is recommended that people should aim to meet their nutrient requirements through a healthy eating pattern that includes nutrient-dense forms of foods. Sufficient evidence is not currently available to support a recommendation for or against the use of multivitamin and mineral supplements.
Multivitamins/multiminerals (MVMs) are the most frequently used dietary supplements, with approximately 40 percent of American adults taking them. MVMs cannot take the place of eating a variety of foods that are important to a healthy diet. Foods provide more than vitamins and minerals. Many foods also have fiber and other substances that can provide health benefits. However, some people who don’t get enough vitamins and minerals from food alone, or who have certain medical conditions or problems, might benefit from taking one or more of these nutrients found in single-nutrient supplements or in MVMs. However, evidence to support their use for overall health or disease prevention in the general population remains limited.
- Most individuals can get all of the vitamins and minerals necessary through a healthy eating pattern of nutrient-dense foods. The Dietary Guidelines for Americans 2010 provides recommendations for specific for specific populations, including women capable of becoming pregnant, women who are pregnant or breastfeeding, and people ages 50 and over.
- Taking a MVM increases overall nutrient intake and helps some people get the recommended amounts of vitamins and minerals when they cannot or do not obtain them from food alone. But taking an MVM can also raise the chances of getting too much of some nutrients, like iron, vitamin A, zinc, niacin, and folic acid, especially when a person takes more than a basic, once-daily product that provides one hundred percent of the Daily Value (DV) of nutrients.
- Keep in mind that there is no standard or regulatory definition for MVMs, or any dietary supplement, as to what nutrients they must contain or at what levels. Manufacturers choose which vitamins, minerals, and other ingredients, as well as their amounts, to include in their products. Simply stated, dietary supplements are not required to be standardized in the United States. However, they are required to bear a Supplement Facts label and ingredients depicting what is in the product.
- Read the Supplement Facts label to identify the MVMs contained in your supplement product. Be sure to check the percent daily value (%DV) to see what your proportion of your daily allotment you are getting.
- People with healthier diets and lifestyles are more likely to take dietary supplements, making it hard to identify any benefits from the use of MVMs. There is no convincing evidence that MVMs help prevent chronic disease.
- Taking a daily dose of a basic MVM is unlikely to pose a health risk for most people. However, if you consume fortified foods and beverages (such as cereals or drinks with added vitamins and minerals) along with dietary supplement products, you should make sure that your total intake of vitamins and minerals is not more than the safe upper limits for any nutrients. One could read the Nutrition Facts label of a cereal box as well as the Supplement Facts label of MVM to see if the level far exceeds 100% Daily Value. For more information on safe upper levels of nutrients, visit the NIH Office of Dietary Supplements at: ods.od.nih.gov/factsheets/list-all/.
- Smokers, and possibly former smokers, should avoid MVM products that provide more than 100% of the Daily Value for vitamin A (either as preformed retinol or beta-carotene or some combination of the two) because two studies have linked high supplemental doses of these nutrients with an increased risk of lung cancer in smokers.
- Taking excess amounts of vitamin A (preformed retinol form, not as beta-carotene) during pregnancy has been shown to increase the risk of birth defects in infants.
- Except in cases of iron deficiency or inadequacy, or unless a physician recommends otherwise, adult males and postmenopausal women should avoid using iron supplements or MVMs containing more than their Recommended Daily Allowance for iron (8 mg/day). Iron supplements may be recommended for women of childbearing age, pregnant women, preterm infants, older infants, and teenage girls because they are at greater risk of developing deficiency. Yet, iron supplements are a leading cause of poisoning in young children, so parents and guardians should keep iron-containing supplements out of the reach of children.
- MVMs providing nutrients at or up to 100% of the DV do not typically interact with medications, with one important exception: If you take medicine to reduce blood clotting, such as warfarin (Coumadin® and other brand names), talk to your health care provider before taking any MVM or dietary supplement with vitamin K. Vitamin K lowers the effectiveness of the medication, and doctors base the medicine dose partly on the amount of vitamin K a patient usually consumes in foods and supplements combined.