LINUS PAULING INSTITUTE RESEARCH REPORT
What to Look for in a Multivitamin Supplement
Jane Higdon, Ph.D.
Why take a multivitamin supplement?
Although it hasn’t been proven that a daily multivitamin supplement containing 100% of the Daily Value of most vitamins and essential minerals will lead to better health for well-nourished people, recent research indicates that several of the nutrients found in standard multivitamin supplements play important roles in preventing chronic diseases like heart disease, cancer, and osteoporosis. A daily multivitamin supplement ensures an adequate intake of several micronutrients that are not always present in the diet in optimal amounts:
Increased folic acid intakes can lower homocysteine levels, and high homocysteine levels are associated with increased risk of cardiovascular diseases and Alzheimer’s disease.
Increased folic acid intake may decrease the risk of some types of cancer, especially in those who drink alcoholic beverages.
Since it is only found in animal products, strict vegetarians also need to get vitamin B12 from a supplement or fortified foods.
Reading supplement labels
Although one would expect the Daily Values (DV) listed on supplement labels to reflect the latest intake recommendations from the U.S. Institute of Medicine, most of them are actually based on outdated recommendations made in 1968.
The latest nutrient intake recommendations from the Institute of Medicine are called Dietary Reference Intakes (DRIs), which have been set for males and females throughout the lifespan. They include the Recommended Dietary Allowance (RDA) as well as the Adequate Intake (AI), which is established for a nutrient when there is insufficient data to calculate an RDA. Supplement labels continue to display the outdated DV. A comparison of the DVs and the DRIs for adults is shown in the table below.
Choosing multivitamin supplements
Most multivitamin supplements contain at least the RDA for folic acid, niacin, pantothenic acid, thiamin, riboflavin, vitamin B6, vitamin B12, chromium, copper, iodine, manganese, molybdenum, and zinc. Supplements that contain more than 100% of the DV for these micronutrients are not necessary for most people.
Don’t worry about the relatively small amounts of chloride, phosphorus, and potassium in multivitamin supplements. Most people get plenty of chloride from salt, and phosphorus and potassium are best obtained from diets rich in fruits, vegetables, and whole grains.
Trace elements like boron, nickel, silicon, tin, and vanadium are not necessary since they may not even be required by humans.
Vitamin A: Vitamin A in supplements may come from retinol, beta-carotene, or both. Recent research suggests there may be an association between higher retinol intakes (5,000 IU/day) and an increased risk of osteoporosis in older men and women. However, vitamin A intakes from beta-carotene have not been associated with an increased risk of osteoporosis. Look for supplements containing no more than 2,500 IU of vitamin A or, if unavailable, supplements containing 5,000 IU, of which at least 50% comes from beta-carotene.
Vitamin C: Although the current RDA for vitamin C is 75-90 mg/day, most multivitamin supplements contain only 60 mg (the DV for vitamin C). Five servings of fruits and vegetables may provide about 200 mg. Aim for a total daily intake of at least 400 mg, which is associated with the saturation of plasma and circulating cells.
Vitamin D: People over the age of 65 may need an additional 200-400 IU/day.
Vitamin E: Few multivitamin supplements contain more than 30 IU, which is close to the RDA of 22 IU/day. LPI recommends an extra supplement of 200 IU natural d-alpha-tocopherol daily.
Vitamin K: The current intake recommendation for vitamin K is 90-120 mcg/day, but few multivitamin supplements contain even as much as the DV (80 mcg). Broccoli and dark green leafy vegetables are excellent sources of vitamin K. Individuals on anticoagulant medicine like warfarin (Coumadin) should avoid sudden changes in their vitamin K intake from supplements or foods.
Biotin: Although the DV is 300 mcg, the most recent recommended intake for biotin is 30 mcg/day.
Calcium: No multivitamin supplement contains the RDA for calcium (1,000-1,200 mg/day) because the resulting pill would be too large to swallow. People who don’t consume the RDA for calcium from their diet will need an extra calcium supplement to make up the difference.
Iron: Premenopausal women should look for a multivitamin supplement that provides 18 mg. Men and postmenopausal women should generally look for a supplement without iron.
Magnesium: Few multivitamin supplements contain more than 100 mg. Because magnesium is plentiful in foods, eating a varied diet that provides green vegetables and whole grains daily should provide the rest of the RDA for magnesium (310-420 mg/day).
Selenium: The RDA for selenium is 55 mcg/day, while the DV for selenium is 70 mcg. One study of people with a history of skin cancer found that selenium supplementation at a dose of 200 mcg/day decreased the incidence of prostate cancer by 50%, but increased the risk of one type of skin cancer (squamous cell carcinoma) by 25%. A much larger clinical trial designed to test the effect of selenium supplementation on the risk of prostate cancer is under way, but final results are not expected for another ten years.
Quality and cost
In March 2003, the U.S. Food and Drug Administration proposed new regulations that would, for the first time, establish standards to ensure that dietary supplements are not adulterated with contaminants or impurities and are labeled accurately. However, these regulations are not yet finalized or implemented.
The United States Pharmacopeia (USP) has a voluntary testing program called the Dietary Supplement Verification Program. The USP Dietary Supplement Verification mark shows that the supplement has passed USP tests to ensure that it contains the ingredients listed on the label, contains the amount of each ingredient listed on the label, dissolves effectively, does not contain harmful contaminants, and was manufactured using safe and sanitary procedures.
Higher costs of particular brands don’t necessarily mean higher quality. Generic brands are often indistinguishable from brand name supplements, but have lower prices. A year’s supply may cost as little as $30.
Last updated November, 2003
Micronutrient Research for Optimum Health
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