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Multiple Vitamin/Mineral What do they do? Multiple vitamin/mineral (MVM) supplements contain a variable number of essential and/or non-essential nutrients. Their primary purpose is to provide a convenient way to take a variety of supplemental nutrients from a single product, in order to prevent vitamin or mineral deficiencies, as well as to achieve higher intakes of nutrients believed to be of benefit above typical dietary levels. Many of these nutrients will be briefly discussed here; however, for more information, refer to individual nutrient sections. An MVM supplement should not take the place of a healthful, well-balanced diet, but it will help prevent deficiencies that often arise. People may consume diets that are deficient in one or more nutrients for a variety of reasons. The typical Western diet often provides less than adequate amounts of several essential vitamins and minerals.1 Weight-loss, pure vegetarian, macrobiotic, and several other diets can also place some people at risk of deficiencies that vary with the type of diet. Aging, some medications, and certain health conditions can effect appetite, which may reduce nutrient intake. Many MVMs contain at least 100% of the U.S. Recommended Dietary Allowance (USRDA) of all vitamins that have been assigned an RDA value. Mineral levels may be lower, or in the case of high potency MVMs, most or all mineral levels may also be at 100% of USRDA. This will include vitamins A, B-complex, C, D, E, K and the minerals calcium, magnesium, zinc, iodine, selenium, and possibly iron (see below). Phosphorus is another essential dietary mineral, but it is so abundant in the human diet that deficiencies are virtually unknown and it does not need to be included in an MVM formula. Many essential nutrients for which RDAs have not been established should also be included in ranges considered to be adequate and safe. These would include biotin (30–100 mcg per day), pantothenic acid (4–7 mg per day), copper (1.5–3.0 mg per day), manganese (2–5 mg per day), chromium (50–200 mcg per day), and molybdenum (75–250 mcg per day).2 Potassium is an unusual case, as adequate amounts of potassium cannot by law be sold in non-prescription products. Thus potassium, when included in an MVM formula, represents only a trivial amount. MVMs that contain iron should be taken only by people who are known to be iron deficient or have a history of frequent past iron deficiencies. Iron deficiency is not uncommon among many groups of people, including the following:
Nonetheless, many people in these groups are not iron deficient. Therefore, people should be tested for iron deficiency by a healthcare professional before assuming that an iron-containing MVM is appropriate. Excessive iron intake has been associated in some studies with heart disease,3 some cancers,4 diabetes,5 increased risk of infection,6 and exacerbation of rheumatoid arthritis.7 While none of these links has yet been proven, people should avoid iron-containing MVMs unless diagnosed with an iron deficiency. Some nutrients may be beneficial at levels above what is possible to obtain from diet alone, and an MVM formula can provide these levels as well. For example, a vitamin E intake of 100–800 IU per day has been associated with prevention of coronary artery disease,8 9 10 but the average Western diet provides only about 10–15 IU per day. Other nutrients that may be useful to most people in larger amounts include vitamin C, folic acid, and calcium. Large amounts of vitamins B1, B2, B3, and pantothenic acid are usually included in MVM formulas because of their low cost, but there is no scientific justification for these high levels. The common inclusion of the non-essential nutrient beta-carotene in MVMs remains speculative. The synthetic beta-carotene found in most MVMs clearly does not prevent cancer and may increase risk of lung cancer in smokers (see Beta-Carotene). Therefore, it should be avoided, at least until more is known, especially about its use by smokers. However, natural beta-carotene and several other carotenoids may be helpful in preventing certain diseases, including some cancers.11 12 13 Beta-carotene also provides a non-toxic form of vitamin A. Increasingly, natural beta-carotene and several other carotenoids are found in better MVMs. Another class of non-essential nutrients is the flavonoids, which have antioxidant and other properties that have been reported by some,14 though not all15 researchers to be linked with a reduced risk of heart disease. MVM supplements also frequently include other non-essential nutrients of uncertain benefit in the amounts supplied, such as choline, inositol, and various amino acids. What about “one-per-day" multiples? One-per-day multiples are primarily B-complex vitamins, with vitamin A and vitamin D sometimes being high and other times being low potency. The rest of the formula tends to be low potency. It does not take much of some of the minerals—for example, copper, zinc and iron—to offer 100% or more of what people normally require, so these minerals may appear at reasonable levels in a one-per-day MVM. One-per-day MVMs do not provide significant amounts of most nutrients people eating a Western diet are most likely to benefit from supplemental amounts of, such as vitamin E, calcium, magnesium, vitamin C, etc. One-per-day MVMs should therefore not be viewed as a way to "cover all bases" in the way that high potency MVMs requiring six or more pills per day are viewed. How many tablets or capsules are required? Because one-per-day formulas are hard to balance with adequate minerals and the key vitamin C and vitamin E, multiples requiring several capsules or tablets per day are preferable. A one-a-day MVM may appear convenient, but is not likely to provide all necessary nutrients at optimal amounts. A complete MVM formula will require a daily intake of several tablets because useful amounts of all important nutrients cannot fit into fewer pills. For example, the RDA for calcium is at least 800 mg per day, an amount that alone requires several tablets or capsules. In general, about six tablets or capsules are required to fit all that is in the one-per-day plus 800–1,000 mg of calcium, 350–500 mg of magnesium, and reasonable amounts of C (300–1,000 mg) and E (400 IU). With two to six per-day multiples, intake of pills should be spread out over the day, instead of taking them all at one sitting. The amount of vitamins and minerals can be easily increased or decreased by taking more or fewer of the multiple. Which is better—capsule or tablet? Multiples are available as a powder inside a hard-shell pull-apart capsule, as a liquid inside a soft-gelatin capsule, or as a tablet. Most multiples have all the ingredients mixed together. Sometimes the B vitamins react with the rest of the ingredients in the capsule or tablet. This reaction is sped up in the presence of moisture or heat. This reaction can cause the B vitamins to “bleed” through the tablet or capsule, discoloring it and also making the multiple “smell.” While the multiple is still safe and effective, the smell is off-putting and usually not very well tolerated. Liquid multiples in a soft-gel capsule—or tablets or capsules that are kept dry and cool—don’t have this problem. Some people find capsules easier to swallow. This is often a function of size. Capsules are usually not as large as a tablet. Some people prefer vegetarian multiples. While some capsules are made from vegetarian sources, most come from animal gelatin. Vegetarians need to carefully read the label to ensure they are getting a vegetarian product. One concern people have with tablets is whether they will break down. Properly made tablets and capsules will both dissolve readily in the stomach. What about timed release? Some multiples are in time-released form. The theory is that releasing vitamins and minerals slowly into the body over a period of time is better than releasing all the nutrients at once. Except for work done on vitamin C—some of which showed time-released C was better absorbed than non-time-released—research on this question has been lacking. What about nutrient interactions? Another area of controversy is whether all the nutrients in a multiple would be better utilized if they were taken separately. While certain nutrients compete with each other for absorption, this is also the case when the nutrients are supplied in food. For example, magnesium, zinc, and calcium compete; copper and zinc also compete. However, the body is designed to cope with this problem, and taking many different pills at different times is awkward and unnecessary. How about chewables? Unfortunately, multiples do not taste very good. In order to make chewable multiples palatable, whether for children or adults, some compromises must be made. First, bad-tasting ingredients must be reduced or eliminated. Second, the rest of the ingredients must be masked with a sweetener. Unless an artificial sweetener like aspartame (Nutri-Sweet) or saccharine is used, the only sweeteners available are sugars. Generally, sugar is sugar (sucrose in white table sugar or fructose from fruit), and not having it in a dietary supplement would be preferable. However, xylitol, a natural sugar rarely used in chewables because it is relatively expensive, does not cause tooth decay or other known problems. Some chewables, such as vitamin C, contain more sugar than any other ingredient. In such products, the sweetener should be listed as the first ingredient, but often isn’t. This means care needs to be exercised when reading labels about chewable vitamins. If it tastes sweet, it contains sugar or a synthetic sweetener. When should I take my multiple? The best time to take vitamins or minerals is with meals. Multiples taken between meals sometimes cause stomach upset and are likely not as well absorbed. References: 1. Pao EM, Mickle SJ. Problem nutrients in the United States. Food
Technology 1981;35:58–79.
Reviewed: 01-Jul-1999 |
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