There are two main ways to use vitamins and mineral supplements: "megadose" and nutritional therapy.
The megadose approach involves taking supplements at doses far above nutritional needs in hopes of producing a specific medical benefit. This technique essentially uses nutrients as natural drugs. The individual supplement articles in this encyclopedia explain what is known about the potential risks and benefits of megadose therapy.
This article addresses the second approach: taking nutrients at the level of nutritional needs. We discuss general issues regarding such "nutritional insurance" and indicate which nutrients you should consider taking on a daily basis.
There is no doubt that it's important to get enough of all necessary nutrients. However, the process of determining proper daily intake levels for vitamins and minerals is far from an exact science and the recommendations issued by experts in various countries often disagree to a certain extent.
In general, while it is fairly easy to determine the minimum nutrient intakes that are necessary to avoid frank malnutrition, there's no straightforward way to determine optimum intake levels. Furthermore, individual needs undoubtedly vary based on numerous factors, including age, genetics, lifestyle, other foods in the diet, and many additional environmental influences; no schedule of official recommendations could possibly take all these factors into account, even if all the necessary data existed (which it doesn't).
Thus, all recommendations for daily nutrient intake must be regarded as approximate. The individual supplement articles in this encyclopedia summarize the current US recommendations.
Common Nutritional Deficiencies
Severe deficiencies of vitamins or minerals are rare in the developed world. However, evidence suggests that slight deficiencies in certain nutrients may be relatively common. These include calcium,15,16 chromium,14 folate,13 magnesium,17 vitamin B6,18-20 vitamin C,21-24 vitamin B12 (primarily in the elderly),25-28 vitamin D,33 vitamin E,40-42 and zinc.16,34-37
While few people are so deficient in these nutrients to show symptoms of outright malnutrition, subtle deficiencies may increase the risk of a number of diseases. For example, insufficient intake of calcium and vitamin D may increase your chances of developing osteoporosis, and inadequate folate and vitamin B 6 may speed the development of heart disease.
Thus, taking supplements to supply these important vitamins and minerals as a form of insurance may be a good idea. For standard dosage recommendations as well as safety issues, follow the links above to the full articles.
Women may develop iron deficiency, but men hardly ever do. Even in women, iron supplements are not beneficial in the absence of true deficiency. We recommend avoiding iron supplements unless tests show that you really need them.
The simplest way to support your nutrition is to take a general multivitamin and mineral supplement providing a broad range of nutrients at standard nutritional levels. However, there are a few caveats to keep in mind.
Taking Individual Supplements
One problem with multivitamin/mineral supplements is that some nutrients may interfere with the absorption of others. For this reason, there may be advantages to taking supplements separately. (The hassle factor is a strong disadvantage!) In addition, this method allows one to avoid taking vitamins and minerals one doesn't need.
If you do use this approach, keep in mind the following:
Natural vs. Synthetic Vitamins
Many people wonder whether "natural" vitamins are better than "synthetic" ones. This question, however, is a bit of a red herring. Ultimately, no vitamin or mineral supplement is "natural." Purified vitamins and minerals are refined, processed products analogous to white sugar or artificial fertilizer. It doesn't much matter whether they are extracted from foods or manufactured in a laboratory: the result is the same. For example, vitamin C made from rose hips is chemically identical to vitamin C synthesized from scratch. Both are ascorbic acid.
Rose hips themselves, however, supply many nutrients along with vitamin C. If you truly wish to get your vitamins naturally, you might consider taking them as freeze-dried or condensed whole food supplements rather than as purified vitamins. This might offer a specific advantage over purified vitamins: as we noted above, fruits and vegetables may provide substances that are not actually essential but that promote better health.
Under certain conditions, the need for many nutrients may increase. These include illnesses such as diabetes, Crohn's disease, HIV, and ulcerative colitis. Furthermore, individuals who smoke cigarettes or overuse alcohol may need additional nutrients. Follow the links to the individual articles for more information.
Medications may increase the need for certain nutrients; if you look up your own medications in the Drug Interaction section of this encyclopedia, you will find what is known about these so-called nutrient depletions.
Other potential uses of multivitamins generally lack strong support.
Some but not all evidence hints that multivitamin/multimineral supplements may help prevent infections in seniors or otherwise enhance immunity.7, 8, 9, 32,38,39,43,57,63-64 However, there are strong suspicions that scientific fraud may have tainted this research, and when the potentially fraudulent studies are disregarded the evidence looks more negative than positive.70
Similarly, some but not all studies suggest that multivitamin/multimineral supplements can enhance mental function, and here, too, there are concerns about potential fraud.11,12,48-51,58,59, 62,71,74 In general, the best designed studies have failed to find benefit. However, it is quite possible that multivitamin/multimineral supplements are helpful for people with marked vitamin or mineral malnutrition.71
One study found that use of a multivitamin tablet improved mood, but not cognitive function, in hospitalized acutely ill seniors.72 Another study failed to find that a mix of multivitamin (either general, or consisting of B-complex vitamins) were more effective than placebo for treating depression in healthy young adults.75
Incomplete, and in some cases contradictory, evidence suggests that use of multivitamin and/or multimineral supplements might reduce antisocial behavior in children and young adults (especially those who are malnourished),40,47,52 prevent pressure ulcers (bed sores),54 lower blood pressure,53 improve fertility in women,10 improve general well-being,47,51, 65 enhance sports performance,67 enhance growth in children,56 speed healing of minor wounds,55 reduce the pain of osteoarthritis,46 reduce pregnancy-related nausea (“morning sickness”),47 decrease risk of numerous birth defects,68 help control menopausal hot flashes,69 decrease symptoms of premenstrual stress syndrome (PMS)1-4 and ordinary stress,5,6 reduce risk of prostate cancer,66 and help prevent cataracts.76
In a double-blind study of 40 people undergoing radiation therapy for breast cancer, use of a standard multivitamin preparation failed to reduce fatigue as compared to placebo.73 (In fact, people in the placebo group may have done somewhat better than those given the vitamin.)
There may be a link between maternal mulitvitamin use during pregnancy and a slight reduction in risk for a child with autism spectrum disorder with an intellectual disability. A population-based study evaluated 273,107 children who were 4-15 years old. Multivitamins, and iron and folic acid supplements were started after the first prenatal visit.77
Standard multivitamin/multimineral tablets contain nutrients at levels believed to be safe for the majority of healthy people, as indicated by amounts at or below the recommended daily allowance. However, even these supplements could be harmful for people with certain diseases, such as kidney or liver disease, or for people taking certain medications, such as warfarin.
There are other multivitamin/multimineral tablets that contain high levels of certain nutrients far above nutritional needs. These could conceivably present risks for healthy people, particularly if they are taken in combination with additional specific supplements. Almost any mineral can be toxic if taken to excess, and there are also risks with excessive intake of vitamins A, B 6, and D.
One study found that use of multivitamin/mineral supplements may actually increase the infectivity of women with HIV.61 The reasons for this are unclear.
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Last reviewed December 2015 by EBSCO CAM Review Board
Last Updated: 3/12/2018