- Other Nutrients
- Dietary Factors
- Food and Beverages
- Life Stages
- Health & Disease
In general, a multivitamin/mineral (MVM) supplement is a dietary supplement that contains about 100% of the Daily Value (DV) of most vitamins and nutritionally essential minerals. However, there are no standardized definitions for MVMs, and the composition of marketed MVM products varies widely (e.g., some contain nonnutrient ingredients like herbs or phytochemicals) (1). No MVM supplement contains the DV for calcium, magnesium, potassium, and phosphorus since the resulting pill would be too bulky.
Similar to food labels, the DVs listed on supplement labels do not reflect the latest recommendations (i.e., the RDA and AI) from the Food and Nutrition Board (FNB) of the US Institute of Medicine; instead, most of the DVs are based on outdated recommendations made in 1968 (2). The DVs for vitamin A and biotin are considerably higher than the current FNB recommendations, but supplement manufacturers may include these vitamins at levels similar to the current recommendation and list that a tablet contains only a fraction of the DV. DVs of many micronutrients are significantly higher than the corresponding RDAs (Table 1). Several MVM products currently on the market are formulated specifically for young men, young women, older adults, or children since micronutrient (vitamins and nutritionally essential minerals) requirements differ by gender and life stage. For example, MVMs marketed to young women generally contain iron, while many of those marketed to men or postmenopausal women typically do not. This article discusses patterns of MVM use, the prevalence and consequences of micronutrient inadequacies, chronic disease prevention, and safety concerns of MVM supplementation in adults.
|Table 1. Comparison between the Daily Values (DV) and the Dietary Reference Intakes (RDA or AI) for Adults|
|Micronutrient||DV||RDA or AI for Adult Males (amount/day)||RDA or AI for Adult Females (amount/day)|
|Biotin||300 μg||30 μg||30 μg|
|Folate||400 μg||400 μga||400 μga|
|Niacin||20 mg||16 mgb||14 mgb|
|Pantothenic Acid||10 mg||5 mg||5 mg|
|Riboflavin||1.7 mg||1.3 mg||1.1 mg|
|Thiamin||1.5 mg||1.2 mg||1.1 mg|
|Vitamin A||5,000 IU||3,000 IUc||2,333 IUc|
|Vitamin B6||2 mg||1.3-1.7 mg||1.3-1.5 mg|
|Vitamin B12||6 μg||2.4 μgd||2.4 μgd|
|Vitamin C||60 mg||90 mg||75 mg|
|Vitamin D||400 IU||600-800 IU||600-800 IU|
|Vitamin E||30 IU||22.5-33 IUe||22.5-33 IUe|
|Vitamin K||80 μg||120 μg||90 μg|
|Calcium||1,000 mg||1,000-1,200 mg||1,000-1,200 mg|
|Chloride||3,400 mg||1,800-2,300 mg||1,800-2,300 mg|
|Chromium||120 μg||30-35 μg||20-25 μg|
|Copper||2 mg||900 μg||900 μg|
|Iodine||150 μg||150 μg||150 μg|
|Iron||18 mg||8 mg||8-18 mg|
|Magnesium||400 mg||400-420 mg||310-320 mg|
|Manganese||2 mg||2.3 mg||1.8 mg|
|Molybdenum||75 μg||45 μg||45 μg|
|Phosphorus||1,000 mg||700 mg||700 mg|
|Potassium||3,500 mg||4,700 mg||4,700 mg|
|Selenium||70 μg||55 μg||55 μg|
|Zinc||15 mg||11 mg||8 mg|
|Cholinef||None established||550 mg||425 mg|
aDietary Folate Equivalents
Abbreviations: DV, daily value; RDA, recommended dietary allowance; AI, adequate intake
Use of nutritional supplements is increasingly common in the United States, with MVMs being the most popular type of dietary supplement (3). A recent national survey found that one-third of Americans ages one year and older take a MVM supplement, which was defined as a supplement containing at least three vitamins and one mineral (4). Dietary supplement use was found to be generally more prevalent among females, non-Hispanic whites, older adults, and individuals with greater than a high-school education and less common among obese individuals (4). Other studies have reported similar trends in use (5-10). Additionally, a few studies have found that MVM users are more likely to have healthier diets (11, 12) or rate their health as excellent or very good (7, 10), suggesting that those who do not take MVMs may be the ones who would benefit the most from supplementation.
Despite MVM use being very common among some population groups, US national surveys indicate that select micronutrient inadequacies are relatively widespread. According to data from the National Health and Nutrition Examination Survey (NHANES), 93% of the US population do not meet the estimated average requirement (EAR) for vitamin E, 56% for magnesium, 44% for vitamin A, 31% for vitamin C, 14% for vitamin B6, and 12% for zinc (13). The EAR is used to establish the recommended dietary allowance (RDA), which is the higher of the two recommendations and should be used in dietary planning for individuals (14). Moreover, vitamin D deficiency is a major problem in the US and elsewhere; it has been estimated that 1 billion people in the world have either vitamin D deficiency or insufficiency (15).
Since more than one-third of American adults aged 20 years or older is considered overweight and another one-third is classified as obese (16), many Americans are exceeding energy (caloric) requirements but not meeting micronutrient recommendations, presumably due to excessive consumption of energy-rich, nutrient-poor foods. Data from NHANES found that energy-dense, nutrient-poor foods comprise 27% of daily caloric intake in the American diet, and alcohol constituted an additional 4% of daily caloric intake (17). This survey also found that higher intakes of energy-dense, nutrient-poor foods were associated with lower serum concentrations of several micronutrients, including vitamin A, folate, vitamin B12, vitamin C, and vitamin E (17). Select micronutrient deficiencies are common in other industrialized nations (18-20), and multiple micronutrient deficiencies, especially iron, vitamin A, zinc, and iodine, are prevalent in the developing world (21). Micronutrient deficiencies, affecting an estimated 2 billion people, contribute to infections and are associated with severe illness and death (22). Although not a comprehensive list, the following individuals may be at increased risk for micronutrient deficiencies (micronutrients of concern are noted in parentheses) (23-35):
Micronutrient inadequacies can increase susceptibility to illness and chronic disease. Deficiencies in select micronutrients can impair immunity, thereby increasing vulnerability to infectious disease (see the article on Immunity). Inadequate intake of certain micronutrients may increase risk for chronic diseases, such as cardiovascular disease, osteoporosis, and cancer, and may also be linked to cognitive dysfunction (see the article on Cognitive Function) (33, 34, 38). Moreover, certain micronutrient deficiencies during pregnancy can cause congenital anomalies (see the article on Micronutrient Needs During Pregnancy and Lactation). Dr. Bruce Ames, a prominent biochemist at the University of California, Berkeley, has hypothesized that when intakes are lower than the recommended levels, short-term requirements for micronutrients in metabolic reactions take precedence over long-term needs, thereby resulting in long-term, cumulative oxidative damage to macromolecules (DNA, RNA, proteins), declines in mitochondrial function, and accelerated cellular aging, increasing the risk of age-related diseases (33). In contrast, micronutrient intakes at the RDA would allow sufficient amounts for normal metabolism, and intakes of the RDA or higher may be needed for optimum health promotion and chronic disease prevention (33). Given the fact that many people are not meeting micronutrient intake recommendations, a daily multivitamin/mineral supplement would offer insurance that most micronutrient needs are met.
It is not known with certainty if taking a daily multivitamin/mineral supplement can reduce the risk of various chronic diseases. Several observational studies (prospective cohort studies and case-control studies) and randomized controlled trials (RCTs) have examined this question. In 2006, a National Institutes of Health (NIH) State-of-the-Science conference on MVMs and chronic disease prevention concluded that there was insufficient evidence to recommend in favor or against taking a MVM supplement (39). However, the panel limited their ‘evidence-based’ review to only long-term RCTs, ignoring the results of other epidemiological studies as well as the mechanistic and biochemical research that suggest an adequate supply of micronutrients is essential for optimal health (40). When used to evaluate the effects of nutrients, RCTs have a number of limitations (see below). Epidemiological studies published since the NIH conference have not provided a definitive answer to whether MVM use could help prevent chronic diseases. Recent systematic reviews or meta-analyses of epidemiological studies have found that MVM use was not associated with breast cancer (41) or prostate cancer (42). In addition, individual studies of MVM use and cardiovascular events or cardiovascular-related mortality are conflicting, with two finding a benefit (43, 44) and another reporting no association (45). Inconsistent findings in epidemiological studies may in part be due to wide variations in MVM supplement composition, dose, and duration of use.
Both observational studies and randomized controlled trials have inherent limitations. Observational studies — studies in which participants are simply observed over time (no experimental intervention or treatment is applied) — can only detect associations, not establish cause-and-effect relationships (46). Even though statisticians usually adjust for several confounding factors, residual confounding is always a concern with observational studies. Accurately measuring MVM use or compliance may also be problematic. Although not typically done, studies that measure micronutrient status in blood and correlate that with health outcomes are more reliable than those that measure supplement use by questionnaires or recall methods. Additionally, people who volunteer to be part of observational studies or RCTs are generally healthier than the average person (i.e., the "healthy enrollee effect," and similarly, people who take MVM supplements often have healthier dietary and lifestyle habits compared to those who don’t take MVMs (11, 12). While RCTs are considered the ‘gold standard’ to evaluate the effect of pharmaceutical drugs, they have a number of limitations and are not well-suited to study the effects of nutrients (46, 47). For example, trials of micronutrient supplementation compare low intakes (from diet) with higher intakes (from supplements) in subjects who have a lifelong intake of these micronutrients; by contrast, drug trials compare the absence of the drug with its presence in subjects who have not been exposed to this drug before. Therefore, the ‘placebo’ group in RCTs of micronutrient supplements is not a true placebo or ‘non-exposed’ group, in contrast to the placebo group in RCTs of drugs. Such a nutrient-free state in RCTs is not possible, and causing micronutrient deficiencies in the control group is unethical. Additionally, primary disease prevention trials using supplemental micronutrients are evaluated in healthy people, not diseased individuals, meaning that any effects of supplementation would be likely small and take years, perhaps decades, to be observed (46, 47). There are several other concerns with RCTs, such as selection of subjects, compliance during a long-term study, the need to recruit a large number of subjects, trial cost, and confounding with dietary intake of nutrients (40). Thus, for many reasons, it is not realistic that a long-term RCT would provide definitive results on whether MVMs are useful in chronic disease prevention. Short-term RCTs that assess DNA damage, inflammation, insulin sensitivity, lipid profile, blood pressure, immune function or other intermediary biomarkers or independent risk factors of chronic disease are more practical and may inform this question (40).
Although there is no consensus that MVM use by the general population benefits overall health or prevents chronic disease, such supplements are generally considered as safe in healthy individuals. Excessive intakes of select micronutrients can be unsafe, but amounts of micronutrients typically included in MVMs approximate or equal the DVs; for adults, the DV for most micronutrients is considerably lower than the tolerable upper intake level (UL) — the highest level of daily intake of a specific nutrient likely to pose no risk of adverse health effects in almost all individuals of a specified age (14). Intake from foods, fortified foods, and supplements should not exceed the UL for each micronutrient (48). In general, dosages of micronutrients included in MVMs are safe. Some supplements may provide excessive vitamin A or iron. For example, daily use of a MVM supplement can supply as much as 5,000 IU/day of vitamin A as retinol, an amount that has been associated with bone fractures in older adults. For this reason, the Linus Pauling Institute (LPI) recommends that adults take a MVM supplement that provides no more than 2,500 IU (750 μg) of preformed vitamin A (usually labeled vitamin A acetate or vitamin A palmitate) and no more than 2,500 IU of additional vitamin A as β-carotene. Additionally, because excess preformed vitamin A (retinol) during pregnancy is known to cause birth defects and because a number of foods in the US are fortified with retinol, LPI recommends that pregnant women avoid a MVM or prenatal supplements that contain more than 5,000 IU (1,500 μg) of vitamin A in the form of retinol. Moreover, children should not be given a MVM supplement that contains more retinol than the RDA for their age group (see the Table 1 in the article on vitamin A). Men and postmenopausal women are not at risk of iron deficiency, and excess iron from the diet and supplements can have adverse effects. Therefore, LPI recommends that men and postmenopausal women take a MVM supplement without iron. A number of MVMs formulated specifically for men or for those over 50 years of age do not contain iron. Concomitant use of certain supplements, such as a daily MVM and a daily B complex supplement, in addition to intake from fortified foods, may result in total intakes that exceed the UL for some micronutrients. Further, even though MVM supplements are safe for most people, individuals should discuss the use of all nutritional supplements with a competent healthcare professional. People taking pharmaceutical drugs to treat certain medical conditions need to be aware of any potential drug-nutrient interactions.
Another safety issue concerns the quality of commercially available MVM supplements. In 2007, the US Food and Drug Administration established standards of current good manufacturing practices (CGMPs), which ensure dietary supplements meet quality standards with respect to identity, purity, strength, and composition (49). All US and foreign companies were required to comply with the CGMPs by June 2010. In addition to these government regulations, at least three independent organizations evaluate the quality of dietary supplements on a fee basis: NSF International, US Pharmacopeia, and ConsumerLab.com. Supplement labels of approved products can bear the certification mark, verification mark, or seal of approval of these organizations. However, many products that are in full compliance do not carry such certification marks on their labels, and absence of a seal does not mean lack of adherence to CGMP or other regulations.
National surveys indicate that many Americans are not getting enough micronutrients from the diet, possibly increasing their risk for osteoporosis, some forms of cancer, and other chronic diseases. Marginal or subclinical micronutrient deficiencies have been linked to general fatigue (50), impaired immunity (51, 52), and adverse effects on cognition (53). Nutrition education campaigns have yet to convince people to make better food choices: the reality is that most Americans eat an energy-rich, nutrient-poor diet lacking in fruit and vegetables (54). Consequently, micronutrient inadequacies are widespread in the US and around the world. Given the facts that dietary habits are difficult to change and that some people cannot afford nutrient-rich fruit and vegetables, a daily multivitamin/mineral supplement is a sensible public health recommendation (55, 56). As part of its Rx for Health, the Linus Pauling Institute recommends a daily MVM supplement as nutritional insurance to meet micronutrient needs (see Supplements in the LPI Rx for Health). MVMs are a simple, inexpensive, and safe way to help fill nutritional gaps and improve micronutrient status. By definition, MVMs are “supplements” and should be used to complement a healthy diet (see Healthy Eating in the LPI Rx for Health). Eating a balanced diet is important to obtain other nutrients and phytochemicals that benefit health. While the specific consequences of chronic micronutrient inadequacies are difficult to document, it is prudent and affordable to ensure adequacy for health by taking a daily MVM supplement.
Written in August 2011 by:
Victoria J. Drake, Ph.D.
Linus Pauling Institute
Oregon State University
Reviewed in August 2011 by:
Jeffrey Blumberg, Ph.D., F.A.C.N., F.A.S.N., C.N.S.
Director, Antioxidants Research Laboratory
Jean Mayer USDA Human Nutrition Research Center on Aging
Professor, Friedman School of Nutrition Science and Policy
This article was underwritten, in part, by a grant from Bayer Consumer Care AG, Basel, Switzerland.
Copyright 2011-2017 Linus Pauling Institute
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