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A multivitamin is a preparation intended to serve as a dietary supplement with , , and other nutritional elements. Such preparations are available in the form of tablets, capsules, , powders, liquids, gummies, or injectable formulations. Other than injectable formulations, which are only available and administered under medical supervision, multivitamins are recognized by the Codex Alimentarius Commission (the United Nations' authority on food standards) as a category of food.
In healthy people, most scientific evidence indicates that multivitamin supplements do not prevent cancer, heart disease, or other ailments, and regular supplementation is not necessary. However, specific groups of people may benefit from multivitamin supplements, for example, people with poor nutrition or those at high risk of macular degeneration, and women who are pregnant or trying to get pregnant.
There is no standardized scientific definition for multivitamin. In the United States, a multivitamin/mineral supplement is defined as a supplement containing three or more vitamins and minerals that does not include , , or , where each vitamin and mineral is included at a dose below the tolerable upper intake level as determined by the Food and Drug Board, and does not present a risk of adverse health effects.National Institutes of Health State-of-the-Science Panel. National Institutes of Health State-of-the-Science Conference Statement: multivitamin/mineral supplements and chronic disease prevention" Am J Clin Nutr 2007;85:257S-64S
Some nutrients, such as calcium and magnesium, are rarely included at 100% of the recommended allowance because the pill would become too large in size. Most multivitamins come in capsule form; tablets, powders, liquids, gummies and injectable formulations also exist. In the United States, the FDA requires any product marketed as a "multivitamin" to contain at least three vitamins and minerals; furthermore, the dosages must be below a "tolerable upper limit", and a multivitamin may not include herbs, hormones, or drugs.
In the 1999–2000 National Health and Nutrition Examination Survey, 52% of adults in the United States reported taking at least one dietary supplement in the last month and 35% reported regular use of multivitamin - multimineral supplements. Women versus men, older adults versus younger adults, non-Hispanic whites versus non-Hispanic blacks, and those with higher education levels versus lower education levels (among other categories) were more likely to take multivitamins. Individuals who use dietary supplements (including multivitamins) generally report higher dietary nutrient intakes and healthier diets. Additionally, adults with a history of prostate and breast cancers were more likely to use dietary and multivitamin supplements.
The health benefit of vitamins generally follows a biphasic dose-response curve, taking the shape of a bell curve, with the area in the middle being the safe-intake range and the edges representing deficiency and toxicity. For example, the Food and Drug Administration recommends that adults on a 2,000 calorie diet get between 60 and 90 milligrams of vitamin C per day.. Retrieved 2011-03-30. This is the middle of the bell curve. The upper limit is 2,000 milligrams per day for adults, which is considered potentially dangerous.
In particular, pregnant women should consult their doctors before taking any multivitamins. For example, either an excess or deficiency of vitamin A can cause birth defects.
Long-term use of beta-carotene, vitamin A, and vitamin E supplements may shorten life, and increase the risk of lung cancer in people who smoke (especially those smoking more than 20 cigarettes per day), former smokers, people exposed to asbestos, and those who use alcohol. Many common brand supplements in the United States contain levels above the DRI/RDA amounts for some vitamins or minerals.
Severe vitamin and mineral deficiencies require medical treatment and can be very difficult to treat with common over-the-counter multivitamins. In such situations, special vitamin or mineral forms with much higher potencies are available, either as individual components or as specialized formulations.
Multivitamins in large quantities may pose a risk of an acute overdose due to the toxicity of some components, principally Iron poisoning. However, in contrast to iron tablets, which can be lethal to children, toxicity from overdoses of multivitamins are very rare. There appears to be little risk to supplement users of experiencing acute side effects due to excessive intakes of micronutrients. There also are strict limits on the retinol content for vitamin A during pregnancies that are specifically addressed by prenatal formulas.
As noted in dietary guidelines from Harvard School of Public Health in 2008, multivitamins should not replace healthy eating or make up for unhealthy eating.Harvard School of Public Health (2008). Food pyramids: What should you really eat?. Retrieved from http://www.hsph.harvard.edu/nutritionsource In 2015, the U.S. Preventive Services Task Force analyzed studies that included data for about 450,000 people. The analysis found no clear evidence that multivitamins prevent cancer or heart disease, helped people live longer, or "made them healthier in any way."
Evidence of health effects of multivitamins comes largely from prospective cohort studies, which evaluate health differences between groups that take multivitamins and groups that do not. Correlations between multivitamin intake and health found by such studies may not result from multivitamins themselves, but may reflect underlying characteristics of multivitamin-takers. For example, it has been suggested that multivitamin-takers may, overall, have more underlying diseases (making multivitamins appear as less beneficial in prospective cohort studies). On the other hand, it has also been suggested that multivitamin users may, overall, be more health-conscious (making multivitamins appear as more beneficial in prospective cohort studies). Randomized controlled studies have been encouraged to address this uncertainty.
A cohort study that received widespread media attention is the Physicians' Health Study II (PHS-II). PHS-II was a double-blind study of 14,641 male U.S. physicians initially aged 50 years or older (mean age of 64.3) that ran from 1997 to June 1, 2011. The mean time that the men were followed was 11 years. The study compared total cancer (excluding non-melanoma skin cancer) for participants taking a daily multivitamin (Centrum Silver by Pfizer) versus a placebo. Compared with the placebo, men taking a daily multivitamin had a small but statistically significant reduction in their total incidence of cancer. In absolute terms, the difference was just 1.3 cancer diagnoses per 1000 years of life. The hazard ratio for cancer diagnosis was 0.92 with a 95% confidence interval spanning 0.86–0.998 (P = .04); this implies a benefit of between 14% and .2% over placebo in the confidence interval. No statistically significant effects were found for any specific cancers or for cancer mortality. As pointed out in an editorial in the same issue of the Journal of the American Medical Association, the investigators observed no difference in the effect whether the study participants were or were not adherent to the multivitamin intervention, which diminishes the dose–response relationship. The same editorial argued that the study did not properly address the multiple comparisons problem, in that the authors neglected to fully analyze all 28 possible associations in the study—they argue if this had been done, the statistical significance of the results would be lost.
Using the same PHS-II study, researchers concluded that taking a daily multivitamin did not have any effect in reducing and other major cardiovascular events, MI, stroke, and CVD mortality.
Another meta-analysis, published in 2013, found that multivitamin-multimineral treatment "has no effect on mortality risk", and a 2013 systematic review found that multivitamin supplementation did not increase mortality and might slightly decrease it. A 2014 meta-analysis reported that there was "sufficient evidence to support the role of dietary multivitamin/mineral supplements for the decreasing the risk of age-related cataracts." A 2015 meta-analysis argued that the positive result regarding the effect of vitamins on cancer incidence found in Physicians' Health Study II (discussed above) should not be overlooked despite the neutral results found in other studies.
Looking at 2012 data, a study published in 2018 presented meta-analyses on cardiovascular disease outcomes and all-cause mortality. It found that "conclusive evidence for the benefit of any supplement across all dietary backgrounds (including deficiency and sufficiency) was not demonstrated; therefore, any benefits seen must be balanced against possible risks." The study dismissed the benefits of routinely taking supplements of vitamins C and D, beta-carotene, calcium, and selenium. Results indicated taking niacin may actually be harmful.
In July 2019, another meta-analysis of 24 interventions in 277 trials was conducted and published in Annals of Internal Medicine, including a total of almost 1,000,000 participants. The study generally concluded that the vast majority of multivitamins had no significant effect on survival or heart attack risk. The study found a significant effect on heart health in a low-salt diet, and a small effect due to omega-3 and folic acid supplements. This analysis supports the results of two early 2018 studies that found no conclusive benefits from multivitamins for healthy adults.
According to the Harvard School of Public Health: "... many people don't eat the healthiest of diets. That's why a multivitamin can help fill in the gaps, and may have added health benefits." The U.S. Office of Dietary Supplements, a branch of the National Institutes of Health, suggests that multivitamin supplements might be helpful for some people with specific health problems (for example, macular degeneration). However, the Office concluded that "most research shows that healthy people who take an MVM multivitamin do not have a lower chance of diseases, such as cancer, heart disease, or diabetes. Based on current research, it's not possible to recommend for or against the use of MVMs to stay healthier longer."
As the 20th century progressed, the use of multivitamins expanded beyond addressing deficiencies. With the rise of the wellness industry, they became popularized as a convenient way to enhance overall health, even for those with access to sufficient nutrition. However, as marketing strategies evolved, the emphasis shifted from necessity to preventative health and general well-being, often without sound scientific backing.
The role of multivitamins has since been increasingly questioned. Some still view them as beneficial, especially in cases of specific deficiencies. A growing body of research suggests that for many people, multivitamins act more as a placebo than a necessary supplement. This indicates a shift in the epistemology of vitamins, where people are generally more aware of them and their properties but there is a gap in their knowledge of the scientific research surrounding them
Studies have shown that multivitamins can have positive effects on mood and energy, but there is little evidence to support an increase in general health and life expectancy.
Under the Dietary Supplement Health and Education Act (DSHEA), passed in 1994 in the United States, the Food and Drug Administration (FDA) is not responsible for testing the risks and efficacy of dietary supplements. Manufacturers are not required to present data on the effectiveness of multivitamins or disclose known side effects to the FDA. Furthermore, manufacturers are not required to test human safety of dietary supplements.
From anthropological and psychological perspectives, the widespread consumption of multivitamins can be seen as an example of 'magical thinking,' a form of reasoning that seeks to explain phenomena through non-scientific means, distinct from 'irrational thinking’. (2013). 9780199983032, Oxford Library of Psychology. ISBN 9780199983032
In 2021, a similar systematic review and meta-analysis examining the relationship between prenatal multivitamins and children being diagnosed with autism spectrum disorder (ASD) was published in Nutrients. The study involved 904,947 children encompassing 8159 cases. The study concluded that while no distinct association was found, there was substantial evidence of reduced risk in high quality studies, multivitamin use during early pregnancy, tested prospective studies and evidence following the removal of a single outlier study.
Because of their categorization as a dietary supplement by the Food and Drug Administration (FDA), most multivitamins sold in the U.S. are not required to undergo the testing procedures typical of pharmaceutical drugs. However, some multivitamins contain very high doses of one or several vitamins or minerals, or are specifically intended to treat, cure, or prevent disease, and therefore require a prescription or medicinal license in the U.S. Since such drugs contain no new substances, they do not require the same testing as would be required by a New Drug Application, but were allowed on the market as drugs due to the Drug Efficacy Study Implementation program.See 36 Fed. Reg. 6843 (Apr. 9, 1971).
The TGA, however, has been criticized, by people such as Allan Asher, a regulatory expert and former deputy chair of the Australian Competition & Consumer Commission, for allowing more than a thousand types of claim, 86% of which are not supported by scientific evidence, including "softens hardness", "replenishes gate of vitality" and "moistens dryness in the triple burner".
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