(originally posted 7/16/2016. libbysfitnutrition.com)
A paper I wrote for my Master's program class on dietary supplements. Bottom line- multi vitamin supplements may do more harm than good. If you cannot get all of your needed nutrients from food (which is totally do-able), then specific single nutrient supplements are a better choice than a multi.
Here is the research:
Use of Multi Vitamin and Mineral Supplements for “Health Insurance” and Disease Prevention
Do “multi vitamin and mineral dietary supplements” have a place in health prevention and treatment? As will be discussed below, the answer appears to be a resounding no.
Background of Multi Vitamin and Mineral Supplements
Multi-Vitamin and Mineral Supplements (MVM) have been available to Americans since the 1940’s (1), and have only increased in use since that time. The general consensus is that a MVM contains three or more vitamins or minerals without other herbs or drugs (3); However, there is no one-definition for what a MVM is or contains (ingredient, number of ingredients, or level of potency). In fact, there are many dietary supplements (DS) on the market that are not labeled as MVMs that are essentially the same as other products labeled MVM (1). The 2011-12 NHANES data shows approximately 40% of Americans took at least one DS in the last 30 days (2). Many of the people surveyed listed to [maintain health, or prevent health problem(s)] as their reason for taking a DS (2). But what is the actual role of MVMs?
Usefulness, role, and dangers of MVMs
In the 1920s, the United States started fortifying major food sources starting with adding iodine to salt to counter widespread deficiency and prevent goiter. In the following years Vitamin D was added to commercially sold milk, and some B vitamins and iron were added to flour (3) minimizing deficiencies in the majority of Americans. Nowadays, many more foods for purchase are fortified with additional vitamins and minerals. With fortification meeting the needs of the general population, benefits of MVMs seem to be limited.
What is the reality of MVM use? MVMs may be beneficial if the blends of ingredients are tailored to the needs to the individual. According to the National Institute of Health (NIH), “several studies have found that MVM users tend to have higher micronutrient intakes from their diet than nonusers. Ironically, the populations at highest risk of nutritional inadequacy who might benefit the most from MVMs are the least likely to take them (1).”
Several large studies show this irony: In a large study of adult participants from Los Angeles and Hawaii, food frequency analysis showed that the majority of people (~75%) had adequate intakes from food alone (1). With MVM adequacy improved, especially for vitamins E, A, and zinc; but there was an increased risk of excessive intake, especially in vitamin A, iron, zinc, and niacin (1). A study of U.S. children under four, concluded that, “usual nutrient intakes were adequate for the majority of US infants, toddlers, and preschoolers, except for a small but important number of infants at risk for inadequate iron and zinc intakes (4).” They also noted that many children were at additional risk of excessive intake for folate, vitamin A, zinc, and sodium even without supplementation (4). Many children with autism are given MVMs, which are unnecessary, and contribute to excessive intake in many. Even with MVMs, there may be additional need for calcium and vitamin D in children, according to the Academy of Nutrition and dietetics (5).
There is an increased risk of nutrient toxicity when taking DS. The NIH states, “MVMs did not reduce the risk of any chronic disease (1).” and “There is potential for adverse effects in individuals consuming dietary supplements that are above the upper level. This can occur...in individuals who consume a healthy diet rich in fortified foods in combination with MVM supplements (3).” Typically MVMs have nutrient levels that are lower than the RDA for a particular nutrient, and without adequate food sources MVM users may need additional supplementation of nutrients (such as magnesium or calcium) not contained in high enough doses from the MVM; however, as discussed above, toxicity from supplementation is all too common (1), sometimes with irreversible health consequences.
Just a few examples of health issues caused by excess vitamin or mineral intake include: excess vitamin A or beta-carotene correlated to increased risk of lung cancer in smokers or former smokers (1); excess vitamin A (as preformed retinol) increasing risk of birth defects in fetuses of pregnant women taking supplements (1); and iron supplements have been noted as a “leading cause of poisoning in children until age 6 years (1),” due to children getting into supplement containers. Additionally, people taking blood thinning medications need to keep vitamin K levels steady, so any supplements should be checked and confirmed with their doctor before taking or changing doses (1).
Though many large-scale studies have been done separately with either male or female participants, there is not a significant difference in health risks between the genders. The Physician’s Health Study II was a large-scale, double-blind, placebo-controlled RCT of over 14,000 male doctors in the United States, the study showed that, “daily multivitamin supplementation modestly but significantly reduced the risk of total cancer (6).” In conflict, another study of the “295,344 men enrolled in the National Institutes of Health (NIH)-AARP Diet and Health Study (7) found that low-dose MVM use had no discernable increase in risk of prostate cancer, but those who took higher doses (more than 7 times/week) of MVMs had an “increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation (7), than non MVM users (1). Another large study (n= 83,639) of male physicians found no association between cardiovascular disease and MVM use(1).
Women were no different in terms of conflicting research. A study of Swedish women (n= 35,329) found an increased risk of developing breast cancer with MVM use (1); while another study of U.S. women (n=37,920) “found no such association but did find indications that MVM use might reduce the risk of estrogen- and progesterone- receptor– negative breast cancer and breast cancer overall in women who consume alcohol (1).” Swedish women in a cohort study had a lower risk “of myocardial infarction when taking MVMs, especially when taken for at least 5 years (8).” A cohort study of Iowa women found a slight increased risk of mortality from long term MVM use compared with non-MVM-users (1). And finally, long-term MVM use appeared to have benefit for men but not women in total cancer and mortality risk in a NIH study, but no benefit to either group for CVD (3). Overall, the data is inconclusive of significant benefit to either gender taking MVMs long-term.
Is there still a use for MVM?
The NIH, Office of Dietary Supplements (ODS) states, “supplements cannot take the place of the variety of foods that are important to a healthy diet (1).” Eating a well-balanced nutritious diet is the goal for everyone, and can be done. That being said, there are populations that do benefit from taking specially-formulated MVMs or DS.
The American Academy of Pediatrics and the (formerly) American Dietetic Association, list potential populations that will benefit from use of MVMs: “[people with] nutritional risk....those who have anorexia or an inadequate appetite, follow fad diets, have chronic disease, come from deprived families or suffer parental neglect or abuse, participate in dietary programs for managing obesity, consume a vegetarian diet without adequate dairy products,..have failure to thrive...people with medical conditions and diseases that impair digestion, absorption, or use of nutrients [bariatric surgery]… some supplements might help people who do not eat a nutritious variety of foods to obtain adequate amounts of essential nutrients (1).”
However, not every MVM on the market is appropriate of any of these populations. In these scenarios, it would be far better to use specific formulations of needed vitamins and minerals to make up for lacking nutrients. The 2010 Dietary Guidelines for Americans, and the NIH–sponsored State-of-the-Science Conference, claims there is no supporting evidence for the general population to take a MVM to prevent chronic diseases (1, 7).
How should MVM be regulated?
Currently the Food and Drug Administration (FDA), or any government body, does not have the ability to test DS, legally (due to the Dietary Supplement Health Education Act, or “DSHEA”), or in resources (staff or funds) to do so. “Both the [FDA] and the Federal Trade Commission (“FTC”) regulate claims made by food and dietary supplement manufacturers (9).” The FDA regulates labeling, which prohibits false or misleading information on the supplement labels “under the Food, Drug and Cosmetic Act” (9). The FDA issues warning letters to manufacturers against law violations in labeling, but rarely uses other methods of enforcement (9) mainly due to inability to keep up with the booming DS industry. This means the regulating agencies are bound to fail when the staff is disproportionately small, and the enforcement of laws is poorly executed (9). If a DS was listed as a food additive, or drug, it would require pre-market approval (3), and there would not be the insurmountable task of keeping up with the production of DS.
While the FDA focuses on the direct product label, the FTC regulates the advertising of DS. This may include “evaluat[ing] dietary supplement labels if they are being used by an advertiser to promote the product...under the FTC Act, claims in advertising made about foods and dietary supplements may not be “unfair” or “deceptive” (9).” As presented in the American Journal of Law & Medicine, a “limited private right of action [private sector lawsuits] under the FTC act” would more easily bring “enforcement actions in federal court” to protect consumers regarding DS (9), and would greatly increase the amount of products being enforced.
The NIH has excellent recommendations regarding change in regulatory laws and action, for instance, “The FDA should have the authority to better inform consumers and health professionals regarding the existence of upper levels as well as the possible risks of exceeding those levels; [the FDA should] develop a formal, mandatory adverse event reporting system for dietary supplements; and mandate provision of a MedWatch toll-free telephone number or Web site on product labels to facilitate reporting of adverse events. Furthermore, we recommend that healthcare professionals, consumers, and manufacturers use the FDA MedWatch adverse event reporting system to report adverse events associated with the use of dietary supplements. Finally, we recommend that Congress revise and update the law to reflect current knowledge...design and conduct rigorous randomized control trials of the impact of individual supplements (or paired supplements, when biologically plausible) to test their efficacy and safety in prevention of chronic disease, using well-validated measures.(3).” Ultimately, DS should be regulated as drugs, due to the fact that they interact and “medicate” like drugs in the body.
Should this information change consumer behavior?
If approached properly, there may be a way to help consumers better understand the dangers and lack of regulation of DS. Two studies on consumer education about DS, showed that consumers taught about DSHEA and the regulation of DS “rated DS as less safe and less effective” than the control group (10). This gives us a starting place on what message needs to be making its way to consumers. “Consumers may be especially susceptible to health claims, because they usually lack the knowledge to assess claims referring to physiology or metabolic processes and may be especially impressed by purported scientific evidence bolstering the claims (9).”
MVMs, particularly due to the lack of content consistency, are not useful in human health and disease prevention or treatment. The Medical Letter, an unbiased publication for pharmacists, declares that long-term use of MVMs, or any substance, is not without risk; and taking vitamins A, C, E, or beta-carotene in high doses or long-term may be more harmful than helpful (12). They furthermore suggest the only beneficial supplements (in healthy people consuming a normal diet) are folic acid, vitamin D and B12, in specific populations (12). If supplemental nutrients are necessary for populations listed previously who cannot obtain enough from diet alone, they should be carefully chosen as individual (well-researched) DS, and not in MVMs which may (with or without accurate labeling) contain excessive levels of substances (vitamin/minerals, or drugs/herbs) that may be harmful. I strongly recommend against the use of MVMs given the research available to us today.
Libby is a Registered Dietitian focusing on eating disorder treatment and prevention. She is working on the central coast to create wellness in individuals and the community
Not Your Average Nutritionist, LLC