Multivitamins are a very common supplement, taken by people of all ages and backgrounds. But are they doing anything for our health? Let’s discuss…
Multivitamins are dietary supplements providing a variety of essential vitamins. They can also contain other nutrients such as minerals, trace elements, and non-essential nutrients such as phytochemicals. In this case they are more precisely known as multinutrients, as they contain more than just vitamins. They are one of the most popular supplements out there: about one in three Americans take a multivitamin daily (1). To understand why, we will discuss a common rationale for their use. Then, we will examine how they relate to health outcomes and discuss whether they are worth taking or not.
More Vitamins = Better Health?
Because vitamins are essential for our body, meaning we must get them from our diet (our bodies can’t make them), they are clearly very important. If we don’t consume vitamins, we die. Therefore, it seems pretty logical to think that because consuming some amount of vitamins is good for health, more must always be better, right? Well, not quite. Once you consume enough to support normal bodily functioning and prevent deficiency, more is not necessarily better, and for some vitamins, too much is a bad thing. For example, consuming too much vitamin A can lead to vitamin A toxicity—which brings with it a host of health issues.
Take a look at the following graph (Figure 1). The space between the RDA (Recommended Daily Allowance) and the UL (upper level of intake) represents a range of intakes for a vitamin that provides sufficient, or adequate, amounts for normal bodily processes. Whether you consume more within this range and experience further health benefits is the question we will attempt to answer. We can see that before the RDA and after the UL the risk for insufficiency and excess increases, respectively, which can each bring health issues. Therefore it’s important to ensure you’re in the range of nutrient intake adequacy, that is, between the RDA and the UL.
Figure 1. Graph indicating dietary reference intakes (2). EAR: Estimated Average Requirement; RDA: Recommended Daily Allowance; UL: upper limit of intake
Multivitamins and Health Outcomes
As alluded to already, the question we are investigating is not whether vitamins are beneficial for health when we are deficient—we know that correcting a deficiency via multivitamin supplementation would improve health. The question on the table is whether regular multivitamin supplementation in people without deficiencies can give added health benefits.
Cancer
In the Cancer Prevention Study II, over 1 million Americans were followed from 1982–1989 and the association between multivitamin use and cancer was investigated (3). Results generally showed no significant association between multivitamin use and cancer. In the Physicians’ Health Study II, which included ~14,000 people followed up for ~11 years, those taking a multivitamin experienced an 8% reduced risk of getting cancer compared to those taking a placebo, but no significant benefit for the risk of death from cancer (4). Similarly, in the recently published COSMOS trial there were no significant associations between multivitamin use and total cancer and most cancer subtypes in a cohort of over 21,000 people followed up for nearly 4 years (5). These prior two trials are some of the largest randomised controlled trials we have on this topic, and therefore hold quite a bit of weight. If we include more randomised controlled trials—like a 2013 meta-analysis of 21 trials did—we also see no significant reduction in cancer incidence for multivitamin or multimineral users (6).
Cardiovascular Disease
The same can be said for cardiovascular disease risk: all of the previously mentioned large-scale studies reported no significant benefit for cardiovascular disease risk and/or the risk of death from cardiovascular disease for those taking multivitamins or multiminerals compared to non-users or those taking a placebo (3, 5, 6, 7).
Risk of Death from any Cause
Once again, when we look at the *highest quality data, we see non-significant reductions in risk of death from any cause for multivitamin and multimineral users (5, 6, 7).
*For this research question, randomised controlled trials are the highest-quality evidence to answer whether multivitamin supplementation reduces the risk of chronic diseases and death.
Are They Worth Taking?
Multivitamins can be worthwhile supplements to the diet in a number of contexts, such as:
A period of energy (kcal) restriction, to ensure you’re getting enough vitamins to support everyday life
For individuals with poor diet quality—multivitamins can ensure these people don’t become deficient in one or many nutrients
For those eating restrictive diets, multivitamins can fill in nutritional gaps
For those who may need more nutrients, e.g., pregnant individuals
For those not eating a balanced diet
Will multivitamins reduce the risk of cancer, cardiovascular disease, and death from any cause? The most robust evidence we have suggests the answer is probably not. The most recent US Preventive Task Forces Vitamin, Mineral, and Multivitamin Supplementation Recommendation Statement concluded, “that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements for the prevention of cardiovascular disease or cancer” —a sentiment we largely agree with (8).
Summary
To bring everything together, we can comfortably say that yes, vitamins are essential for life and multivitamins can be helpful in a number of scenarios. But whether they go beyond helping to maintain adequate nutritional status, towards reducing the risk of conditions like cancer and cardiovascular disease and the risk of death from any cause, the answer is most likely no.
Key Takeaway: If you're papering over a poor-quality diet with a multivitamin and thinking that this will promote similar long-term health as a high-quality diet, you're sorely mistaken.
Now that you have levelled up your nutrition knowledge, come and train with us and level up on the pitch, too. Contact [email protected] to get started.
That’s all for this week, have a lovely weekend!
Patrick Elliott, BSc, MPH
Health and Nutrition Science Communication Officer at Training121
Founder of Just Health — IG: @just.health.info
Health Disclaimer: this article is for informational and educational purposes only, and is not a substitute for professional advice. For health advice, speak to a physician or other qualified health-care professional, and for nutrition advice, speak to a qualified nutrition professional (e.g., registered dietitian). The use of information on this site is solely at your own risk.
References
(1) Bailey RL, Gahche JJ, Lentino CV, et al. Dietary supplement use in the United States, 2003-2006. J Nutr. 2011;141(2):261-6. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021445/
(2) Carr AC, Lykkesfeldt J. Discrepancies in global vitamin C recommendations: a review of RDA criteria and underlying health perspectives. Crit Rev Food Sci Nutr. 2021;61(5):742-55. Available at: https://pubmed.ncbi.nlm.nih.gov/32223303/
(3) Watkins ML, Erickson JD, Thun MJ, Mulinare J, Heath CW Jr. Multivitamin use and mortality in a large prospective study. Am J Epidemiol. 2000;152(2):149-62. Available at: https://academic.oup.com/aje/article/152/2/149/87699
(4) Gaziano JM, Sesso HD, Christen WG, et al. Multivitamins in the prevention of cancer in men: the Physicians' Health Study II randomized controlled trial [published correction appears in JAMA. 2014 Aug 6;312(5):560]. JAMA. 2012;308(18):1871-80. Available at: https://jamanetwork.com/journals/jama/fullarticle/1380451
(5) Sesso HD, Rist PM, Aragaki AK, et al. Multivitamins in the prevention of cancer and cardiovascular disease: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial. Am J Clin Nutr. 2022;115(6):1501-10. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9170475/
(6) Macpherson H, Pipingas A, Pase MP. Multivitamin-multimineral supplementation and mortality: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2013;97(2):437-44. Available at: https://pubmed.ncbi.nlm.nih.gov/23255568/
(7) Sesso HD, Christen WG, Bubes V, et al. Multivitamins in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA. 2012;308(17):1751-60. Available at: https://jamanetwork.com/journals/jama/article-abstract/1389615
(8) US Preventive Services Task Force, Mangione CM, Barry MJ, et al. Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2022;327(23):2326-33. Available at: https://jamanetwork.com/journals/jama/fullarticle/2793446
Technical Terms
Multivitamin: A dietary supplement providing a variety of essential nutrients. They most often come in a pill form, but can come in powder form.
Essential: In the context of human nutrition, essential nutrients must be obtained through diet, i.e., our bodies cannot make them.
Vitamins: molecules that are essential for specific metabolic reactions in the body and for promoting normal growth and development. There are water-soluble (B, C) and fat-soluble (A, D, E, K) vitamins.
Minerals: Also known as macrominerals, these are molecules like vitamins that are essential for the body. Examples include potassium, calcium, and magnesium.
Trace elements: Also known as microminerals, these are needed in smaller quantities than minerals. Examples include iron, zinc, and selenium.
Phytonutrients: These are non-essential nutrients, but are essential for optimal health. They are only found in plant foods and examples include flavonoids, polyphenols, and isoflavones.
RDA: Otherwise known as the Recommended Daily Allowance, this refers to the amount of a nutrient needed to be consumed for 97.5% of the population to achieve adequacy.
UL: This is the upper limit of intake of a nutrient, which means that consuming above this level can cause negative health consequences.
EAR: Otherwise known as the Estimated Average Requirement, this refers to the amount of a nutrient needed to be consumed for 50% of the population to achieve adequacy.
Randomised controlled trials: Also known as RCTs, these are a type of intervention study where a group of recruited individuals are randomly assigned to groups within a study. The rationale for randomisation is to reduce bias, that is, to evenly distribute among groups any factors that may influence (or bias) the result of interest. For example, if we have a group of 100 people who will either be given a multivitamin or placebo and followed for 10 years to see how many in each group dies, we would randomise so that each group is on average similar for factors like age, physical activity status, smoking status, and so on. If we didn't randomise, there's a greater chance that one group may end up being different enough from another group such that the results of the study may be biased, e.g., one group could have a lot more smokers or sedentary individuals, which would likely influence the outcome of interest (death).