Do multivitamins work? Perhaps yes, for some; but for many, the research (including a large scale study just published) shows more than likely not. Given the prevalence of supplements in our society, many people struggle to accept that they are not as effective as the data shows.
Advocates of multivitamins highlight the absence of strong evidence indicating that long-term multivitamin use is harmful. Although the risk of harm is minimal (but not necessarily Zero), the likelihood of a significant health benefit is also quite low, and there is little definitive proof of such benefits yet. Others argue that, despite the lack of clear evidence for health benefits, multivitamin supplementation is both low-risk and low-cost. They believe it can help address potential dietary gaps.
What is the evidence for their benefit or lack of benefit?
Below we review recent meta-analyses and systemic reviews on how multivitamins impact different areas of health, for better or worse. We are "quoting" from key areas in each study, to hear it from the scientists, not from us.
As ever, please talk to your doctor or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle, especially if you are under treatment.
Mortality - Risk of Death
Study date June, 2024: “In this cohort study of 390 124 generally healthy US adults with more than 20 years of follow-up, daily multivitamin (MV) use was not associated with a mortality benefit. In contrast, we found that daily MV use vs nonuse was associated with 4% higher mortality risk. The results of the time-varying analysis, incorporating a second MV use assessment, were consistent with the pooled baseline estimates and support our conclusion of no mortality benefit.
In this cohort study of 390 124 US adults without a history of major chronic diseases, we did not find evidence to support improved longevity among healthy adults who regularly take multivitamins. However, we cannot preclude the possibility that daily MV use may be associated with other health outcomes related to aging.”
Loftfield E, O'Connell CP, Abnet CC, Graubard BI, Liao LM, Beane Freeman LE, Hofmann JN, Freedman ND, Sinha R. Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts. JAMA Netw Open. 2024 Jun 3;7(6):e2418729. doi: 10.1001/jamanetworkopen.2024.18729. PMID: 38922615.
Cognitive Health in the Elderly
Study date March 2024:“In COSMOS-Clinic, daily multivitamin (MVM) supplementation leads to a significantly more favorable 2-year change in episodic memory. The meta-analysis within COSMOS cognitive substudies indicates that daily MVM significantly benefits both global cognition and episodic memory. These findings within the COSMOS trial support the benefits of a daily MVM in preventing cognitive decline among older adults.”
Vyas CM, Manson JE, Sesso HD, Cook NR, Rist PM, Weinberg A, Moorthy MV, Baker LD, Espeland MA, Yeung LK, Brickman AM, Okereke OI. Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial and meta-analysis of 3 cognitive studies within COSMOS. Am J Clin Nutr. 2024 Mar;119(3):692-701. doi: 10.1016/j.ajcnut.2023.12.011. Epub 2024 Jan 18. PMID: 38244989; PMCID: PMC11103094.
Cardiovascular Disease and Cancer
Study date June 2022:"This updated evidence review examined the use of vitamins and minerals for primary prevention of cardiovascular disease and cancer; the evidence is summarized in the Table. The findings from 84 RCTs and 6 cohort studies suggest that most vitamin and mineral supplements provide no clinically important protective effects for cardiovascular disease, cancer, or all-cause mortality in healthy adults without known nutritional deficiencies. One exception was a slightly lower risk of cancer incidence with multivitamin use. However, the evidence for multivitamins had important limitations, including only 3 adequately powered trials, 1 with a median of only 3.6 years of multivitamin use and another that was limited to antioxidants.
Other than the new finding related to multivitamin use and lower cancer incidence, these conclusions are generally consistent with those of the previous review for the US Preventive Services Task Force on this topic. Vitamin E had the strongest body of evidence demonstrating no benefit for outcomes relevant to this review. These updated review findings also confirm the previous review’s finding that beta carotene supplementation, especially with concomitant vitamin A use, likely increases the risk of lung cancer incidence, particularly in those at high risk for lung cancer. New evidence in this update was predominately for vitamin D supplementation. Despite the new inclusion of 32 RCTs and 2 cohort studies, pooled estimates for all-cause mortality were similar to that in the prior review with confidence intervals only slightly crossing 1 and point estimates suggesting at most a very small benefit.
Vitamin and mineral supplementation was associated with little or no benefit in preventing cancer, cardiovascular disease, and death, with the exception of a small benefit for cancer incidence with multivitamin use. Beta carotene was associated with an increased risk of lung cancer and other harmful outcomes in persons at high risk of lung cancer."
O'Connor EA, Evans CV, Ivlev I, Rushkin MC, Thomas RG, Martin A, Lin JS. Vitamin and Mineral Supplements for the Primary Prevention of Cardiovascular Disease and Cancer: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2022 Jun 21;327(23):2334-2347. doi: 10.1001/jama.2021.15650. PMID: 35727272.
and, study date June 2022..."
Consumption of vitamin and mineral supplements is common despite the lack of evidence supporting efficacy for prevention of cardiovascular disease (CVD).
Folate and B vitamins reduce the risk of stroke, but methylcobalamin or oxocobalamin may be preferred over cyanocobalamin.
Consuming plant-based food is a safe approach to increasing micronutrient intake.
In general, over the past 2 years, no new associations between micronutrients and CVD or mortality have been found. The data on the popular supplements, multivitamins, vitamin D, calcium, and vitamin C, continue to show no consistent benefit for the prevention of cardiovascular disease, MI, or stroke, nor is there a benefit for all-cause mortality despite further studies on some of these micronutrients (n = 23, vitamin D; n = 4, calcium; no new studies identified for vitamin C and multivitamins). Many of the vitamin D studies were small and of short duration. If longer and larger studies were included, a benefit for all-cause mortality may have been seen.
In the last 2 years, there have been no trials of sufficient size and consistency to alter the advice previously given by the U.S. Preventive Services Task Force 7 years ago that identified a general lack of effect of vitamin and minerals in altering the risk of CVD or total mortality, with the exception of folic acid and the B vitamins that reduce stroke. Data on diets such as PREDIMED, the Lyon Heart Study, and the Ornish diet that encourage a move to more plant-based diets have respectively shown reductions with respect to stroke and all-cause mortality, myocardial infarction (MI), and angiographic change. In the absence of very clear micronutrient health benefits and with concerns that excess consumption of certain micronutrients may have undesirable consequences, it appears that more certain CVD gains can be achieved by dietary change that follows the move to more plant-based diets, as advised now internationally."
Jenkins DJA, Spence JD, Giovannucci EL, Kim YI, Josse RG, Vieth R, Sahye-Pudaruth S, Paquette M, Patel D, Blanco Mejia S, Viguiliouk E, Nishi SK, Kavanagh M, Tsirakis T, Kendall CWC, Pichika SC, Sievenpiper JL. Supplemental Vitamins and Minerals for Cardiovascular Disease Prevention and Treatment: JACC Focus Seminar. J Am Coll Cardiol. 2021 Feb 2;77(4):423-436. doi: 10.1016/j.jacc.2020.09.619. PMID: 33509399.
Blood Pressure (BP) - Hypertension
Study date August 2018:“In the present study, we observed a lowering effect of multivitamins (MVMS) on Systolic BP and Diastolic BP. The lowering effect of MVMS on blood pressure has a biological basis. Previous animal studies indicated that vitamins and minerals can directly influence blood pressure by modulating sympathetic activity, vascular endothelial and smooth muscle function, vascular membrane ion exchange, and vascular tone. In addition, vitamins and minerals may also indirectly influence blood pressure by modulating inflammation and oxidative stress. C-Reactive protein (CRP), an acute phase reactant protein, is an independent risk factor for cardiovascular disease including hypertension, and previous Randomised Control Trials (RCTs) indicated that vitamins and minerals had a significant lowering effect on C-Reactive Protein. Oxidative stress is another important factor contributing to hypertension, and many vitamins and minerals play an important role in antioxidation, such as vitamin C, vitamin E and selenium. These evidences above can help explain the mechanism by which MVMS lowers blood pressure.
Although MVMS had a significant lowering effect on blood pressure in normotensive subjects, the lowering effect was too small to effectively prevent future hypertension. MVMS may be an effective method for blood pressure control in subjects with chronic disease including hypertension, but the sample size of subjects with hypertension or other chronic disease was too small, and more well-designed RCTs are needed to confirm this result.”
Li K, Liu C, Kuang X, Deng Q, Zhao F, Li D. Effects of Multivitamin and Multimineral Supplementation on Blood Pressure: A Meta-Analysis of 12 Randomized Controlled Trials. Nutrients. 2018 Aug 3;10(8):1018. doi: 10.3390/nu10081018. PMID: 30081527; PMCID: PMC6116168.
Now that you have had the chance to read the latest evidence, what do you think? Might this change the way you consume vitamins or not?
Who might benefit?
Those at risk of nutrient gaps, for example, people with dietary restrictions such as vegetarians, vegans or those on ketogenic diets or that have food allergies.
Those with specific needs, for example, pregnant women need more folic acid and iron, older adults may require more vitamin D and B12, individuals with certain medical conditions may benefit from additional nutrients.
Those with conditions that affect nutrient absorption, such as Crohn's disease or celiac disease.
And here is the category with most room for interpretation...
Those with poor diet quality due to lifestyle, socioeconomic factors or personal choices might benefit from multivitamins to compensate for an unbalanced diet.
I used to take a palmful of vitamin and mineral pills every day, based on the evidence at that time. Since then the science has evolved as has my use of supplements.
Now I take a single, relatively low dose multivitamin - specifically as a supplement to a balanced diet.
And if I miss a day or two, no problem. Importantly, on a daily basis we enjoy a variety of different whole - real - foods that provide essential nutrients. Multivitamins cannot take the place of eating a healthy diet; Food (with a capital F) provides far more nutrition than vitamins and minerals alone. For most people, those in relatively good health, supplements are not necessary but perhaps occasionally useful. Single vitamin supplements may be of value where there are measured and known deficiencies, some can even cause harm.
Notably, recent research on omega-3 supplementation also shows that in healthy people (those without CVD / heart disease) supplementation might increase risk of atrial fibrillation and stroke. Better to eat oily fish such as mackerel (saba) or sardines.
As part of a whole health lifestyle we recognise that health and longevity is more than just diet... exercise, good sleep, a healthy social life. These all play a significant role in enjoying life to the full, they are not simply 'boxes to be checked'.
Stay Healthy!
Alastair
What about single vitamins or mineral tablets, do we need them? Recently, for example, there has been much online discussion concerning magnesium supplements. Read more here.
'Greens Blends' have also become popular, with AG1 being aggressively promoted across social media.
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