The Myth of Multivitamins and Other Supplements
“In 2021, people in the US spent an estimated $50 billion on dietary supplements and the dietary supplement industry spent about $900 million on marketing”
Billions of dollars are being spent by consumers each year on products marketed as health promoting without solid evidence supporting such claims. In contrast to pharmacological treatments which have to be FDA approved before they can be sold to patients (even if they bit the placebo by less than 10%), these unregulated products only have to be safe and can’t make any claims about effectiveness in the treatment of a particular disease. Some of the best-known examples are gluten-free products (annual 8 billion US $ market), probiotics (62 billion), and an incredible array of supplements, including vitamins. More than half of adults take dietary supplements, and use of supplements in the US is projected to increase. In 2021, people in the US spent an estimated $50 billion on dietary supplements and the dietary supplement industry spent about $900 million on marketing. These marketing messages (and messengers) have flourished in the social media, and even the medical establishment has adopted some of the largely unfounded recommendations. Cleverly disguised promotions by internet influencers have become one of the most popular ways of fueling the supplement market and selling supplements has become a lucrative income stream for both physicians and allopathic healthcare providers.
“In theory, vitamins, minerals and phytochemicals have antioxidative and anti-inflammatory effects that should translate into a reduction of cardiovascular disease and cancer…”
As pointed out by Dr F. Perry Wilson of the Yale School of Medicine in a commentary in the online publication Medscape, the appeal of supplements is obvious. In theory (at least in the test tubes and animal models), vitamins, minerals and phytochemicals have antioxidative and anti-inflammatory effects that should translate into a reduction of cardiovascular disease and cancer, which has remained an elusive goal to reach. However, arguments can be made about the benefits of taking supplementary vitamins in otherwise healthy people. For example, it is well established in the literature that individuals with vitamin deficiencies are at higher risk for bad health outcomes. Even people with lower levels of certain vitamins, not in the deficiency range, are at higher risk for cancer and cardiovascular disease.
On the other hand, as I have discussed extensively in The Gut Immune Connection, eating a largely plant based diet, like the traditional Mediterranean, the MIND, and the DASH diets, with lots of fruits and vegetables has repeatedly shown to be associated with decreased cardiovascular disease and cancer risk in large epidemiological studies and in some clinical trials.
In order to generate a profit over and above selling these healthy food items, it is reasonable to think that key vitamins, botanicals, and minerals could be extracted from fruits and vegetables, packaged into a pill, and people could avoid the difficulty and expense of maintaining a balanced diet. This is the logic of a large number of health-conscious people who are not willing to abandon the traditional Standard American Diet (SAD) devoid of sufficient amounts of plant-based foods, and rather pop their supplement pills every morning.
“Micronutrients in isolation may act in a combinatorial manner and affect the body differently than when naturally packaged with a host of other dietary components”
As pointed out by Dr. Jenny Jia in an editorial published in the Journal of the American Medical Association (JAMA) entitled Multivitamins and Supplements—Benign Prevention or Potentially Harmful Distraction, the most common reason people report taking supplements is to improve or maintain overall health. However, in contrast to a single ingredient supplement pill, whole fruits and vegetables contain a mixture of vitamins, phytochemicals, fiber, and other nutrients that probably act synergistically to deliver health benefits. There are thousands of phytochemicals contained in different combinations in fruits and vegetables, and the same concept applies to fiber. Micronutrients in isolation may act in a combinatorial manner and affect the body differently than when naturally packaged with a host of other dietary components.
“…current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements, single supplements, or most paired supplements for the prevention of cardiovascular disease or cancer..”
In a rare event, two recent large-scale studies have provided evidence-based information related to health benefits of regular vitamin intake. For otherwise healthy, nonpregnant adults, the US Preventive Services Task Force (USPSTF) has updated its recommendation about the use of supplements to prevent cardiovascular disease or cancer. The USPSTF is an independent panel of experts involved in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services
This updated recommendation is based on a new evidence report and systematic review of 84 studies, including 52 new studies since the last USPSTF recommendation on this topic in 2014. It is worth mentioning that these were general-population studies, not studies of people with known vitamin deficiencies. The USPSTF concluded that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements, single supplements, or most paired supplements for the prevention of cardiovascular disease or cancer. No analyses of individual vitamins — beta-carotene, vitamin A, vitamin E, vitamin D (with a whopping 32 randomized trials), and calcium supplements — showed significant benefit in terms of either cardiovascular disease or cancer. Notable findings for the harm analysis included evidence that vitamin A use might increase the risk for hip fracture, that vitamin E use might increase the risk for hemorrhagic stroke, and that vitamin C or calcium use might increase the risk for kidney stones.
As correctly commented by Dr Wilson in the Medscape article, “why are the observational data that show lower vitamin levels linked to worse healthy outcomes so powerful, and the randomized trial data of vitamin supplementation so weak? This is classic confounding. Basically, healthier people have higher vitamin levels, and healthier people have less cardiovascular disease and cancer. Vitamin levels are a marker of overall health, not a driver of overall health.”
“…the results of the Harvard study failed to show a significant effect of a daily MVM on breast or colorectal cancer, prostate cancer or melanoma …”
Howard D Sesso and collaborators from the COSMOS Research Group at the Division of Preventive Medicine, Brigham and Women’s Hospital and Department of Epidemiology, and the Harvard T.H. Chan School of Public Health, both at the Harvard Medical School published results from another, large randomized, double-blind, placebo controlled clinical trial, evaluating the benefits of daily consumption of multivitamins for the prevention of cancer and cardiovascular disease. The study population included 21,442 US adults (12,666 women aged ≥65 y and 8776 men aged ≥60 y) free of major cardiovascular disease at the time of study begin and recently diagnosed cancer. The intervention phase was from June 2015 through December 2020.
Participants were randomly assigned to daily multivitamin multimineral (MVM) supplement or placebo. The primary outcome was total invasive cancer, (excluding non-melanoma skin cancer). Secondary outcomes included major site-specific cancers, total cardiovascular disease, all-cause mortality, and total cancer risk among those with a baseline history of cancer.
Consistent with the results of the USPSTF analysis of a large number of published studies, the results of the Harvard study failed to show a significant effect of a daily MVM on breast or colorectal cancer, prostate cancer or melanoma but showed a protective effect on lung cancer. The study did not show a significant association between MVM use and all-cause mortality or mortality from cardiovascular disease. Based on their results, the authors concluded that a daily MVM supplement, compared with placebo, did not significantly reduce the incidence of total cancer or cardiovascular disease among older men and women.
The take home message from these two studies is that unless you have a proven vitamin deficiency, or don’t have access to a variety of fresh fruit and vegetables for financial or geographical reasons, you should not expect a health benefit from taking your daily vitamin cocktail for common forms of cancer and for cardiovascular disease. If you get non-specific benefits from the regular MVM, such as higher energy, less brain fog or improved immune function, these benefits may be attributed to the placebo effect, so masterfully orchestrated by your brain.
Dr. Emeran Mayer is a Distinguished Research Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA and the Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience at UCLA.