Multivitamin efficacy all in our heads? Industry lashes back at study finding no improvements

11 Nov 2020 --- The health benefits of multivitamin and multimineral supplementation (MVM) perceived by users may not be clinically substantiated, according to a new BMJ-published study.

While MVM users self-reported 30 percent better overall health, the researchers found no clinically measurable differences in health outcomes between users and non-users. 

“Because nutritional supplements constitute a multibillion-dollar industry and can even be harmful when taken in excess, understanding the determinants of widespread MVM use has significant medical and financial consequences,” write the study authors.

“The onus is on the makers of multivitamins to show that they are efficacious,” co-author Manish Paranjpe, health sciences and technology at Harvard Medical School, US, tells NutritionInsight.

“We hope that some of this data can try to convince people that their money might be spent in more evidence-based strategies for improving mortality and morbidity.” 

Industry rushes to defence
The Council for Responsible Nutrition (CRN) has called the study a “disservice to the public,” noting multivitamins play a “valuable role” in filling essential nutrient gaps unmet by diets. 

“[Multivitamins] are not intended to serve as magic bullets for the prevention of serious diseases,” Dr. Andrea Wong, senior vice president of scientific and regulatory affairs at the CRN, tells NutritionInsight.

“However, the average price of a multivitamin is about a dime a day and [provides] a healthy choice to help consumers get the recommended levels of nutrients essential to everyday life, activity and body function,” she highlights.

The BMJ study found that MVM users reported better overall health because they believed in the efficacy of multivitamins.A survey of users versus non-users
Among 4,933 adult MVM users and 16,670 adult non-users – taken from a 2012 annual US National Health Interview Survey – MVM users self-reported 30 percent better overall health than non-users. 

The researchers compiled five psychological, physical and functional health outcomes from survey questions. These were subjective assessments of health, the need for help with routine daily activities, as well as medical history like high blood pressure, asthma, diabetes and arthritis.

They also investigated the degree of psychological distress and the presence of 19 common health conditions in the preceding 12 months, including infections, memory loss, neurological and musculoskeletal problems.

The study found no clinically observable differences between actual health status of MVM users versus non-users. No effect modification was observed after stratification by sex, education and race.

Questioning the methodology
Nevertheless, the CRN has questioned the credibility of the study’s methodology. “For instance, the study results are based on survey data, so rather than being determined by a clinician, all measured outcomes are self-reported and, therefore, less reliable.” 

The CRN has also scrutinized the composition of MVM products consumed, as well as reported duration or frequency of supplementation. “Additionally, the cross-sectional design of this study only provides a snapshot in time of multivitamin use and health outcomes, preventing any determination of causality.”

The researchers admit that this is an observational study, meaning it cannot prove a causal relationship between use of MVMs and subjectively assessed health. 

“What’s more, subjectively assessed health is not always reliable and the researchers didn’t track changes in health before and after taking supplements over the long term,” the study authors write.

In response, Paranjpe highlights that there are several large randomized control trials that show that taking a daily multivitamin has no benefit on cardiovascular, cancer or all-cause mortality.

The CRN has been quick to defend multivitamins, noting their role in filling nutrient gaps.Belief in the multivitamin
The study results suggest that the belief in the efficacy of MVMs may explain why MVM users self-reported better health in the absence of clinically measurable benefits. MVM users also intrinsically harbor a more positive outlook on their personal health.

MVM users in general were significantly older and earned more income. They were also more likely to be female, a college graduate, married and have health insurance compared with non-users.

Moreover, MVM users were also less likely to be unemployed, to have a minor child in their household and not to have an office visit for healthcare in the past two weeks compared with non-MVM users. 

Personalization kicking out MVMs?
Multivitamins may not be as popular as they once were given the boom of the personalized nutrition trend. Consumers are increasingly interested in dietary supplements that are tailored to their specific health needs.

Innova Market Insights crowned “Tailored to Fit” as its third top trend for 2021. An Innova Consumer Survey from 2020 shows that 64 percent of global consumers have found more ways to tailor their life and products to their individual style, beliefs and needs.

“While supplement personalization is likely to grow in the future, it does not make the multivitamin any less relevant or less useful for a large number of consumers,” Wong emphasizes.

She shares that data from the 2020 CRN Consumer Survey reveals that 75 percent of supplement users take a multivitamin, making it the most popular dietary supplement across all CRN-registered demographics. 

While personalized nutrition may appeal to health-conscious consumers aiming for more than a “cookie cutter” supplement, some researchers have advocated for multivitamins as an affordable means of boosting the immune system throughout the pandemic.

“The reality remains that the majority of US consumers fail to achieve recommended levels of essential nutrients through food alone,” concludes Wong.

By Anni Schleicher