Writing in the BMJ Open, the US-based team finds multivitamin/mineral supplement (MVM) users reporting 30% better health than non-users with no difference between the two groups when testing psychological, physical or functional health outcomes.
“The effect of positive expectations in [those who take multivitamin/mineral supplements] is made even stronger when one considers that the majority of [them] are sold to the so-called ‘worried-well’,” the team from Harvard Medical School writes.
“The multibillion-dollar nature of the nutritional supplement industry means that understanding the determinants of widespread [multivitamin/mineral] use has significant medical and financial consequences.”
Vitamin D in spotlight
Interest in multivitamins or mineral supplements has surged this year owing to the pandemic, in which consumers have turned to vitamins, minerals and botanical ingredients to support immune function.
This is no where more clearly shown than with vitamin D, where a spate of news linking its efficacy against the coronavirus is giving credence to its effectiveness.
Its cost effectiveness and ease of distribution is also a factor as the UK government looks to follow Scotland’s example by offering free vitamin D supplies to those shielding during lockdown.
While multivitamin/mineral supplementation is justified for individuals at high risk because of disease-related deficiency, their consumption has not produced robust evidence for the health benefits expected by the general adult population.
Notable research includes the Physicians’ Health Study II (PHS II), which found no reduction in major cardiovascular disease (CVD) events, myocardial infarction, stroke, and CVD mortality, and these results were independent of baseline nutritional status.
Drawing upon research that asked 21,603 US adults about their use of complementary medicine, the team identified five psychological, physical, and functional health outcomes from the questions asked.
These were: subjective assessment of health; need for help with routine daily activities; history of 10 long term conditions (i.e. high blood pressure, asthma, diabetes, and arthritis).
Other outcomes included the presence of 19 common health conditions in the preceding 12 months (infections, memory loss, neurological and musculoskeletal problems); and degree of psychological distress, measured on a validated scale (K6).
Around 4933 individuals said they regularly took multivitamin/mineral supplements compared to 16670 respondents, who said they didn’t.
Results found that regular multivitamin/mineral supplement users reported 30% better overall health than those who didn’t take them.
This was despite no differences noted between users and non-users in any of the five psychological, physical or functional health outcomes assessed.
More analysis found regular consumption of multivitamin/mineral supplements was linked to better self-reported overall health across all race, sex, and education groups, as well as in the under 65s and those on low household incomes.
“MVM users believe in the efficacy of MVMs by harbouring a positive expectation regarding the health benefits of MVMs; and MVM users intrinsically harbour a more positive outlook on their personal health regardless of MVM usage,” the team suggests
“In the case of MVM usage, it is interesting that the presence of positive expectations did not influence clinically measurable health outcomes, unlike in other treatments.
“It is possible that members of this population are more susceptible to positive expectations and may thereby continue to use MVMs in the absence of clinical benefits.”
'Snapshot of multivitamin use'
The study was met with criticism from industry groups that included the Council for Responsible Nutrition’s (CRN) Andrea Wong, who says, “CRN stresses the findings in no way discount the multivitamin’s benefits in combatting insufficient nutrient levels and promoting optimum health.
“It does not provide a basis for consumers to reconsider their decision to take a multivitamin or to take one in the future.
“The results of the study are based on survey data, so rather than being determined by a clinician, all measured outcomes are self-reported and therefore, less reliable.
“The study also does not capture the composition of the multivitamin or multimineral products reported by respondents or the duration or frequency of consumption.
“It is impossible to know which products were taken or how often respondents took them over the 12-month period covered by the survey, or even how long the subjects had previously been on their regimens.
“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 Health Food Manufacturers’ Association (HFMA) reports that 69% of adults in the UK consume supplements with almost half taking multivitamins.
The Association’s executive director Graham Keen said, “Vitamins and minerals are essential for a healthy life.
“Supplements are an essential requirement for some groups of people with characteristics which put them at risk of nutrient deficiencies, a position supported by the Department for Health. This is never more relevant than now.
“A number of micronutrients are important for normal function of the immune system, such as vitamins D, C, A, B6, B12 and folic acid, plus the minerals selenium, zinc, copper and iron. Maintaining sufficient intake of these nutrients is important for a healthy immune system.”
Source: BMJ Open
Published online: doi: 10.1136/bmjopen-2020-039119
“Self-reported health without clinically measurable benefits among adult users of multivitamin and multimineral supplements: a cross-sectional study.”
Authors: Manish Paranjpe et al