In 2017, Americans spent an estimated $36.1 billion on vitamins and nutritional supplements, many believing the supplements help prevent illnesses such as cardiovascular disease, according to Statista.
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And projections show the global nutritional supplement industry is expected to reach $278 billion by 2024.
But a new meta-analysis published in the journal Circulation: Cardiovascular Quality and Outcomes, negates any claims that multivitamin/mineral supplements are actually beneficial for heart health.
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"There is no scientific evidence that (these) supplements promote cardiovascular health," lead author Joonseok Kim of the University of Alabama at Birmingham told Reuters Health. "We hope that our paper helps to settle the debate."
Kim and his colleagues performed a systematic review of 18 different studies investigating associations between MVM supplements and an array of CVD outcomes, including coronary heart disease and stroke. More than 2 million participants were involved in the studies with an average 12 years of follow-up.
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Supplements with herbs, hormones or drugs were not included in the analysis.
Key findings
Researchers found that overall, there was no association between MVM supplements and CVD mortality, even after adjusting for participant diets, sex, age, smoking habits, physical activity, study sites and other factors.
While MVM was associated with a slightly lower risk of developing heart disease in studies outside of the U.S., the association was not significant in randomized controlled trials and did not take into account participant fruit and vegetable intake.
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“It is unclear why MVM supplement use was associated with lower risk of CHD incidence in studies done outside of the United States, whereas no benefit was found among studies performed in the United States,” study authors wrote. “Nutritional studies have established that fruits and vegetables are a good source of many vitamins and are associated with a lower risk of stroke and CHD, with a strong dose-response relationship.”
But, authors noted, data from Atlanta-based Centers for Disease Control and Prevention shows 87 percent of the U.S. population doesn’t meet the recommended fruit and vegetable recommendations.
“I would like to encourage people to discuss the use of MVM supplements with their physicians and reallocate their resources to something that is proven to improve cardiovascular outcomes, such as fruit and vegetable intake and exercise,” Kim told Reuters.
Healthcare professionals and researchers will now have enough evidence to correctly inform the public, Kim added.
Limitations
Researchers noted multiple limitations of the study, though its large meta-analysis and long-term follow-up, plus rigorous statistical methods are considerable strengths.
Only five of the 18 studies actually specified the dose and type of MVM supplements examined − and the market of MVM supplements is quite diverse.
“We attempted to perform a subgroup analysis of those who used MVM supplements more frequently but were unable to do so because of the lack of specific data,” authors wrote.
Additionally, some studies included in the meta-analysis were not free of potential confounding biases. But even when they adjusted for risk factors, researchers note their rigorous analysis did not alter the overall outcome.
In conclusion, “our study supports current professional guidelines that recommend against the routine use of MVM supplements for the purpose of CVD prevention in the general population,” they wrote. The U.S. Preventive Services Task Force and the National Institutes of Health have long recommended against the use of MVM supplements for heart health.
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