A new meta-study, gathering data from over two million participants, has concluded that multivitamins and mineral supplements do not improve cardiovascular health or protect against heart attack and stroke. The systematic review suggests if a person is generally healthy then multivitamin/mineral dietary supplements confer no cardiovascular benefits.

Back in May a massive meta-analysis comprising 179 different clinical trials concluded that most common vitamin supplements provided no health benefits. Whereas that study broadly evaluated data across all causes of mortality, this new meta-study homed in on specific issues related to cardiovascular health.

After a broad literature search, the researchers targeted 18 specific studies to include in the meta-analysis. Over two million subjects were evaluated, with an average follow-up duration of 12 years. The results were reasonably conclusive, with no evidence found to suggest multivitamin/mineral dietary supplements reduce risk of cardiovascular disease, coronary heart disease or stroke.

"It has been exceptionally difficult to convince people, including nutritional researchers, to acknowledge that multivitamin and mineral supplements don't prevent cardiovascular diseases," says Joonseok Kim, from the University of Alabama at Birmingham and lead author on the study. "I hope our study findings help decrease the hype around multivitamin and mineral supplements and encourage people to use proven methods to reduce their risk of cardiovascular diseases – such as eating more fruits and vegetables, exercising and avoiding tobacco."

It's estimated that over half of all older adults in the United States use at least one vitamin or mineral dietary supplement. The global vitamin industry makes billions of dollars every year selling its wares, but a growing body of evidence suggests that in the absence of a specific medically diagnosed deficiency, most of these supplements are useless.

An editorial by Alyson Haslam and Vinay Prasad accompanying the latest metastudy presents a hypothesis to explain why vitamin supplements tend to not confer any general health benefits. They suggest that in the past when diets were limited there were many diseases with clear vitamin deficiency causes, but in 2018 modern diets are much more varied.

"Now that diets are more varied, supplemented, and fortified, diseases of frank vitamin deficiency are rare, and the most commonly occurring diseases have a multifactorial cause," write Haslam and Prasad. "It may be unlikely for a supplement ingested once a day to confer a health benefit."

It's important to note that this research doesn't suggest that vitamin or mineral supplements are useless in clinical cases where a patient actively needs those supplements. But, for a healthy adult with no specific diagnosed deficiency, this research affirms that taking vitamin supplements unnecessarily will only result in expensive urine.

"Although multivitamin and mineral supplements taken in moderation rarely cause direct harm, we urge people to protect their heart health by understanding their individual risk for heart disease and stroke and working with a healthcare provider to create a plan that uses proven measures to reduce risk," says Kim, who points out there are a multitude of better proven methods to help maintain cardiovascular health. "These include a heart-healthy diet, exercise, tobacco cessation, controlling blood pressure and unhealthy cholesterol levels, and when needed, medical treatment."

The study was published in the journal Cardiovascular Quality and Outcomes.