People who use vitamin and mineral supplements to keep their heart in tiptop shape probably aren't getting much out of it, suggests a new review published in the Journal of the American College of Cardiology. The study found that most popular supplements, such as vitamin C and calcium, seemed to provide no benefits in preventing cardiovascular disease or early death. Some even appeared to slightly raise the risk of death.
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Researchers analysed more than 150 randomised clinical trials published from 2012 to 2017. In total, they looked at trials of 15 vitamin and mineral supplements, including multivitamins. The four most commonly used supplements in the US - vitamins C and D, calcium, and multivitamins in general - were found to have no significant effects on any cardiovascular health outcomes, or on the chances of dying prematurely.
Across 43 studies, for instance, there were 2908 deaths among 18,719 people who took vitamin D, compared to 2968 deaths among 18,831 people in control groups.
"We were surprised to find so few positive effects of the most common supplements that people consume," said lead author David Jenkins, a professor in the department of Nutritional Sciences at the University of Toronto in Canada, in a statement. "Our review found that if you want to use multivitamins, vitamin D, calcium or vitamin C, it does no harm - but there is no apparent advantage either."
Jenkins and his team also found there was a very small but noticeable risk of early death from trials of vitamin B3, or niacin, as well as combined supplements containing two or more antioxidants such as Vitamin A, E, β-carotene, selenium and zinc.
This isn't the first review to find that most supplements do nothing to help heart health. The US Preventive Services Task Force (USPSTF), a government-appointed but independently staffed panel of experts that guide nationwide screening and preventive care practices, came to a similar conclusion in 2014. But their takeaway wasn't entirely the same as this new study's.
Back then, the USPSTF found that taking vitamin B9, or folic acid, supplements didn't prevent cardiovascular problems. But their conclusion was based on a single study. Looking at other trials, including new research published since 2014, the current review found that taking folic acid supplements was associated with a lower risk of stroke and cardiovascular disease, as was taking supplements that had folic acid in combination with B6 and B1.
Jenkins and his team say there's still more research that needs to be done in studying folic acid's possible benefits. Even if it does help the heart, it might not be worth taking in supplement form for people in Australia and the US, since many products in these countries are already fortified with it. The single new study after the USPSTF review that found a heart-boosting effect was conducted in China, where most products aren't fortified with folic acid.
And taking it as a supplement might not be entirely risk free, because some research has suggested folic acid could raise the risk of certain cancers.
It's estimated that around 50 per cent of Americans regularly take at least one vitamin supplement, and around 30 per cent take a multivitamin. In Australia, over 60 per cent of the population takes a supplement. And while most of these products aren't doing any damage, the researchers think their findings offer a clear lesson on priorities.
"In the absence of significant positive data - apart from folic acid's potential reduction in the risk of stroke and heart disease - it's most beneficial to rely on a healthy diet to get your fill of vitamins and minerals," he said. "So far, no research on supplements has shown us anything better than healthy servings of less-processed plant foods including vegetables, fruits and nuts."