There's no point in taking vitamin supplements if you don't have a deficiency, new research has found.
Researchers looked at five years of trials and data that looked at the effectiveness of a range of supplements. Not only did they find there was no advantage in many commonly sold products, some actually appear to increase the likelihood of cardiovascular disease, heart attack, stroke and premature death.
"We were surprised to find so few positive effects of the most common supplements that people consume," said Dr David Jenkins, lead author of the study, which was published earlier this week in the Journal of the American College of Cardiology.
"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."
Other supplements that didn't show any benefit include beta-Carotene and selenium.
And for niacin and supplements marketed as 'antioxidant mixtures', the researchers found they increased the risk of death.
"These findings suggest that people should be conscious of the supplements they're taking and ensure they're applicable to the specific vitamin or mineral deficiencies they have been advised of by their healthcare provider," said Dr Jenkins.
There was a sliver of hope however, with the research digging up a link between folic acid and a reduced risk of stroke and cardiovascular disease. A study in 2016 on pregnant women had similar results, finding that supplements were largely useless - except folic acid and vitamin D.
And while vitamin B6 had no effect on longevity, scientists in Australia earlier this year published research claiming it helps people remember their dreams.
But in general, unless your doctor instructs you to, you're better off spending your money on proper food than supplements.
"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," Dr Jenkins 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."