Many scientists claim that, for most people, the only outcome from taking vitamin supplements is expensive urine. Now an international team of scientists has added weight to that belief in a large-scale meta-analysis that has concluded that most common vitamin supplements provide no health benefits, particularly in the prevention of cardiovascular disease, heart attack, stroke and premature death.
The researchers systematically evaluated 179 clinical trials, published between 2012 and 2017. The trials were testing the impact of a range of vitamin and mineral supplements on decreasing the risk of heart disease, stroke and all deaths, regardless of the cause (aka all-cause mortality). The four most commonly used supplements (multivitamins, vitamin D, calcium, and vitamin C) showed no statistically significant benefits in reducing the risk of any of the targeted conditions.
"We were surprised to find so few positive effects of the most common supplements that people consume," says David Jenkins, lead author on the study. "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."
The only significant effects of note found in the study were a positive correlation between folic acid and stroke or heart disease prevention, and a very small negative correlation indicating niacin (vitamin B3) and antioxidants could actually increase the risk for all-cause mortality.
The researchers conclude by suggesting a healthy diet consisting of unprocessed foods such as fruits, vegetables and nuts is still the most effective way to consume vitamins and minerals. Australian nutritionist Rosemary Stanton affirms the findings of the study, and urges people to avoid wasting money on unnecessary vitamin and mineral supplements.
"There may be lots of money to be made selling supplements to gullible people," says Stanton, "but these products cannot match the literally thousands of important components available in healthy foods such as fruit, vegetables, wholegrains, fish, nuts and seeds."
A minor limitation in the study could be seen to be its broad focus. John Funder, from Monash University, points out that the study does not suggest vitamin or mineral supplements are useless in clinical cases where a patient actively needs those supplements.
As an example he highlights the niacin conclusion from the study, which suggests an association with a mild increase in all-cause mortality. This data point is only generated from three specific trials examining the supplement when taken alongside statins in patients with a higher risk for cardiovascular disease. Funder stresses that data such as this should not be misinterpreted by groups of people such as pregnant women who are advised to take niacin.
"This would be a great pity," Funder says of the risk the study resulting in those needing supplements subsequently refusing them, "given the recent discovery of mutations in the enzymes required for the synthesis of NAD (nicotinamide adenine dinucleotide) in children with major developmental abnormalities, and the ability of giving equivalently genetically compromised pregnant mice vitamin B3 to normalize outcomes for their offspring."
Perhaps the most fundamental takeaway from this study is defiantly unsurprising but always worth restating. For those eating a normal, healthy diet, vitamin and mineral supplements are simply a waste of money. Extra boosts of vitamins we do not need will not confer enhanced protective benefits from disease or help us live longer.
The study was published in the Journal of the American College of Cardiology.
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