Dietary supplements typically offer no health benefits and could even be harmful, a new study suggests.
Researchers have revealed that common pills, like vitamin C and calcium capsules, have not been proven to provide health benefits while some could even increase the risk of death.
Similarly, healthy eating patterns, including Mediterranean and low fat diets, were found to have no effect on cardiovascular risk.
Published in the journal Annals of Internal Medicine, researchers from the University of West Virginia in the US reviewed 277 previous randomised trials involving almost one million people who took supplements.
The study looked into the effects of 16 different nutritional supplements and eight dietary interventions on mortality and cardiovascular outcomes in the adult participants.
Dr Safi Khan, lead author of the study, said: “We found out only a few of the 16 nutritional supplements and one of the eight dietary interventions evaluated had some protective effect in cardiovascular risk reduction.”
The researchers found that while some supplements, such as omega-3 and folic acid, were protective against heart disease and stroke, others could do more harm than good.
For example, combining vitamin D with a calcium pill was found to make a stroke more, rather than less, likely.
”Other supplements did not seem to have significant effect on mortality or cardiovascular outcomes,” Khan added.
These included multivitamins, selenium, vitamin A, vitamin B6, vitamin C, vitamin E, vitamin D alone, calcium alone, folic acid, and iron.
When it came to dietary changes, such as Mediterranean diet, reduced dietary fat, modified dietary fat and reduced saturated fat intake, the researchers said there was even less evidence of benefits.
Khan explained that just two dietary interventions had notable benefits and that these only applied to specific patients.
Reduced salt intake was found to protect against deaths from any cause in participants with normal blood pressure, while omega-3 fats found in fish were protective against heart attacks and coronary heart disease.
Dr Eric Topol, of the Scripps Research Translational Institute, who reviewed the findings for the journal, highlighted that the results were limited by the quality of the evidence and that areas such as geographic considerations among the studies need to be considered.
“The reported benefit of folate seems to be largely driven by the inclusion of one study from China, where a folate-rich diet is not routine,” Topol stated, referring to the form of vitamin B9.
Topol also noted that most studies relating to supplements rely on food diaries, “which are based on a person’s memory of what they consumed and therefore are not wholly reliable”.
The findings follow a similar report by Tufts University earlier this year which found that taking calcium supplements could double a person’s risk of dying from cancer.
The scientists suggested people could be putting themselves at risk by taking calcium supplement doses higher than 1,000 milligrams per day.
During their research, they found that after more than 12 years’ follow-up, there were roughly 24 cancer related deaths among supplement users compared to 12 in non-users, suggesting a 53 per cent greater risk of death from cancer.
According to a recent study by 4Homeopathy, an organisation campaigning to promote and defend homeopathy, adults in the UK spend an average of £123.60 on vitamins supplements every year.
The survey also found that men were more likely to spend money on vitamins, protein powders and exercise supplements to stay healthy, while women prioritise their spend on healthy foods.
The NHS states that vitamins and minerals are nutrients your body needs in small amounts to work properly and stay healthy.
While most people get all the nutrients they need by having a varied and balanced diet, the NHS explains that some people may need to take extra supplements.
It adds that taking too many supplements or taking them for too long can be harmful.
The Department of Health recommends certain supplements for some groups of people who are at risk of deficiency such as folic acid during pregnancy and vitamin D for people who are not often exposed to the sun.