Some vitamin supplements unhealthy

A new study has found that some vitamin and mineral supplements may be detrimental to health, and recommends that patients adopt a balanced diet rather than rely on supplements.

Published in the Journal of the American College of Cardiology, the study reviewed 179 randomised controlled trials published from January 2012 to October 2017, testing the impact of supplements on developing and treating heart disease and on all-cause mortality. With the exception of folic acid for reducing stroke risk, the research found little evidence that vitamin or mineral supplements were beneficial for preventing or treating heart disease, and that some supplements could worsen health outcomes.

Researchers found that data on the four most commonly used supplements — multivitamins, vitamin D, calcium and vitamin C — showed no consistent benefit for the prevention of cardiovascular disease, myocardial infarction or stroke, nor for all-cause mortality. Folic acid alone, and B-complex vitamins in which folic acid was a component, did show a reduction in stroke; but niacin (vitamin B3) and antioxidants were associated with an increased risk of all-cause mortality. 

However, Professor John Funder AC, Department of Medicine, Monash University, cautioned against "damning" Vitamin B3 entirely as it is known for its neonatal benefits, especially "given the recent discovery of mutations in the enzymes required for the synthesis of NAD (nicotinamide adenine dinucleotide) in children with major developmental abnormalities", he said. He noted that the study examined B3 (also known as niacin or nicontinic acid) at significantly higher doses than normally provided to expectant mothers.

Over relying on supplements

Vitamins and minerals have long been used to treat nutrient deficiencies, but in recent years, supplements have been promoted as a means for overall health and longevity. "In Australia, supplement use is very common with almost 30% of Australians reporting consuming supplements in our latest Australian Health Survey (2011–12, Australian Bureau of Statistics)," said Dr Carly Moores, College of Nursing & Health Sciences, Flinders University. "Supplements are widely available but their use should be informed and monitored by a qualified healthcare professional.

"They are most effective when they address an existing deficiency or when the required intake of some nutrients is difficult to meet from the diet alone, eg, in women planning pregnancy or currently pregnant," she said.

Nutritionist Dr Rosemary Stanton OAM, concurs. "More than half of Australians have swallowed the line that it's good to take supplements," she said. "It makes much more sense to enjoy healthy (and delicious) foods ... Guidelines are available at eatforhealth.gov.au."

The study has some limitations, including: the researchers did not consider data from cohort studies, which are longer and more representative of the general population than randomised clinical trials. Also, grouping many types of antioxidants may have been suboptimal since their mechanisms of action may also be very different.

Image credit: ©stock.adobe.com/au/ Leigh Prather