The most commonly consumed vitamin and mineral supplements provide no consistent health benefit or harm, suggests a new study led by researchers at St Michael’s Hospital and the University of Toronto.
The systematic review of existing data and single randomised control trials published in English from January 2012 to October 2017 found that multivitamins, vitamin D, calcium and vitamin C – the most common supplements – showed no advantage or added risk in the prevention of cardiovascular disease, heart attack, stroke or premature death.
Generally, vitamin and mineral supplements are taken to add to nutrients that are found in food. “We were surprised to find so few positive effects of the most common supplements that people consume,” said Dr David Jenkins*, the study’s lead author.
“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 study found folic acid alone and B-vitamins with folic acid may reduce cardiovascular disease and stroke. Meanwhile, niacin and antioxidants showed a very small effect that might signify an increased risk of death from any cause.
“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,” Jenkins said.
His team reviewed supplement data that included A, B1, B2, B3 (niacin), B6, B9 (folic acid), C, D and E; and Beta-carotene; calcium; iron; zinc; magnesium; and selenium. The term ‘multivitamin’ in this review was used to describe supplements that include most vitamins and minerals, rather than a select few.
“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,” 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.”
The authors identified individual randomized controlled trials from previous meta-analyses and additional searches, and then performed meta-analyses on cardiovascular disease outcomes and all-cause mortality. The authors assessed publications from 2012, both before and including the US Preventive Service Task Force review. Their systematic reviews and meta-analyses showed generally moderate- or low-quality evidence for preventive benefits (folic acid for total cardiovascular disease, folic acid and B-vitamins for stroke), no effect (multivitamins, vitamins C, D, β-carotene, calcium, and selenium), or increased risk (antioxidant mixtures and niacin [with a statin] for all-cause mortality). Conclusive evidence for the benefit of any supplement across all dietary backgrounds (including deficiency and sufficiency) was not demonstrated; therefore, any benefits seen must be balanced against possible risks.
David JA Jenkins, J David Spence, Edward L Giovannucci, Young-in Kim, Robert Josse, Reinhold Vieth, Sonia Blanco Mejia, Effie Viguiliouk, Stephanie Nishi, Sandhya Sahye-Pudaruth, Melanie Paquette, Darshna Patel, Sandy Mitchell, Meaghan Kavanagh, Tom Tsirakis, Lina Bachiri, Atherai Maran, Narmada Umatheva, Taylor McKay, Gelaine Trinidad, Daniel Bernstein, Awad Chowdhury, Julieta Correa-Betanzo, Gabriella Del Principe, Anisa Hajizadeh, Rohit Jayaraman, Amy Jenkins, Wendy Jenkins, Ruben Kalaichandran, Geithayini Kirupaharan, Preveena Manisekaran, Tina Qutta, Ramsha Shahid, Alexis Silver, Cleo Villegas, Jessica White, Cyril WC Kendall, Sathish C Pichika, John L Sievenpiper