Study links frequent multivitamin use and advanced prostate cancer
Men who take too many multivitamins could be increasing their risk of advanced prostate cancer, research has shown.
A study published in the Journal of the National Cancer Institute shows that men who use multivitamins more than seven times a week are at a higher risk of advanced prostate cancer than men who do not use multivitamins.
However, regular multivitamin use was not linked with early or localised prostate cancer.
Researchers from the National Cancer Institute in Bethesda followed 295,344 men who were enrolled in the National Institutes of Health-AARP's diet and health study.
After five years, 10,241 men had been diagnosed with prostate cancer, including 1,476 with advanced cancers.
The researchers found that those men who took multivitamins more than seven times a week had an increased risk of advanced prostate cancer, and the association was strongest among men with a family history of prostate cancer and those who also took selenium, beta-carotene or zinc supplements.
The team, led by Dr Karla Lawson, pointed out that that the study did not show which component of vitamin supplements was responsible.
"Because multivitamin supplements consist of a combination of several vitamins, and men using high levels of multivitamins were also more likely to take a variety of individual supplements, we were unable to identify or quantify individual components responsible for the associations that we observed," she said.
However, Dr Goran Bjelakovic of the University of Nis in Serbia and Dr Christian Gluudof from Denmark's Copenhagen University Hospital wrote in an accompanying editorial that the research had highlighted the possibility "that antioxidant supplements could have unintended consequences for our health".
Liz Baker, science information officer at Cancer Research UK, said: "It's still not entirely clear what factors can affect a man's risk of developing prostate cancer. And there is conflicting evidence on the pros and cons of vitamin supplements.
"These products don't seem to give us the same benefits as vitamins that naturally occur in our food. Cancer Research UK encourages people wanting to reduce their risk of cancer to eat a diet rich in fibre, vegetables and fruit, and low in red and processed meat."