Over-the-Counter Vitamin Use by Smokers ‘Quadruples Cancer Risk’
Smokers who take over-the-counter vitamins can quadruple their risk of contracting lung cancer, researchers have warned.
A new study suggests men multiply the danger of lung tumours if they take high doses of vitamins B6 and B12, long touted by the complementary medicine industry for improving metabolism and boosting energy.
The research highlights the contrary relationship between dietary supplements and cancer risk, with vitamins normally peddled as potential saviours.
A study published yesterday implicated low levels of vitamin C in leukemia, and a paper this month suggested vitamin B3, nicotinamide, could prevent melanoma.
Australian researchers captured world headlines two weeks ago with a study indicating that supplementation with yet another form of vitamin B3, niacin, could prevent miscarriages and birth defects, but the team warned women to stick to recommended niacin doses until further research was carried out.
The latest analysis, published in the Journal of Clinical Oncology, crunched data from more than 77,000 older patients from a long-term US study investigating the relationship between dietary supplements and cancer risk.
The researchers found that compared with nonsmokers who did not use supplements, those who took daily doses of more than 20 mg of vitamin B6 or 55 micrograms of vitamin B12 for 10 years faced double the danger of developing lung cancer. For smokers the risks tripled among those using vitamin B6 and quadrupled for those taking B12.
The findings applied only to men, and lead researcher Ted Brasky stressed they involved doses well above those in multivitamins. Australian dietary guidelines recommend a maximum daily intake of 1.7mg of vitamin B6 and 2.4 micrograms of vitamin B12. Supplements far exceeding these levels are readily available in chemists and supermarkets.
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