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【科普】大量服用维生素增加前列腺癌风险
Mega Multivitamin Use Risks Prostate Cancer
BETHESDA, Md., May 15 -- Men who take multi-vitamin supplements more than once a day are twice as likely to die of prostate cancer as men who never take supplements, researchers confirmed. Action Points
Explain to interested men that more than daily use of multivitamin supplements does not appear to reduce their risk of prostate cancer and may even increase it.
Caution patients that the study did not suggest that regular multivitamin use, whether occasionally or once daily, significantly increased risk of prostate cancer.
They were also at elevated risk of advanced prostate cancer compared with never users, reported Karla A. Lawson, Ph.D., of the National Cancer Institute here, and colleagues.
The researchers reported the outcomes of the National Institutes of Health -- AARP Diet and Health Study in the May 16 issue of the Journal of the National Cancer Institute.
The large, prospective investigation adds credence to the possibility of harm from antioxidant supplements as found in prior systematic reviews and meta-analyses, according to an accompanying editorial.
The findings "underscore the possibility that antioxidant supplements could have unintended consequences for our health," wrote Goran Bjelakovic, M.D., of the University of Nis, Serbia, and Christian Gluud, M.D., of the Copenhagen University Hospital.
The few previous prospective studies had suggested that multivitamin use may protect men from developing prostate cancer but speed its progression once begun, Dr. Lawson and colleagues wrote.
Because more than a third of American adults take vitamins, the researchers noted, "any association between intake of multivitamin supplements and the risk or severity of prostate cancer would have important consequences for public health," the researchers wrote.
The prospective study included 295,344 men aged 50 to 71 and free of cancer at enrollment in 1995 and 1996.
Their multivitamin use was assessed at baseline using a self-administered, food-frequency questionnaire. Five percent used multivitamins more than seven times a week; 36% took a multivitamin daily.
Among the participants, 41% reported using a one-a-day type supplement, 12% reported using a theragran type (vitamins plus iron) supplement, and 6% reported use of a stress-tab type supplement (primarily B vitamins). Half of the supplements used were multivitamins.
Outcomes were followed using subsequent questionnaires, Social Security Administration death records, and state cancer registries.
Over five years of follow-up, 10,241 developed incident prostate cancer. These cases included 8,765 localized and 1,476 advanced cancers. A separate mortality analysis found 179 cases of fatal prostate cancer over six years of follow-up.
Among the findings in a multivariate adjusted analysis, the researchers reported (more than daily use versus never users):
No association between multivitamin use and risk of prostate cancer overall (relative risk 1.06, 95% confidence interval 0.97 to 1.17).
No association between multivitamin use and risk of localized prostate cancer (RR 1.02, 95% CI 0.92 to 1.14).
Increased risk of advanced prostate cancer (RR 1.32, 95% CI 1.04 to 1.67).
Elevated risk of fatal prostate cancers (RR 1.98, 95% CI 1.07 to 3.66).
Higher incidence rates for advanced prostate cancer (143.8 versus 113.4 per 100,000 person-years).
Higher incidence rates for fatal prostate cancer (18.9 versus 11.4 per 100,000 person-years).
The associations were strongest in men with a family history of prostate cancer or those who took selenium, β-carotene, or zinc.
"Thus, excessive intake of certain individual micronutrients that are used in combination with multivitamins may be the underlying factor that is related to risk and not the multivitamins themselves," the researchers wrote.
Among men with prostate cancer in the family, heavy multivitamin use (more than seven times per week) more than doubled advanced prostate cancer risk (RR 2.48, 95% CI 1.45 to 4.23) and fatal prostate cancer risk (RR 16.41, 95% CI 2.62 to 102.68).
Heavy use of selenium yielded a 37% increased risk of localized prostate cancer (P=0.008 for interaction) Although based on a small sample, those who took more than seven multivitamins a week and were also taking a selenium supplement were at 5.8-fold higher risk of fatal prostate cancer than those not taking a selenium supplement (P=0.037 for interaction).
The association between heavy multivitamin use and advanced prostate cancer was somewhat modified by β-carotene use (P=0.036 for trend).
Men who used a zinc supplement in addition to heavy multivitamin use were at significantly elevated risk of fatal prostate cancer (RR 4.36, 95% CI 1.83 to 10.39 versus daily or less than daily multivitamin use).
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作者:admin@医学,生命科学 2011-05-07 17:11
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