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据研究咖啡可能能够预防癌症

2011-11-29

 Friday, November 25, 2011. A report published this month in the American Association for Cancer Research journal Cancer Epidemiology, Biomarkers & Prevention revealed a connection between coffee drinking and protection against the development of endometrial cancer (cancer of the lining of the uterus). Preliminary research findings involving coffee suggest that the beverage may be protective against obesity-associated cancers, as well as those that have been associated with insulin and the major female hormone estrogen.

"Coffee has already been shown to be protective against diabetes due to its effect on insulin," remarked senior researcher Edward Giovannucci, MD, ScD, who is a professor of nutrition and epidemiology at the Harvard School of Public Health. "So we hypothesized that we\'d see a reduction in some cancers as well."
 
The Harvard team analyzed data from 67,470 participants in the Nurses\' Health Study who were aged 34 to 59 in 1980. Dietary questionnaires completed at seven time points between 1980 and 2002 provided information on the type and frequency of coffee consumption. Biennial questionnaires ascertained endometrial cancer diagnoses during the preceding two years.
 
Six hundred seventy-two endometrial cancer cases were documented over the 26 year follow-up period. A declining risk of the disease was observed in association with increasing consumption of coffee. Following adjusted analysis of the data, a 25 percent lower risk of endometrial cancer remained in association with the intake of four or more cups of coffee per day in comparison with women who consumed less than one cup. The association was stronger when women who were diagnosed during the first two years of follow-up were excluded from the analysis.
 
When coffee intake was examined by type, consuming two or more cups per day of decaffeinated coffee was associated with a 22 percent lower risk of endometrial cancer compared to one cup, and consuming 4 or more cups of regular coffee was associated with a 30 percent lower risk.
 
In their discussion of the findings, Youjin Je and colleagues note that the chlorogenic acid contained in coffee has strong antioxidant properties that help prevent oxidative DNA damage and improve insulin resistance. Additionally, the caffeine contained in coffee upregulates the liver\'s expression of an enzyme that oxidizes estradiol to 2-methoxyestradiol which may have antitumor properties. In previous research conducted by the team, a reduction C-peptide and an increase in serum hormone binding globulin levels was found to be associated with a higher intake of caffeinated coffee by postmenopausal women, suggesting that coffee could reduce the risk of endometrial cancer via an ability to lower insulin and free estradiol, in addition to other mechanisms.
 
"To our knowledge, this is the largest prospective cohort study that has evaluated coffee and tea consumption using repeated dietary questionnaires, and the first cohort study to examine the long-term intake of decaffeinated coffee on risk of endometrial cancer," the authors write. "Drinking of coffee, given its widespread consumption, might be an additional strategy to reduce endometrial cancer risk. However, addition of substantial sugar and cream to coffee could offset any potential benefits."
 
"Coffee has long been linked with smoking, and if you drink coffee and smoke, the positive effects of coffee are going to be more than outweighed by the negative effects of smoking," Dr Giovannucci added. "However, laboratory testing has found that coffee has much more antioxidants than most vegetables and fruits."
 



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