Coffee and tea lovers may have a slightly reduced risk of developing kidney cancer, research hints.

The findings, based on an analysis of 13 previous studies, suggest that coffee and tea may be protective against kidney cancer, while milk, soda and juice seem to have no effect one way or the other.

Across the studies, people who drank three or more cups of coffee a day were 16 per cent less likely to develop kidney cancer than those who averaged less than a cup per day. And those who sipped just one cup of tea each day had a 15 per cent lower risk of the disease than non-drinkers.

The findings appear in the International Journal of Cancer.

While the study cannot show that coffee or tea directly lower kidney cancer risk, there are reasons why the beverages could be beneficial, according to the researchers, led by Dr Jung Eun Lee of Harvard Medical School in Boston.

For example, they explain, coffee and tea may increase the body's sensitivity to the blood-sugar-regulating hormone insulin, and researchers say that insulin levels determine whether the kidney is healthy or gets sick.

Coffee and tea also contain antioxidant compounds that may help protect cells in the kidney from cancer-promoting damage, the researchers point out.

For their study, the investigators combined the results of 13 long-term studies that included a total of 530,469 women and 244,483 men. Each study collected information on participants' diets at the outset and then followed them for seven to 20 years.

Coffee and tea consumption were linked to a lower risk of kidney cancer even when the researchers accounted for a number of factors known to affect people's risk of the disease – such as obesity, smoking and high blood pressure.

"Our results suggest that coffee and tea consumption may be associated with a modestly lower risk of (kidney) cancer, whereas intakes of milk, juice and soda were not associated with risk," Lee's team writes.

一项研究表明，爱喝咖啡和茶的人患肾癌的风险可能略低。

研究人员对此前十三项研究的结果进行了分析，分析结果表明，喝咖啡和茶能够预防肾癌，而喝牛奶、汽水和果汁对肾脏健康则似乎没什么影响。
之前的研究显示，每天喝三杯或三杯以上咖啡的人比平均每天喝咖啡不足一杯的人患肾癌的风险低16%；而且每天只喝一杯茶的人比不喝茶的人患肾癌的风险低15%。

该研究结果在《国际癌症研究期刊》上发表。

研究人员称，尽管研究不能直接证明喝咖啡和茶能够预防肾癌，但还是能找到一些科学依据的。该研究由波斯顿哈佛医学院的李贞恩博士负责。

比如，咖啡和茶能够增加人体对血糖调节激素——胰岛素的敏感度。研究人员称，胰岛素水平是影响肾脏健康的主要因素。

此外，研究人员指出，咖啡和茶中含有的抗氧化物质能够保护肾脏细胞免受伤害。

研究人员综合分析了13项长期研究的结果，这13项研究共有530469名女性和244483名男性参加。每项研究最初都搜集了研究对象的饮食信息，然后对他们进行了为期7年至20年的跟踪调查。

这一研究结果是在综合考虑了可能诱发肾癌的各种因素后得出的，比如肥胖、吸烟和高血压。

研究人员在研究报告中写道：“研究结果表明，喝茶和咖啡能略微降低患肾癌的风险，而喝牛奶、果汁和苏打水等饮料对此则没什么影响。”