女性多吃豆類 男性多吃魚

Women who ate soy regularly as children have a lower risk of breast cancer, American researchers report. And men who eat fish several times a week have a lower risk of colon cancer, a second team of researchers have told the American Association for Cancer Research.

The studies add to a growing body of evidence about the role of diet in cancer.Cancer experts now believe that up to two-thirds of all cancers come from lifestyle factors such as smoking, diet and lack of exercise.

The US National Cancer Institute and researchers at the University of Hawaii found that women who ate the most soy-based foods, such as tofu and miso, when aged 5 to 11, reduced their risk of developing breast cancer by 58 per cent. It was not clear how soy might prevent cancer, though compounds in soy called isoflavones have estrogen-like effects.

A second study showed that men who ate fish at least five times a week had a 40 per cent lower risk of developing colorectal cancer compared with men who ate fish less than once a week.

Many kinds of fish are rich in omega-3 fatty acids, which interfere with the cyclooxygenase-2 or COX-2 enzyme. COX-2 affects inflammation, which may play a role in tumour growth.

據美國研究人員報告，兒童時期經常吃豆類食品的女性患乳腺癌的風險較小。另一組研究人員則向美國癌癥研究協會提出，一周吃幾次魚的男性患結腸癌的幾率較小。

這兩項研究進一步證明了飲食對于防癌的作用。癌癥防治專家認為，在所有種類的癌癥中，多達三分之二都是由吸煙、節食及缺乏鍛煉等不健康的生活方式造成的。

美國全國癌癥研究所和夏威夷大學的研究人員發現，在5歲至11歲時經常吃豆腐、味噌等豆類食品的女性患乳腺癌的幾率要低58%。至于豆類食品為什么可以防癌還不清楚，不過大豆中所含的名叫異黃酮的化合物具有雌性激素的作用。

另一項研究表明，一周吃魚至少五次的男性患結腸癌的風險要比那些一周都吃不到一次魚的男性低40%。

很多魚類中所富含的Omega-3脂肪酸能夠抑制環氧化酶2的活性。環氧化酶2會引起發炎，這可能會刺激腫瘤的生長。