摘要：

Breast cancer is still relatively infrequent in Japan. However, both mortality and morbidity rates have sharply increased in recent years, especially in ages 45–59. The risk was noted to be 8.5 times higher in women of high socioeconomic strata eating meat daily compared with women of low socioeconomic strata who do not eat meat daily, when 142,857 women aged 40 years were followed for 10 years. A high positive correlation was found between per capita fat intake and adjusted death rates of breast cancer in different districts of Japan. It was estimated that the breast cancer death rate will rise to the U.S. level when Japanese dietary fat intake approaches present day U.S. levels. The close correlation with fat intake was noted to come mainly from the consumption of pork and animal fat. The ratio of recent increase in breast cancer death rates was also found to be under the combined influence of animal fat and AF2, a highly mutagenic food additive widely used in Japan from 1965 to 1975 and shown to produce mammary carcinoma in rats. A series of case-control studies reveals the higher risk of breast cancer with the increase in body size especially in postmenopausal women. The recent breast cancer increase could therefore be a reflection of the fact that women in Japan are becoming heavier, especially after age 30.

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