Epidemiological study on relationship between breast cancer mortality and dietary factors.

To elucidate the effects of nutritional factors on regional differences in breast cancer mortality in Japan, the statistical analysis was made using the results of the national nutrition surveys in 12 districts from 1966 to 1980 and age-adjusted mortality from breast cancer from 1966 to 1990. The correlation analysis between food or nutrient intake and breast cancer mortality was performed with a fixed time lag of 10 years. Dietary factors such as wheat, milk, meats, animal fat, animal protein, total fat, saturated fatty acid (SF) and monounsaturated fatty acid (MUF) were correlated highly positively with breast cancer mortality. The correlation analysis between increase rates in age-adjusted mortality from breast cancer and increase rates in food or nutrient intake was also examined. Highly positive correlations were obtained between breast cancer mortality and following dietary factors; oils and fats, fruits, milk, total fat, vegetable fat, SF, MUF and n-6 polyunsaturated fatty acid. Factor analysis using fat intake by 12 districts revealed the factor representing the intake of fat component resulting from ingestion of animal fat. This factor showed a positive correlation with age-adjusted mortality from breast cancer. The findings suggested that the dietary factors due to intake of Westernized meals, especially SF had the effect on breast cancer mortality in Japan.