The paper presents an epidemiological study of breast cancer mortality in relation to food consumption. It was found that younger and older women (possibly pre- and post-menopausal women) differ with respect to such correlations. In older women a strong correlation was found between breast cancer mortality and sugar consumption (correlation coefficient = 0.9), and a weaker correlation, possibly of marginal interest, with fat consumption (correlation coefficient = 0.7). In younger women the correlation with diet seems weak. A possible connecting link between sugar consumption and breast cancer is insulin. This is an absolute requirement for the proliferation of normal mammary tissue and experimental mammary tumours may regress in its absence. Insulin secretion occurs in response to blood glucose level and could be excessive if the regulatory mechanism is overtaxed by large sugar intake. The same mechanism might account for the increased risk of mammary cancer in diabetics.