Milk consumption in relation to incidence of prostate, breast, colon, and rectal cancers: is there an independent effect?

Milk contains a wide variety of ingredients, such as nutrients, hormones, and chemical contaminants. Whether milk consumption is associated with the risk of prostate, breast, colon, and rectal cancers is unclear and was evaluated in this study. Data on milk consumption for 9 time periods (1964-1994) and incidence rates of prostate, female breast, colon, and rectal cancers, mostly around 1993-1997, in 38 countries were obtained from the Food and Agriculture Organization and World Health Organization, respectively. Milk consumption was strongly correlated with incidence rates of prostate cancer (r = 0.65-0.69; all P < 0.0001) and breast cancer (r = 0.64-0.74; all P < 0.0001) in all the nine time periods examined. A modest positive correlation was found for colon and rectal cancers in both sexes (all P < 0.05, except for rectal cancer in the first three time periods). The previous findings remained essentially unchanged after adjustment for vegetable, alcohol, and cigarette consumption but disappeared after further adjustment for non-milk fat consumption, except for breast cancer in the last three time periods. The present study does not support an overall substantial effect of milk consumption on the risk of prostate, breast, colon, and rectal cancers at the population level.