American Journal of Clinical Nutrition, Vol. 76, No. 1, 257-258,
July 2002
© 2002 American Society for Clinical Nutrition
Reply to JJ Segall
June M Chan
Departments of Epidemiology and Biostatistics and of Urology University of California, San Francisco 3333 California Street Suite 280 San Francisco, CA 94143-1228 E-mail: jchan{at}epi.ucsf.edu
Dear Sir:
Segall presents an interesting point regarding the potential interaction between calcium and lactose and prostate cancer risk. He suggests that we provide results for cheese consumption because cheese has less lactose than does milk. As stated in our article, of the 5 dairy foods we assessed, only skim milk was statistically significantly associated with prostate cancer risk. Although this result is consistent with Segall's hypothesis, there was too little statistical power to assess this directly. Cheese consumption accounted for a far smaller proportion of total dairy calcium intake than did skim milk (24% compared with 57%) and was probably measured with less accuracy than was milk. Thus, the lack of a significant association may simply have been due to too little exposure or to measurement error. This potential interaction may be important, and we concur that further consideration of this hypothesis is warranted.
