© 2000 by Oxford University Press
Journal of the National Cancer Institute, Vol. 92, No. 1, 78A-78,
January 5, 2000
© 2000 Oxford University Press
CORRESPONDENCE |
RESPONSE: Re: Meta-analysis: Dietary Fat Intake, Serum Estrogen Levels, and the Risk of Breast Cancer
Affiliation of authors: Department of Preventive Medicine, University of Southern California Medical School, Los Angeles.
Correspondence to: Anna H. Wu, Ph.D., University of Southern California/Norris Comprehensive Cancer Center, 1441 Eastlake Ave., MS#44, P.O. Box 33800, Los Angeles, CA 90089-9013 (e-mail: annawu{at}hsc.usc.edu).
"Traditional" women in Asia, who are at low risk for breast cancer, have been consistently shown to have lower urinary and blood levels of estrogens than do Caucasian women generally in the United States and the United Kingdom. One possible explanation for this difference in endogenous estrogen levels is, at least in part, the very low intake of dietary fat among these Asian women. Our meta-analysis suggests that such an effect of dietary fat on endogenous estrogen levels is still a viable hypothesis (1).
Cohen points out that, in rat models using the carcinogen 7,12-dimethylbenz[a]anthracene, the percent of calories from fat has an effect in both normal animals and in estrogen-depleted (ovariectomized or treated with antiestrogens) animals, so that—even if fat does not directly alter estrogen levels—a very low-fat (0.5% corn oil) compared with a high-fat (20% corn oil) diet may still protect against the development of mammary tumors (2,3).
A recent study by McMichael-Phillips et al. (4) shows that important questions regarding the effects of various dietary constituents may be investigated in short-term studies using women who are awaiting treatment for various symptomatic breast problems. In their study, the rate of breast epithelial proliferation was compared in women randomly assigned to either a control diet or a soy-supplemented diet, to assess the purported estrogenic or antiestrogenic effects of soy. Such short-term, mechanistic studies in humans that are designed to investigate changes in the breast should complement both animal studies and more traditional dietary intervention studies, in which circulating estrogen level is the end point of interest. Studies that use breast cell proliferation (or other intermediate markers) in conjunction with serum hormone measurements should allow the assessment of responses to specific factors (e.g., dietary fat) that may be more directly reflective of their effects on breast cancer risk.
REFERENCES
1
Wu AH, Pike MC, Stram DO. Meta-analysis: dietary fat intake,
serum estrogen levels, and the risk of breast cancer. J Natl Cancer Inst 1999;91:529-34.
2 Chan PC, Cohen LA. Effect of dietary fat, antiestrogen, and antiprolactin on the development of mammary tumors in rats. J Natl Cancer Inst 1974;52:25-30.cancerlit;74702692
3 Cohen LA, Chan PC, Wynder EL. The role of a high-fat diet in enhancing the development of mammary tumors in ovariectomized rats. Cancer 1981;47:66-71.[CrossRef][Web of Science][Medline]cancerlit;81608516
4 McMichael-Phillips DF, Harding C, Morton M, Roberts SA, Howell A, Potten CS, et al. Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast. Am J Clin Nutr 1998;68(6 Suppl):1431S-1435S.[Abstract]
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