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April 2001; Volume 4; 45-46
Comment: The primary problem with the article "Can Dietary Choices Prevent Prostate Cancer?" (see Alternative Medicine Alert, January 2001, pp. 1-5) is that it lists fat, rather than calcium, as the high risk factor for prostate cancer. While the references include some as recent as 2000 and by authors who have done some of the best research on the topic, Giovannucci and Chan, Dr. Barrette probably wrote the article based on attitudes regarding diet and prostate cancer prevalent up until a few short years ago. Now, both the cohort and ecologic approaches are in full agreement that calcium, derived from milk or other calcium sources, is the primary dietary risk factor for prostate cancer. No, the mechanism is not understood. However, the epidemiologic findings are very compelling. If the author had taken the step of going to PubMed and searching "prostate cancer diet," he would have found these references. In addition, vitamin D and solar UVB radiation are risk reduction factors for prostate cancer, although Giovannucci has stepped back from his suggestion that calcium reduces serum vitamin D.
William B. Grant, PhD
Newport News, VA
Response: Dr. Grant overstates his case, as two cohort studies have implicated calcium but other studies have not confirmed this. Calcium intake did appear to increase the risk of prostate cancer in men enrolled in the Health Professionals’ Follow-up Study.1 The relative risk (RR) for advanced tumors was an impressive 2.97. However, this was true for men consuming more than 2,000 mg/d of calcium—fewer than 3% of all men. The same investigators found a similar risk with calcium intake in a population-based, case-control study from Sweden.2 However, in this study a similar RR also was seen for meat intake.
Review of the many case-control studies of diet and prostate cancer show slightly more trials suggesting an association with meat or fat intake than with dairy or milk intake.3 Among the cohort studies the risk of meat/fat intake is cited about as often as dairy/milk.
Three recent additional studies have not clarified this question. In a large case-control study including 697 prostate cancer cases, calcium supplement use did not increase the risk of prostate cancer.4 A large U.S. case control with 932 prostate cancer cases found an increased risk with foods high in animal fat and no association with calcium intake.5 A very large prospective Netherlands cohort (58,279 men, 642 prostate cancer cases) found an association with cured meats and milk but no association with calcium.6 These three studies are much larger than almost all the prior studies.
Lastly, ecologic studies are useful in generating hypotheses but are unable to control for potential confounders.
A sensible, strongly evidence-based recommendation to our patients is to avoid a diet high in dairy and meats and low in fruits since such a diet may be associated with an increased risk of prostate cancer. This recommendation is supported by most case-control and cohort studies, and should be made by physicians to men at risk for prostate cancer.
E-P. Barrette, MD, FACP
Assistant in Medicine
Massachusetts General Hospital, Boston
1. Giovannucci E, et al. Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res 1998;58: 442-447.
2. Chan JM, et al. Dairy products, calcium, phosphorus, vitamin D, and risk of prostate cancer (Sweden). Cancer Causes Control 1998;9:559-566.
3. Giovannucci E. Dietary influences of 1,25 (OH)2 vitamin D in relation to prostate cancer: A hypothesis. Cancer Causes Control 1998;9:567-582.
4. Kristal AR, et al. Vitamin and mineral supplement use is associated with reduced risk of prostate cancer. Cancer Epidemiol Biomarkers Prev 1999;8:887-892.
5. Hayes RB, et al. Dietary factors and risks for prostate cancer among blacks and whites in the United States. Cancer Epidemiol Biomarkers Prev 1999;8:25-34.
6. Schuurman AG, et al. Animal products, calcium, and protein and prostate cancer risk in The Netherlands Cohort Study. Br J Cancer 1999;80:1107-1113.