Harvard School of Public Health
Possible Increased Risk of Ovarian Cancer
High levels of galactose, a sugar released by the digestion of lactose in milk, have been studied as possibly damaging to the ovaries and leading to ovarian cancer. Although such associations have not been reported in all studies, there may be potential harm in consuming high amounts of lactose. A recent pooled analysis of 12 prospective cohort studies, which included more than 500,000 women, found that women with high intakes of lactose—equivalent to that found in 3 cups of milk per day—had a modestly higher risk of ovarian cancer, compared to women with the lowest lactose intakes. (15) The study did not find any association between overall milk or dairy product intake and ovarian cancer. Some researchers have hypothesized, however, that modern industrial milk production practices have changed milk's hormone composition in ways that could increase the risk of ovarian and other hormone-related cancers. (16) More research is needed.
Probable Increased Risk of Prostate Cancer
A diet high in calcium has been implicated as a probable risk factor for prostate cancer. (17) In a Harvard study of male health professionals, men who drank two or more glasses of milk a day were almost twice as likely to develop advanced prostate cancer as those who didn't drink milk at all. (18) The association appears to be with calcium itself, rather than with dairy products in general: A more recent analysis of the Harvard study participants found that men with the highest calcium intake—at least 2,000 milligrams a day—had nearly double the risk of developing fatal prostate cancer as those who had the lowest intake (less than 500 milligrams per day). (19)
Clearly, although more research is needed, we cannot be confident that high milk or calcium intake is safe.
oh here are the references:
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15. Genkinger JM, Hunter DJ, Spiegelman D, et al. Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies. Cancer Epidemiol Biomarkers Prev. 2006; 15:364–72.
16. Ganmaa D, Sato A. The possible role of female sex hormones in milk from pregnant cows in the development of breast, ovarian, and corpus uteri cancers. Med Hypotheses. 2005; 65:1028–37.
17. World Cancer Research Fund, American Institute for Cancer Research. Food, nutrition, physical activity, and the prevention of cancer: a global perspective. Washington DC: AICR, 2007.
18. Giovannucci E, Rimm EB, Wolk A, et al. Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res. 1998; 58:442–447.
19. Giovannucci E, Liu Y, Platz EA, Stampfer MJ, Willett WC. Risk factors for prostate cancer incidence and progression in the Health Professionals Follow-up Study. International Journal of Cancer. 2007; 121:1571–78.
20. Larsson SC, Bergkvist L, Rutegard J, Giovannucci E, Wolk A. Calcium and dairy food intakes are inversely associated with colorectal cancer risk in the Cohort of Swedish Men. Am J Clin Nutr. 2006; 83:667–73; quiz 728–29.
21. Cho E, Smith-Warner SA, Spiegelman D, et al. Dairy foods, calcium, and colorectal cancer: a pooled analysis of 10 cohort studies. J Natl Cancer Inst. 2004; 96:1015–22.
22. Martinez ME, Willett WC. Calcium, vitamin D, and colorectal cancer: a review of the epidemiologic evidence. Cancer Epidemiol Biomarkers. Prev 1998; 7:163–68.
23. Hyman J, Baron JA, Dain BJ, et al. Dietary and supplemental calcium and the recurrence of colorectal adenomas. Cancer Epidemiol Biomarkers Prev. 1998; 7:291–95.
24. Dickinson HO, Nicolson DJ, Cook JV, et al. Calcium supplementation for the management of primary hypertension in adults. Cochrane Database Syst Rev. 2006:CD004639.
25. Cappuccio FP, Elliott P, Allender PS, Pryer J, Follman DA, Cutler JA. Epidemiologic association between dietary calcium intake and blood pressure: a meta-analysis of published data. Am J Epidemiol. 1995; 142:935–45.
26. Bolland MJ, Avenell A, Baron JA, Grey A, MacLennan GS, Gamble GD, Reid IR. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010; 341:c3691. doi: 10.1136/bmj.c3691.