From: The Physicians Committee for Responsible Medicine
Prostate and breast cancers have been linked to consumption of dairy products, presumably related to increases in a compound called insulin-like growth factor (IGF-I).15 IGF-I is found in cow’s milk and has been shown to occur in increased levels in the blood of individuals consuming dairy products on a regular basis.16,17 Other nutrients that increase IGF-I are also found in cow’s milk.
Case-control studies in diverse populations have shown a strong and consistent association between serum IGF-I concentrations and prostate cancer risk.18 One study showed that men who had the highest levels of IGF-I had an almost two-fold increased risk of prostate cancer, compared with those who had the lowest levels.19 Other findings show that prostate cancer risk was elevated with increased consumption of low-fat milk, suggesting that too much dairy calcium could be a potential threat to prostate health.18
Dairy products account for approximately 65 percent of estrogens consumed. Estrogens (and their metabolites) are a risk factor for breast, ovarian, and prostate cancers due, in part, to their ability to influence cell proliferation.20 A study suggesting that milk consumption may contribute to breast cancer risk reported that 15 different estrogen metabolites were found in various milk products. (There were no appreciable amounts of estrogen metabolites found in soymilk.)20 Cutting fatty foods is priority No. 1 when you endeavor to lower your risk for breast cancer, and, as noted above, dairy products are the No. 1 source of saturated fat in the diet.
Ovarian cancer may also be related to the consumption of dairy products. The milk sugar lactose is broken down in the body into another sugar, galactose. Research suggests that the dairy sugar galactose might be toxic to ovarian cells.21 In a study conducted in Sweden, consumption of lactose and dairy products was positively linked to ovarian cancer.22 Additionally, a study conducted in Denmark—where the incidence of ovarian cancer is one of the highest in the world—found that women who consumed more than two servings of milk per day had nearly two times the risk of developing ovarian cancer than women who drank less than half a serving per day.23
- Voskuil DW, Vrieling A, van’t Veer LJ, Kampman E, Rookus MA. The insulin-like growth factor system in cancer prevention: potential of dietary intervention strategies. Cancer Epidemiol Biomarkers Prev. 2005;14:195-203.
- Young NJ, Metcalfe C, Gunnell D, et al. A cross-sectional analysis of the association between diet and insulin-like growth factor (IGF)-I, IGF-II, IGF-binding protein (IGFBP)-2, and IGFBP-3 in men in the United Kingdom. Cancer Causes Control. 2012;6:907-917.
- Gonzalez CA, Riboli E. Diet and cancer prevention: Contributions from the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Cancer. 2010;46:2555-2562.
- Leitzmann MF, Rohrmann S. Risk factors for the onset of prostatic cancer: age, location, and behavioral correlates. Clin Epidemiol. 2012;4:1-11.
- Price AJ, Allen NE, Appleby PN, et al. Insulin-like growth factor-I concentration and risk of prostate cancer: results from the European Prospective Investigation into Cancer and Nutrition. Cancer Epidemiol Biomarkers Prev. 2012. Published ahead of print July 3, 2012.
- Farlow DW, Xu X, Veenstra TD. Quantitative measurement of endogenous estrogen metabolites, risk-factors for development of breast cancer, in commercial milk products by LC-MS/MS. J Chromatogr B Analyt Technol Biomed Life Sci. 2009;877:1327-1334.
21.Cramer DW, Greenberg ER, Titus-Ernstoff L, et al. A case-control study of galactose consumption and metabolism in relation to ovarian cancer. Cancer Epidemiol Biomarkers Prev. 2000;9:95-101.
- Larsson SC, Bergkvist L, Wolk A. Milk and lactose intakes and ovarian cancer risk in the Swedish Mammography Cohort. Am J Clin Nutr. 2004;80:1353-1357.
- Faber MT, Jensen A, Søgaard M, et al. Use of dairy products, lactose, and calcium and risk of ovarian cancer - results from a Danish case-control study. Acta Oncol. 2012;51:454-464.