A 1995 prospective study from Norway once showed that a high consumption of whole milk increased the risk of breast cancer: "Consumers of 0.75 litres or more of full-fat milk daily had a relative risk of 2.91 compared with those who consumed 0.15 litres or less" (Gaard 1995).
However, a new study from the Norwegian Women and Cancer contradicts this. The authors looked at the consumption of specific dairy products, as well as total dairy, in almost 65,000 women between the years 1996 and 2006. During this time, 218 of the premenopausal and 1,189 of the postmenopausal women developed breast cancer. Their conclusion was that "total dairy, adult, and childhood milk consumption was not associated with either pre- or postmenopausal breast cancer risk."
Previous studies also have failed to establish a dairy-breast cancer link. These have included two epidemiological studies (Moorman, 2004 and Parodi 2005), a metaanalysis (Boyd 1993) and a pooled analysis of cohort studies (Missmer 2002). They all concluded that there is no evidence for a strong association between dairy consumption and breast cancer risk.
This is similar to the conclusions of Shin et al. at Harvard that there was "no association between intake of dairy products and breast cancer in postmenopausal women" (Shin 2002). However, this recent Norwegian study failed to confirm Shin's finding that "among premenopausal women, high intake of low-fat dairy foods, especially skim/low-fat milk, was associated with reduced risk of breast cancer" (ibid.).
Defenders of the low-fat vegan (LFV) diet, such as Prof. T. Colin Campbell, point out that there was no group in this Norwegian study that avoided dairy on principle (Campbell 2010).
In the study's convoluted English, the low dairy consumption group was defined as those participants who had "‘no milk consumption as a child or 1st quartile of dairy consumption as adult and not more than next-lowest consumption (1–3 glasses/day)...." Thus, by my reading, if you did not drink milk as a child but now consumed a limitless amount of dairy, you were still ranked as a low consumer! On the other hand, you are also a low consumer if you drink the equivalent of an 8 oz. glass of milk per day. The low consumer group could therefore contain alot of people who, by vegan standards, would be high consumers. Any difference between such "low consumers" and strict vegans would not show up in this analysis.
While the present study certainly does not support the LFV hypothesis in regard to breast cancer, advocates of that diet do have a point when they object that any beneficial effect of strict dairy avoidance would be unlikely to show up in such a study.
Boyd NF, Martin LJ, Noffel M, Lockwood GA, Trichler DL. A meta-analysis of studies of dietary fat and breast cancer risk. Br J Cancer. 1993;68:627–636.
Campbell TC. Personal communication, Nov. 17, 2010.
Gaard M, Tretli S, Løken EB. Dietary fat and the risk of breast cancer: a prospective study of 25,892 Norwegian women. Int J Cancer. 1995;63(1):13-17.
Hjartåker A, Thoresen M, Engeset D, Lund E. Dairy consumption and calcium intake and risk of breast cancer in a prospective cohort: the Norwegian Women and Cancer study. Cancer Causes Control. 2010;21(11):1875-1885.Moorman PG, Terry PD. Consumption of dairy products and the risk of breast cancer: a review of the literature. Am J Clin Nutr. 2004;80:5–14.
Missmer SA, Smith-Warner SA, Spiegelman D et al. Meat
and dairy food consumption and breast cancer: a pooled analysis
of cohort studies. Int J Epidemiol. 2002;31:78–85.
Parodi PW. Dairy product consumption and the risk of breast cancer. J Am Coll Nutr. 2005;24:556S–568S.
Shin M, Holmes MD, Hankinson SE, et al. Intake of dairy products, calcium, and vitamin d and risk of breast cancer. J. Natl. Cancer Inst. 2002;94(17):1301-1311.