Cheese is not recommended for breast cancer
While there are cheeses on the market made from various oils and from the milk of goats, sheep, and other animals, the discussion in this webpage refers to cheese made from cow's milk. Also, "cheese" refers to full-fat cheese rather than reduced fat or non-fat cheese. Cheese is a rich dietary source of calcium, conjugated linoleic acid (CLA), and stearate, all of which have been shown to have anticarcinogenic properties. Numerous studies have found that the consumption of cheese and other high-fat dairy foods is related to lower risk of colon cancer. Cheese consumption also appears to reduce the risks of stomach and pancreatic cancer. On the other hand, studies indicate that the consumption of cheese may increase the risks of developing testicular, ovarian, and thyroid cancers, as well as non-Hodgkin lymphoma. Higher intake of cheese has been associated with increases in prostate cancer risk in many, but not all, studies that have examined the association. Cheese consumption also has been found to increase the risk of new skin cancer (squamous cell carcinoma) among people with previous skin cancer.Breast cancer-related effects of eating cheese
Components of cheese, including calcium, vitamin D, stearate, and conjugated linoleic acid have been found to induce apoptosis of breast cancer cells or reduce mammary tumor size and incidence in the laboratory. However, many (but by no means all) population studies have found that cheese consumption is associated with an increased risk of breast cancer. The factors that may contribute to this increased risk include the fact that much of the milk we drink today is produced from pregnant cows (in which estrogen and progesterone levels are markedly elevated), as well as the presence of saturated fat, recombinant bovine growth hormone, and various environmental contaminants in cheese. On the other hand, like fermented milk products, consumption of low-fat or non-fat cheese may be protective against breast cancer.
Conjugated linoleic acid has been found to inhibit breast cancer in the laboratory at concentrations close to human consumption levels. Several population studies have been performed specifically to evaluate the possible association between consumption of CLA in cheese and other dairy products and the risk of breast cancer. The study results have been contradictory. A large prospective Netherlands population study found a weak positive association between CLA intake and the risk breast cancer (i.e., the association was in the opposite direction expected if CLA was protective) and concluded that the apparent anticarcinogenic properties of CLA in animal and tissue culture models had not been confirmed in humans. However, an earlier Finnish study of women who already had breast cancer found that dietary CLA and levels of CLA in the blood were significantly lower in the postmenopausal breast cancer cases than in the postmenopausal controls without cancer.
Recombinant bovine growth hormone (a synthetic version of the bovine growth hormone that occurs naturally in cows), which is administered to cows to increase milk production, has been suggested to increase breast cancer risk. This hormone is thought to be biologically inactive in humans. However, it causes the cow liver to produce insulin-like growth factor 1 (IGF-1), which enters the blood and milk as well. The bovine form of IGF-1 is identical to the human form. IGF-1 is required for mammary development at puberty and has been implicated in increased risk of breast cancer. Several studies have found a modest positive association between circulating IGF-I levels and breast cancer risk among premenopausal women. In fact, substances that inhibit IGF-I action in the mammary gland are being developed in the hope that they can eventually play a role in breast cancer chemoprevention.
Additional comments
Since calcium and vitamin D both have been shown to be very significant in protecting against several cancers, and since cheese is a major source of both in the typical American diet, it is important that those who start to decrease their overall consumption of cheese add new sources of calcium and vitamin D.
While consuming low-fat dairy products may reduce breast cancer risk compared to full-fat dairy products, it also can increase the risk of infertility in women due to lack of ovulation. High intake of low-fat dairy foods has been found to increase the risk of anovulatory infertility whereas intake of high-fat dairy foods has been associated with lower risk.
Selected studies
Growth Hormone and Insulin-Like Growth Factor-I in the Transition from Normal Mammary Development to Preneoplastic Mammary Lesions Endocrine Reviews, February 2009Adult female breast development begins at puberty and proceeds by means of tightly regulated cross-talk between hormones and growth factors. While estrogen and luteal phase progesterone are crucial, both of these hormones require growth hormone-induced insulin-like growth factor 1 (IGF-I) in the mammary gland in order to act. The same group of hormones, when experimentally manipulated, can lead to the development of hyperplastic lesions and increase the chances, or be precursors, of breast cancer. For example, systemic administration of growth hormone or IGF-I causes mammary hyperplasia, and overproduction of IGF-I in laboratory animals can initiate the development of usual or atypical hyperplasias and sometimes carcinoma. The theoretical model of progression from normal development to cancer through precursor lesions sensitive to hormones and growth factors described above is gaining support for humans as well. Indeed, elevation of estrogen receptor, growth hormone, IGF-I, and IGF-I receptor during breast cancer progression suggests a role for these pathways in this process. New substances targeting the growth hormone/IGF-I mechanism may provide a means to avert formation and progression of precursor lesions to overt breast cancer. For example, a novel somatostatin analog has been shown to prevent mammary development in rats via IGF-I action inhibition. In addition, the growth hormone antagonist pegvisomant and IGF-I antagonists such as IGF binding proteins 1 and 5 also block mammary gland development. The authors conclude that inhibition of IGF-I action, or perhaps growth hormone, in the mammary gland may eventually play a role in breast cancer chemoprevention by preventing actions of both estrogen and progesterone, especially in women at extremely high risk for developing breast cancer such as those with BRCA gene 1 or 2 mutations.
Dairy food, calcium, and risk of cancer in the NIH-AARP diet and health study Archives of Internal Medicine, February 2009
In the present large prospective cohort study, researchers from the National Institute of Health’s Diet and Health Study set out to determine whether dairy food and calcium in the diet were associated with risk of various cancers, as well as total cancer. A food frequency questionnaire was used to measure intakes of dairy food and calcium from foods and supplements. State cancer registries were used to identify new cancer cases during the follow-up period. During an average of seven years of follow-up, 36,965 male and 16,605 female cancer cases were identified. In both men and women, dairy food and calcium intakes were found to be inversely associated with cancers of the digestive system. Dairy food, dietary calcium, supplemental calcium, and total calcium were not associated with total cancer mortality for both men (8,787 deaths) and women (4,479 deaths). The researchers also found that in women, total calcium intake was not linearly associated with total cancer incidence: the risk decreased up to approximately 1300 mg of calcium per day, after which no further risk reduction was gained by consuming more calcium.
Nested Case-Control Study of the Association of Circulating Levels of Serum Insulin-like Growth Factor I and Insulin-like Growth Factor Binding Protein 3 with Breast Cancer in Young Women in Norway Cancer Epidemiology, Biomarkers & Prevention, August 2008
The present case-control population study was designed to determine the association between circulating levels of insulin-like growth factor (IGF-I) and the risk of breast cancer. It is thought that high circulating levels of insulin-like growth factor (IGF-I) might increase breast cancer risk in premenopausal women, possibly by increasing cell proliferation and reducing apoptosis. Study participants were 35,105 Norwegian women aged 40 to 42 years who participated in a health screening survey. The women were followed for an average period of 4.3 years after enrollment. During this period, 325 women were diagnosed with breast cancer. 647 women without breast cancer matched to the subjects based on age and time of blood sampling were selected as controls. Blood levels of IGF-I and its main binding protein (IGFBP-3) were measured. The average age at blood collection was 41.1 years for both groups, and the average age at diagnosis for the cases was 45.4 years, with a range of 40 to 51 years of age. Logistic regression analysis was used to adjust for relevant covariates. The median IGF-I level was found not to differ between the breast cancer cases (205 ng/mL) and controls (202 ng/mL). However, when analyzed by level of serum IGF-I, the relative risk for women in the highest versus the lowest quintile of circulating IGF-1 was 1.46 (95% confidence interval, 0.93 - 2.32; P trend = 0.15) after adjusting for serum IGFBP-3, age, and year of blood collection. The authors conclude that they found only a modest positive association between serum IGF-I levels and risk of breast cancer in women younger than 50 years of age.
Dairy product consumption and the risk of breast cancer Journal of the American College of Nutrition, December 2005
This review starts with a brief overview of the roles of fat, bovine growth hormone, insulin-like growth factor-1, and estrogens and then examines the evidence from animal studies and epidemiology regarding the role of milk fat in the etiology of breast cancer. The daily intake of insulin-like growth factor-1 and biologically active estrogens from dairy products is minute in comparison to the daily endogenous secretion of these factors in women, and bovine growth hormone is biologically inactive in humans. On the other hand, milk contains rumenic acid, vaccenic acid, branched chain fatty acids, butyric acid, cysteine-rich whey proteins, calcium and vitamin D, all of which have the potential to help prevent breast cancer. Furthermore, the authors conclude, evidence from over 40 case-control studies and 12 cohort studies does not support an association between dairy product consumption and the risk of breast cancer.
Intake of conjugated linoleic acid, fat, and other fatty acids in relation to postmenopausal breast cancer: the Netherlands Cohort Study on Diet and Cancer American Journal of Clinical Nutrition, October 2002
Conjugated linoleic acid (CLA), which is present in milk and meat from ruminants, has been shown to have anticarcinogenic activity against breast cancer in animal and in vitro experiments. The present study was designed to evaluated the association between intakes of CLA and other fatty acids and the risk of breast cancer in the Netherlands Cohort Study. Information obtained by means of a validated 150-item food-frequency questionnaire was linked to an existing database with information on specific fatty acids in European foods. There were 941 new cases of breast cancer during a follow-up period of 6.3 years. Associations were calculated for energy-adjusted intakes of fatty acids and CLA-containing food groups (e.g., butter, cheese, milk, other milk products, and meat). CLA intake was found to have a weak, positive association with breast cancer incidence (rate ratio for highest compared with lowest quintile: 1.24, 95% CI: 0.91, 1.69; P for trend = 0.02). Statistically significant positive associations also were found with total trans fatty acids and with saturated fatty acids (borderline). Significant inverse relations were found with monounsaturated and cis-unsaturated fatty acids, whereas the total fat and energy intake of CLA-containing food groups were found not to be related to breast cancer incidence. The authors conclude that the apparent anticarcinogenic properties of CLA in animal and tissue culture models was not confirmed in this epidemiological study of humans.
Inverse association between dietary and serum conjugated linoleic acid and risk of breast cancer in postmenopausal women Nutrition and Cancer, January 2000
The present 1992-1995 study was designed to assess levels of dietary and serum conjugated linoleic acid (CLA) in Finnish patients with breast cancer. Conjugated linoleic acid has been found to be anticarcinogenic in animal studies. The study participants included 195 women with breast cancer (68 premenopausal and 127 postmenopausal) and 208 population-based controls (75 premenopausal and 133 postmenopausal) who were matched for age and area of residence. Diet was determined by a food frequency questionnaire and the fatty acid composition of the blood was assessed by gas-liquid chromatography. In postmenopausal women, dietary CLA, serum CLA, myristic acid, and trans-vaccenic acid were found to be significantly lower in the breast cancer cases than in the controls. The odds ratio for breast cancer in the highest quintile vs. the lowest was 0.4 [95% confidence interval = 0.2-0.9] for CLA. The odds ratio remained similar after adjustment for known breast cancer risk factors. The authors conclude that a diet composed of CLA-rich foods, particularly cheese, may protect against breast cancer in postmenopausal women, but that it is impossible to assess the independent effects of CLA in this study.
Dairy foods and risk of breast cancer: a case-control study in Montevideo, Uruguay European Journal of Cancer Prevention, October 2002
The current 1999-2001 case-control study was designed to investigate possible associations of milk and dairy products and the risk of breast cancer in Montevideo, Uruguay. 333 women were interviewed with a questionnaire, of whom 111 had been diagnosed with breast cancer and 222 were matched healthy women with a recent normal mammography. The questionnaire included questions regarding food frequencies, as well as socio-demographic, reproductive, familial, medical and lifestyle variables. The food questions regarding types of milk and dairy products were detailed. A multivariate analysis was performed, controlling for age, age at menarche, menopausal status, years of urban status, level of education, body mass index, family history of breast cancer, number of childbirths, total energy and total fruit. It was found that high intakes of whole milk, chocolate milk and Gruyère cheese were associated with significant increased risk of breast cancer, whereas ricotta cheese and skim yoghurt were associated with significant decreased risks. The authors conclude that low-fat and fermented products appear to be the most protective dairy foods.
Dietary factors and breast cancer risk in Vaud, Switzerland Nutrition and Cancer, 1993;19(3)
The present Swiss case-control pilot study was designed to evaluate the relationship between dietary factors and the risk of breast cancer. 107 incident breast cancer cases and 318 cancer-free hospital controls (who had been admitted to hospital for acute conditions not related to hormonal, gynecological, or metabolic problems) were interviewed. Significant direct trends in risk were found for total energy intake [relative risk (RR) for highest vs. lowest intake third = 1.9] and, after allowing for energy intake, for the frequency of consumption of various types of meat (RR = 2.1 for the highest tertile), cheese (RR = 2.7), and alcohol (RR = 2.1). Significant protection against breast cancer (approximate reductions of 40% to 60% for the highest vs. lowest consumption tertile) were conferred by total green vegetable consumption, certain types of vegetables and fruits (cucumbers, onions, pears), and beta-carotene intake (RR = 0.4 for highest consumption tertile). The authors concluded that they had confirmed the existence of an unfavorable dietary pattern for breast cancer risk characterized by overall high calorie intake and significant consumption of alcohol and selected sources of animal fat.
The role of fat, animal protein and some vitamin consumption in breast cancer: a case control study in southern France International Journal of Cancer, April 1991
This hospital-based French case-control population study examined the relationship between the consumption of fat, animal protein and vitamins and the risk of breast cancer. A total of 924 patients (409 cases and 515 controls) were included. A detailed dietary questionnaire was administered by interview and was used to estimate the intake of total fat and fat constituents, animal protein, retinol, β-carotene, vitamin E and alcohol. It was also used to obtain information on medical history and other personal characteristics. It was found that all of the foods associated with significantly elevated risk of breast cancer contained a high proportion of animal fat. These foods included high-fat cheese, desserts, chocolate, and processed pork meat. This high-animal-fat correlation is reflected in the nutrient analysis, which found a significant linear trend (as well as an elevated odds ratio (OR)) for the highest third of consumption of total fat [OR = 1.6 Confidence Interval (CI): 1.1-2.2], animal fat [OR = 1.6 CI: 1.1-2.2], saturated fat [OR3 = 1.9 CI: 1.3-2.6] and mono-unsaturated fat [OR = 1.7 CI: 1.2-2.5)]. A particularly strong association with saturated fat [OR = 3.3 CI: 1.4-7.8] was found for post-menopausal women. No evidence was found of an increase in risk associated with the intake of animal protein and no risk reduction was found with increased consumption of vegetables, β-carotene or vitamin E. The authors conclude that the results support the hypothesis that dietary fat is a risk factor in breast carcinogenesis.
