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 web page 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 bladder, 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 CLA 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. High intake of animal fats has been linked in several studies to increased breast density, a risk factor for breast cancer and recurrence. 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 (CLA) and breast cancer
CLA 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 and IGF-1
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. The hormone itself 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.
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.
Below are links to recent studies concerning this food. For a more complete list of studies, please click on cheese.