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Does Saturated Fat Promote Breast Cancer?

breast cancerStudies document a definitive relationship between diets higher in saturated fat and elevations of LDL cholesterol.1-5 In spite of efforts of the dairy and meat industry to support and produce dubious, highly promoted research that exonerates their products and to use their media partners to confuse the public, the reality is that overwhelming evidence exists that diets high in animal products are exceedingly dangerous, placing the public at an increased risk of a premature death. The advocates of popular diet programs, such as Atkins, Dukan, Paleo and others saturate the internet with propaganda aiming to absolve animal products as a cause of heart disease, but heart disease is not the only concern. Not much attention has been paid to the data suggesting that saturated fat (or saturated fat-rich foods) may impact cancer risk. Two new studies have added more convincing evidence by reporting a link between saturated fat and breast cancer.

One study investigated the intake of different types of fats with respect to the risk of different subtypes of breast cancer (breast cancers are divided into subtypes based on whether the tumor cells contain receptors for certain hormones such as estrogen and progesterone). Dietary information was collected from 300,000 women living in 10 different countries throughout Europe, who were then followed for 11.5 years. The women with the highest intakes of saturated fat showed a greater risk of two subtypes of breast cancer: ER+PR+ (estrogen receptor and progesterone receptor-positive) and HER2- (human epidermal growth factor receptor 2 negative).6 This suggests that saturated fat could have some influence on the development of HER2- breast cancer and ER+PR+ breast cancer, which is a very common subtype; about 80 percent of breast cancers are positive for the estrogen receptor, and 65 percent of those are also positive for the progesterone receptor.7 A second study, based on data from the Nurses’ Health Study II, collected dietary information from 26-45 year old women and followed them for 20 years. Similarly in this study, a higher intake of saturated fat was associated with greater risk of breast cancer. An interesting point in this study, is that their data suggested that the saturated fat source likely responsible for the link was red meat.8 These results are in agreement with the conclusion of a 2003 meta-analysis of 35 studies, which reported that the highest levels of saturated fat intake in women were associated with a 19 percent increase in breast cancer risk, and also implicated meat as the food most likely to be responsible.9

A question arises out of these results: does saturated fat promote cancer? Or is saturated fat just a marker for a cancer-promoting substance in saturated fat-rich foods? There is very limited evidence that saturated fat itself increases cancer risk. A saturated fat-rich diet may promote insulin resistance, which could be a contributing factor.10 But it is likely that a combination of factors in saturated fat-rich foods, red meat in particular, is responsible for the increase in cancer risk:

  • In addition to saturated fat, red and processed meats also contain a significant amount of arachidonic acid, an omega-6 fat shown to promote breast tumors in animals, likely by promoting inflammation.11-14
  • Carnitine (abundant in red meat) and choline (abundant in eggs, dairy, and meats) are metabolized by gut bacteria into a pro-inflammatory compound called trimethylamine-N-oxide (TMAO) that may contribute to the development of cancers.15-17
  • Eating red meat exposes us to dietary carcinogens such as N-nitroso compounds and heterocyclic amines.18-21
  • The heme iron content of red meat is also problematic, since excess iron causes oxidative stress.22, 23
  • Finally, dietary animal protein increases circulating levels of insulin-like growth factor 1 (IGF-1), a hormone that promotes tumor cell growth and is associated with an increased risk of cancer.24, 25


Regardless of the specific actions of saturated fat, the saturated fat-rich foods common in the standard American diet, red meat in particular, contains numerous disease-promoting substances. However, greens, beans, onions, mushrooms, berries, and seeds (G-BOMBS) have documented breast cancer-preventive properties. By focusing our diet on G-BOMBS and other vegetables and minimizing animal foods, we provide the body with the tools it needs to build the best possible defenses against cancer.


References:

1. Hodson L, Skeaff CM, Chisholm WA: The effect of replacing dietary saturated fat with polyunsaturated or monounsaturated fat on plasma lipids in free-living young adults. Eur J Clin Nutr 2001;55:908-915.
2. Abbey M, Noakes M, Belling GB, et al: Partial replacement of saturated fatty acids with almonds or walnuts lowers total plasma cholesterol and low-density-lipoprotein cholesterol. Am J Clin Nutr 1994;59:995-999.
3. Barr SL, Ramakrishnan R, Johnson C, et al: Reducing total dietary fat without reducing saturated fatty acids does not significantly lower total plasma cholesterol concentrations in normal males. Am J Clin Nutr 1992;55:675-681.
4. Ginsberg HN, Kris-Etherton P, Dennis B, et al: Effects of reducing dietary saturated fatty acids on plasma lipids and lipoproteins in healthy subjects: the DELTA Study, protocol 1. Arterioscler Thromb Vasc Biol 1998;18:441-449.
5. Siri-Tarino PW, Sun Q, Hu FB, et al: Saturated fatty acids and risk of coronary heart disease: modulation by replacement nutrients. Curr Atheroscler Rep 2010;12:384-390.
6. Sieri S, Chiodini P, Agnoli C, et al: Dietary Fat Intake and Development of Specific Breast Cancer Subtypes. J Natl Cancer Inst 2014.
7. Breastcancer.org: How to Read Hormone Receptor Test Results [http://www.breastcancer.org/symptoms/diagnosis/hormone_status/read_results]
8. Farvid MS, Cho E, Chen WY, et al: Premenopausal dietary fat in relation to pre- and post-menopausal breast cancer. Breast Cancer Res Treat 2014;145:255-265.
9. Boyd NF, Stone J, Vogt KN, et al: Dietary fat and breast cancer risk revisited: a meta-analysis of the published literature. Br J Cancer 2003;89:1672-1685.
10. Riccardi G, Giacco R, Rivellese AA: Dietary fat, insulin sensitivity and the metabolic syndrome. Clin Nutr 2004;23:447-456.
11. National Cancer Institute: Food Sources of Arachidonic Acid [http://appliedresearch.cancer.gov/diet/foodsources/fatty_acids/table4.html]
12. Wynder EL, Rose DP, Cohen LA: Diet and breast cancer in causation and therapy. Cancer 1986;58:1804-1813.
13. Makarem N, Chandran U, Bandera EV, et al: Dietary fat in breast cancer survival. Annu Rev Nutr 2013;33:319-348.
14. de Lorgeril M, Salen P: New insights into the health effects of dietary saturated and omega-6 and omega-3 polyunsaturated fatty acids. BMC Med 2012;10:50.
15. Tang WH, Wang Z, Levison BS, et al: Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk. N Engl J Med 2013;368:1575-1584.
16. Wang Z, Klipfell E, Bennett BJ, et al: Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature 2011;472:57-63.
17. Richman EL, Kenfield SA, Stampfer MJ, et al: Choline intake and risk of lethal prostate cancer: incidence and survival. Am J Clin Nutr 2012;96:855-863.
18. WCRF/AICR Expert Report, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective.: World Cancer Research Fund; 2007.
19. Lunn JC, Kuhnle G, Mai V, et al: The effect of haem in red and processed meat on the endogenous formation of N-nitroso compounds in the upper gastrointestinal tract. Carcinogenesis 2007;28:685-690.
20. Kuhnle GG, Story GW, Reda T, et al: Diet-induced endogenous formation of nitroso compounds in the GI tract. Free Radic Biol Med 2007;43:1040-1047.
21. Zheng W, Lee S-A: Well-Done Meat Intake, Heterocyclic Amine Exposure, and Cancer Risk. Nutr Cancer 2009;61:437-446.
22. Brewer GJ: Iron and copper toxicity in diseases of aging, particularly atherosclerosis and Alzheimer's disease. Exp Biol Med 2007;232:323-335.
23. Brewer GJ: Risks of copper and iron toxicity during aging in humans. Chem Res Toxicol 2010;23:319-326.
24. Thissen JP, Ketelslegers JM, Underwood LE: Nutritional regulation of the insulin-like growth factors. Endocr Rev 1994;15:80-101.
25. Kaaks R: Nutrition, insulin, IGF-1 metabolism and cancer risk: a summary of epidemiological evidence. Novartis Found Symp 2004;262:247-260; discussion 260-268.

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