DIETARY PHYTOESTROGENS & LUNG CANCER RISK*
Eating foods that are rich in phytoestrogens appears to lower lung cancer risk in both smokers and non-smokers. This is the message of a study published in the Journal of the American Medical Association (JAMA) (volume 294, No. 12, 2005). The title of the paper is Dietary Phytoestrogens and Lung Cancer Risk. The study, the largest of its kind to examine dietary intake and lung cancer risk in the United States, involved 3409 people.
What are Phytoestrogens?
Dietary phytoestrogens are plant-derived non-steroidal compounds with a weak oestrogen-like activity. There are several types:
· Isoflavones, a subgroup of flavonoids. Isoflavones are the most common form, and most extensively investigated, of the phytoestrogens. The two major isoflavones, genistein and daidzein, are formed from the precursors genistin and daidzin. They are found in a variety of sources, including soy products, soybeans, alfalfa sprouts, chickpeas and red clover, peanuts and other legumes.
· Lignans, such as silymarin. These are derived from rye grains, linseeds (flaxseed), carrots, spinach, broccoli and other vegetables, and tea.
· Coumesterol.This is found mainly in beans, peas, clover, spinach and sprouts.
· Phytosterols. These are derived from the intestinal absorption of vegetable oils, grains and certain fruits and vegetables. They are structurally similar to cholesterol.
Phytoestrogens are phytochemicals. They are non-nutritive plant chemicals that have protective or disease-preventive properties. For details of phytochemicals, see my January 2010 newsletter Phytochemicals.
The objective of the study was to examine the relationship between dietary intake of phytoestrogens and risk of lung cancer.
The participants of the study, as reported in JAMA, involved 1674 patients treated for lung cancer and 1735 matched healthy controls. The design of the study was such that, from July 1995 through October 2003, participants were personally interviewed with epidemiologic and food frequency questionnaires to collect demographic information and to quantify dietary intake of 12 individual phytoestrogens. Full details of the methodology, statistical analysis and the results can be accessed from the publication at jama.ama-assn.org/cgi/content/full/294/12/1493.
The “Main Outcome Measure” was the risk of lung cancer, estimated using unconditional multivariable logistic regression analyses stratified by sex and smoking status and adjusted for established and putative lung cancer risk factors.
Results: The main findings were “that patients with lung cancer tended to consume lower amounts of phytoestrogens than controls, that there were sex-specific differences both in intake and in protective effects, and that the apparent benefits were evident in both never and current smokers but less so in former smokers.”
Overall, those who ate the most foods with dietary phytoestrogens had a 46 percent lower risk of developing lung cancer than those who ate the least.
Men who ate the most foods with soy isoflavones lowered their risk of lung cancer by 72%.
Women who ate the most fruits and vegetables lowered their risk by 41%.
Lung cancer risk for both smokers and non-smokers was decreased when large quantities of phytoestrogens were consumed. Among former smokers, the effect was less significant.
In summary: “These data provide further support for the limited but growing epidemiologic evidence that estrogens and phytoestrogens are associated with a decrease in risk of lung cancer, especially in never and current smokers.” The authors point out that confirmation of the findings is still required in large-scale longitudinal studies.
Even if you are eating lots of phytoestrogens, the researchers caution that it does not mean that you can smoke without risk.
The American Lung Association says that “every year in the U.S. over 392,000 people die from tobacco-caused disease, making it the leading cause of preventable death. Another 50,000 people die from exposure to second-hand smoke” (www.lungusa.org).
It is estimated worldwide that approximately 1 million people die from lung cancer every year.
The Australian Bureau of Statistics indicated that, in 2008, deaths from “Malignant neoplasms of respiratory and intrathoracic organs (C30-C39)” were 8262, which accounted for 20% of all malignant cancers, and lung cancer (C34) was the underlying cause of 7941 (96%) of these deaths. The deaths from lung cancer in 2007 were 7623 (www.abs.gov.au).
While smoking is the major cause of lung cancer (accounting for some 87% of lung cancer cases), other factors like radon gas asbestos and air pollution also contribute.
The Cancer Council of Australia (2006) states “Tobacco smoking is the largest single preventable cause of death and disease in Australia”.
The best lung cancer prevention advice continues to be to stop smoking, Refer to my January 2010 newsletter Smoking Statistics - and How to Quit Forever.
However, as can be seen from the results of the above study, a diet in accordance with the guidelines set out in my book How To Live To 100+ Years free from Symptoms and Disease (see homepage), which will include adequate supplies of phytoestrogens, may afford some degree of protection against lung cancer, both in smokers as well as non-smokers.
*Copyright 2011: The Huntly Centre.
Disclaimer: All material in the huntlycentre.com.au website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.
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