Women who live in neighborhoods with lots of nighttime illumination are at increased risk for developing breast cancer, according to a study published in the journal Chronobiology International. Based on satellite images of night lights in 147 communities in Israel, researchers determined that the areas with the greatest amount of light at night had approximately 73 percent higher breast cancer incidence compared with the areas with the lowest level of nighttime illumination. Scientists have known for years that excessive exposure to light may interfere with the tumor-suppressing hormone melatonin, which is produced at night and at decreased levels with light exposure. Women who are blind produce large amounts of melatonin and have a below-average rate of breast cancer. The use of energy-efficient fluorescent bulbs during nighttime hours suppresses melatonin more than conventional incandescent bulbs.
Kloog I, Haim A, Stevens RG, Barchana M, Portnov BA. Light at night co-distributes with incident breast but not lung cancer in the female population of Israel. Chronobiol Int. February 2008;25(1):65-81.
Progesterone in Dairy Products May Increase Breast Cancer Risk
Consuming high-fat dairy products may increase breast cancer risk because of high levels of bovine progesterone, according to a study presented at the annual San Antonio Breast Cancer Symposium. Since the 1950s, dairy farmers have kept cows continually pregnant, which has increased the level of progesterone in milk. Researchers measured salivary levels of progesterone in male volunteers 24 hours after they ate three servings of high-fat dairy products: 2 tablespoons of butter, 2 ounces of cheese, and a quart of ice cream. Salivary progesterone levels rose by 30 percent to 100 percent in nearly all subjects. Male subjects were used because their progesterone levels are lower and less cyclic than females, making changes easier to detect. Because progesterone dissolves readily in fat, it is absorbed more efficiently in high-fat products. In previous studies, the consumption of dairy products—including low-fat varieties—has been linked to premenopausal breast cancer risk, possibly because of increased blood levels of insulin-like growth factor-1.
William H. Goodson III, MD. Milk products are a source of dietary progesterone. Abstract 202, San Antonio Breast Cancer Symposium, December 2007. Available at: http://www.abstracts2view.com/sabcs/view.php?nu=SABCS07L_1108&terms=. Accessed June 9, 2008.
Cancer Survivors Aren’t Pursuing Healthy Lifestyles
Only 5 percent of cancer survivors meet three common recommendations for fruit and vegetable consumption, physical activity, and smoking cessation, according to a study examining the diets and lifestyles of 9,105 breast, prostate, colorectal, bladder, uterine, and skin melanoma cancer survivors. While 83 percent to 92 percent are nonsmokers, just 15 percent to 20 percent are meeting the fruit and vegetable recommendation, and 30 percent to 47 percent are meeting the recommendation for physical activity. The research showed that the more recommendations cancer survivors met, the higher their health-related quality of life became. The American Cancer Society published recommendations in 2006 for cancer survivors: Get at least 150 minutes of moderate to strenuous exercise, or one hour of strenuous exercise every week; eat at least five servings of fruits and vegetables every day; and quit smoking. PCRM’s Cancer Project provides detailed information on nutrition for cancer prevention and survival.
Blanchard CM, Courneya KS, Stein K; American Cancer Society’s SCS-II. Cancer survivors’ adherence to lifestyle behavior recommendations and associations with health-related quality of life: results from the American Cancer Society’s SCS-II.J Clin Oncol. May 1, 2008;26(13):2198-2204.
The Cancer Project is a nonprofit PCRM subsidiary that advances cancer prevention and survival through nutrition education and research.