Can Diet Reduce Your Risk of Breast Cancer?
by Dana Denis, MSPH., RD (topic expert: nutrition)

Breast cancer is the most prevalent type of cancer among women. Risk of breast cancer is dependent on many factors out of our control: genetic factors, early onset of menarche, late onset of menopause, never bearing children or having the first child after age thirty. So what can we do to reduce our risk?

The American Cancer Society recommends the following guidelines for reducing cancer risk:

1. Maintain a healthful weight throughout life.
   • Balance caloric intake with physical activity.
   • Lose weight if currently overweight or obese.
   • Achieve and maintain a healthy weight if currently overweight or obese.
2. Adopt a physically active lifestyle.
   • Adults: Engage in at least moderate activity for 30 minutes of moderate to vigorous physical activity, above usual activities, on 5 or more days of the week; 45 to 60 minutes of intentional physical activity are preferable.
   • Children and adolescents: Engage in at least 60 minutes per day of moderate to vigorous physical activity at least 5 days per week.
3. Eat a healthy diet, with an emphasis on plant sources.
   • Choose food or beverages in amounts that help achieve and maintain a healthy weight
   • Eat 5 or more servings of a variety of vegetables and fruits every day.
   • Choose whole grains in preference to processed (refined) grains.
   • Limit consumption of processed and red meats.
4. If you drink alcoholic beverages, limit consumption.
   • Drink no more than 1 drink per day for women or 2 per day for men.

Do these recommendations have an impact on whether or not you develop breast cancer?

Results of initial studies supported that a diet low in fat and high in fruits and vegetables was protective against breast cancer. More recently, however, larger studies have not been able to confirm this effect. Studies examining intakes of fat, carbohydrate, fiber, red meat, fish or caffeine have found either no association or insufficient evidence to link them to breast cancer. The evidence on the potential benefits of fruit and vegetable intake related to breast cancer is inconsistent.

Since estrogen is a known cause of breast cancer, recent research has focused on phytoestrogens. Phytoestrogens can compete with estrogen and, therefore, limit the potentially harmful effects. Phytoestrogens can be found in soy products and other legumes, linseed (flaxseed), whole grains, berries, nuts, and bean sprouts. Despite initial results showing protective benefits, the findings could not be confirmed in the larger studies. Of interest, however, is some evidence that a diet high in phytoestrogens earlier in life (adolescence) may be beneficial.

Was any factor confirmed to be associated with breast cancer? Yes. Alcohol consumption of two or more drinks per day was associated with increased risk. Obesity in postmenopausal women was also found to be a significant contributor to breast cancer risk. Maintaining physical activity, especially postmenopausal, is associated with a reduced risk.

Current research studies are focusing on the differences in pre- and postmenopausal women as well as the effect of diet, specifically phytoestrogens earlier in the life cycle, and studies on calcium and Vitamin D. Many researchers are also investigating how diet may affect the survival and cancer recurrence of women who have been treated for breast cancer.

One recent study looked at the combination of increased fruit and vegetable intake coupled with physical activity and how it affected survival in women previously treated for breast cancer. Only women with both a high fruit and vegetable intake and high physical activity increased their rate of survival. This result was seen in both normal weight and obese women. What was the physical activity? Walking at a moderate pace for 30 minutes 6 days a week.

Keep up those steps!

Maintain a healthy weight.

Eat "colorful" meals (i.e. include various vegetables & fruits)

Reduce alcohol intake.

References:

1. American Cancer Society. The Complete Guide - Nutrition and Physical Activity. May 19, 2006. Available at: http://www.cancer.org/. Accessed on Spetember 8, 2007.
2. Pierce JP, Natarajan LC, Caan BJ, et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: the Women's Healthy Eating and Living (WHEL) randomized trial. JAMA. 2007; 298(3): 289-98.
3. Pierce JB, Stefanick ML, Flatt SW, et al. Greater survival after breast cancer in physically active women with high vegetable-fruit intake regardless of obesity. J Clin Oncol. 2007; 25(17):2335-7.
4. Kesse-Guyot E. Bertrais S. Duperray B. et al. Dairy products, calcium and the risk of breast cancer: results of the French SU.VI.MAX prospective study. Ann Nutr Metab. 2007; 51(2):139-45.
5. Robien K. Cutler GJ. Lazovich D. Vitamin D intake and breast cancer risk in postmenopausal women: the Iowa Women's Health Study. Cancer Causes Control. 2007; 18(7):775-82.
6. Holmes MD, Liu S, Hankinson SE Colditz GA, Hunter DJ, Willet WC. Dietary carbohydrates, fiber and breast cancer risk. Am J Epidemio. 2004; 159(8):732-9.
7. Keinan-boker L, van Der Schouw YT, Grobbee DE, Peeters PH. Dietary phytoestrogens and breast cancer risk. Am J Clin Nutr. 2004; 79(2):282-8.
8. Ziegler RG. Phytoestrogens and breast cancer. Am J Clin Nutr. 2004; 79(2):183-4.
9. Baer HJ, Schnitt SJ, Connolly JL, Byrne C, Cho E, Willett WC, Colditz GA. Adolescent diet and incidence of proliferative benign breast disease. Cancer Epidemiol Biomarkers Prev. 2003; 12(11 Pt 1):1159-67.
10. Cho E, Spiegelman D, Hunter DJ, Chen WY, Colditz GA, Willett WC. Premenopausal dietary carbohydrate, glycemic index, glycemic load, and fiber in relation to risk of breast cancer. Cancer Epidemiol Biomarkers Prev. 2003; 12(11 Pt 1):1153-8.
11. Hirose K, Takezaki T, Hamajima N, Miura S, Tajima K. Dietary factors protective against breast cancer in Japanese premenopausal and postmenopausal women. Int J Cancer. 2003; 107(2):276-82.
12. Patel AV, Callel EE, Bernstein L, Wu AH, Thun MJ. Recreational physical activity and risk of postmenopausal breast cancer in a large cohort of US women. Cancer Causes Control. 2003; 14(6):519-29.
13. Riboli E, Norat T. Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. Am J Clin Nutr. 2003; 78(3 Suppl):559S-569S.
14. Okasha M, McCarron P, Gunnell D, Smith GD. Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature. Breast Cancer Res Treat. 2003; 78(2):223-76.
15. Shannon J, Cook LS, Stanford JL. Dietary intake and risk of postmenopausal breast cancer (United States). Cancer Causes Control. 2003; 14(1):19-27.
16. Peeters PH, Keinan-Boker L, van der Schouw YT, Grobbee DE. Phytoestrogens and breast cancer risk. Review of the epidemiological evidence. Breast Cancer Res Treat. 2003; 77(2):171-83.
17. Feigelson HS, Jonas CR, Robertson AS, McCullough ML, Thun MJ, Calle EE. Alcohol, folate, methionine and risk of incident breast cancer in the American Cancer Society Cancer Prevention Study II Nutrition Cohort. Cancer Epidemiol Biomarkers Prev. 2003; 12(2):161-4.
18. Holmes MD, Colditz GA, Hunter DJ, Hankinson SE, Rosner B, Speizer FE, Willett WC. Meat fish and egg intake and risk of breast cancer. Int J Cancer. 2003; 104(2):122-7.
19. Terry P, Jain M, Miller AB, Howe GR, Rohan TE. Dietary carotenoids and risk of breast cancer. Am J Clin Nutr. 2002; 76(4):883-8.
20. Key TJ, Allen NE, Spencer EA, Travis RC. The effect of diet on risk of cancer. Lancet. 2002; 360(9336):861-8.
21. Dai Q, Shu XO, Jin F, Gao YT, Ruan ZX, Zheng W. Consumption of animal foods, cooking methods and risk of breast cancer. Cancer Epidemiol Biomarkers Prev. 2002; 11(9):801-8.
22. Horn-Ross PL, Hoggatt KJ, West DW, Krone MR, Stewart SL, Anton H, Bernstei CL, Deapen D, Peel D, Pinder R, Reynolds P, Ross RK, Wright W, Ziogas A. Recent diet and breast cancer risk: the California Teachers Study (USA). Cancer Causes Control. 2002; 13(5):407-15.
23. Michaels KB. The contribution of the environment (especially diet) to breast cancer risk. Breast Cancer Res. 2002; 4(2):58-61.
24. Terry P, Suzuki R, Hu FB, Wolk A. A prospective study of major dietary patterns and the risk of breast cancer. Cancer Epidemiol Biomarkers Prev. 2001; 10(12):1281-5.