More women than ever before are surviving breast cancer due to better awareness, screening and improved treatments. However, some of these breast cancer survivors feel anxious or depressed, particularly about the possibility of the cancer coming back. Therefore, looking after the physical and emotional well being continues to be important after the breast cancer treatment is complete.
Breast cancer is a complex disease, and it is believed to be caused by interactions between our genes, lifestyle and environment. There isn’t any one single factor that is responsible for causing it. A combination of factors play a part in why some women develop the disease and others don’t. This article focuses on the breast cancer risk factors; the information may help you to minimize the risk of breast cancer recurrence.
Some of the modifiable established risk factor for breast cancer are:
1) Excessive body weight
Studies1-2 show that being overweight or obese after menopause may increase the risk of breast cancer. This may be because, fat tissue after the menopause becomes the main source of the female hormone oestrogen. The more fat tissue you have, the more oestrogen your body may produce, in turn, may increase your risk of breast cancer. Research studies have shown that the more weight a woman gains over the course of her adult life, the higher her risk of developing breast cancer will be after she has gone through the menopause. All women are therefore encouraged to maintain a healthy weight throughout life.
2) Regular alcohol intake
Studies4-7 show that regular alcohol intake is associated with an increased risk of breast cancer. The more you regularly drink, the higher your chance of getting breast cancer. Current evidence5 suggests that all types of alcohol are associated with this increased risk. A new study3 shows that among women who have had breast cancer, drinking alcohol may increase their risk of developing second primary breast cancer.
3) Lacking exercise
Scientific evidence show that regular exercise helps to reduce the risk of post-menopausal breast cancer8-9. The reasons are not known, but it is known that regular exercise prevents weight gain, which is known to increase breast cancer risk. he exact amount of physical activity needed to reduce your risk is not yet clear. However, studies have shown that one and a half to four hours per week of brisk walking (or equivalent) reduces the risk of breast cancer in post-menopausal women. However, no such association was found for pre-menopausal women10-11.
4) Never breastfeed
Scientific evidence12-15 show that breast cancer risk is lower among women who have breastfed their babies for five months or more in total. The longer the length of time you breastfeed overall, the greater the reduction in your risk of breast cancer. Oestrogen stimulates the growth of many breast cancers. Breastfeeding delays the restarting of menstrual periods after childbirth; this reduces the levels of oestrogen in the body for a time and may therefore help to reduce the overall chance of developing breast cancer.
Some studies have also looked at the relationships between breast cancer risks and the intake of saturated fat intake, phyto-oestrogen, fruit and vegetables, and omega 3 fatty acids. The results from these studies don’t all agree, more studies are necessary to fully understand the relationships. Some of these doubtful risk factors are:
1) Saturated fat intake
Some studies16,18 have found that women who ate high levels of saturated fat were more likely to develop breast cancer than those who ate low levels of fat. However, other studies17,19-21 have found no link between any type of dietary fat and breast cancer. It is clear that very high fat diets can lead to weight gain and obesity, both of which can increase breast caner risk after the menopause.
2) Omega 3 fatty acids
Some studies have suggested that omega 3 fatty acids can inhibit the growth of breast cancer cells. However, a review22 of many studies looked at dietary omega 3 fatty acids did not clearly show the same protective effect. More research is therefore needed to establish the link between omega 3 fatty acids and breast cancer.
3) Fruits and vegetables
Studies show that fruit and vegetables have little or no effect on the breast cancer risk. However, fruits and vegetables are rich in antioxidants and fibre, which are all known to have protective effects on our overall health. Therefore fruits and vegetables should be included daily in our diet.
Phyto-oestrogens are chemicals in plant foods (such as soya bean products, whole grains, fruits, vegetables, legumes, and tea and flaxseed), that have a similar structure to the female hormone oestrogen. Some studies23-28 found that regularly eating foods that contain phyto-oestrogens might lower the risk of breast cancer, particularly if eaten during adolescence. However, other studies29-32 found no effect. Until it is clear how phyto-oestrogens affect breast cancer risk, it is sensible for all women to eat them only as part of their normal diet rather than as an intentional supplement.
Even though more scientific research is needed before we can be sure about the links between some dietary components and breast cancer, we are all encouraged to follow a healthy lifestyle and eating a healthy balanced diet, as this will help to maintain general good health, a healthy body weight and reduce the risk of many diseases.
- Trentham-Dietz A et al. Body Size and Risk of Breast Cancer. American Journal of Epidemiology 1997 Vol. 145, No. 11: 1011-1019
- Radimer K et al. Relation between Anthropometric Indicators and Risk of Breast Cancer among Australian Women. American Journal of Epidemiology 1993 Vol. 138, No. 2: 77-89
- Knight JA et al. Alcohol Intake and Cigarette Smoking and Risk of a Contralateral Breast Cancer: The Women’s Environmental Cancer and Radiation Epidemiology Study. American Journal of Epidemiology 2009 169(8):962-968
- Zhang SM et al. Alcohol Consumption and Breast Cancer Risk in the Women’s Health Study. American Journal of Epidemiology 2007 165(6):667-676
- Ellison RC et al. Exploring the Relation of Alcohol Consumption to Risk of Breast Cancer. American Journal of Epidemiology 2001 Vol. 154, No. 8 : 740-747
- Brandt et al. Alcohol and Breast Cancer: Results from the Netherlands Cohort Study. American Journal of Epidemiology 1995 Vol. 141, No. 10: 907-915
- Nasca PC et al. Alcohol Consumption and Breast Cancer: Estrogen Receptor Status and Histology. American Journal of Epidemiology 1994 Vol. 140, No. 11: 980-988
- Friedenreich CM et al. Case-Control Study of Lifetime Physical Activity and Breast Cancer Risk. American Journal of Epidemiology 2001 Vol. 154, No. 4 : 336-347
- Gilliland FD et al. Physical Activity and Breast Cancer Risk in Hispanic and Non-Hispanic White Women. American Journal of Epidemiology 2001 Vol. 154, No. 5 : 442-450
- Steindorf K et al. Case-Control Study of Physical Activity and Breast Cancer Risk among Premenopausal Women in Germany. American Journal of Epidemiology 2003; 157:121-130
- Gammon MD et al. Recreational Physical Activity and Breast Cancer Risk among Women under Age 45 Years. American Journal of Epidemiology 1998 Vol. 147, No. 3: 273-280
- Tryggvadóttir L et al. Breastfeeding and Reduced Risk of Breast Cancer in an Icelandic Cohort Study. American Journal of Epidemiology 2001 Vol. 154, No. 1 : 37-42
- Newcomb PA et al. Lactation in Relation to Postmenopausal Breast Cancer. American Journal of Epidemiology 1999 Vol. 150, No. 2: 174-182
- Freudenheim JL et al. Lactation History and Breast Cancer Risk. American Journal of Epidemiology 1997 Vol. 146, No. 11: 932-938
- Sikind v et al. Breast cancer and breastfeeding: results from an Australian case-control study. American Journal of Epidemiology 1989 vol. 130, no. 2: 229-236
- Sieri S et al. Dietary fat and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition. American Journal of Clinical Nutrition, Vol. 88, No. 5, 1304-1312, November 2008
- Kim EHJ et al. Dietary Fat and Risk of Postmenopausal Breast Cancer in a 20-year Follow-up. American Journal of Epidemiology 2006 164(10):990-997
- Voorrips LE et al. Intake of conjugated linoleic acid, fat, and other fatty acids in relation to postmenopausal breast cancer: the Netherlands Cohort Study on Diet and Cancer. American Journal of Clinical Nutrition, Vol. 76, No. 4, 873-882, October 2002
- Hunter DJ et al. Cohort Studies of Fat Intake and the Risk of Breast Cancer — A Pooled Analysis. The New England Journal of Medicine 1996 Volume 334:356-361
- Rose DP et al. The effects of a low fat dietary intervention and tamoxifen adjuvant therapy on the serum oestrogen and sex-hormone-binding globulin concentrations of post menopausal breast cancer. Breast Cancer Res Treat 1993; 27:253–62
- Knekt P et al. Dietary fat and risk of breast cancer. American Journal of Clinical Nutrition, Vol 52, 903-908, 1990.
- Terry PD et al. Intakes of fish and marine fatty acids and the risks of cancers of the breast and prostate and of other hormone-related cancers: a review of the epidemiologic evidence. American Journal of Clinical Nutrition, Vol. 77, No. 3, 532-543, March 2003
- Trock BC et al. Meta-Analysis of Soy Intake and Breast Cancer Risk. Journal of the National Cancer Institute 2006 98(7):459-471
- Dai Q et al. Population-based case-control study of soy food intake and breast cancer risk in Shanghai. Br J Cancer 2001;85:372–378
- Shu XO et al. Soyfood intake during adolescence and subsequent risk of breast cancer among Chinese women. Cancer Epidemiol Biomarkers Prev 2001;10:483–488.
- Lee HP et al. Risk factors for breast cancer by age and menopausal status: a case-control study in Singapore. Cancer Causes Control 1992;3:313–322.
- Hirose Ket al. A large-scale, hospital-based case-control study of risk factors of breast cancer according to menopausal status. Jpn J Cancer Res 1995;86:146–154
- Wu AH et al. Tofu and risk of breast cancer in Asian-Americans. Cancer Epidemiol Biomarkers Prev 1996;5:901–906
- Keinan-Boker L et al. Dietary phytoestrogens and breast cancer risk. American Journal of Clinical Nutrition, Vol. 79, No. 2, 282-288, February 2004
- Horn-Ross PL et al. Phytoestrogen consumption and breast cancer risk in a multiethnic population: the Bay Area Breast Cancer Study. Am J Epidemiol 2001;154:434–441.
- Zheng W et al. Urinary excretion of isoflavonoids and the risk of breast cancer. Cancer Epidemiol Biomarkers Prev 1999;8:35–40
- Yuan JM et al. Diet and breast cancer in Shanghai and Tianjin, China. Br J Cancer 1995;71:1353–1358