This article was written by our regular contributor; registered dietitian – Maeve Hanan.
Breast cancer is the most common form of cancer in the UK, and the second most common form worldwide (1, 2). Close to 56,000 cases occur in the UK every year (3).
Although cancer is complex and we can never pin-point the specific reason/reasons why an individual has developed cancer, it’s estimated that 23% of breast cases may be preventable (3).
This article will explore the evidence related to lifestyle factors that may impact the risk of developing breast cancer.
Consuming a balanced diet, as outlined in The Eatwell Guide, is recommended for overall health, including breast cancer prevention.
Consuming less fat has been linked with a lower risk of breast cancer (4). However, a more recent randomised controlled-trial found no association between reducing fat intake and breast cancer risk (50).
From a summary of the evidence base in 2018, the World Cancer Research Fund found limited evidence that consuming the following foods may be associated with a lower risk of breast cancer (6):
- Non-starchy vegetables – examples include brussels sprouts, broccoli, carrots, cauliflower, celery, mushrooms
- Foods containing carotenoids – a type of antioxidant found mainly in yellow, red, and orange plants such as: tomatoes, peppers, carrots, oranges, mango – also present in spinach and kale
- High-calcium foods – but there was only a link found with dairy for premenopausal breast cancer
Some more recent studies have found that a higher intakes of fruit and vegetables; specifically cruciferous vegetables, yellow and orange vegetables, apples and pears was linked with a lower risk of breast cancer (7, 8, 9). Consuming more fibre and carbohydrate has also been associated with a lower breast cancer risk (7, 9).
Naturally occurring compounds in soybeans called isoflavones have been significantly associated with a reduced risk of breast cancer in Asian populations, but not in Western populations (10). As with diet and breast cancer research as a whole, more evidence is needed to investigate this.
There is a strong link between alcohol consumption and breast cancer risk, particularly in postmenopausal women (6, 7, 9).
This risk has been seen with drinking a low to moderate amount of alcohol, as well as with higher intakes, and is thought that this might be related to increased oestrogen levels (6, 11, 12).
Limiting or avoiding alcohol is also recommended for reducing overall cancer risk (6). See here for information about reducing your alcohol intake.
Smoking is the leading cause of cancer, due to exposure to carcinogens from tobacco (13). As well as significantly increasing the risk of lung cancer, smoking increases the risk of many other types of cancer, including breast cancer.
A large study of women from the UK found that smoking was significantly linked with an increased risk of breast cancer, particularly for those with a family history of breast cancer, or who started smoking in adolescence or close to the time of their first period (14).
Vaping is thought to be a much safer alternative to smoking, partially as they do not contain tobacco which is the main cancer-causing aspect of smoking (15). However, ongoing research is needed, particularly in terms of longer term health outcomes.
If you are looking for support to quit smoking please with your GP, you can find information about smoking cessation from the NHS here.
The World Cancer Research Fund (WCRF) lists vigorous physical activity and physical activity overall as factors that probably reduce the risk of breast cancer for postmenopausal women (6). For premenopausal women, vigorous physical activity is also listed as probably reducing this risk, whereas physical activity overall is linked with a possible risk reduction (6).
A higher levels of physical activity has been linked with a 12–25% lower risk of breast cancer, particularly for those who participated in regular, long-term exercise of moderate to vigorous intensity (16, 17).
This benefit may be related to the impact of physical activity on inflammation, cell-signalling, insulin, sex hormones, and fat cells (17).
Breastfeeding is associated with a lower risk of breast cancer, especially for women who breastfeed for a longer period of time (6, 18, 19).
The reason for this isn’t entirely clear, but it may be related to hormonal changes such a less exposure to androgens, or changes in the cells in the breasts and breast tissue (20).
Having a higher body weight is often said to be a risk factor for breast cancer, but it is a more complicated picture than this.
For example, the WCRF have identified that (6):
- Higher body fat in young adulthood – associated with a probable lower risk of pre and postmenopausal breast cancer
- Higher body fat in adulthood – associated with a probable lower risk of premenopausal breast cancer, but a convincing higher risk of postmenopausal breast cancer
- Adult weight gain – associated with a convincing increased risk of postmenopausal breast cancer.
A more recent large analysis of weight change and premenopausal breast cancer risk found that (21):
- Weight gain between the ages of 18-24 to 35-44 years or 18-24 to 45-54 was associated with a reduced risk of premenopausal breast cancer.
- These associations were stronger for breast cancer types that had oestrogen or progesterone receptors (ER or PR positive, respectively); particularly with weight gain between the ages of 25-34 and a lower risk of ER-positive breast cancer.
- Weight loss was not consistently associated with breast cancer risk after adjusting for initial early-adult weight.
This may be related to differences in breast tissue during puberty and changes in oestrogen metabolism, sex hormone and IGF-1 hormone levels (21, 22, 23, 24.).
Whereas, for postmenopausal women, higher levels of inflammation and changes in hormone levels and gene expression have been linked with a higher risk of breast cancer (6, 25). Those with a higher weight are also seen to have worse outcomes once they are diagnosed with cancer (26).
When discussing body size and weight loss it is always important to highlight:
- Weight loss is not straight-forward or achievable in the long-term for many people; the current evidence base shows that weight regain occurs for most people within 2-5 years of losing weight (27, 28). Intensive face-to face input and focusing on healthy behaviour change may make this more realistic for some people, but ongoing research is needed (29, 30).
- Many who try to diet and lose weight end up in cycles of gaining and losing weight, which is associated with poor health and higher inflammation levels (28). Research related to weight cycling and cancer risk is mixed, but there is currently no strong link between weight cycling and breast cancer risk (31, 32, 33).
- Weight stigma, the discrimination that those with a bigger body often face, isn’t accounted for in a lot of studies. Although weight stigma isn’t currently directly associated with breast cancer risk, it is linked with disengaging from healthcare services, depression, higher stress levels in the body, inflammation and metabolic changes (28, 34, 35, 36).
- Pursuing weight loss has also been linked with worsened mental health and body image, a reduction in healthy behaviours and a higher risk of disordered eating (28).
- A lot of health gains can be achieved regardless of whether weight changes, as discussed throughout this article in relation to breast cancer risk.
Therefore overall it seems that weight gain and higher body fat levels may decrease the risk of premenopausal breast cancer risk but increase the risk of postmenopausal breast cancer, and ongoing research is needed in this field.
Endocrine disruptors are natural or synthetic chemicals that can interfere with our endocrine system and hormones. These can be found in a variety of products, such as plastic containers, cosmetics, drugs, toys, detergents, flame retardants, pesticides and food.
A recent systematic review found that exposure to endocrine disruptors is associated with an increased risk of breast cancer (38). Although it also highlighted that further research is needed to see whether this is a direct, or causal, link, rather than being related to another factor.
This potential link may be related to the effect of synthetic substances that have estrogen-like effects called xenoestrogens on hormonal levels and breast tissue (39). This type of endocrine disruptor is found in certain plastics, pesticides, cosmetics, chemicals and tap water systems.
Overall, there seems to be a possible link between endocrine disruptors and breast cancer risk.However, for many chemicals, evidence is inconsistent or still limited. Dose, duration, and age at exposure also are important factors to consider. Also, many EDC’s coexist in the environment so it’s difficult to tease apart their independent and interactive effects on breast cancer risk (40).
Although there are significant factors that impact breast cancer risk that are beyond our control, such as social, genetics and environmental factors, there are a number of lifestyle strategies that are linked with a lower risk.
These lifestyle factors include:
- Consuming a nutritious diet
- Limiting or avoiding alcohol intake
- Avoiding or quitting smoking
- Staying active
Reducing exposure to endocrine disruptors may also be protective. Higher body fat levels may reduce the risk of premenopausal breast cancer risk but increase the risk of postmenopausal breast cancer. Ongoing research is needed in these areas.
- WCRF Website “Breast Cancer” [accessed October 2021 via: https://www.wcrf-uk.org/uk/preventing-cancer/cancer-types/breast-cancer]
- WCRF Website “Breast Cancer Statistics” [accessed October 2021 via: https://www.wcrf.org/dietandcancer/breast-cancer-statistics/]
- Cancer Research UK Website “Breast Cancer Statistics” [accessed October 2021 via: https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer]
- Prentice (2008) “Women’s health initiative studies of postmenopausal breast cancer”. Adv Exp Med Biol; 617:151-60. [accessed October 2021 via: https://pubmed.ncbi.nlm.nih.gov/18497039/]
- Martin et al. (2011) “A randomized trial of dietary intervention for breast cancer prevention”. Cancer Res; 71(1):123-33. [accessed October 20201 via: https://pubmed.ncbi.nlm.nih.gov/21199800]
- WCRF (2018) “Diet, Nutrition, Physical Activity & Cancer: A Global Perspective” [accessed October 2021 via: https://www.wcrf.org/wp-content/uploads/2021/02/Summary-of-Third-Expert-Report-2018.pdf]
- Health et al. (2020) “Nutrient-wide association study of 92 foods and nutrients and breast cancer risk”. Breast Cancer Research; 22:5. [accessed October 2021 via: https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-019-1244-7]
- Farvid et al. (2019) “Fruit and vegetable consumption and breast cancer incidence: Repeated measures over 30 years of follow-up”. Int J Cancer; 144(7):1496-1510. [accessed October 2021 via: https://pubmed.ncbi.nlm.nih.gov/29978479/]
- Key et al. (2019 ) “Foods, macronutrients and breast cancer risk in postmenopausal women: a large UK cohort”. Int J Epidemiol; 48(2):489-500. [accessed October 2021 via: https://pubmed.ncbi.nlm.nih.gov/30412247/]
- Dong & Qin (2010) “Soy isoflavones consumption and risk of breast cancer incidence or recurrence: a meta-analysis of prospective studies”. Breast Cancer Res Treat; 125(2):315-23. [accessed October 2021 via: https://pubmed.ncbi.nlm.nih.gov/21113655/]
- Al-Sader et al. (2019) “Alcohol and Breast Cancer: The Mechanisms Explained”. J Clin Med Res; 1(3): 125–131. [accessed October 2021 via: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3318874]
- Allen et al. (2009) “Moderate alcohol intake and cancer incidence in women”. J Natl Cancer Inst; 101(5):296-305. [accessed October 2021 via: https://pubmed.ncbi.nlm.nih.gov/19244173/]
- WCRF Website “Smoking and cancer risk” [accessed October 2021 via: https://www.wcrf-uk.org/uk/preventing-cancer/what-can-increase-your-risk-cancer/smoking-and-cancer-risk]
- Jones et al. (2017) “Smoking and risk of breast cancer in the Generations Study cohort”. Breast Cancer Research; 19: 118. [accessed October 2021 via: https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-017-0908-4 ]
- PHE (2021) “Vaping in England: 2021 evidence update summary” [accessed October 2021 via: https://www.gov.uk/government/publications/vaping-in-england-evidence-update-february-2021/vaping-in-england-2021-evidence-update-summary]
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