The most common cancer in women second to skin cancer, is breast cancer, both in the U.S. and worldwide. In 2021, the US experienced an estimated 281,500 new diagnoses of invasive breast cancer and an additional 49,290 cases of in situ breast lesions.
Reliable estimates demonstrate that that at least one third of breast cancer cases could be prevented by lifestyle
modification. Even more striking is that if these changes were initiated early in life, that number may be 50% to 70%. This is just one more powerful reason to educate girls and inform families of the importance of these lifestyle influences on future health. And, in 2018, the World Cancer Research Fund and the American Institute for Cancer Research published a report called, Diet, Nutrition, Physical Activity and Cancer: A Global Perspective and updated cancer prevention guidelines emphasizing the importance of lifestyle modifications for cancer prevention. (World Cancer Research Fund/American Institute for Cancer Research. Continuous Update Project Expert Report 2018. Diet, nutrition, physical activity and breast cancer. )
Let’s break it down a bit in terms of the big areas where we can make a difference. About 42% of US women aged 20 years and older were obese as of 2017-2018. There are many potential health reasons to be concerned about with this striking number, such as risks of type 2 diabetes and cardiovascular disease as well as some cancers. I do want to mention a concept here that an obese woman can make great strides in being healthy, even if obese. I encourage you to read the information from Health at Every Size (HAES). The HAES® Principles promote health equity, support ending weight discrimination, and improve access to quality healthcare regardless of size. And yet, I return to some bothersome data when it comes to breast cancer risk. A postmenopausal women with obesity, is at a 20% to 40% increased risk of breast cancer, particularly estrogen receptor (ER)-positive breast cancer and especially if she does not use hormone therapy. An obese premenopausal woman is at a higher risk of the more aggressive kind of breast cancer, called, triple-negative breast cancer. (Picon-Ruiz M, Morata-Tarifa C, Valle-Goffin JJ, Friedman ER, Slingerland JM. Obesity and adverse breast cancer risk and outcome: mechanistic insights and strategies for intervention. CA Cancer J Clin 2017;67:378-397.) Of further concern is that if a woman is obese, she has a worse outcome with her breast cancer, meaning a shorter time to recurrence and an increased chance of dying. That familiar difficult to lose abdominal fat is particularly problematic in that it increases the risk of development and progression of breast cancer due to the hyperinsulinemia, increased estrogen and inflammation. There are specific mechanisms at play here including disrupted cellular mechanisms leading to abnormal cell proliferation, induced blood supply to sites of tumor formation (called angiogenesis), reduction in abnormal cell death (apoptosis), down regulation of the immune system, the increased tendency for DNA mutations and dysregulated cellular functions, all of which drive the formation of tumors and metastasis.
The big question is then, what can we do in one’s daily life and lifestyle habits to reduce the risk of breast cancer, especially if we are at increased risk? The good news is that we have helpful and compelling research in this area. The dietary approach that is most impressive to me in this area is the Mediterranean diet. The evidence is convincing that the Mediterranean diet reduces the risk of weight gain and obesity. There are also hundreds of observational research studies that suggest that poor dietary habits increase the risk of breast cancer and increase the death rate from breast cancer. The Women’s Health Initiative Dietary Modification randomized trial in almost 49,000 postmenopausal women demonstrated a 21% reduction in breast cancer-related deaths in women in the 20% of less low fat dietary group compared with those on the > 32% fat of the Standardized American Diet plan. This was after 19-20 years of follow-up. (Chlebowski RT, Aragaki AK, Anderson GL, et al; Women’s Health Initiative. Dietary modification and breast cancer mortality: long-term follow-up of the Women’s Health Initiative Randomized Trial. J Clin Oncol 2020;38:1419-1428.) A large review and analysis of many studies, published in 2021 suggested that a diet high in total fruits and vegetables is associated with a reduced risk of postmenopausal, estrogen/receptor -positive and negative breast cancer although one very important caveat: fruit juice consumption was actually associated with an increased risk of breast cancer. (World Cancer Research Fund/American Institute for Cancer Research. Continuous Update Project Expert Report 2018. Diet, nutrition, physical activity and breast cancer. )
We can also look to the Swedish Mammography Study of more than 31,000 postmenopausal women who were followed for 15 years. There was a 51% reduced breast cancer risk in the women who met at least six of the following recommendations vs. two or less. (Harris HR, Bergkvist L, Wolk A. Adherence to the World Cancer Research Fund/American Institute for Cancer Research recommendations and breast cancer risk. Int J Cancer 2016;138:2657-2664.)
- Limit alcohol consumption.
- Eat a diet rich in whole grains, vegetables, fruit, and legumes….at least 30 g/day of fiber from food; Eat at least five portions or servings daily of a variety of non-starchy fruits/vegetables.
- Limit “fast” foods.
- Limit red and processed meat.
- Limit sugar-sweetened drinks.
- Be physically active every day; walk more and sit less. (150-300 minutes of moderate intensity exercise weekly or 75 minutes of vigorous physical activity weekly.)
- Keep weight in a healthy range.
- Breast feeding history.
In the Vitamins and Lifestyle study of more than 30,000 postmenopausal women there was a 60% reduction in breast cancer risk in women who met at least five of the recommendations compared with those who met none. (Hastert TA, Beresford SAA, Patterson RE, Kristal AR, White E. Adherence to WCRF/AICR cancer prevention recommendations and risk of postmenopausal breast cancer. Cancer Epidemiol Biomarkers Prev 2013;22:1498-1508.)
The second area where we can make a difference is physical activity. According to the CDC, physical activity can prevent one in eight breast cancers. Regardless of weight of body mass index, this benefit can occur. One meta-analysis showed a 17% lower risk of breast cancer in premenopausal women with the highest amount of vigorous physical activity and a 13% lower risk in postmenopausal women with the highest total physical activity. In the large Women’s Health Initiative study of 155,723 postmenopausal women over a period of 7.3 years, there was a 15% to 23% lower breast cancer risk in those who had the highest recreational activity when compared to those with the lowest. (Phipps AI, Chlebowski RT, Prentice R, et al. Body size, physical activity, and risk of triple‐ negative and estrogen receptor‐positive breast cancer. Cancer Epidemiol Biomarkers Prev 2011;20:454‐463.)
It is estimated that 12.1% of breast cancers in women is due to alcohol. The evidence is compelling linking alcohol to seven major cancers, including breast cancer. (Sauer AG, Fedewa SA, Bandi P, et al. Proportion of cancer cases and deaths attributable to alcohol consumption by US state, 2013-2016. Cancer Epidemiol 2021;71:101893.) For cancer prevention, women should avoid alcohol as any amount increases the risk of breast cancer. The more you drink the higher the risk, whether one is premenopausal or postmenopausal. Alcohol intake induces inflammation, elevates acetaldehyde, interferes with folate metabolism, and increases estradiol in the body.
Summary cliff notes:
- For postmenopausal women, weight gain as an adult and excess body fat, especially in the abdominal region, increases breast cancer risk.
- Body mass index (BMI) is not as important as that abdominal fat, especially if one is postmenopausal.
- A Mediterranean diet should be the theme with increased vegetables, fruits and whole grains. Please look online to see some good descriptions, guidelines, recipes and meal plans for the Mediterranean diet.
- Alcohol is a carcinogen. Any amount increases risk. The things you might have read about not exceeding 7 drinks a week is still too much. From my readings, 0-3 per week is a much better rule.
- We didn’t talk about this, but another lifestyle influence: breastfeeding decreases a woman’s future risk of breast cancer.
If you are not a practitioner and reading this, please find a practitioner who knows these things and can assist you in accomplishing these. Either a new practitioner than the one you have or someone added to your health care team. If you are a practitioner and reading this, it’s up to us to educate our patients and empower them with information and resources to help them make healthy lifestyle changes for prevention of breast cancer.
