Breast Density- environmental and lifestyle factors
What is breast density?
(Article originally publish in the Townsend Letter Feb/March 2022)
Breast density is a finding on mammography and correlates with the amount of fibroglandular tissue verses fatty tissue. Density is categorized by the radiologist as almost entirely fatty, scattered fibroglandular densities, heterogeneously dense, and extremely dense. The last two categories (heterogeneously dense and extremely dense) are commonly lumped together and a woman with these finding is considered to have “dense breasts.” About 43% of women aged 40–74 in the U.S. have heterogeneously or extremely dense breasts on mammography. 1 In general, breast density decreases as a woman gets older, increases with hormone replacement therapy, and decreases with increasing body mass index (BMI). Yes, being thin, younger, and on hormone replacement therapy are risk factors for breast density. Around menopause breast density tends to decrease unless other risk factors are present such as being thin or taking hormone replacement therapy. The reason density is even noted on mammography is that women with breast dense have an increased risk of breast cancer. It is estimated that women with extremely dense breasts have four- to six-fold higher risk of developing breast cancer compared to those with fatty, non-dense, breasts. 2 Density accounts for 39% of premenopausal and 26% of postmenopausal breast cancer. 2 Density noted on mammography means there is an increased risk for the radiologist not being able to detect breast cancer, often called a masking effect. Aside from density masking the detection of breast cancer, it is important to note that some risk factors for developing breast density are similar to the risk factors for developing breast cancer. This is especially true of lifestyle and environmental factors.
Lifestyle and environmental factors linked to breast density
Alcohol
Recent research has shown that alcohol consumption among women increased during the pandemic. In 2020 heavy drinking increased 41% in women compared to 2019. 1 in 10 women reported an increase in alcohol‐related problems in 2020. 3 Whether this was due to stress, boredom, or isolation during the pandemic is unclear but the consequences of excess alcohol intake on breast health is clear. Women who drink greater than 7 drinks a week have 5x higher odds of having mammographic breast density compared to women who drink less than one drink per week. 4,5 Alcohol intake is also linked to breast cancer. Alcohol may increase aromatase activity, decrease liver catabolism of androgens, and increase adrenal steroid production. Alcohol intake of more than 1 drink a day is associated with an 82% greater risk for breast cancer. 4,5
Sugar
A 2014 study looked at the association of sweet foods and sugary drinks with mammographic density among 776 premenopausal and 779 postmenopausal women. Overall, postmenopausal women consumed more sweet foods (11.8 servings versus 7.7 servings per week), than premenopausal women, with a higher total caloric intake per day. The intake of high sugar content beverages was similar in both groups (1.9 versus 2.1 servings per week for postmenopausal and premenopausal women respectively). 14 items were classified as sweet foods (ice cream, chocolate, candy with chocolate, candy, homemade cookie, commercial cookie, brownie, donut, homemade cake, commercial cake, homemade pie, commercial pie, other homemade pastries, and other commercial pastries). 4 items were classified as sugar-sweetened beverages (cola with sugar, cola with sugar but caffeine free, other carbonated beverage with sugar and sweet fruit juice). The study found that sugar-sweetened beverage intake was positively associated with mammographic density among all women, both premenopausal and post-menopausal. The intake of sweet foods-mostly desserts was associated with breast density in postmenopausal women and sugar-sweetened beverages intake of more than three servings per week presented a 3% difference in percent density compared with those who did not drink sugary drinks. 6 Sugar is also linked to breast cancer. In a 2020 study of over 100,000 women, even after accounting for weight and other risk factors, it found that breast cancer was associated with the intake of added sugars, free sugars, sucrose, sugars from milk-based desserts, dairy products, and sugary drinks, but not sugar from fruits. 7
Air pollution
Air quality across the world is getting worse each year. Climate change, wildfires, dust storms, pesticide use in agriculture, increased auto exhaust, and population density all contribute to air pollution. The recent wildfires in the west and southwest are contributing to poor air quality across the U.S. According to the U.S. department of agriculture, wildfire smoke emits toxic chemicals such as carbon monoxide, particulate matter, silica, aldehydes, formaldehyde, solvents, polyaromatic hydrocarbons, sulphur dioxide, benzene, and acrolin, volatile organic compounds, nitrous oxide, heavy metals and more. Studies looking at the link between air pollution and breast health show that women with dense breast were 20% more likely to have been exposed to higher levels of air pollution PM 2.5. 8 There is also a link between emissions of nitrogen oxides, carbon monoxide, sulfur dioxide and volatile organic compounds (VOCs) and an increase in the incidence of breast cancer. 9 These are common chemicals in cities with known air quality and air pollution problems. The American Lung Association each year lists the cities in the U.S with the worst pollution based on particulate matter and Ozone. Most are in the Southwest and west. You can find the updated list at; Most Polluted Cities | State of the Air | American Lung Association-https://www.lung.org/research/sota/city-rankings/most-polluted-cities.
Phthalates and BPA
Both phthalates and bisphenol-A are known endocrine disrupting compounds. They are linked to breast cancer, thyroid disease, uterine fibroids, endometriosis, polycystic ovarian syndrome, and many other hormonally driven conditions. 10 A 2019 study looked specifically at the link to phthalates and breast density in adolescent girls and found that exposure during the critical window of development during adolescent could affect breast health later in life. It concluded that adolescent exposure to dietary phthalates is linked to higher percent volume of breast density and fibroglandular tissue and an increased risk of adult breast cancer. 11 Phthalates have been found in dairy products, meats, fish, oils & fats, baked goods, infant formula, processed foods, and fast foods. Phthalates easily escape from food processing equipment, food packaging, and food preparation materials, and contaminate food at points all along the supply chain. Phthalates are in vinyl products, carpeting, personal care products, fragrances, cleaning products, and paints and primers used in the home. 10,11 Several studies link blood bisphenol-A levels to breast density on mammography in post-menopausal women. 12, 13 Bisphenol A (BPA) can be released from consumer products such as canned food, hard plastic beverage bottles, paper receipts, dental materials, and personal care products. Some recent reviews have summarized the known mechanisms of endocrine disruptions by BPA in human diseases, including obesity, and reproductive disorders. 13 There is an association between increased incidence of breast cancer and BPA exposure at doses below the safe reference doses.
References
1. Lee CI, Chen LE, Elmore JG. Risk-based Breast Cancer Screening: Implications of Breast Density. Med Clin North Am. 2017;101(4):725-741. doi:10.1016/j.mcna.2017.03.005
2. Vourtsis A, Berg WA. Breast density implications and supplemental screening. Eur Radiol. 2019;29(4):1762-1777. doi:10.1007/s00330-018-5668-8
3. Pollard MS, Tucker JS, Green HD. Changes in Adult Alcohol Use and Consequences During the COVID‐19 Pandemic in the US. JAMA Netw Open. 2020;3(9). E2022942.
4. Frydenberg H, et al Alcohol consumption, endogenous estrogen and mammographic density among premenopausal women. Breast Cancer Res. 2015;17(1):103.
5. Duffy SW, Morrish OWE, Allgood PC, et al. Mammographic density and breast cancer risk in breast screening assessment cases and women with a family history of breast cancer. Eur J Cancer. 2018; 88:48‐56.
6. Duchaine CS, Dumas I, Diorio C. Consumption of sweet foods and mammographic breast density: a cross-sectional study. BMC Public Health. 2014;14:554.
7. Charlotte Debras, et al. Total and added sugar intakes, sugar types, and cancer risk: results from the prospective NutriNet-Santé cohort. The Am J of Clinical Nutrition, 2020:112(5); 1267–1279.
8. Yaghjyan, L., Arao, R., Brokamp, C. et al. Association between air pollution and mammographic breast density in the Breast Cancer Surveilance Consortium. Breast Cancer Res 2017:19;36.
9. Gabet S, et al. Breast Cancer Risk in Association with Atmospheric Pollution Exposure: A Meta-Analysis of Effect Estimates Followed by a Health Impact Assessment. Environ Health Perspect. 2021;129(5):57012.
10. Marchese, M. 8 Weeks to Women’s Wellness. Petaluma, CA. Smart Publications 2011.
11. Binder AM, Corvalan C, Pereira A, et al. Prepubertal and Pubertal Endocrine-Disrupting Chemical Exposure and Breast Density among Chilean Adolescents. Cancer Epidemiol Biomarkers Prev. 2018;27(12):1491-1499.
12. Sprague BL, et al. Circulating serum xenoestrogens and mammographic breast density. Breast Cancer Res. 2013;15(3):R45.
13. Wang Z, Liu H, Liu S. Low-Dose Bisphenol A Exposure: A Seemingly Instigating Carcinogenic Effect on Breast Cancer. Adv Sci (Weinh). 2016;4(2):1600248.