What Is Breast Density?

Breast density is a finding on mammography and correlates with the amount of fibroglandular tissue versus 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 US 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 dense breasts 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. One 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 seven drinks a week have five times 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 one 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). Fourteen 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). Four 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 US. According to the US Department of Agriculture, wildfire smoke emits toxic chemicals such as carbon monoxide, particulate matter, silica, aldehydes, formaldehyde, solvents, polyaromatic hydrocarbons, sulfur dioxide, benzene, and acrolein, 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 US with the worst pollution based on particulate matter and ozone. Most are in the Southwest and West. You can find the updated list at 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 and 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.

Case Example

A healthy 53-year-old, post-menopausal woman presented with recent abnormal mammogram. She has been in menopause for three years and never took hormone replacement therapy. Her MD had ordered routine screening mammogram, which showed a right breast 1.8 cm fibroadenoma and VERY dense breast tissue. It was labelled at 75% fibroglandular density and given a BI-RADS rating of 0 and additional imaging was recommended. A diagnostic mammogram with ultrasound was ordered by her MD and showed very dense breast tissue and the same 1.8 cm mass present but now labeled a benign cyst and not fibroadenoma. The ultrasound was better able to visualize the mass through her dense breast tissue. This imaging was rated a BI-RADS three- and a six-month right side targeted ultrasound was recommended. She didn’t want to wait six months; she wanted to be proactive and came for a consult. She had a BMI of 20, normal vitals, and the physical exam was unremarkable. A thorough history and labs were done.

Medical history

• No Medications
• Supplements: B12 (1,000 mcg); Fish oil (1,500 mg); Calcium (600 mg); Magnesium (300 mg); Vitamin D (4000 IU a day)
• Never took HRT, no family history of BRCA, and no personal history of benign breast disease
• Diet is high in sugar—loves deserts and sweets. Eats candy, desserts, and sweets daily. No sodas or juices
• Drink 8-10 alcoholic drinks a week

Environmental exposure history (all past)

• Grew up in Iowa on a farm with well water
• Lived in Arizona for 26 years-Past. Since 2014 Phoenix has an increasing air pollution problem due to population growth, traffic (auto exhaust), dust storms, and wildfires.
• Uses revere osmosis water for cooking and drinking!!!!
• No occupational or hobby exposures, no smoking, some dietary fish
• Uses standard cleaning and personal care products and lots of plastics

Labs ordered

• CBC, CMP, LIPID, iron, ferritin, ESR were all normal
• TSH was 1.5, iodine was 61, Vitamin D was 49, B12 was 986
• Blood mercury was 3 (ordered because she ate some fish)
• Blood lead was <2
• 24-hour urine arsenic was 15

At this point she has very dense breast tissue and a benign cyst. Her thin body size, higher than average alcohol and sugar intake, use of standard personal care products, cleaning products, plastics, and non-organic foods, and Phoenix air quality issues are her only risk factors for breast density and breast health concerns. In the past she grew up on a farm with well water indicates possible pesticide exposure but doing a pesticide panel now would not capture exposure from so long ago. Treatment began with education on avoidance of BPA, phthalates, and other toxicants at home and in her cleaning and personal care products. She got rid of plastics and changed her products and bought mostly organic dairy, meats, and other foods. She purchased a HEPA room air filter to run at night in the bedroom and during the day on high pollution advisory days, which are now common in the Phoenix metropolitan area. A detailed list of avoidance can be found in my book 8 Weeks to Woman’s Wellness. She agreed to stop eating all refined sugars—candy, sweets, treats and deserts and cut back alcohol to three drinks a week.

She embarked on a diet plan that included the following:

• Organic and Non-GMO foods
• 1 Tbsp ground flax meal a day
• 1 teaspoon of psyllium husk powder a day
• 3-4 cups of green tea either regular or de-cafe is fine
• No refined sugar, no artificial sweeteners, no candy, no sweets no treats
• No cow milk products
• Fish low in mercury is okay
• 3-4 servings of cruciferous veggies a day
• Complex carbohydrates like quinoa and brown rice are okay
• Increase legumes, fruits, veggies
• Limit alcohol to two-to-three times a week

She was given three supplements to take for four months.

• Liver herbs – Milk thistle, burdock root, dandelion root, beet root, artichoke leaf.
• Estrogen metabolism – Methyl donors, DIM, calcium-d-glucarate, ALA, NAC
• Cofactors – High-dose multivitamin and mineral with methylated forms, green tea, and turmeric

She completed the treatment plan and felt great. She stuck with the diet and stayed off sugar and limited alcohol and dairy and mostly ate organic. The room air filter helped her husband’s nasal congestion. She did not do the six-month right breast target ultrasound and, instead a year later, did both a diagnostic mammogram with U/S. The mass was no longer seen on mammogram and the breast density reduced from 76% to 50%. The ultrasound showed that the cyst shrunk from 1.8 mm to 9 mm and imaging was rated a BI-RADS 2. She stopped the supplements after four months but stuck with the diet changes and avoidance measures. The following year, two years after initial visit, she did both a diagnostic mammogram and ultrasound and the cyst was gone, and breast density rated at 40% (initially was 75%). The imaging was given a BI-RADS rating of 2, and she was placed on an annual breast screening plan with both diagnostic mammogram and ultrasound due to the density.

Summary

Dense breast tissue is becoming a common finding on mammography. When imaging shows that there is more glandular and connective tissue than fatty tissue, the breast is considered dense. Breast density makes it difficult to see potential cancer on mammograms. Some states have passed legislation that require health care providers to inform women of the increased risk of breast cancer and reduced sensitivity of mammography, and several states require additional testing such as ultrasound for women with dense breasts. About 43% of women aged 40–74 in the US have heterogeneously or extremely dense breasts by mammography. Some women are more likely to have dense breasts, such as those who are premenopausal, use menopausal hormone replacement therapy (HRT), and have a lower body mass index (BMI). Often overlooked risk factors linked to breast density include a diet high in sugary foods and drinks, having more than seven alcoholic drinks a week, living in areas of high air pollution and poor air quality, and exposure to endocrine disrupting chemicals from food, personal care products, and plastics. When practitioners are discussing mammographic findings of breast density, it is important to address these modifiable environmental factors.

References

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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.
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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.