Dense breasts — a risk factor in breast cancer influenced by diet

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Breast cancer is the leading cause of cancer deaths in women globally. According to the WHO report of 2022, there were 0.67 million deaths and 2.3 million cases of breast cancer worldwide. These alarming figures call for a concerted effort by various stakeholders and organizations to address this issue. Early screening through mammography is the fundamental and recommended approach for identifying women at risk of developing breast cancer [1].

High breast density, also known as mammographically dense breasts, is a feature identified from a breast mammogram. A mammogram is an X-ray machine that uses low-dose radiation to generate an image of breast tissue. During breast cancer screening, the breast appears as a white spot due to a high amount of fibrous and glandular tissue compared to fatty tissue. High breast density does not refer to the actual size or feel of the breast but is an interpretation of the images generated through mammography [2].

Breast tissue and Mammography

The association between high breast density and breast cancer was first demonstrated by John Wolfe in the 1970s using a xeromammogram. This imaging machine was developed by Jerry Hedstrom in the late 1960s, and has since been replaced by modern mammograms. The studies by Wolfe showed that women with high mammographic density were 4 to 6 times more likely to develop breast cancer [3]. Structurally, the breast is composed of three tissues: fatty tissue, the glandular portion (milk ducts and glands), and fibrous connective tissue. During screening, the fatty tissue appears darker on a mammogram (film) because X-rays can pass through it easily. In contrast, the epithelial and connective tissues, including glands, appear white because they effectively block X-rays [4].

A mammogram machine is not only used in screening but also for breast cancer diagnosis. In screening, mammography is applied to women who do not show any signs or symptoms of breast cancer. If a tumor is identified at this stage, it can be managed before spreading to other parts of the body. As a diagnostic tool, the mammogram can detect a breast tumor based on a previously observed sign or symptom, either from a patient with a history of the disease or a biopsy result revealing the presence of a tumor [5].

Mammogram findings are reported in a standardized system recommended by the American College of Radiology — Breast Imaging Reporting and Data System (BI-RADS). In this system, breast imaging is categorized as almost entirely fatty, scattered areas of fibroglandular density, heterogeneously dense breast, and extremely dense breast. Women with the latter two categories are considered to have dense breasts [6]. It is important to note that the risk of developing breast cancer can also be influenced by other factors such as age, hormones, mutations (BRCA genes), and lifestyle and environmental factors (such as diet and chemical exposure) [7, 8].

Limitation of Mammography

While mammography is the standard method for assessing breast density, its sensitivity is reduced in extremely dense breasts. This decrease in sensitivity is primarily due to masking, where dense breast tissue can obscure potential tumors. This makes it difficult to differentiate between dense tissue and malignant tumors as they both appear white on mammograms (films). Masking can, therefore, impede cancer detection through mammography [4]. However, this challenge can be overcome by using more advanced techniques such as breast ultrasound, 3D mammography, or magnetic resonance imaging (MRI) [9].

Effect of diet on breast density

Diet plays a significant role in breast cancer risk. A study published in Obstetrics and Gynecology revealed that overweight and obese women who adhere to a Western diet have higher breast density, which is a known risk factor for breast cancer. In contrast, women following a Mediterranean diet exhibit lower breast density and a reduced risk of breast cancer [10]. The effect of diet on breast density is also supported by the study of Vachon et al. which found an inverse relationship between saturated fat intake and breast density. This finding was in contrast to that of premenopausal women who showed high breast density due to a diet rich in polyunsaturated fats, vitamin C, B12, and alcohol [11].

Further insight into the role of diet on breast density is provided by Castello et al.  In his study, he demonstrated that a Mediterranean diet was linked to lower breast density, as opposed to a Western diet, which increased breast density in obese women. The Mediterranean diet offers balanced nutrition with lower fat content, and it includes vegetables, fruits, cereals, and olive oil. In contrast, a Western diet consists of processed foods high in sugar, calories, and unhealthy fats [12].

Conclusion

 Understanding the link between high breast density and breast cancer is crucial for women when it comes to breast cancer screening. While mammography is the primary method for detecting breast cancer, its sensitivity is lower in women with high breast density, which can result in missed diagnoses due to masking effects. However, advanced imaging techniques can offer more accurate results that enhance early detection rates. Importantly, the link between diet and high breast density can assist women in making informed choices between a Western and a Mediterranean diet.

References

1.            WHO, Assessment of breast cancer control capacities in the WHO African Region in 2022. https://www.who.int/news-room/fact-sheets/detail/breast-cancer, 2024.

2.            ACS, Breast Cancer Research Highlights American Cancer Society, 2025

3.            Carlile, T., et al., Breast Cancer Prediction and the Wolfe Classification of Mammograms. JAMA, 1985. 254(8): p. 1050-1053.

4.            Nazari, S.S. and P. Mukherjee, An overview of mammographic density and its association with breast cancer. Breast Cancer, 2018. 25(3): p. 259-267.

5.            Institute of, M., D. National Research Council Committee on New Approaches to Early, and C. Diagnosis of Breast, The National Academies Collection: Reports funded by National Institutes of Health, in Saving Women's Lives: Strategies for Improving Breast Cancer Detection and Diagnosis, J.E. Joy, E.E. Penhoet, and D.B. Petitti, Editors. 2005, National Academies Press (US), National Academy of Sciences.: Washington (DC).

6.            Destounis, S.V., A. Santacroce, and A. Arieno, Update on Breast Density, Risk Estimation, and Supplemental Screening. AJR Am J Roentgenol, 2020. 214(2): p. 296-305.

7.            Obeagu, E.I. and G.U. Obeagu, Breast cancer: A review of risk factors and diagnosis. Medicine (Baltimore), 2024. 103(3): p. e36905.

8.            Sun, Y.S., et al., Risk Factors and Preventions of Breast Cancer. Int J Biol Sci, 2017. 13(11): p. 1387-1397.

9.            Gilbert, F.J. and K. Pinker-Domenig, Diagnosis and Staging of Breast Cancer: When and How to Use Mammography, Tomosynthesis, Ultrasound, Contrast-Enhanced Mammography, and Magnetic Resonance Imaging, in Diseases of the Chest, Breast, Heart and Vessels 2019-2022: Diagnostic and Interventional Imaging, J. Hodler, R.A. Kubik-Huch, and G.K. von Schulthess, Editors. 2019, Springer International Publishing: Cham. p. 155-166.

10.          Castelló, A., et al., Association Between Western and Mediterranean Dietary Patterns and Mammographic Density. Obstet Gynecol, 2016. 128(3): p. 574-581.

11.          Vachon, C.M., et al., Association of diet and mammographic breast density in the Minnesota breast cancer family cohort. Cancer Epidemiol Biomarkers Prev, 2000. 9(2): p. 151-60.

12.          Castelló, A., et al., High adherence to Western dietary pattern increases breast cancer risk (an EPIC-Spain study). Maturitas, 2024. 179: p. 107868.

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