I’ve been told I have ‘dense breasts’. How does that affect my risk for breast cancer and is there anything I can do about it?

By Dr. Sharon Gurm

Your breasts are comprised of two types of tissue – fibroglandular tissue and fat tissue. Breast density refers to the amount of fibroglandular tissue present in the breast. Dense breasts are most often identified by mammogram, as most of the breast tissue will appear ‘white’ (radiographically dense) indicating presence of either cancerous or fibrous tissue, whereas fatty tissue will appear ‘black’ (radiographically lucent) [1].

In the past 20 years, many researchers have observed a strongly elevated breast cancer risk in women with a high percent density identified by mammographic evaluation [2,3]. Results published in a 2011 study on mammographic density and breast cancer risk found that women who have both a large area of fibroglandular tissue and a large area of fat tissue have the highest breast cancer risk [1]. Does the size of your breasts influence risk? Maybe. The study found there is greater risk from having dense tissue than non-dense (fat) tissue, despite whether a woman has small or large breasts. Hence, the resulting risk depends on the composition of the breast and not simply on the size.

How Exactly Does Breast Density Affect My Cancer Risk?

Most women have some mammographic density and the more density, the greater the risk of breast cancer. Women with the greatest density (50% or higher), have a 4-6 fold increased risk of breast cancer compared to women with the least dense breasts [4].  It is estimated that 10% of post-menopausal women and 20% of pre-menopausal women have mammographic density above 50% [5].

No one knows the exact mechanism of how dense tissue influences breast cancer risk. Researchers agree that the most likely explanation is that the area of dense tissue reflects the effect of estrogens on the breast, since most of the factors associated with dense breasts are hormonal in nature [6]. A study published 2011 by Vachon et al showed higher aromatase activity in dense than non-dense tissue [7]. Aromatase is an enzyme found in many fatty tissues throughout the body and it has the ability to convert androgens (DHEA and testosterone) to estrogen. The more fat that surrounds the dense tissue, the more local estrogen is present since estrogen is stored in adipocytes (fat cells) and there is more conversion of androgens to estrogen by aromatase. Estrogen is a ‘mitogen’ or cancer promoter. The more fat cells present, the greater the aromatase activity, hence more local effect of estrogen.

We know that dense tissue is associated with more cells than non-dense tissue. Therefore, the other explanation for the linear increase in risk of cancer with breast density is that there are simply more cells present that can be influenced by cancer promoting agents such as estrogen, insulin and ionizing radiation [8]. The specific characteristics of dense tissue appear to lend itself to the cancer environment in the breast, making it more likely that a normal cell will turn into a cancerous one – much like a humid environment is more conducive to the growth of mold [8].

The Limited Effectiveness of Mammography in Women With Dense Breasts

The sensitivity of a mammogram, or the ability of detecting an existing cancer is reduced significantly in women who have dense breasts [9,10]. In this case, MRI or ultrasound should be performed to better evaluate and screen for cancer, but this is not routine practice in conventional medicine due to the additional costs and limited resources in public health. Some women are not even told they have dense breasts, which brings up a number of ethical concerns in medical practice.

Harms associated with mammography include small concentrations of ionizing radiation exposure and the risk of false negatives and false positives. If the benefits outweigh the harms – and this MUST be determined on a case-by-case basis – then routine mammography may make sense for you. However, if you have dense breasts, not only are mammograms less useful for screening, the harms (ionizing radiation exposure, tissue compression and high risk of false negatives/positives and increased likelihood of unnecessary biopsies) far out weigh the benefits.

What Can I Do If I Have Dense Breasts?

A large part of my clinical practice revolves around treating cancer and I can tell you that preventing cancer is far less costly – emotionally and financially – than having to treat it. Don’t wait for a diagnosis to tell you have cancer – be PROACTIVE about your health and do your part to optimize your health NOW.

Some doctors will tell you there is nothing you can do about your breast density. Nothing could be further from the truth! The genetic factors play a small (although significant) role, but are largely affected by the more influential non-genetic or ‘epi-genetic’ factors [4]. Epigenetic refers to those factors that influence the function of our genes. These factors have been well studied [11-15] and are largely environmental and lifestyle-related. They can either directly or indirectly turn on genes that cause cancer and/or turn off genes that prevent cancer. The critical point is that they are modifiable. The following is a list of common, modifiable epigenetic factors that influence breast density:

• Maintain a healthy BMI or body mass index [4]: ideally between 20-24. To find out your BMI, divide your weight in kilograms by the square of your height in metres, or divide your weight in pounds by the square of your height in inches, then multiply by 703.

• Follow a low-glycemic diet to promote healthy insulin levels, maintain blood sugar balance and reduce inflammation [4].

• Avoid or minimize alcohol and coffee [19,20].

• Ensure healthy bowel habits: our body will reabsorb estrogen in stool if you don’t have a bowel movement at least once daily.

• Minimize animal food products so you limit the amount of exogenous (external) sources of estrogen.

Manage your stress: stress increases cortisol levels, a hormone that can negatively affect development and activity of mammary (breast) cells [21].

• Avoid or minimize the duration of post-menopausal hormone use: combined estrogen and progestin therapy is clearly associated with higher mammographic density [16,17].

• Be mindful of reproductive factors: nulliparity (women who have not had children), later age at first birth and use of hormones (ring, IUD, birth control pill) contribute to greater breast density [14,15].

• Certain medications (i.e. tamoxifen) and natural substances (i.e. indole-3-carbinol) can reduce estrogen activity in tissues where estrogen-receptors are highly concentrated, such as the breast, thereby reducing the influence of estrogen on breast cells [4,22].

Start by evaluating your hormones with a salivary hormone test [23]. Salivary hormone levels are consistent with local tissue levels of estrogen, progesterone and androgens. On the other hand, blood tests only reflect circulating levels of these hormones. Circulating levels of estrogen do not correlate with breast cancer risk, whereas local levels of estrogen do correlate with risk [19]. Then, work with a naturopathic physician or integrative medical doctor with expertise in the genetics and epigenetics of breast cancer to help you reduce your breast density – thereby lowering your risk of breast cancer.

If you have been diagnosed with breast cancer, the risk of recurrence is significantly higher if you have dense breasts. The same advice applies: if you reduce the amount of dense tissue in the breast, it will also lower your risk of recurrence. If you haven’t been diagnosed with breast cancer, time is of the essence. Get your baseline salivary hormone levels tested – the earlier, the better. Often, simple dietary and lifestyle changes are enough to reduce density if intervention is early (i.e. in adolescent women and those in the 20-30 age range).

It takes 8-10 years for cancer to develop. You don’t have time to think about it later because it’s affecting you NOW. Become educated, empower yourself with knowledge and take action. Cancer is largely a preventable disease.

Make the decision to take action and do what is in your power to avoid hearing the phrase “you have cancer”. Whether your goal is to prevent an initial diagnosis, or a recurrence of cancer, we’ll do our part to help you if you’re ready to do yours!

I’ve been told I have ‘dense breasts’. How does that affect my risk for breast cancer and is there anything I can do about it?Dr. Sharon Gurm BSc, ND, Naturopathic Physician, Clinic Founder & Clinical Director received her Bachelor of Science Degree from UBC and her Doctorate of Naturopathic Medicine from CCNM in 2005. As an American board-certified Naturopathic Physician, Dr. Gurm is also a Fellow to the American Board of Naturopathic Oncology (FABNO). As the founder and clinical director of Port Moody Health (since 2007), Dr. Gurm is dedicated to the pursuit of excellence in whole-person integrative health care. Read Dr. Gurm’s full bio.



1. Lokate M, Peeters P, Peelen LM, Haars G, Veldhuis WB, Gils CH: Mammographic density and breast cancer risk: the role of the fat surrounding the fibroglandular tissue. Breast Cancer Research 2011, 13:R103

2. Vachon CM, van Gils CH, Sellers TA, Ghosh K, Pruthi S, Brandt KR, Pankratz VS: Mammographic density, breast cancer risk and risk prediction. Breast Cancer Research 2007, 9:217.

3. McCormack VA, dos Santos Silva I: Breast density and parenchymal patterns as markers of breast cancer risk: a meta-analysis. Cancer Epidemiol Biomarkers Prev 2006, 15:1159-1169.

4. Ursin G, Qureshi S: Mammographic density – a useful biomarker for breast cancer risk in epidemiologic studies. Norsk Epidemologi 2009; 19(1):59-6.

5. McCormack VAMcCormack VA, dos Santos Silva I. Breast density and parenchymal patterns as markers of breast cancer risk: a meta-analysis. Cancer Epidemiol Biomarkers Prev, 15: 1159-69, 2006.

6. Martin LJ, Boyd NF: Mammographic density. potential mechanisms of breast cancer risk associated with mammographic density: hypotheses based on epidemiological evidence. Breast Cancer Res 2008, 10:201.

7. Vachon CM, Sasano H, Ghosh K, Brandt KR, Watson DA, Reynolds C, Lingle WL, Goss PE, Li R, Aiyar SE, Scott CG, Pankratz VS, Santen RJ, Ingle JN: Aromatase immunoreactivity is increased in mammographically dense regions of the breast. Breast Cancer Res Treat 2011, 125:243-252.

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