Are you wondering if running can lessen the density of your breasts and thus lower your breast cancer risk?
Or maybe they’re mostly fat tissue and you’re afraid that running will bring density to them – and thus raise your disease risk.
What exactly is breast density?
“Breast density refers to the proportion of fat to fibroglandular tissue in the breasts and can ONLY be assessed by imaging,” explains Anjali Malik, MD, a board certified diagnostic radiologist with Washington Radiology in Washington, DC. She interprets mammograms, breast MRIs and ultrasounds, and performs biopsies.
Even a doctor cannot tell if breasts are dense simply by palpating them.
There are four classes of breast makeup, as determined by a mammogram.
• Fatty. Most of the tissue is fat. A thin women can have mostly fatty breasts.
• Scattered. Amid fatty areas are dense areas mixed in but not evenly throughout.
• Heterogeneous. The density is distributed uniformly throughout.
• Extremely. Also uniformly throughout, but just more concentrated.
The risk of breast cancer in a woman with extremely dense breasts is four to six times higher than in a woman with fatty tissue.
This is alarming news to those with dense breasts because, unlike alcohol intake and diet, the breast makeup cannot be modified. Or can it?
Dr. Malik explains, “Breast density varies with age and weight. For many premenopausal women, postmenopausal women and slender women of any age, dense breast parenchyma is secondary to their overall low body fat percentage.
“For other women it is related to their hormone status – postmenopausal women on hormones often maintain their tissue density, while those not on hormones may have decreased fibroglandular tissue with age.”
The Effects of Running
“Active women are more likely to have dense breast parenchyma – again — based on their overall body fat percentage, but in general, breast density cannot be actively changed unless there are marked shifts in weight.”
Suppose you’re obese and, due to this, have dense breasts (cup size is irrelevant).
You decide to take up running, even if at the beginning, it’s mixed with walking, but eventually you’re running nonstop outdoors or on a treadmill.
As a result you lose a significant amount of weight over time. This might reduce the density of your breasts, but this doesn’t necessarily mean you’re going to go from the extremely class to the fatty class.
Remember, there are athletic trim women, not on hormones, who are already runners or participate in some form of aerobic exercise – but who have heterogeneously and even extremely dense breasts.
There are also obese women who have fatty or scattered compositions.
All in all, running or other rigorous aerobic exercise is not a fix for dense breasts nor will it cause a replacement of fatty tissue with fibroglandular tissue.