Exercise Can Help Prevent Breast Cancer. But Does How Much You Run Matter? – runnersworld.com

• According to a new study in the journal Cancer Epidemiology, Biomarkers & Prevention, regular moderate-duration and high-duration aerobic activity may help reduce your risk of developing breast cancer.
• Both groups experienced a significant improvement in biomarkers of breast cancer risk.
• Moderate aerobic activity qualified as 150 minutes (2.5 hours) per week and high aerobic activity qualified as 300 minutes (5 hours) per week.

Lacing up on a regular basis not only helps your mental health and tamps down stress, but it also boosts your physical health, too: Running helps reduce your risk of conditions like type 2 diabetes, heart disease, and even certain types of cancer.

But how much do you need to exercise to reap those benefits? When looking at breast cancer prevention, the answer may not be as much as you think, a new study published in the journal Cancer Epidemiology, Biomarkers & Prevention suggests.

The study, which is a two-year followup to the Breast Cancer and Exercise Trial in Alberta (BETA), included 400 cancer-free women ages 50 to 74 with the goal of comparing the effect of either moderate aerobic activity (150 minutes a week) or high aerobic activity (300 minutes a week) on something called intermediate breast cancer biomarkers—or substances in your blood or urine that are indicators of breast cancer risk. These included biomarkers such as insulin, glucose, estrone (a female sex hormone), estradiol (a form of estrogen), and HOMA-IR (which measures insulin resistance).

Five days a week for one year, the participants could do any type of aerobic activity they wanted. Those in the “moderate” group worked out for 30 minutes a day and those in the “high” group worked out for one hour a day.

After one year, the biomarkers overall improved for both groups—but neither group saw a significantly bigger or better improvement over the other. This means that doing either moderate-duration or high-duration exercise can still reduce your risk of breast cancer. (It’s worth noting that some biomarkers—like estrogen and insulin—stayed the same because they are already low in postmenopausal women.)

“If you have high insulin resistance, inflammation, body fat levels, or other biomarkers, you are at an increased risk of developing breast cancer,” Christine Friedenreich, Ph.D., scientific director of Alberta Health Service’s Department of Cancer Epidemiology and Prevention Research, told Runner’s World. “And we know that if you are physically active, it does reduce your risk [of breast cancer].”

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Previous research has indeed found that exercise reduces insulin resistance (a condition where your body has trouble absorbing glucose, which can cause blood sugar to build up in your blood), inflammation, and body fat—and that’s important, because each have been linked to an increased risk of breast cancer.

Does this mean that there are no benefits to fitting in longer runs or longer training? Not exactly.

Women who performed 300 minutes of exercise per week had much larger reductions in body fat than those who exercised for less time, said Friedenreich. That’s especially important, since many studies have shown that being overweight or obese increases the risk of developing postmenopausal breast cancer, according to Friedenreich. “Hence, reducing body fat—which is a marker of obesity—is a means of reducing breast cancer risk after menopause,” she said.

The takeaway, according to Friedenreich, is that while getting in 150 minutes (2.5 hours) of aerobic activity per week is already fantastic—and will help reduce your risk of getting breast cancer—hitting that weekly 300-minute mark (5 hours) offers even more of a benefit. So keep doing your long runs, speed workouts, and daily runs. Even if they’re just a couple of quick miles, they’ll add up.

Associate Health & Fitness Editor Danielle specializes in interpreting and reporting the latest health research and also writes and edits in-depth service pieces about fitness, training, and nutrition.