Can Exercise as a Teen Reduce Breast Cancer Risk?

Teen girls who exercised for at least two hours a week had biomarkers (or molecules in the body that can give clues about your health) linked to lower breast density,  according to a new study published in Breast Cancer Research. High breast density is a known breast cancer risk factor in adult women. 

Researchers have known since at least the early 2000s that physical activity — like brisk walking, running, and swimming — lowers breast cancer risk in adult women. Even doing four minutes of vigorous exercise a day can reduce a person’s cancer risk by around 18%, according to one study. But there’s been little research on how exercise as a teen might protect against breast cancer in the future. Rebecca Kehm, PhD, an assistant professor of epidemiology at Columbia University and lead author of this new study, is trying to change that. 

Kehm said in a press release that her research is especially important now given that more young women are getting breast cancer while teens across the United States and globally are exercising less. 

Kehm decided to study whether exercise might protect teens from breast cancer. She used three biomarkers that measure breast density, inflammation, and  oxidative stress (an imbalance of molecules that leads to cell damage) — all of which  can influence breast cancer risk. 

She then analyzed exercise data from a group of 191 Hispanic and Black teen girls between 11 and 20 years old. The participants reported how much they exercised in the past week and Kehm’s team compared those answers with the biomarkers in their blood, urine, and breasts. 

Roughly half of the participants reported no physical activity in the past week and only 27% participated in organized activities like school sports. 

Girls who participated in two or more hours a week of organized activities had lower breast water content — a biomarker of breast density — compared to those who didn’t exercise. They also had lower markers of oxidative stress in their urine. Inflammation was unaffected in all participants. 

Kehm says these findings could have “important implications for breast cancer risk,” though further research is needed. Still, she says these findings are important because Hispanic and Black girls face higher risks of developing more aggressive breast cancers at younger ages and are less likely to exercise than white peers. 

The authors plan to track how these biomarkers of stress and breast density might translate into breast cancer risk later in life.