Young women whose diets where high in saturated fat and low in mono- and polyunsaturated fat as teenagers have greater breast density and a higher risk of developing breast cancer, according to the study “Dietary Fat Intake During Adolescence and Breast Density Among Young Women,” published in the Cancer Epidemiology, Biomarkers and Prevention journal.

During adolescence, when breasts undergo structural changes and develop, breast tissue is particularly sensitive to stimuli. Although an association between fat intake and breast cancer risk is not established, the researchers hypothesized this lack could be due to disregard for fat intake during adolescence, when breasts develop.

The team analyzed data from the Dietary Intervention Study in Children (DISC) randomized trial, which enrolled 633 children, 301 of which were girls ages 8-10, in 1988, who registered their dietary habits on several occasions throughout their adolescence. One DISC follow-up study, DISC06, used magnetic resonance imaging to measure breast density in 177 of the female DISC participants when they were 25–29 years old, allowing researchers to look for associations between dietary intake in adolescence and breast density in young adulthood.

Investigators adjusted the data for multiple variables, including education, race, number of births, adulthood fatness, and total energy and protein intake. They then observed that higher intake of saturated fat and lower intake of mono- and polyunsaturated during adolescence were associated with increased breast volume in adulthood. Particularly, women in the highest quartile for intake of saturated fat revealed a mean dense breast volume (DBV) of 21.5 percent, whereas those in the lowest quartile had only 16.4 percent DBV.

“There is no clinical cut-point to define high versus low percent DBV to indicate women at increased risk of breast cancer. However, because there is a gradient of increasing breast cancer risk with increasing breast density, the differences in percent DBV we observed across extreme quartiles in our study, if confirmed, could potentially be of interest with regards to later breast cancer risk,” Seungyoun Jung, ScD, fellow in the Department of Epidemiology and Public Health at the University of Maryland School of Medicine, and Joanne Dorgan, PhD, MPH, professor in the Department of Epidemiology and Public Health at the school, said in a press release.

“Overall, our results suggest possible long-term effects of fat intake during adolescence on young adult breast composition,” Jung added. “If confirmed, the take-home message from our results is that diet consumed in early life is important and may confer chronic disease risk or protective benefits later in life. In particular, the timing of dietary exposures might be important, and appropriate dietary modifications during adolescence may potentially contribute to lowering breast density and, consequently, breast cancer risk as well as preventing obesity, diabetes, and cardiovascular disease.”