Omega-3 fatty acid supplements in women at high risk of breast cancer have dose-dependent effects on breast adipose tissue fatty acid composition.

Randomized, fixed-block dose-ranging trial in women at high risk of breast cancer enrolled at The Ohio State University Medical Center in Columbus, Ohio, United States. The active intervention consisted of 4 dose groups with n=12 per group (active-arm N=48 total); participants were adult women with varying menopausal status and were asked to maintain their usual diet.

Women received oral Omacor omega-3 ethyl ester capsules once daily for 6 months in one of four active dose groups: 1 capsule/day, 3 capsules/day, 6 capsules/day, or 9 capsules/day. This corresponded to 0.84 g, 2.52 g, 5.04 g, and 7.56 g EPA+DHA per day, respectively; each 1-g capsule provided predominantly EPA and DHA.

Daily omega-3 supplementation was well tolerated and increased serum and breast adipose tissue EPA and DHA in a dose-dependent manner. A dose of 2.52 g EPA+DHA per day (3 capsules/day) was identified as the most appropriate for elevating EPA and DHA in breast adipose tissue, while increases at 3, 6, and 9 capsules/day were not significantly different from each other in tissue. Compliance over 6 months was 92.9 ± 9.2%, and no severe or serious toxicities were reported. BMI and baseline fatty acid levels moderated the response, and there were no significant effects on the selected serum biomarkers.

Small dose-group sizes (n=12 per arm) and 6-month follow-up limit precision and long-term inference. The trial had no placebo or inert control, which restricts causal interpretation of changes over time. Findings are also specific to women at high risk of breast cancer and may not generalize broadly.