Dietary intake and tissue biomarkers of omega-6 fatty acids and risk of colorectal cancer in adults: a systematic review and dose-response meta-analysis of prospective cohort studies.

Findings on the associations of dietary/tissue levels of omega-6 polyunsaturated fatty acids (n-6 PUFAs) with the risk of colorectal cancer (CRC) are conflicting. We conducted a dose-response meta-analysis to assess the associations of dietary/tissue levels of n-6 PUFAs [total, linoleic acid (LA), and arachidonic acid (AA)] with CRC risk in adults. Twenty prospective cohort studies with a total sample size of 787,490 participants were included. Comparing extreme intake levels of LA revealed the summary relative risks (RR) of 1.15 (95% confidence interval (CI): 1.05-1.27) for CRC, and 1.30 (95% CI: 1.00-1.68) for rectal cancer, indicating a significant positive association for LA. However, neither total n-6 PUFAs nor AA were associated with cancers. A significant positive association was also found between a 1 gr/day increase in dietary LA intake and risk of colon cancer (RR: 1.01, 95% CI: 1.00-1.02). There were no significant associations between tissue levels of total n-6 PUFAs (RR: 0.94, 95% CI: 0.75-1.19), LA (RR: 0.93, 95% CI: 0.61-1.41), and AA (RR: 0.97, 95% CI: 0.70-1.33) and CRC risk. In conclusion, these findings suggest that dietary intake, but not tissue levels, of LA was associated with an increased risk of colorectal, colon, and rectal cancers. (PROSPERO registration: CRD42024516584).