Dietary intake and serum levels of trans fatty acids and risk of breast cancer: A systematic review and dose-response meta-analysis of prospective studies

Although the relationship between dietary intake and serum levels of trans fatty acids and risk of breast cancer has been investigated extensively, findings are inconsistent. To summarize earlier findings on the association of dietary intake and serum levels of trans fatty acids with risk of breast cancer through a dose-response meta-analysis. The online databases of PubMed, ISI Web of Science, Scopus, ProQuest, Science Direct and Embase were searched for relevant publications up to June 2018, using MeSH and non-MeSH keywords. In total, 7 prospective studies [6 cohort studies and one nested case-control study] were included on total dietary trans fat intake, and five studies [1 cohort study and 4 nested case-control studies] were included about serum trans fatty acids. Assessment of study quality was conducted using the Newcastle-Ottawa scale. Study-specific RRs were combined via fixed-effects model to compute overall RRs. Participants were apparently healthy aged 26 years or older. We observed no significant relationship between dietary intake of total trans fatty acids and risk of breast cancer (pooled effect size: 1.02, 95% CI: 0.95–1.10, P = 0.403). Combining 3 effect sizes from 2 prospective and one nested case-control study, no significant relation was seen between dietary intake of CLA and risk of breast cancer (pooled effect size: 1.05, 95% CI: 0.95–1.17, P = 0.513). Based on 5 effect sizes, each additional 1 g/day dietary intake of total trans fats was not significantly associated with risk of breast cancer (RR = 1.00; 95% CI = 0.99–1.01). In addition, it seems that serum levels of trans fats might be associated with an increased risk of breast cancer only among postmenopausal women (Pooled effect size: 1.37, 95% CI: 1.04–1.81, P = 0.02). In conclusion, dietary intake of trans fatty acids was not associated with risk of breast cancer; however, a significant positive association was seen between serum trans fats and risk of breast cancer in postmenopausal women.