Scientific evidence of the association between oral intake of OMEGA-3 and OMEGA-6 fatty acids and the metabolic syndrome in adolescents: A systematic review

Aims: To conduct a systematic review of the literature on the scientific evidence of the oral intake of omega-3 and omega-6 FAs and metabolic syndrome (MS) in adolescents. Data synthesis: The study was registered in PROSPERO (number 42020185370). Studies were carried out with adolescents aged 10–19 years, who presented as intervention/exposure the oral intake of omega-3 and/or omega-6 fatty acids (FAs), in the databases PubMed, Scopus, Web of Science, LILACS, CENTRAL, and PQDT Global e BDTD. The tools used to assess the risk of bias were RoB 2.0, Agency for Healthcare Research and Quality (AHRQ), and Newcastle-Ottawa Scale. Fifteen papers retrieved published from 2010 to 2019 were included (n = 3534); nine were randomized studies and controlled clinical trials, four were cross-sectional studies, one was a retrospective cohort study, and one case-control study. No studies have evaluated the effect or association of omega-3 and/or of omega-6 FAs with actual MS, only with its components. The randomized clinical trials identified the effects of omega-3 FA on the decrease in blood pressure (n = 1 out of six), glycemia (n = 2 out of seven), and triglycerides (n = 5 out of eight), and the increase in HDL-c (n = 2 out of eight) considering the comparison between the group that received omega-3 FA and the control group. Conclusions: Scientific evidence is controversial on the association between oral intake of omega-3 FAs and MS in adolescents, due to the heterogeneity between studies and the divergence of results for the same MS component.