Omega-3 Polyunsaturated Fatty Acids and Adipose Tissue Inflammation in Humans: A Scoping Review

Adipose tissue (AT) inflammation is a topic of increasing interest given its role in initiating systemic subclinical inflammation. Evidence from preclinical studies suggests that n-3 polyunsaturated fatty acids (PUFAs) may ameliorate AT inflammation through various pathways. However, fewer data are available from humans, and existing studies are heterogeneous in design and findings. The objective of this scoping review was to identify, review, and map the current literature on the relationship between n-3 PUFAs and AT inflammation in healthy humans. MEDLINE, EMBASE, and Cochrane databases were searched from inception to August 4, 2022. Eligible studies included experimental trials and observational studies, enrolling nonpregnant adult study populations free of diagnosed chronic/infectious diseases. Screening and data extraction were performed on study characteristics. Overall, the 25 retained studies were heterogeneous in study design, intervention formulation/exposure assessment, comparator, study duration, and methods used to characterize AT inflammation. Most experimental trials used EPA+DHA [eicosapentaenoic acid (EPA, 20:5n-3) and docosapentaenoic acid (DPA, 22:5n-3)] supplementation and measured circulating adiponectin and leptin to characterize AT inflammation. A wide range of comparators were employed, including saturated/unsaturated oils, ketogenic diets, and n-6 PUFAs. All observational studies reported a significant association with ≥1 of their primary outcomes, while 15 of 20 experimental trials documented a significant effect of n-3 supplementation on ≥1 outcomes. Existing human literature on n-3 PUFAs and AT inflammation is inconclusive due to the limited number of studies available and their heterogeneous designs. Therefore, larger, longer-term longitudinal studies and experimental trials using AT biopsy measures or validated AT-specific biomarkers are needed. Registration: Open Science Framework (https://doi.org/10.17605/OSF.IO/29WGQ).