Effects of seal oil supplementation on lipid profile biomarkers: A systematic review and meta-analysis of randomized controlled trials

Background: Seal oil (SO) supplementation has been purported to have cardiovascular health benefits due to its content of omega-3 fatty acids; however, the clinical evidence base for this intervention has yet to be comprehensively assessed. Objective: We aimed to evaluate the effects of oral SO supplementation on lipid profile biomarkers. Methods: A systematic search was performed on Pubmed, Embase, Web of Science and Cochrane Library, from inception to August 2024. Only randomized controlled trials (RCTs) assessing the effect of SO on lipid profile biomarkers were included. A random-effects meta-analysis was applied to determine the overall effect estimate. The certainty of evidence (CoE) was evaluated using the GRADE approach. Results: Nine RCTs were included in the review after the screening of 242 studies, comprising a total of 626 patients. Supplementation of SO resulted in no statistically significant effects on LDL-C (MD -0.07 mmol/L; 95 % CI [-0.19, 0.05]; CoE: Low) and total cholesterol (MD -0.12 mmol/L; 95 % CI [-0.30, 0.06]; CoE: Very low). There were statistically significant results of modest-to-trivial clinical importance on triglycerides (MD -0.19 mmol/L, 95 % CI [-0.30, -0.08]; CoE: Low) and trivial importance on HDL-C (MD 0.07 mmol/L, 95 % CI [0.003, 0.13]; CoE: Very low). Conclusion: There is no sufficiently certain evidence to determine the effects of SO on cardiovascular lipid biomarkers. Our analyses may suggest a modest-to-trivial, clinically uncertain beneficial effect on triglyceride levels; and little to no effect on LDL-C. Effect estimates for HDL-C and total cholesterol levels were highly uncertain. Further evidence is required to conclusively determine the effects of oral SO on lipid biomarkers. Protocol registration number: CRD42024583739