Fish oil supplementation in type 2 diabetes - A quantitative systematic review

OBJECTIVE - To determine the effects of fish oil supplementation on lipid l evels and glycemic control in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS - A comprehensive search of Medline, Embase, Li lacs, the Cochrane Clinical Trials Registry, bibliographies of relevant pap ers, and expert input updated through September 1998 was undertaken. All ra ndomized placebo-controlled trials were included in which fish oil suppleme ntation was the only intervention in subjects with type 2 diabetes. Three i nvestigators performed data extraction and quality scoring independently wi th discrepancies resolved by consensus. Eighteen trials including 823 subje cts followed for a mean of 12 weeks were included. Doses of fish oil used r anged from 3 to 18 g/day. The outcomes studied were glycemic control and li pid levels. RESULTS - Meta-analysis of pooled data demonstrated a statistically signifi cant effect of fish oil on lowering triglycerides (-0.56 mmol/l [95% CI -0. 71 to -0.41]) and raising LDL cholesterol (0.21 mmol/l [0.02 to 0.41]). No statistically significant effect was observed for fasting glucose, HbA(1c), total cholesterol, or HDL cholesterol. The triglyceride-lowering effect an d the elevation in LDL cholesterol were most marked in those trials that re cruited hypertriglyceridemic subjects and used higher doses of fish oil. He terogeneity was observed and explained by the recruitment of subjects with baseline hypertriglyceridemia in some studies. CONCLUSIONS - Fish oil supplementation in type 2 diabetes lowers triglyceri des, raises LDL cholesterol, and has no statistically significant effect on glycemic control. Trials with hard clinical end points are needed.