A Cochrane review included 23 studies with a total of 1075 adults with type 2 diabetes mellitus. No trials with vascular events or mortality endpoints were identified. Among those taking omega-3 polyunsaturated fatty acid (PUFA) triglyceride levels were significantly lowered by 0.45 mmol/L (95% CI -0.58 to -0.32, P < 0.00001; 18 studies, n=969) and VLDL cholesterol lowered by -0.07 mmol/L (95% CI -0.13 to 0.00, P = 0.04; 7 studies, n=238). LDL cholesterol levels were raised by 0.11 mmol/L (95% CI 0.00 to 0.22, P = 0.05; 16 studies, n=565). No significant change in total or HDL cholesterol, HbA1c, fasting glucose, fasting insulin or body weight was observed. No adverse effects of the intervention were reported.
A systematic review including 26 studies with a total of 425 subjects was abstracted in DARE. According to the results, fish oil has no adverse effects on HbA1c and it lowers triglyceride levels effectively by 30%.: for triglycerides: all studies, -0.60 (95% CI: -0.84, -0.37, P<0.05); NIDDM, -0.81 (95% CI: -1.16, -0.46, P<0.05); IDDM, -0.29 (95% CI: -0.50, -0.07, P<0.05). For LDL cholesterol: all studies, 0.18 (95% CI: 0.04, 0.32, P=0.01), non significant increases in both controlled and uncontrolled trials; NIDDM, 0.20 (95% CI: 0.0, 0.40, P<0.05); IDDM, 0.13 (95% CI: -0.14, +0.41). Neither study duration nor baseline LDL had a significant effect on LDL.
Comment: The quality of evidence is downgraded by study quality (inadequate allocation concealment) and by potential reporting bias.