Objective: To study the effects of a low dose of omega-3 fatty acids on platelet function and other cardiovascular risk factors in patients with non-insulin-dependent diabetes mellitus (NIDDM).
Research design and methods: We performed a randomized, prospective, double-blind, controlled study of a low dose of omega-3 fatty acids (2.5 g/day) in 20 ambulatory subjects with NIDDM. Subjects ingested five 1-g fish oil capsules each containing 0.5 g omega-3 fatty acids or five 1-g safflower oil capsules per day for 6 weeks followed by a 6-week washout period.
Results: Nine subjects completed the study in each group. Both groups exhibited moderate control of glucose levels; modest elevations in baseline total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglyceride (TG) levels; and normal blood pressure values. In the fish oil group, plasma omega-3 fatty acid levels increased significantly. Fish oil significantly reduced the slope of the dose-response curves for collagen-induced platelet aggregation to one-third the value observed with safflower oil. No difference was observed in collagen-induced production of thromboxane A2 (TXA2, measured as the stable derivative TXB2), or in adenosine-5'-diphosphate- (ADP) induced platelet aggregation or TXA2 generation. Patients with high initial collagen-induced platelet TXA2 production showed a significantly larger drop after fish oil than safflower oil. Fish oil significantly reduced TG levels by 44 mg/dl and decreased upright systolic blood pressure (sBP) by 8 mmHg compared with safflower oil. Fish oil caused a significant but small increase in HbA1c (0.56%) and total cholesterol (20 mg/dl) but had no effect on fasting glucose, high-density lipoprotein cholesterol, or LDL-cholesterol levels.
Conclusions: Small doses of fish oil inhibit platelet aggregation and TXA2 production, reduce upright sBP and TG levels, and have only a small effect on glucose and cholesterol levels in patients with moderately controlled NIDDM. Small quantities of omega-3 fatty acids or dietary fish are safe and potentially beneficial in NIDDM patients.