Meta-analysis of the effects of n-3 polyunsaturated fatty acids on haematological and thrombogenic factors in type 2 diabetes

Systematic review and meta-analysis of 12 randomized controlled trials in adults with type 2 diabetes. The included studies enrolled 847 subjects overall, with both men and women represented, and some trials excluded pre-menopausal women; pooled analyses for some outcomes were based on nine trials and 297 participants.

Marine-derived n-3 polyunsaturated fatty acid supplementation, mainly EPA and DHA, was tested in adults with type 2 diabetes. Regimens varied across trials, with doses ranging from 0.9 g/day to 10 g/day and durations averaging 8.5 weeks; comparators included olive oil, corn oil, safflower oil, sunflower oil, fibre, placebo, or diet alone.

Overall, n-3 PUFA supplementation produced a small reduction in diastolic blood pressure and an increase in factor VII, but did not show significant effects on systolic blood pressure, fibrinogen in the main comparison, or heart rate. In pooled analyses, diastolic blood pressure fell by -1.79 mmHg (95% CI -3.56 to -0.02, p=0.05), factor VII increased by 24.9% (95% CI 7.2 to 42.6, p=0.006), systolic blood pressure changed by -1.69 mmHg (95% CI -5.04 to 1.65, p=0.32), and heart rate by -2.0 beats/min (95% CI -8.1 to 4.1, p=0.52). Fibrinogen was not significantly changed versus fibre control (-0.91 μmol/l, 95% CI -3.11 to 1.28, p=0.42), although an exploratory analysis versus olive oil showed a decrease (-1.96 μmol/l, 95% CI -3.13 to -0.79, p=0.001).

The evidence base was limited by small trial sizes, short intervention duration, and heterogeneity in doses, formulations, and comparators. Only a subset of trials contributed to each pooled outcome, and adverse events were not clearly reported in the provided text, limiting interpretation of clinical relevance and safety. The findings are also indirect for clinical cardiovascular outcomes because they focus on surrogate risk markers rather than events.