Objective: Recent studies in nondiabetic kidney diseases suggest that dietary supplementation with n-3 polyunsaturated fatty acids (fish oil) may have beneficial effects on albuminuria, kidney function, arterial blood pressure, and dyslipidemia. Therefore, we evaluated the long-term effect of fish oil in diabetic nephropathy.
Research design and methods: A 1-year double-blind randomized controlled study comparing fish oil (4.6 g n-3 fatty acids/day) with placebo (olive oil) was performed in an outpatient clinic in a tertiary referral center. Thirty-six normotensive IDDM patients with diabetic nephropathy were included; 18 were treated with fish oil. Seven patients dropped out (four received fish oil), and results for the remaining 29 are presented. Albuminuria (enzyme immunoassay), glomerular filtration rate (51Cr-labeled EDTA plasma clearance), 24-h ambulatory blood pressure, and lipid profile were determined every 6 months.
Results: Albuminuria increased by 22% (1-46%) (mean [95% CI]) in the fish oil group vs. 15% (-11-49%) in the placebo group (NS). Glomerular filtration rate decreased from 116 +/- 7 to 105 +/- 7 ml.min-1.1.73 m-2 (mean +/- SE) vs. from 108 +/- 6 to 103 +/- 7, fish oil and placebo, respectively (NS). No significant changes occurred in 24-h ambulatory blood pressure: from 141 +/- 4/82 +/- 2 mmHg to 142 +/- 5/83 +/- 2 vs. from 140 +/- 4/78 +/- 2 to 144 +/- 4/80 +/- 3, fish oil and placebo, respectively (NS). In the fish oil group, serum triglycerides (median [range]) decreased from 0.97 (0.5-4.0) mmol/l to 0.8 (0.4-3.0) vs. from 1.01 (0.4-2.0) to 1.09 (0.4-2.0) in the placebo group (P < 0.05) and VLDL cholesterol decreased from 0.45 (0.23-1.88) to 0.37 (0.21-1.43) mmol/l vs. from 0.44 (0.21-0.94) to 0.41 (0.17-1.94) (P < 0.05), but total and LDL cholesterol rose in the fish oil compared with the placebo group.
Conclusions: Our study does not suggest that fish oil has beneficial effects on albuminuria, kidney function, blood pressure, and dyslipidemia in normotensive IDDM patients suffering from diabetic nephropathy.