EFFECTS OF N-3 POLYUNSATURATED FATTY-ACIDS ON GLUCOSE-HOMEOSTASIS ANDBLOOD-PRESSURE IN ESSENTIAL-HYPERTENSION - A RANDOMIZED, CONTROLLED TRIAL

Objective: To determine whether dietary supplementation with fish oil adversely affects glycemic control in patients with hypertension. Desi gn: Randomized, double-blind, placebo-controlled study. Patients: 78 p ersons with untreated hypertension recruited from a population survey. Intervention: Participants were randomly assigned to receive eicosape ntaenoic and docosahexaenoic acids, 4 g/d, or corn oil placebo, 4 g/d, for 16 weeks. Measurements: An oral glucose tolerance test; assessmen ts of insulin release, glucose disposal, and insulin sensitivity done using the hyperglycemic clamp technique to keep plasma glucose levels at 10 mmol/L for 180 minutes; assessment of insulin sensitivity done u sing a euglycemic hyperinsulinemic clamp technique (infusing insulin a nd glucose to keep plasma glucose levels at 5 mmol/L); assessments of lipid levels and blood pressure. Measurements were done before and aft er intervention. Results: Changes in integrated glucose and insulin re sponse after the oral glucose challenge did not differ between the fis h oil and corn oil groups after intervention (-0.6 +/- 0.7 compared wi th -1.0 +/- 0.6 mmol/L [P > 0.3] for integrated glucose and 143 +/- 76 compared with 169 +/- 84 pmol/L [P > 0.3] for insulin response). Chan ges in first-phase insulin release (34 +/- 72 pmol/L in the fish oil g roup compared with 191 +/- 112 pmol/L in the corn oil group [P > 0.3]) , second-phase insulin release (179 +/- 66 pmol/L compared with 257 +/ - 122 pmol/L [P > 0.3]), and insulin sensitivity index (-0.03 +/- 0.01 compared with -0.01 +/- 0.01 [mu mol/kg . min divided by pmol/L]; P > 0.3) were also similar in both groups after treatment. Fish oil lower ed systolic blood pressure by 3.8 mm Hg more than control (P = 0.04) a nd lowered diastolic blood pressure by 2.0 mm Hg more than control (P = 0.10). After fish oil treatment, triglyceride levels decreased by 0. 28 +/- 0.08 mmol/L more than control (P = 0.01), and very-low-density lipoprotein cholesterol levels decreased by 0.13 +/- 0.04 mmol/L more than control (P = 0.01). Conclusion: Fish oil, in doses that reduce bl ood pressure and lipid levels in hypertensive persons, does not advers ely affect glucose metabolism.