Earlier studies have reported a lower prevalence of impaired glucose tolerance and type 2 diabetes in populations who took large amounts of omega-3 fatty acids found mainly in fish. People with type 2 diabetes are known to be at increased risk of heart attack or stroke. Diabetics typically have high levels of fats (TGs) in the blood, low levels of good cholesterol (HDL cholesterol) and abnormal LDL (low-density lipoprotein) composition. Omega-3 fatty acids from fish lower TGs, reduce abnormal heart rhythms, lower blood pressure and improve blood clotting regulation. Clinical studies have shown that consumption of omega-3 fatty acids has cardioprotective effects in persons with type 2 diabetes without adverse effects on glucose control and insulin activity.
Fish oil may be useful in treating dyslipidemia in diabetes. Fish oil supplementation improved plasma VLDL cholesterol, VLDL TGs, and total TGs while having a transient deterioration in LDL cholesterol in patients with noninsulin-dependent diabetes (NIDDM). Furthermore, fish oil supplementation had no significant deleterious effect on glycemic control. Plasma LDL cholesterol was temporarily increased in the fish oil group at 6 weeks, but the effect was no longer present at 12 weeks. A diet rich in fish and other sources of omega-3 fatty acids reduces the chances of children with a family history of diabetes to develop the disease. In type 2 diabetic patients, supplementation with 1.7 g/day to all patients for a further six months produced no deterioration of glucose control after one year of treatment. Preliminary evidence suggests increased consumption of n-3 PUFAs with reduced intake of saturated fat may reduce the risk of conversion from impaired glucose tolerance to type 2 diabetes in overweight persons.