NAPLES, ITALY. Animal studies have shown that fish oil supplementation has a beneficial effect on insulin resistance and can prevent its development in animals fed a high-fat diet. It is also known that a high fish intake can delay the development of diabetes in glucose-intolerant individuals. Researchers at the Federico II University recently set out to investigate if long-term supplementation with fish oils would improve insulin sensitivity in patients with non-insulin-dependent diabetes (NIDDM). The clinical trial involved 16 NIDDM patients (average age of 56 years) who, after a 3 week run-in period during which they received 3 olive oil capsules per day, were assigned to receive either fish oil capsules or olive oil capsules for a further 6-month period. For the first two months the participants received either 3 fish oil capsules daily (320 mg eicosapentaenoic acid and 530 mg docosahexaenoic acid [EPA and DHA, respectfully] per capsule) or 3 placebo capsules (each containing 1 gram of olive oil). During the last four months these dosages were reduced to 2 fish oil or 2 placebo capsules daily. The patients were evaluated at the beginning and end of the trial and maintained their usual diet and medications (except for cholesterol- lowering drugs) during the entire trial period.
The researchers concluded that fish oil supplementation (which contains EPA and DHA) induced a significant decrease in triglyceride concentrations particularly in the level of very-low-density lipoprotein (VLDL) triglycerides (a reduction of 45%). There was also a significant decrease in VLDL cholesterol levels (47% drop) and a 14% increase in LDL cholesterol. There was no significant change in blood glucose control and, contrary to expectations, no significant improvement in insulin resistance despite the fact that red blood cell levels of EPA and DHA increased significantly. The researchers conclude that long-term fish oil supplementation lowers triglyceride levels in NIDDM patients without adversely affecting blood glucose control.
Rivellese, Angela A., et al. Long-term effects of fish oil on insulin resistance and plasma lipoproteins in NIDDM patients with hypertriglyceridemia. Diabetes Care, Vol. 19, November 1996, pp. 1207-13.
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