Fish Oil and Diabetes

CLEVELAND, OHIO. Patients with non-insulin-dependent diabetes mellitus (NIDDM) often suffer from abnormal lipid (fat) and lipoprotein metabolism resulting in unfavourable cholesterol levels and an accompanying increase in the risk of heart disease. Numerous studies have shown that fish oil supplementation lowers the levels of very-low-density-lipoprotein (VLDL) and triglycerides (triacylglycerol), but has little effect on the levels of low-density-lipoprotein (LDL) and total cholesterol. There has also been some reports that fish oil supplementation may worsen glycemic (glucose) control. Now medical researchers at the Case Western Reserve University report that adding soluble fiber to the supplementation regimen is highly beneficial.

Their experiment involved 15 non-obese NIDDM patients (12 men and 3 women) aged 32 to 74 years. For the first four weeks the patients received 20 grams of fish oil per day (equivalent to six grams of n-3 fatty acids). During the next four weeks all patients received the fish oil plus 15 grams/day of soluble apple pectin. During the final four weeks both supplements were withdrawn. The patients continued their usual diabetic diet and medication during the entire study period. Analysis of blood samples showed that fish oil supplementation alone lowered the levels of triacylglycerol and VLDL cholesterol by 41 per cent and 36 per cent respectively. No changes were observed in total cholesterol, LDL cholesterol or HDL cholesterol. When apple pectin was added to the treatment triacylglycerol and VLDL cholesterol levels were both lowered by 38 per cent, but in addition total cholesterol levels decreased by 13 per cent and LDL cholesterol by 7 per cent. There was no significant change in HDL cholesterol level. Fasting and two-hour postprandial plasma glucose concentrations were not affected by the fish oil or combination supplementation and no changes in serum levels of zinc, magnesium, and copper were observed. Plasma levels of triglycerides and cholesterols returned to pre-treatment levels four weeks after discontinuation of supplementation. The researchers conclude that a combination of fish oil supplementation and increased fiber intake (up to 40 grams/day total) may be a beneficial addition to the conventional treatment of high cholesterol levels in NIDDM patients.
Sheehan, John P., et al. Effect of high fiber intake in fish oil-treated patients with non-insulin-dependent diabetes mellitus. American Journal of Clinical Nutrition, Vol. 66, November 1997, pp. 1183- 87.

For internists and family medicine physicians: internal medicine CME courses discussing hyperlipidemia and diabetes mellitus.

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Category: Diabetes