Supplementation with long-chain n-3 fatty acids in non-insulin-dependent diabetes mellitus (NIDDM) patients leads to the lowering of oleic acid content in serum phospholipids.

BACKGROUND

The dietary supplementation with EPA (eicosapentaenoic acid; 20:5n3) and DHA (docosahexaenoic acid; 22:6n3) has been recommended because of their favourable effects on the cardiovascular system (including complications of NIDDM). Oleic acid (18:1n9) from olive oil has some analogous and complementary effects. Potential competitive relations between long-chain n-3 fatty acids (FAs) and the oleic acid would therefore mean a problem.

AIM OF THE STUDY

We focused primarily on the oleic acid changes in serum phospholipids (SPL) after a supplementation with EPA and DHA.

METHODS

Thirty-five patients with type 2 diabetes mellitus (NIDDM) were supplemented for 28 days with 1.7 g of EPA plus 1.15 g of DHA/day (as Maxepa capsules, Seven Seas, U. K.). After that, a 3-month wash-out control period with 21 patients followed. A fatty acid composition of serum phospholipids (SPL) was determined by capillary gas-chromatography. Values were calculated as relative percentages of all FAs.

RESULTS

After the supplementation with the Maxepa capsules, there was a very strong increase in EPA, docosapentaenoic acid (22:5n3) and DHA content in SPL. It was followed by a strong decrease after the wash-out (all p < 0.0001). The oleic acid SPL content after the intervention significantly decreased from 10. 105 +/- 0.307% (mean +/- S. E. M.) to 9.082 +/- 0.276 % (p < 0.0003). During the wash-out, the change was in the opposite direction (p < 0.0001). When the intervention and the wash-out periods were taken together, changes in the oleic acid were inversely correlated with changes in EPA, docosapentaenoic acid and DHA (r = -0.729; r = -0.552; r = -0.629, respectively; p < 0.0001; n = 56). On the background of the overall n-6 FA reduction, the decline in the arachidonic acid after the supplementation (p < 0.0001) and its rise after the wash-out (p < 0.0003) were similar. There were no significant changes in the saturated FA spectrum.

CONCLUSIONS

Supplementation with long-chain n-3 FAs in NIDDM patients leads to the lowering of oleic acid SPL content. Whereas the reduction of the arachidonic acid may have some desirable aspects (e. g. suppression of thromboxane TxA2 or 4 series leukotriene production), the decline of the former is to be regarded as a potential problem. Therefore, the search for optimally balanced blends of n-3 polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs) seems to be more promising than a supplementation with only one type of FA.