Changes in plasma triacylglycerol concentrations after sequential lunch and dinner in healthy subjects.

OBJECTIVES: The present study examines the kinetic of plasma triacylglycerol (TAG) after sequential ingestion of lunch and dinner as well as the contribution of dietary fat ingested at lunch to subsequent post-dinner TAG composition. METHOD: Six healthy subjects were included. After standardized breakfast (7: 30AM), 2 mixed meals with fat loads composed of 44 g olive oil (rich in oleic acid) at lunch (12PM) and 44 g sunflower oil (rich in linoleic acid) at dinner (7PM) were ingested. [1-13C] palmitate was added in lunch only. Plasma TAG and chylomicron-TAG (CMTAG) levels were measured sequentially after meals. [1-13C] palmitate enrichment and concentrations of oleic acid and linoleic acid were measured in all lipid fractions. RESULT: Post-dinner plasma TAG peak was delayed as compared to lunch (3 hours vs 1 hour, p=0.002) whereas the magnitude of the postprandial peaks was not significantly different between lunch and dinner (2.4+/-0.3 vs 2.0+/-0.4 mmol/L, p=0.85). [1-13C] palmitate enrichment was maximal 5 hours after lunch in all lipid fractions and decreased slowly thereafter. After dinner ingestion, the rate of decline of [1-13C] palmitate enrichment plateaued during the first 60 minutes. Oleic acid increased slightly and immediately after dinner and remained the predominant fatty acid in all lipid fractions during the first hour after dinner. A delayed peak of plasma and CM-TAG was observed after dinner as compared to lunch without difference in the magnitude of peaks. CONCLUSION: The contribution of dietary fat ingested at lunch to post-dinner lipemia is confirmed despite the relatively long lasting interval between the 2 meals (7 h) and the absence of any early peak of plasma TAG after dinner.

Dependence of human milk essential fatty acids on adipose stores during lactation.

The relationships between essential fatty acid (EFA) composition of colostrum, mature milk, and white adipose tissue (WAT) were examined on days 5 and 30 postpartum in 24 healthy French mothers. Fatty acid composition was assessed by capillary gas chromatography. In WAT, the proportion of individual polyunsaturated fatty acids (PUFAs) did not change during lactation and was greater (18:2n-6) or lower (18:3n-3, long-chain PUFAs) than values found in colostrum or mature milk (P < 0.04). The 18:2n-6 content and the ratio of 18:3n-3 to 18:2n-6 correlated between WAT and colostrum (r = 0.52 and r = 0.57, respectively) or mature milk (r = 0.64 and r = 0.65, respectively). These relationships agree with an expected qualitative effect of WAT fatty acid composition on interindividual variability of milk parent EFA content. The decrease in the long-chain PUFA content observed from colostrum to mature milk and the concomitant occurrence of a precursor-product relationship between the linoleate and its long-chain PUFA are consistent with the mobilization of a preformed long-chain PUFA pool during early lactation.