Oxidation of dietary linoleate occurs to a greater extent than dietary palmitate in vivo in humans

Background: It has been suggested that dietary polyunsaturated fatty acids (PUFA) are partitioned into oxidation pathways to a greater extent than dietary saturated fatty acids (SFA). Whilst this has been demonstrated in animal models, evidence in humans is lacking. The potential divergence in the meta-bolic fate of these dietary fatty acids (FA) may explain some of the reported differences in ectopic fat deposition with SFA and PUFA enriched diets. Aims: To compare whole-body oxidation of dietary palmitate and linoleate after consumption of a single test meal. Methods: In a randomized, crossover design 24 healthy volunteers (12 males and 12 females, matched for age and BMI) underwent two study days separated by 2-week washout period. During each study day participants consumed a standardized test meal which contained [(UC)-C-13]palmitate or [(UC)-C-13]linoleate. Blood and breath samples were collected over the 6 h postprandial period and the C-13 enrichment in breath CO2 samples and plasma lipid fractions was determined. Results: Appearance of C-13 in expired CO2 was significantly (p < 0.05) increased after consumption of the meal containing [(UC)-C-13]linoleate compared to the meal containing [(UC)-C-13]palmitate. The recovery of tracer was 8.9 +/- 1.2% [(UC)-C-13]linoleate vs. 5.6 +/- 0.4% [(UC)-C-13]palmitate (p < 0.05). The incorporation of C-13 from [(UC)-C-13]palmitate was greater in plasma triacylglycerol and non-esterified fatty acids than [(UC)-C-13]linoleate, whereas the incorporation of C-13 from [(UC)-C-13]linoleate was greater than [(UC)-C-13]palmitate in plasma phospholipids. Although (CO2)-C-13 was significantly (p < 0.05) higher in females compared to males after consumption of [(UC)-C-13]palmitate, there was no difference in (CO2)-C-13 between sexes after consumption of [(UC)-C-13]linoleate. Conclusions: We demonstrate that whole-body oxidation of dietary linoleate is comparatively higher than that of dietary palmitate in humans following consumption of a single mixed-test meal. We found indications of sexual dimorphism for dietary palmitate but not dietary linoleate. Study registration: http://www.clinicaltrials.org/ ID number NCT03587753. (C) 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Automated summary

The study demonstrates that the whole-body oxidation of dietary linoleate is higher than that of palmitate in humans after consumption of a single mixed-test meal. There were indications of sexual dimorphism for dietary palmitate but not for dietary linoleate.