Dairy product consumption is associated with a lowering of linoleic acid within serum TAG in adolescent females with overweight or obesity: a secondary analysis

Abstract

Dairy fat is rich in saturated fatty acids such as palmitic acid (16:0) but low in linoleic acid (18:2n-6). The natural carbon 13 enrichment (δ13C) of 16:0 is higher in dairy fat than in most of the food supply. In adults, serum levels of pentadecanoic acid (15:0) and heptadecanoic acid (17:0) are recognized as biomarkers of dairy intake. In adolescents, no study has evaluated serum fatty acid levels or δ13C in response to chronic dairy consumption. The objectives of this study were to evaluate whether increased dairy product consumption can modulate 1) serum fatty acid levels and 2) 16:0 δ13C in adolescents with overweight/obesity who followed a 12-week weight management program. This secondary analysis of a RCT included two groups of adolescent females: recommended dairy (RDa; n=23) and low dairy (LDa; n=23). The RDa group was given 4 servings/d of dairy products while the LDa group maintained dairy intakes at ≤2 servings/d. Blood was sampled before and after the intervention. Lipids were extracted, separated, and fatty acids were quantified by gas chromatography. Isotope ratio mass spectrometry was used to assess 16:0 δ13C. There were no group differences on serum changes of 15:0 or 17:0. Within triglycerides, 18:2n-6 was lowered by 7.4% only in the RDa group (p = 0.040). The difference in delta 16:0 δ13C between the LDa and RDa group did not reach statistical significance (p = 0.070). Reductions in serum 18:2n-6 by dairy consumption could have positive health implications but more studies are needed to confirm this assertion.

Analysis of omega-3 and omega-6 polyunsaturated fatty acid metabolism by compound-specific isotope analysis in humans

“…For the secondary analysis, ten participants from each dietary group who completed the study protocol were randomly selected by a computer-generated random number list for fatty acid analysis. Total lipids were extracted from 300 μl of plasma using a modified Folch method ( 21 ), as previously described ( 22 , 23 ). Lipid extraction was performed with 2:1 chloroform:methanol in the presence of 10 μg of unesterified heptadecanoic acid, cholesteryl ester (CE), triglyceride (TG), and phosphatidylcholine (17:0 FFA, CE, TG; Nu-Chek Prep, Inc; phosphatidylcholine; Avanti Polar Lipids) as the internal standard.…”