Trans -11–18: 1 is effectively δ9-desaturated compared with Trans -12–18: 1 in humans

Abstract

The aim of this human intervention study was to evaluate the Δ9-desaturation of trans -11–18:1 ( trans -vaccenic acid; t VA) to cis -9, trans -11–18:2 ( c 9, t 11 conjugated linoleic acid; CLA) and of trans -12–18:1 ( t 12) to cis -9, trans -12–18:2 after a short-term (7d) and a long-term (42d) supplementation period. The conversion rates of both trans -18:1 isomers were estimated by lipid analysis of serum and red blood cell membranes (RBCM). Subjects started with a 2-week adaptation period without supplements. During the 42d intervention period, the diet of the test group was supplemented with 3g/d of t VA and 3g/d of t 12. The diet of the control group was supplemented with a control oil. Serum t VA and t 12 levels in the test group increased by fivefold and ninefold after 7d, respectively, and by eight- and 12-fold after 42d, respectively, when compared with the adaptation period ( p ≤0·002). The serum c 9, t 11CLA levels increased by 1·7- and 2·0-fold after 7d and 42d, respectively ( p ≤0·001). After 42d, the test group's RBCM c 9, t 11CLA content was elevated by 20% ( p =0·021), whereas in the control group it was decreased by 50% ( p =0·002). The conversion rate of t VA was estimated at 24% by serum and 19% by RBCM. No increase in c 9, t 12–18:2 was observed in the serum and RBCM, and thus no conversion of t 12 could be determined. In conclusion, the endogenous conversion of dietary t VA to c 9, t 11CLA contributes approximately one quarter to the human CLA pool and should be considered when determining the CLA supply.