Volume 90, Issue 6, December (2003), pp. 1039-1048 © The Author 2003
doi:10.1079/BJN20031002

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Effects of dietary cis 9, trans 11-18 : 2, trans 10, cis 12-18 : 2, or vaccenic acid (trans 11-18 : 1) during lactation on body composition, tissue fatty acid profiles, and litter growth in mice

Juan J. Loor^1,2, Xiaobo Lin^1,3, Joseph H. Herbein^1
1Dairy Science Department, Virginia Tech, , Blacksburg, VA 24061-0315, , USA
²Department of Animal Sciences, University of Illinois, 206 ERML, Urbana, IL 61801, , USA
³Division of Atherosclerosis, Nutrition and Lipid Research, Department of Medicine, Washington School of Medicine, Box 8046, St Louis, MO 63110, , USA

 (Received 12 February 2003–Revised 26 June 2003–Accepted 14 August 2003)

Cis 9, trans 11 (c9, t11)-18 : 2 and trans 10, cis 12 (t10, c12)-18 : 2 are the major conjugated linoleic acid (CLA) isomers in dietary supplements which reduce milk fat content in nursing women. The present study evaluated the effects of each CLA isomer or vaccenic acid on body composition and tissue fatty acids during lactation in mice. Dams were fed 30 g rapeseed oil (control)/kg diet or 20 g control plus 10 g 18 : 0, trans 11-18 : 1 (t11-18 : 1), c9, t11-18 : 2, or t10, c12-18 : 2. Dietary t10, c12-18 : 2 reduced food intake by 18 % and carcass fat weight of the dams by 49 % compared with the other treatments. Milk fat percentage ranked by treatment was 18 : 0>t11-18 : 1=c9, t11-18 : 2>t10, c12-18 : 2. The sum of saturated 12 : 0 to 16 : 0 in milk fat was lower when c9, t11-18 : 2 was fed compared with the control, 18 : 0, or t11-18 : 1 treatments. Dietary t10, c12-18 : 2 caused further reductions in milk fat 12 : 0 to 16 : 0. The proportion of CLA isomers was 3-fold greater in milk fat than in the carcasses of the dams. The pups nursing from the dams fed t10, c12-18 : 2 had the lowest body weights and carcass fat, protein, and ash contents. Nursing from the dams fed c9, t11-18 : 2 also resulted in lower carcass fat compared with the 18 : 0 or t11-18 : 1 treatments. The ratios of cis 9-16 : 1:16 : 0 or cis 9-18 : 1:18 : 0, proxies for Δ⁹-desaturase activity, were markedly lower in the carcasses of the dams and pups fed t10, c12-18 : 2. The ratio of 20 : 4n-6:18 : 2n-6, a proxy for Δ⁶- and Δ⁵-desaturase and elongase activity, in the liver of the dams and pups fed t10, c12-18 : 2 also was lower. Dietary t11-18 : 1 enhanced the content of c9, t11-18 : 2 in milk fat and carcasses. As in previous studies, the reduction in food intake by t10, c12-18 : 2 could not entirely account for the marked decrease in carcass fat content and milk fat concentration. T10, c12-18 : 2 probably had a negative effect on Δ⁹-desaturase and mammary de novo fatty acid synthesis. Although these effects need to be confirmed in lactating women, the results suggest that the consumption of supplements containing t10, c12-18 : 2 should be avoided during the nursing period.

Keywords:
Conjugated linoleic acids, Vaccenic acid, Body composition, Milk fat, Lactation

Abbreviations:
c9, t11, cis 9, trans 11, CLA, conjugated linoleic acid, t10, c12, trans 10, cis 12, t11-18 : 1, trans 11-18 : 1