A study by Rist et al looked at whether the incorporation of organic dairy and meal products in the maternal diet affects the contents of the conjugated linoleic add isomers (CLA) and trans-vaccenic acid (TVA) in human breast milk.
The term conjugated linoleic acid describes a mixture of positional and geometric isomers of linoleic acid (C18:2n-6) which contain a conjugated double-bond system instead of the more common isolated double bonds
. Rumenic or cis-9.trans-11-octadecadienoic acid (cis 9 trans 11-C18:2) is the most common conjugated linoleic acid isomer and is often regarded as the biologically most relevant one. The various conjugated linoleic acids are produced in the rumen of ruminant animals mainly by the bacteria Butyrivibrio fibrisolvens through reactions of iso-merization and biohydrogenation. These reactions lead as well to the formation of a wide variety of trans- and cis-monoenic fatty acids (especially C18: 1 trans isomers). In addition, trans-vaccenic acid trans 11-C18: 1,) which originates, from linoleic and linolenic acid plays an important role as precursor of rumenic acid.
Conjugated linoleic acids are currently receiving much attention in nutritional research, since there is experimental evidence suggesting that these fatty acids might have anti-carcinogenic, anti-atherosclerotic, anti-diabetic and immune-modulating effects, as well as a favourable influence on body fat composition, i.e. on the proportion of fat tissue to muscle mass .
Milk samples from 312 breastfeeding mothers participating in the KOALA Birth Cohort Study have been analysed. The participants had documented varying lifestyles in relation to the use of conventional or organic products. Breast milk samples were collected 1 month postpartum and analysed for fatty acid composition. The content of rumenic acid (the main conjugated linoleic acid) increased in a statistically significant way from a conventional diet (no organic dairy/meat products. 0.25 weight % (wt%), to a moderately organic diet (50-90% organic dairy/meat,.0.29 wt%.) and to a strict organic diet (> 90% organic dairy/meat. 0.34 wt%,).
The levels of trans-vaccenic acid were increased among the participants with a moderate organic diet (0.54 wt %) and those with a strict organic diet (0.59 wt%,). in comparison with the conventional group (0.48 wt % ).
Eating organic dairy products changes the conjugated linoleic acid content of mother’s breast milk.

Rist et al 2007 Influence of organic diet on the amount of conjugated linoleic acids in breast milk of lactating women in the Netherlands. British Journal Nutrition vol 97, 735-743

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