Biological Explanation for the Disparate Effects

About one-fourth of the TFAs in ruminant fat is represented by RA, which is by far the predominant natural isomer of conjugated linoleic acid (CLA). The remaining TFAs are mainly trans monounsaturated acids of which vaccenic acid (VA /ra/iv-11-Cisi) is predominant. On the other hand, hydrogenated vegetable oils contain predominantly elaidic acid (trans-9-Ci8 i) and have a more even distribution of the other trans-C n acids, but contain little or no RA (Parodi, 2004). 

Animal and human tissues contain the enzyme A9-desaturase that can introduce a cA-double bond at carbon 9 in VA to produce RA. Santora et al. (2000) fed VA to mice and found that 12% of this VA or 50% of the VA stored in carcase adipose tissue was converted to RA. Humans fed increasing 

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