Bioconversion of vaccenic acid to conjugated linoleic acid in humans.
BACKGROUND
Vaccenic acid (11-trans octadecenoic acid; VA), a major trans fatty acid in the fat of ruminants, is produced in the rumen and converted in tissues to rumenic acid (9-cis, 11-trans octadecenoic acid; RA), an isomer of conjugated linoleic acid, by Delta(9)-desaturase. There are indications that this conversion also occurs in humans.


OBJECTIVE
The aim of this controlled intervention was to study the conversion of VA to RA in humans after consumption of diets with increasing amounts of VA.


METHODS
Thirty healthy subjects consumed a baseline diet rich in oleic acid for 2 wk. The subjects were then divided into 3 groups (n = 10 per group) and provided a diet containing 1.5, 3.0, or 4.5 g VA/d for 9 d. All diets contained equal amounts of macronutrients and differed only in their fatty acid compositions. The fats were mixed into conventional foods, and nearly all food was provided during the study.


RESULTS
The proportion of VA in serum total fatty acids increased 94%, 307%, and 620% above baseline with the 1.5-, 3.0-, and 4.5-g diets, respectively. This was associated with a linear increase in the proportion of RA. The conversion rate was 19% on average, with significant interindividual differences with all 3 intakes of VA. The urinary excretion of 8-iso-prostaglandin F(2alpha) increased in all groups (P < 0.001).


CONCLUSIONS
The results quantify the desaturation of VA to RA in humans. Conversion is likely to contribute significantly to the amount of RA available to the body, and dietary intakes of VA should thus be taken into account when predicting RA status.
Department of Applied Chemistry, University of Helsinki, Finland.
Anu M
AM
Turpeinen
Marja
M
Mutanen
Antti
A
Aro
Irma
I
Salminen
Samar
S
Basu
Donald L
DL
Palmquist
J Mikko
JM
Griinari
D000328:Adult; D000818:Animals; D004032:Diet; D004041:Dietary Fats / Q000008:administration & dosage; D015237:Dinoprost / Q000031:analogs & derivatives*; D028441:F2-Isoprostanes / Q000652:urine; D005227:Fatty Acids / Q000097:blood; D005260:Female; D006801:Humans; D007700:Kinetics; D019787:Linoleic Acid / Q000378:metabolism*; D008055:Lipids / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008297:Male; D009829:Oleic Acids / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism; D013229:Stearic Acids / Q000378:metabolism; D014280:Triglycerides / Q000097:blood
C114874:5-octadecenoic acid; D004041:Dietary Fats; D028441:F2-Isoprostanes; D005227:Fatty Acids; D008055:Lipids; D008079:Lipoproteins, VLDL; D009829:Oleic Acids; D013229:Stearic Acids; D014280:Triglycerides; C075750:8-epi-prostaglandin F2alpha; D019787:Linoleic Acid; D015237:Dinoprost; C050413:11-octadecenoic acid