Fatty acid composition of serum cholesteryl esters and erythrocyte membranes as indicators of linoleic acid intake in man.

We compared the suitability of the linoleic-oleic acid ratio (L:O) of serum cholesteryl esters and erythrocyte membranes as indicators of dietary fatty acid composition. Forty-seven volunteers received a mixed natural diet with a polyunsaturated-saturated fatty acids ratio (P:S) of 0.2 for 3 wk and with P:S 2.0 for another 3 wk (HA group, 24 subjects) or vice versa (HY group, 23 subjects). Duplicate portion analysis revealed that dietary fat type was the only variable. The change in L:O in cholesteryl esters relative to the low P:S diet was 91.3 +/- 25.9% (means +/- SD) in the HA group and 85.1 +/- 18.8% in the HY group. The changes in erythrocyte membranes were 33.0 +/- 7.9% in the HA group and 22.8 +/- 4.9% in the HY group. Thus the effect on erythrocyte fatty acids was smaller but also less variable and the precision of the two measures was similar. Therefore the L:O of either blood component can be used as a marker of a subject's adherence to experimental diets differing in type of fat.