Increased alpha-linolenic acid intake increases tissue alpha-linolenic acid content and apparent oxidation with little effect on tissue docosahexaenoic acid in the guinea pig

The essential fatty acids do not have identical roles in nutrition. Linolei c acid (LA) accumulates throughout the body of most mammals, whereas alpha- linolenic acid (ALA) is rarely found in tissue lipids to the same extent as LA. It has been argued that this is the result of metabolism of ALA to doc osahexaenoic acid (DHA) or that ALA is rapidly beta-oxidized to acetyl CoA and CO2. In this study, we consider the effect of high and low ALA levels o n the tissue distribution of ALA and other n-3 polyunsaturated fatty acids (PUFA) in all tissues. Guinea pigs were fed one of two defined diets for 3 wk from weaning with both diets containing 1.8% (by weight) of LA and eithe r 1.7% ALA or 0.03% ALA. The high ALA diet was associated with significantl y increased ALA levels in all tissues except the brain and significantly in creased levels of long-chain n-3 PUFA in all tissues except intestines brai n, carcass, and skin. The long-chain n-3 PUFA content of the whole body was less than 5% of that of the ALA content in both diet groups, and the major long-chain n-3 PUFA (>66% of total) in the body was 22:5n-3. The brain was the only tissue where the DHA content exceeded that of 22:5n-3. On the low ALA diet, there appeared to be conservation of ALA based on a comparison o f the ratio of LA to ALA in the tissues compared with that in the diet. On the high ALA diet there was a lass of ALA relative to LA in the tissues com pared with the diet. These studies suggest that the low levels of tissue AL A in the guinea pig are likely the result of beta-oxidation or excretion vi a the skin and fur rather than metabolism to DHA.