Effects of dietary alpha-linolenic acid deficiency during pregnancy and lactation on lipid fatty acid composition of liver and serum in the rat.

The effects of a dietary alpha-linolenic acid (18:3 n-3) deficiency on lipid fatty acid composition of the liver and serum of lactating rats have been studied during three gestations and over three generations. These females were compared to corresponding females which remained sterile. Two lots of female rats received, respectively, a diet containing lipids either in the form of 1.50 g of sunflower oil per 100 g of diet (deficient diet) or as 1.87 g of soya oil per 100 g of diet (control diet). Both diet contained the same amount of linoleic acid (18:2 n-6), i.e. 940 mg/100 g of diet, but the sunflower diet supplied 43 times less 18:3 n-3 than the soja diet, or 3 mg vs 130 mg/100 g of diet. Results show that successive gestations appeared to be more efficient means of depleting material n-3 PUFA stores than successive generations. The 18:3 n-3 deficient diet caused a considerable decrease in the level of n-3 polyunsaturated fatty acids (n-3 PUFA) in liver and serum lipids, and particularly of 22:6 n-3. This decline was compensated by an increase in the level of n-6 polyunsaturated fatty acids (n-6 PUFA), and particularly by a very high augmentation of 22:5 n-6. The ratio n-6 PUFA/n-3 PUFA in liver phospholipids and in serum lipids was a good index of the adequacy of dietary n-3 PUFA supply. However, the ratio 22:5 n-6/22:6 n-3 was a finer index. This ratio appeared to be a reliable index of dietary n-3 PUFA deficiency when it was higher than 1 in serum lipids of a fasting animal. The proportion of 22:5 n-6 as well as the ratios n-6/n-3 and 22:5 n-6/22:6 n-3, were also increased in the liver phospholipids of lactating females receiving the soya oil diet; this suggested that a supply of 130 mg/100 g of diet, corresponding to a ratio of n-6/n-3 = 7.2, was not sufficient for these rats during pregnancy and lactation. A supply of 200 mg of n-3 PUFA/100 g of diet, corresponding to a ratio of n-6/n-3 = 5, is recommended for these animals.