Effect of maternal dietary linoleic acid and trans-octadecenoic acid on the fatty acid composition and prostaglandin content of rat milk.

The effects of seven levels of dietary linoleic acid (18:2), with and without trans-octadecenoic acid (18:1t), on the fatty acid composition and prostaglandin content of milk were investigated in lactating rat dams. At parturition, 14 groups of 4 rats each were fed diets containing 20% fat, with mixtures of coconut and safflower oils providing seven concentrations of 18:2 ranging from 3.6 +/- 0.5 to 44.5 + 2.3% of total fatty acids. Hydrogenated soybean oil was added such that 18:1t comprised 10.3 +/- 0.3% of total fatty acids. Milk samples were collected on day 12 postpartum for prostaglandin analyses and on day 16 for fatty acid analyses. The relationship of dietary 18:2 to milk 18:2 was linear (r = 0.98; P = 0.0001), with milk 18:2 ranging from 2.6 +/- 0.1% of total fatty acids at the lowest level of dietary 18:2 to 27.9 +/- 1.6% at the highest. Milk 18:1t was highly correlated (r = 0.99; P = 0.0001) with the amount of dietary 18:1t. In rats fed hydrogenated fat, milk 18:1t averaged 7.0 +/- 0.2% of total fatty acids. Transfer from diet to milk was 46.4 +/- 4.2% for 18:2 and 37.5 +/- 1.7% for 18:1t. Mean concentrations of prostaglandin F2 alpha and E in rat milk were 269 +/- 16 pg/mL and 477 +/- 24 pg/mL respectively. There were no significant differences in the concentrations of either prostaglandin relative to 18:1t consumption at any level of 18:2.

The effect of hydrogenated fat in the diet of nursing mothers on lipid composition and prostaglandin content of human milk.

To study the effects of hydrogenated fat in the maternal diet on lipid composition and prostaglandin content of human milk, eight nursing mothers, 2 months postpartum, were provided with two 5-day diets in a cross-over design with an intervening 2-day period. Diets for the two periods were identical except that sources of hydrogenated fat were used in the meals for one period and nonhydrogenated fat in the other. Trans-isomers of octadecenoic acid (18:lt) comprised 11.8% of the total fatty acids in the hydrogenated fat diet compared with 1.0% in the nonhydrogenated fat diet. The 18:lt content of milk collected daily during hydrogenated fat consumption was 6.5% of the total fatty acids and was significantly higher (p less than 0.01) than the 18:lt content (1.8% of the total fatty acids) of milk collected during nonhydrogenated fat consumption. The amount of 18:lt in the milk was positively correlated (r = 0.909) with the 18:lt content in the previous day's diet. Although detectable concentrations of prostaglandins PGF2 alpha and PGE were found in human milk, their concentrations were not affected by hydrogenated fat in the maternal diet.