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.