Influence of diet on trans fatty acids in human milk.

In two experiments on relations between diet and milk lipids, subjects recorded food intake for 1 week and saved duplicate portions of foods consumed on 3 days. Diet collections were analyzed for selected nutrients and percent fatty acids. In the first experiment, for 1 week five subjects took morning and evening milk samples for fatty acid analysis. Significant differences were found in percentages of trans- 18:1 and total trans fatty acids between subjects' milks but not between morning and evening samples. In the second experiment six additional subjects collected milk samples in the morning only. Subjects were significantly different in the percentages of trans- 18:1 and total trans acids in their milks. In nine of the 11 subjects the fluctuation of percent total trans acids in the milk appeared to follow dietary trans changes after a 12 to 36 hr lag period. A significant correlation was found for diet and evening milk of the same day. Polyunsaturated/saturated ratios of the fatty acids in the diet lipids were related to those for milk lipids from the same evening and the next morning. Although other factors are involved, diet lipids influence trans fatty acids and polyunsaturated/saturated ratios of the fatty acids in human milk.