Trans, n-3, and n-6 fatty acids in Canadian human milk.

The presence of trans fatty acids in human milk may be a concern because of their possible adverse nutritional and physiological effects on the recipient infant. The mother's diet is the source of human milk trans fatty acids, and since these fatty acids are prevalent in many common foods of the Canadian diet, the trans fatty acid content and the fatty acid composition of Canadian human milk were measured by gas-liquid chromatography coupled with silver nitrate-thin layer chromatography. In samples obtained from 198 lactating mothers across Canada, the average percentage of total trans (sum of t18:1, t18:2, and t18:3) was 7.2% of breast milk fatty acids with a range of 0.1-17.2%. Analysis of t18:1 isomer distribution indicated that partially hydrogenated vegetable oils are the major source of these trans fatty acids in human milk, whereas contribution from dairy products appeared to be relatively minor. Linoleic and alpha-linolenic acid levels were inversely related to the total trans fatty acids, indicating that the elevation of trans fatty acids in Canadian human milk is at the expense of n-3 and n-6 essential fatty acids. Levels of arachidonic and docosahexaenoic acids did not correlate with their parent fatty acids, indicating that it might be difficult to elevate the levels of n-6 and n-3 c20-22 polyunsaturated fatty acids in breast milk by increasing levels of linoleic and alpha-linolenic acids in the mother's diet.