Fatty acid composition of the milk lipids of Nepalese women: correlation between fatty acid composition of serum phospholipids and melting point

Milk was collected from 36 Nepalese women, 15 to 32 years of age, in order to investigate relationships between the proportions of intermediate chain- length (C10-C14) fatty acids and critical n-3 and n-6 polyunsaturated fatty acids in the milk lipids they were producing. Serum was also obtained from these lactating women and the fatty acid composition of their serum phosph olipid fraction was determined and compared with that of the corresponding milk lipid fraction. Compared to women in technologically advanced parts of the world, the serum phospholipids of the Nepalese women contained nutriti onally adequate proportions of linoleic acid (LA) (16.8%), alpha -linolenic acid (ALA) (0.53%), arachidonic acid (AA) (5.69%), and docosahexaenoic aci d (DHA) (1.42%). However, although the milk lipids contained adequate propo rtions of ALA (1.81%), AA (0.43%), and DHA (0.23%), the lipids contained lo w to moderate percentages of LA (mean, 9.05%). Positive correlations were o bserved between the proportions of AA (P = 0.001, r = 0.50) and ALA (P = 0. 03, r = 0.36) in the serum phospholipids and milk lipids of the women. As t he proportion of C10-C14 fatty acids in the milk lipids increased from 10% to 40%, there was preferential retention of three critical n-3 and n-6 fatt y acids (ALA, AA, and DHA) at the expense of two relatively abundant noness ential fatty acids, namely stearic acid and oleic acid. In addition, using fatty acid melting point data and the mol fraction of the 9 most abundant f atty acids in the milk, we estimated the mean melting point (MMP) of the mi lk lipids of the Nepalese women. The MMPs ranged from 29.3 to 40.5 degreesC (median, 35.5 degreesC). These results indicate that: 1) the levels of AA and ALA in the blood of la ctating mothers influence the levels of these fatty acids in the milk they produce; 2) when the mammary gland produces a milk that is rich in C10-C14 fatty acids, it somehow regulates triglyceride synthesis in such a way as t o ensure that the milk will provide the exclusively breast-fed infant with the amounts of the critical n-3 and n-6 fatty acids it requires for normal growth and development; and 3) the melting point of the milk lipid fraction is determined mainly by the mol % of the intermediate chain-length (C10-C1 4) fatty acids, oleic acid, linoleic acid, and alpha -linolenic acid. (C) 2 001 Harcourt Publishers Ltd.