The amount of human milk ingested by the nursing infant is about 600 ml per day. The average lipid content of the mature ranges from 3.2 to 3.5% and the amount does not appear to be influenced by diet. About 98% of the lipid is triacylglycerol in which most of the secondary ester is palmitic acid, a unique structure possibly responsible for the relatively high absorbability of the fat. Small quantities of other lipids are present. Amounts of cholesterol reported, range from 200 to 564 mg per 100 g of lipid. While 167 fatty acids have been positively and tentatively identified as being present in human milk lipids, the major fatty acids are palmitic, stearic, oleic, and linoleic. The composition can be changed by diet, which linoleic acid contents of from 1.0 to 45.0% having been found. The "average" linoleic acid is about 10% and this amount is apparently adequate for the essential fatty acid requirements of the infant. The quantity of vitamin E also appears to be satisfactory. The hypothesis that a cholesterol challenge to the breast fed infant would enable the adult to more efficiently metabolize the sterol does not seem to be supported by available evidence, primarily, because the cholesterol content of human milks varies so markedly; 26 to 52 mg per 8 ounces. The compositions of most infant formulas currently in use in the United States are presented for comparison and convenience and a few possible problems associated with their consumption are discussed. We have suggested several areas where, in our opinion, additional research would provide useful information.
The comparative absorption of cocoa butter (25.5% C16:0, 34.4% C18:0, 34.4% C18:1, 3.4% C18:2) and corn oil (11.4% C16:0, 2.0% C18:0, 26.4% C18:1, 60.0% C18:2) was assessed in six healthy male subjects. During 3-d experimental diet periods, free-living subjects consumed either cocoa butter or corn oil as virtually the sole source of dietary fat, provided at 40% of the total energy intake in the form of specially formulated cookies. Fat absorption was determined by quantifying total fecal lipid excretion over the 3-d period. Total fecal lipid and fecal fatty acids were determined. The percentage of fat excreted was significantly higher (p less than or equal to 0.001) when subjects consumed the cocoa butter (10.8 +/- 3.2%) vs the corn oil (3.5 +/- 1.0%) diet. These results indicate that the digestibility of cocoa butter is significantly less than corn oil and may explain, in part, previous reports of a neutral effect of dietary cocoa butter on plasma cholesterol concentrations.
Glucose intolerance was induced in rats by iv infusion of streptozotocin (STZ) in doses of 30, 40, 50, and 100 mgjkg. Serum glucose concentrations were elevated versus controls and weight gains were reduced in a dose-dependent fashion up to 50 mgjkg. Urine outputs and blood urea nitrogen (BUN) values were higher than control values in the animals treated with 40 and 50 mg/kg and serum albumin concentrations were decreased after infusion with 50 mg STZ/kg. Lung phosphatidylcholine (PC) concentrations and dry-to-wet weight ratios were unchanged by STZ treatment, while lung protein and disaturated phosphatidylcholine (DSPC) concentrations were depressed in the 50-mg/kg group. Animals surviving treatment with lo0 mg/kg demonstrated increased fasting blood glucose levels, BUN values, and 48-hr urine outputs, and decreased lung protein levels. However, these alterations were less than those found in the 50-mg/kg animals. Pulmonary concentrations of PC, DSPC, and lung dry-to-wet weight ratios were unchanged. It was found advantageous to express the results relative to fasting blood glucose levels. This demonstrated that urine output and BUN values increased and weight gain decreased with rising glucose concentrations, but serum albumin decreased only in moderate and severe hyperglycemia. Fasting glucose concentrations greater than 400 mddl were associated with reduced lung DSPC and protein levels, while pulmonary PC and dry-to-wet weight ratios demonstrated no change with increasing hyperglycemia.
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