Effect of Amino Acid Diets upon Serum Lipids in Man

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Abstract
Formula diets containing the eight essential amino acids required by man in adequate amounts plus glutamate as a source of nonessential nitrogen to provide a nitrogen intake total of 16.0 g caused a marked fall in serum cholesterol and phospholipids and an indifferent effect upon serum triglycerides in human subjects. The β-lipoprotein fraction most affected is the LDL Sf 0-12 family. Formula diets identical in all respects except for the replacement of glutamate by glycine plus ammonium acetate in equimolar quantities did not show this effect. Likewise, formulas containing amounts of all l-amino acids present in 100 g protein did not affect serum lipid concentrations in the subjects studied. The hypocholesteremic effect of the glutamate formula is greater than that of an essentially nitrogen-free diet identical in other respects and greater than the effect of feeding 25 g vegetable-cereal protein. The hypolipidemic effects of glutamate and of polyunsaturated fatty acids in the diet were not additive. It is possible that these two dissimilar agents affect a final common pathway in the metabolism or distribution of serum lipids.