Black beans, a staple food consumed in large amounts in Central and South America, were used as a model for the studies of the effect of fish or amino acids present in fish on iron absorption from vegetable food.
The iron absorption rate in 137 subjects showed an asymmetric distribution. The mean iron absorption was 2.6 per cent and the limit of one standard deviation was from 0.8-8.2 per cent.
Iron absorption from black beans increased about twice when the food was administered with either fish or with amino acids in number and proportion as present in 100 Gm. of fish. Further experiments showed that the absorption is not enhanced if the black beans were mixed with either basic amino acids (Histidine, Arginine and Lysine), aromatic amino acids (phenylalanine, Tyrosine and Tryptophan) or other amino acids grouped as "aliphatics" (Glycine, Alanine, Leucine, Isoleucine, Serine, Threonine, Aspartic acid and Glutamic acid). However, either cysteine plus methionine, or cysteine alone enhances iron absorption from black beans in similar proportion as observed when this food was mixed with fish or total amino acids present in fish.