Metabolism of taurine during reproduction in women.

The pattern of excretion of taurine was measured in four omnivore and four vegan/vegetarian women during pregnancy and lactation, and was compared with the changes in urinary excretion of other amino acids, including the precursors of endogenous taurine, observed in ten pregnant omnivores. The loss of taurine in breast milk was also determined in fourteen omnivore and fourteen vegan mothers. In contrast to the rise in excretion of all amino acids during pregnancy, including methionine and cysteine, taurine excretion fell dramatically from week 9 of pregnancy in all subjects, and, in the vegan/vegetarian subjects, fell still further during lactation. Although the concentration of taurine in breast milk was lower in vegan subjects, the mean value fell within the range found in omnivore subjects. Our findings indicate that the suppression of urinary taurine excretion, both during pregnancy and lactation, is a physiological response to reproduction that satisfies the needs of the fetus and the suckling infant for this amino acid. The data also suggest that taurine is stored in the maternal tissues in early pregnancy for later transfer to the fetus.