Visual acuity loss in rhesus monkey infants fed a taurine-free human infant formula.

This study examined the effects of dietary taurine deprivation on visual development in rhesus monkeys. From birth to 3 months of age, rhesus monkeys were fed a taurine-free, soy protein-based infant formula, or the same formula supplemented with taurine. The early postnatal development of visual function was assessed with behavioral measurements of visual acuity. Plasma taurine levels in the taurine-deprived group fell to 35-50% of control values, as in human infants fed similar formulas. The visual acuity of the taurine-deprived infants was significantly impaired: acuity thresholds differed from control values by nearly a factor of 2 at 4, 8, and 12 weeks of age. The loss of acuity is associated with morphological changes in photoreceptors, particularly cones in the foveal region. These results provide direct evidence that taurine is essential for normal visual development in primates, and they support the nutritional importance of taurine for human infants.