Retinal degeneration in 3-month-old rhesus monkey infants fed a taurine-free human infant formula

Rhesus monkey infants were raised from birth on a taurine-free soy protein-based human infant formula or on the same formula supplemented with taurine. The monkeys were killed 3 months after birth and the retinas examined by light and electron microscopy. All of the monkeys raised on formula alone showed degenerative ultrastructural changes in photoreceptor outer segments that ranged from swelling and disorientation to fragmentation and disorganization. Cones were more severely affected than rods, and changes were most pronounced in the foveal region. Changes were also noted in the fine structure of the retinal pigment epithelium. These changes were prevented in all but one monkey fed the same formula supplemented with taurine. These results provide further support for the addition of taurine to commercial human infant formulas.