Infant vitamin B-6 status changes with age and with formula feeding.

To study the effect of type of feeding on infant vitamin B-6 status, we determined erythrocyte pyridoxal 5'-phosphate concentration (EPLP) and erythrocyte aspartate aminotransferase basal activity (EASTo) and its activation coefficient (alpha EAST) in 109 infants at 2, 4, 6, 9, and 12 mo of age. Thirty-six infants were exclusively breast-fed for 9 mo. Forty-six infants were exclusively breast-fed for 6 mo, and then given solid foods in addition. Twenty-seven infants were weaned by 2-3 mo to an adapted cow milk-based formula (15 g protein/L and 0.6 mg pyridoxine/L) and given solid foods from 3 to 4 mo. Infant vitamin B-6 status was age-dependent; it was highest at 4 mo and thereafter gradually approached adult values. The larger the intake of formula, the higher the vitamin B-6 status. In formula-fed infants at ages 2-6 mo, 71-96% of the EPLP values and 57-70% of the EASTo values were above the 95th percentile, and 35-53% of the alpha EAST values were below the 5th percentile for these values in breast-fed infants. These findings raise the question of whether the vitamin B-6 content of formulas, especially in relation to protein content, should be reduced.