Yogurt protects against growth retardation in weanling rats fed diets high in phytic acid

The purpose of this study was to determine the effects of adding yogurt to animal diets that were high in phytic acid (PA) and adequate in zinc (38 microg Zn/g). The PA:Zn molar ratio was 60:1. Zinc status was determined by documenting growth and measuring the zinc concentration in bone (tibia) and plasma. For 25 days, six groups (n=6) of Sprague-Dawley weanling rats were fed one of six AIN-76 diets. Half of the diets contained PA. Four of the diets contained yogurt with either active or heat-treated (inactive) cultures added at 25% of the diet. The diets were as follows: (a) AIN, (b) AIN with active yogurt, (c) AIN and inactive yogurt, (d) AIN with PA, (e) AIN with PA plus active yogurt and (f) AIN with PA plus inactive yogurt. Body weight, weight gain and zinc concentration in bone and plasma were measured, and food efficiency ratio was calculated. Rats fed diets with PA and yogurt had normal growth compared to the control group. Growth retardation was evident in the group fed the diet with PA and no yogurt. This group had significantly lower body weight compared to all other groups (P<.05). Rats fed diets with PA, with or without yogurt, had significantly lower zinc concentration in bone and plasma (P<.05). Adding yogurt to diets high in PA resulted in normal growth in weanling rats; however, zinc concentration in bone and plasma was still suboptimal.