Plasma zinc, rate of weight gain, and the energy cost of tissue deposition in children recovering from severe malnutrition on a cow's milk or soya protein based diet.

Thirty-four malnourished children were rehabilitated on either a cow's milk or a soya protein based formula diet. The soya diet contained 25% less zinc than the cow's milk diet and 1.33 mmol/l phytic acid. When the marasmic children were given either of these diets they had a dramatic fall in their plasma zinc concentration. Children given the soya formula had an even more profound drop in plasma zinc, to levels associated with acrodermatitis enteropathica. Plasma zinc remained low throughout the phase of rapid weight gain, but rose when a mixed diet was given and the children ceased gaining weight. There was a negative correlation between the rate of weight gain and the plasma zinc concentration, the rate of new tissue synthesis being the predominant modulator of the plasma zinc concentration. The energy cost of tissue deposition was initially low on the cow's milk diet and relatively high on the soya diet. Later, the energy costs rose in the cow's milk fed children. The rate of weight gain was less on the soya diet; however, the appetite, as measured by the ad libitum dietary intakes, did not differ between the diets, or correlate with the plasma zinc concentration. This may be due to the relatively low protein content of the diets used. It is concluded that dietary zinc may limit the rate of weight gain during periods of recovery in body mass and may be a cause for the excessive deposition of adipose tissue.