The subjects were all Chinese male adults. The average age, body weight and height were 37.9 (24-44) yr, 64.3 (51.5-74.0) kg and 173 (157-180) cm respectively in the first group, and 30.2 (24-41) yr, 67.7 (56.5-70.0) kg and 171 (170-176) cm respectively in the second group.The subjects in the first group were studied for 70 days for the N balance response at graded protein intakes of 0.42, 0.60, 0.73, 0.90 and 1.05 g/kg /day on Chinese mixed diet, during 5 experimental periods respectively. Each period took ten days preceded by one day of low protein diet, and was followed by three days of free choice diet The sequence of protein intakes during the study was 0.60, 0.73, 0.42, 0.90 and 1.05 g/kg/day. Six subjects in the second group were given a mixed diet ata protein level of 0.93 (0.91-0.94) g/kg/day for three months.In the N balance data of the first group, all subjects were in negative balance at protein intake of 0.42, 0.60 and 0.73 g/kg/day and all in positive N balance at 1.05 g/kg/day. Most of the subjects were in positive N balance at 0.90 g/kg/day. The linear regression analysis of N balance response of individual subject is that the intercept at zero balance of individuals ranged from 129.4-192.5 mg N/kg/day with the mean of the group of 147.7? 18.6mg N/kg/day or 0.92?0.12 g protein/kg/day. The five of the six subjects in the second group were in positive N balance, when on a mixed diet of 0.93 ?0.02 g protein/kg/day for three months.The results obtained indicated the mean protein requirement of these subjects based on the linear regression analysis of N balance response of individuals was 147.7 ? 18.6 mg N/kg/day or 0.92?0.12 g protein/kg/day. If 97.5% is to be covered, the safe level of protein intake should be 1.16 g protein/ kg/day.

The growth curves and diet of 185 babies in rural area near Beijing from 6 months to 18 months old have been studied. Infants were divided into 3 groups according to their diet taken:(1) 89 babies had breast milk only;(2) 66 babies took more than 250g animal milk per day besides breast milk;(3) 30 babies who did not have breast milk and only animal milk was taken. All the babies were gradually transferred to an ordinary cereal based diet during the weaning period. To half of them a soybean and cereal based formula fortified with minerals and vitamins was supplied, which would provide 6.6g protein and 141 kcal and some other nutrients per day.The results showed that the growth curves of body weight and height of children were much better than the data obtained in 1975, but still lagged behind that of the urban children, especially for the body weight. The weight curves of the babies who took animal milk seemed higher than the other groups. Female babies who were fed with breast milk and supplemented with the weaning food have a better weight and height curves than non-supplemented ones, but this was not seen in males. The hemoglobin contents of the babies who took animal milk when they were 18 months old were lower than that of the 6 months old, but there were no differences in the breast milk groups, and the lowering of the hemoglobin level in the animal milk groups could be corrected by adding weaning food in the diet. When the babies were 6 months old, 39.3% of them had a hair zinc content below the lower limit of the normal range, and it became to 47.6% when they were 18 months old. So zinc deficiency of the babies were present in this local area, and it should be fortified into the weaning food.