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Adult protein requirements - standard protocol

8. Assessment of protein energy needs of indian adults using short-term nitrogen balance methodology
9. Protein requirements of Chinese male adults
10. Protein requirements of Egyptian women
11. Nitrogen balances of young Turkish adults on graded levels of protein intake
12. The protein requirements of Brazilian rural workers: studies with a rice and bean diet

8. Assessment of protein energy needs of indian adults using short-term nitrogen balance methodology

K.N. Agarwal, B.D. Bhatia, D.K. Agarwal, and R. Shanker

Department of Paediatrics, Preventive and Social Medicine and Biochemistry, Institute of Medical Sciences, Varanasi, India

Objective

The purpose of the study was to evaluate the protein requirements of healthy Indian adult males and females fed a local vegetarian diet using short-term N-balance response to graded levels of protein intake

Experimental Details

Subjects. Eleven "healthy" (without clinical disease or laboratory abnormality) female (5) and male (6) volunteers, ages 25 to 39 years, from North India, Kerala and Bengal, belonging to the middle socioeconomic class, were studied. The subjects were all moderately active workers, the male subjects were involved in active swimming for 20 minutes. Individual heights, weights, and customary protein energy intakes are given in tables 1 and 2

Environment. Subjects were free-living; the temperature range and humidity during the experimental diets are given in table 3.

Physical Activity. Physical activity for the group was maintained at a moderate level.

Diets. Customary intake is included in tables 1 and 2. The energy content of the diet was calculated by proximate composition and Atwater factors. Subjects were fed 0.7, 0.6, 0.5, and 0.4 9 protein/kg/day in the vegetarian diet for 10 days following a descending pattern. Some minor variations in composition of protein intake occurred at the higher levels of protein intake A diet survey and on-spot feeding were done to find the subjects' usual caloric and protein intakes. Subjects were maintained on their usual caloric intake throughout the study. The diet was served in four equal meals (8 a.m. 12 noon, 4 p.m., and 10 p.m.) Vitamin and mineral supplements were given. Traditional methods of cooking were adopted and natural foods were used.

TABLE 1. General Characteristics of Female Subjects

a. Figures in parentheses indicate per kg caloric and protein intakes.
b. Subject No 4 was excluded because of infection.
c. Plus 2 eggs.

TABLE 2 General Characteristics of Male Subjects

a. Figures in parentheses indicate per kg caloric and protein intakes

TABLE 3. Temperature and Humidity Variation during Experimental Diets

The constituents of vegetarian diets were cereals (wheat-flour and rice), pulses* (red gram/bengalgram (egg plant)), vegetables (potatoes, brinjal, spinach, bottle gourd, pumpkin, papaya (green), lady's finger (okra), tomatoes and onions), and fruits (bananas. grapes, papayas (ripe). apples), butter, oil, and condiments.

Experimental design. Four 10-day balance periods were used in a descending fashion. Urinary N was averaged out from the last five days and faecal N was measured for the last eight days of the study.

N balance. Nitrogen content of diet, faeces, and urine was measured.

Weight. Weight did not vary significantly during the study.

Summary of Main Results

N balance. These data are summarized in tables 4 and 5. The individual regression equations relating N balance and N intake appear in table 6. The mean requirements are estimated to be 0.59 g protein/kg body weight (94 mg N/kg) for females and 0 51 g/kg (82 mg N/kg) for males. These values are significantly different (p < 0 05)

TABLE 4 Nitrogen Balance Data in Females (23 February to 3 May 1981; Humidity: 71-82 per Cent)

UN = Urinary nitrogen (mg/kg) (derived from pooled data for last five days of experiment)
FN = Faecal nitrogen (mg/kg) (derived from pooled data for last eight days of experiment)
ETNB = IN - UN - FN-5 a. Fever and diarrhoea on sixth day

TABLE 5. Nitrogen Balance Data in Males (8 May to 30 June 1981; Humidity: 58-86 per Cent)

UN = Urinary nitrogen (mg/kg) (derived from pooled data for last five days of experiment)
FN = Faecal nitrogen (mg/kg) (derived from pooled data for last e;9ht days Of experiment)
ETNB = IN - UN - FN-5 a. Diarrhoea for one day.

TABLE 6. Determination of Mean Protein Requirements

9. Protein requirements of Chinese male adults

Chen Xuecun, Yin Taian, Yang Xunjiu, Bai Jiguo, and Huang Zhisheng

Institute of Health, Chinese Academy of Medical Sciences, Beijing, China

Objective

To determine by the N-balance response method the protein requirements of Chinese male adults consuming a customary mixed Chinese diet.

Experimental Details

Subjects. The subjects were ail male Chinese adults. The average age, body weight, and height were 37.9 (24-44) years, 64.3 (51.5-74.8) kg, and 173 (157-180) cm, respectively, in the first group, and 30.2 (24 41) years, 67.7 (56.5-70) kg, and 171 (170-176) cm, respectively, in the second group, as shown in table 1. They were in good health and well nourished as determined by medical history, physical examination, urine analysis, stool exmaination, chest X-ray, and blood GPT determination. No medication or major surgical procedures were necessary during this study and all subjects remained healthy throughout the experiment.

Study environment. The entire study was conducted in the laboratories at the Institute of Health from October 1980 to February 1981. The room temperature, outdoor temperature, and relative humidity were 15 to 22°C, 12 to -14°C, and 13 to 90 per cent, respectively.

Physical activity. During the experiment, all subjects were allowed to continue their usual work without extra exercise.

Duration of the study. Ten subjects (the first group) were studied for 70 days for N balance response at graded levels of protein intake of 0.42, 0.6, 0.73, 0.9 and 1.05 g/kg/day from a mixed Chinese diet, during five experimental periods, respectively. Each experimental period was ten days, preceded by one day on a protein-free diet and followed by three days on a free-choice diet after each experimental period The sequence of protein intakes during the study was 0.6, 0.73, 0.42, 0.9, and 1.05 g/kg/day. Six subjects (the second group) were given a mixed diet at a protein level of 0.93 (0.91-0.94) g/kg/day for three months.

TABLE 1. Physical Characteristics of the Experimental Subjects

Diet. Food ingredients of the ordinary mixed Chinese diet were selected according to the Chinese Food Composition Table of 1976. Details of food items are shown in table 2. The subjects were given three meals per day at 7.30 a.m., 12 noon and 5.30 p.m. The daily energy intake of the subjects was kept constant at about 45 kcal/kg/day, and was calculated from proximate analysis and Atwater factors. Fat provided approximately 30 per cent of the daily energy intake. Multiple vitamin supplements were given in tablets. Water was ad libitum.

Indicators and measurements. Nitrogen balance data were plotted against nitrogen intake, and regression analysis was performed to obtain the mean protein requirements and 97.5 per cent confidence limits. Nitrogen content in the diet, urine, and faeces was determined by the semi-microKjeldahl method.

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