Contents - Previous - Next

This is the old United Nations University website. Visit the new site at http://unu.edu

Protein-energy interactions

23. Energy intakes and protein requirements of adult Thai men
24. Habitual Guatemalan diets and catch-up growth of children with mild to moderate malnutrition
25. The effect of different intakes of calories on the nitrogen intake for nitrogen equilibrium with habitual diets based on corn and beans
26. Nitrogen balance and whole body nitrogen flux in children consuming dietary energy and protein around maintenance requirements

23. Energy intakes and protein requirements of adult Thai men

Kraisid Tontisirin, Kallaya Thongprasert, and Aree Valyasevi

Institute of Nutrition, c/o Ramathibodi Hospital, Rama Vl Road, Mahidol University, Bangkok, Thailand

Objective of Phase I Study

The objective of phase I study was to evaluate the adequacy of the FAO/WHO recommended "safe level" of protein intake at various levels of energy intake.

Twelve healthy village men were studied under field conditions in one village of Ubon Province, in northeast Thailand. The ages of the subjects ranged from 19 to 28 years, with a mean of 23 years, and the means of their body weight and height were 53.9 kg and 162 cm, respectively.

They were given a constant protein intake of 0.72 g/kg/day provided by sticky rice and fish in a ratio of 80:20, with an amino acid score of 87 and an assumed digestibility of 90 per cent. Five levels of energy intakes varying from 36 to 55 kcal/kg/day were studied. Each dietary period lasted for 10 days, preceded by one day on a protein-free diet. Between each dietary period the subjects received a freechoice diet at home for three days. They were also given vitamin and mineral supplements daily throughout the study. The level of energy intake of 45 kcal/kg/day was considered to be 100 per cent of requirement. A constant fat intake was provided at about 10 per cent of energy intake. N balance was performed on the last five days of each dietary period. Body weight was recorded daily, and blood samples were taken initially and at the end of each dietary period.

Tables 1 and 2 show the summary of the data from phase I study. Most subjects lost weight at all levels of energy intakes, even at the highest intake of 55 kcal/kg/day. Their energy expenditure, calculated from the records of daily activities, however, were 43 to 45 kcal/kg/day. There have been inadequate explanations for these weight losses, because energy absorption as well as fat absorption appeared normal (table 1).

At the two lower levels of energy intakes, of 36 and 40.5 kcal/kg/day, the N balances were strongly negative, being -28 and -12 mg N/kg/day, respectively. At the three higher levels of energy intakes, however, nitrogen level was approaching positive balance.

TABLE 1 Summary of Phase I Study on Energy Intakes and Protein Requirements of Adult Thai Men Given a Protein Intake of 0 72 g/kg/day

a. Each dietary period lasted for ten days, preceded by one day of a protein-free diet, and three days of a free-choice diet b Mean + SD

TABLE 2 Mean Values of Blood Constituents of Study on Adult Thai Men Fed a Protein Level of 0.72 g/kg/day and Variable Energy Intake

a Each dietary period lasted for ten days, precedent by one day of a protein-free diet and three days of a free-choice d,et.

b P < 0 05 compared with initial value

TABLE 3. Initial Characteristics of 11 Adult Village Men

a Left mid-arm circumference.

Protein digestibility was about 82-88 per cent, slightly lower than the assumed digestibility. BV and NPU were strikingly low. Serum urea N increased slightly during the lowest level of energy intake and decreased steadily with increases in energy intakes. Serum aminotransferase activities (AST and ALT) were increased slightly during the study. However, haemoglobin, haematocrit, total protein, and albumin showed almost no changes during the study, as indicated in table 2.

Because the subjects in this study lost weight during the experiments, no firm conclusions can be drawn about the adequacy of the protein intake at the "safe level" until an explanation has been found for the weight loss.

Objective of Phase II Study

The major objective of this study was to determine the cause of the weight loss during phase I study. An attempt was also made to evaluate the protein requirement of adult Thai village men given ample energy intake.

Experimental Design

Environment

The study was conducted during the period from April to June 1980 at Rai-Tai Village in Ubon Province, north-east Thailand. The means of temperature were 33.0 ± 1.8°, 29.4 ± 0.7°, and 29.0 ± 0.8° C during April, May and June, respectively. This was the summer season.

Subjects

Eleven healthy, adult village men participated in the study. The initial characteristics of the subjects are shown in table 3. The mean age was 22.3 years, weight 51.9 kg, height 162.1 cm, and left mid-arm circumference 23.3 cm. They were quite lean and without much fat reserve, as indicated by the thin tricep and subscapular skin-fold thickness values of 6.4 and 9.6 mm, respectively.

The subjects were divided into two groups according to the experimental design described in the next section.

Diet

The subjects were given the usual Thai diet consisting mainly of rice, fish. papaya salad, and green leafy vegetables. Fat intake was maintained at about 8 to 10 per cent of energy intake. The study was divided into three periods. Each period lasted for 21 days without interruption.

In period I, the diets were calculated to provide an energy intake of approximately 45 kcal/kg/day. The protein intake was 0.72 g/kg/day, provided by rice and fish, with a ratio of 80:20. However, the subjects were allowed ad libitum rice intake, while other parts of the diets were controlled. Therefore, the actual mean energy and protein intakes during the last week of this period were 56.9 kcal/kg/day and 1.06 g/kg/day. Reported energy intakes correspond to net values obtained by food bomb calorimetry minus faecal energy-loss measurements.

In period 11, the study design was similar to that in period I except for the calculated protein intake, which was 1 g/kg/day. Rice intake was again ad libitum.

During period ill, each subject was given a fixed-energy intake at the average level observed during the last 14 days of period 1. Protein intake was approximately 0.8 g/kg/day.

The subjects were divided into two groups because the sequences of the experiments were different. After completing period 1, subjects were assigned to two sequences: group I dietary protocol for period I followed by 11 and III, while group 11 began with period I followed by protocols for periods III and 11 respectively.

TABLE 4 Average of Daily Dietary Intake of Subject SB "weighed 50.1 kg) during the Last 14 Days of Each Period

a. One serving of mixed vegetables consisted of 100 g raw papaya, 100 g gourd, 50 g cucumber (without seed), 27 g watercress, 15 g tomato, 14 g garlic, 8 g onion, 17.5 g lime juice and 2 g dried chili

The details of an average of daily dietary intake for one subject (S.B.) are shown in table 4.

Neither vitamins nor mineral supplements were given to the subjects during the study.

Duration

The entire study lasted for 63 days. or nine weeks, divided into three periods, as described in the previous section.

Maesuraments Taken

1. Dietary intakes of protein, energy, and fat were calculated daily from actual measurement of food intakes. A whole day's diet sample (except rice} was analysed for nitrogen, energy (bomb calorimetry), and fat. Rice intake was analysed separately.

2. Blood samples were taken in the morning after midnight-to-morning fast at the beginning of the study and at the end of each period for measurements of haematocrit, retinol-binding protein (RBP), transferrin, and zinc.

3. Twenty-four-hour urine samples were collected during days 1-2 of period 1, day 8-9, and during the last week (third week) of each period for analysis of total N and creatinine excretions.

4. Seven-day faecal collections were carried out at the end of each period for measurements of total N, energy, and fat.

5. Body weight was recorded daily before breakfast, and other anthropometric measurements were done at the beginning of the study and the end of each period.

6. N balance was calculated from the data obtained during the last seven days of each period, with an allowance of 5 mg N/kg/day for integumentary losses.

Physical Activities

The subjects were allowed to continue their usual activities but not allowed to participate in any heavy sports. They were asked to keep a record of their daily physical activities for estimation of energy expenditure.

Main Results

The subjects maintained their body weight well during all periods of the study, even when energy intakes were changed during periods I and 11, as indicated in table 5. Initially, the energy intake was 66 kcal/kg/day, which gradually decreased to 57 kcal/kg/day during the third week of the first period. In period 11, energy intakes were also decreased significantly. from 54 to 50 kcal/kg/day. Protein intakes showed trends similar to energy intakes, varying from 1.22 g/kg/day initially to 1.02 g/kg/day during the third week of the second period. During period III protein intake was constant at a level of 0.82 g/kg/day. The energy intake of individual subjects was also kept constant. Energy intakes ranged from 47.4 to 73.6. with a mean intake of 58.0 kcal/day.

TABLE 5. Body Weight. Energy Metabolism, Fat Intake and Absorption, and Protein Intake of 11 Thai Adult Village Men

a P < 0.05; b P c 0.01; c P c 0.005; d P < 0 001 compared with initial value

TABLE 6. True N Balance (mg/kg/day) of 11 Adult Thai Village Men Fed Their Usual Diets

N intake. urinary N. and faecal N were measured during the last seven days of each period Integumentary N loss of 5 mg/kg/day was used in the calculation of true N balance.

TABLE 7. Urinary Total N (g/d) during Various Periods of the Study with 11 Thai Adult Village Men

As indicated in table 5, the estimated daily energy expenditure of the subjects varied from 43.4 to 47.5 kcal/kg/day. Energy and fat absorption were over 94 and 92 per cent of intakes, respectively.

N Balance

Table 6 shows the data on true N balance for all subjects. Ten of eleven subjects were in positive N balance during each period. The data obtained from periods I and II were almost identical: N intakes were 169 and 164; total urinary N was 91.1 and 93.4. faecal N was 46.3 and 41.1, and N balance was 26.9 and 24.2 mg/kg/day, respectively. The energy intakes, however, were about 13 per cent lower during period 11 than during period I.

In period III the level of energy intake was similar to that in period I, but protein intake was fixed at 0.82 g/kg/day, or 130.8 mg N/kg/day, which was almost 23 per cent lower than the intake during period I. All except one subject were in positive N balance.

There were no differences in N balance whether the subjects were designed to be studied in period II or III after the first period.

Table 7 shows total daily urinary N excretion measured initially during day 1 and 2 of the first period, and day 8 and 9 of all periods, compared with the data obtained from a seven-day urine collection. Except for the data in period 11, the total daily urinary N excretions were quite similar whether the collections were for two or seven days. Daily creatinine excretions measured from two- and seven-day collections were also almost identical, as shown in table 8. Table 9 shows protein-quality indices. Digestibility values varied from 80 to 84.5. The biological value and net protein utilization were around 40 to 60. and were significantly increased during period III compared with the previous periods.

Other Maesurements

The levels of haematocrit and retinol-binding protein (RBP) were within normal ranges. However, there were significant decreases from initial values in haematocrit and RBP levels during period III, as indicated in table 10. Serum transferin and zinc levels showed no significant changes during the entire study period.

TABLE 8. Average Urinary Creatinine Excretion (g/d) during Various Periods of the Study with 11 Adult Thai Village Men

TABLE 9. Protein Quality Indices of Habitual Diets Given to 11 Thai Adult Village Men

TABLE 10. Blood Constituents of 11 Adult Thai Village Men

P<0.01

Conclusions and Comments

Phase I

During study phase 1, the subjects were given a constant level of protein intake provided by rice and fish in a ratio of 80:20, with energy intakes varying from 36 to 55 kcal/kg/day. There were striking weight losses in the subjects throughout the study. They were also in negative N balance except at the highest level of energy intake.

Phase II

In study phase 11 the subjects were given similar, customary diets, but there was no one-day proteinfree diet before the beginning of each dietary period. They were also provided rice ad libitum initially. and each dietary period lasted 21 days, which was longer than the 10-day period of the previous study. The subjects in study phase 11 therefore maintained their body weights well, even when their energy intakes decreased gradually during periods I and 11. The estimated energy expenditures, based on daily records of physical activities. decreased slightly as the study went on, but the values were much lower than the measured energy intakes. This observation indicated that the estimation of energy expenditure by this method was insensitive.

Fat and energy absorption was quite satisfactory, being about 92-96 and 95-96 per cent, respectively.

Ten out of eleven subjects were in positive N balance during each period of the study. There were no significant differences in N balance whether energy intake was decreased by 13 per cent (periods I and 11) or protein intake was decreased by 23 per cent (periods I and ill). The energy intakes of the subjects in this study were strikingly high, at about 50 58 kcal/kg/day. The reason might be that they were quite lean and had little subcutaneous fatty tissue. Their major body composition consisted of active cell masses that required energy for metabolism.

Because this study was conducted in summer when the temperature varied from 29-33° C, the integumentary losses of N might have been higher than the allowance of 5 mg/kg/day. The N balance data were therefore strongly positive. However, skin losses of N were probably compensated for by decreased urinary nitrogen excretion, as reported in the study in adult Taiwanese men.'

Blood constituents, including haematocrit, RBP, transferrin, and serum zinc, measured initially and at the end of each dietary period, showed little change except for haematocrit and RBP, which decreased significantly during period ill. The reasons for these decreases are unknown, but they may reflect inadequacy of some nutrients.

In summary, the results from this study indicate that the subjects given their usual diets with ad libitum rice intake maintained N balance well when protein and energy intakes ranged from 0.82 to 1.08 g/kg/day and 50 to 66 kcal/kg/day, respectively. These levels of intake were adequate for maintaining body weight and blood constituents. Energy intakes were much higher than expected, mainly from rice. The results of this study also suggest that, in a population where rice is a dietary staple, adult men would receive adequate protein and energy if rice were freely provided and combined with other foods to make it more palatable.

Acknowledgement

This study was supported by research funds from the Danish International Development Agency (DANIDA) through FAO and WHO.

Contents - Previous - Next