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15. Long-term protein requirements of adult Filipinos consuming local diets at two levels of energy intake

Carmen Intengan

Food and Nutrition Research Institute, Manila, Philippines

Objectives

1. To conduct long-term nitrogen balance studies to see if the recommended level of protein currently used for Filipinos consuming local diets is a practical allowance, and to explore the effect of energy deficit.

2. To use other parameters besides N balance in assessing adequacy of protein intake.

3. To evaluate adequacy of energy requirement.

Experimental Design

Environment

Location: Nutrition Evaluation Laboratory, Nutritional Biochemistry Division, Food and Nutrition Research institute (FNRI), National Science Development Board (NSDB), Manila, Philippines.

Climate: Tropical

Temperature: 27-36° C (day): 26 29° C (evening)

Months: September-December 1980; January-April 1981

Subjects

Seven female adults, 21 to 35 years old, were studied for N balance and other characteristics. The average weight of the subjects was 47 kg. This falls a little above the lower limit of normal range for their mean height of 155 cm.* Based on the dietary calculation of their habitual food intake prior to the study, daily protein intake was 1.5 g/kg, which adequately meets protein needs. They were in good health, based on physical examination, urinalysis, chest X-ray, and routine blood count. Stool examination indicated very mild infestation with Trichuris trichiura (0-2 HPF) and was negative for ascaris except for one subject (see table 1).

TABLE 1. Initial Characteristics of Young Female Filipino Adults Studied for N Balance on Local Diets

TABLE 2. Composition of a Sample Diet (Subject: 50 kg, 2,000 kcal, 56 g Protein)

The subjects were all staff members of FNRI: three chemists, three nutritionists, and one food technologist, belonging to the middle socio-economic class. Their work activities were mostly routine laboratory work. The subjects were aware of the objectives of the study and of the importance of following the protocol of the study very strictly.

Diets

A five-day-cycle menu was prepared containing 1.12 9 protein per kg body-weight. Food was served in three meals and two snacks daily. A sample diet for a 50 kg female is shown in table 2. The major sources of protein are rice and fish. Approximately 60 per cent of the protein came from vegetable sources and 40 per cent from animal sources. This is in accordance with the findings of the 1978 nationwide food-consumption survey of Philippine households. Cereals contributed about 40 per cent to the total protein. The menu pattern of the five-day cycle was essentially the same, only fruits, vegetables, and snack items being varied:

Breakfast: Papaya, boiled rice, dried fish, tomatoes.
Morning snack: Broas (lady-finger), butter, kalamansi juice.
Lunch snack: Squash and white beans sauteed in pork and shrimp; rice, pomelo.
Afternoon snack: Mamon (cup-cake).
Dinner: Fish with ginger, onions, and garlic; sweet potato tops, rice, banana.

Energy content of the diet was calculated from proximate composition and Atwater factors.

The daily energy intake of the first four subjects was 42 kcal per kilogram body-weight, but towards the end of the second week of the study, the caloric intake of two subjects (G.B. and B.M.) was reduced to 40 kcal to maintain their body-weight The daily energy intake of the other three subjects was maintained at 40 kcal. The caloric intake of another subject (S.A.) was reduced by 11.4 per cent (percentage energy adequacy of Filipino diets based on latest FNRI surveys was 88.6 per cent) after eight weeks. This was a preliminary test on the effect on nitrogen retention of reduced calorie intake. In the second phase, four of the seven subjects were placed for 42 days on a 15 per cent calorie restriction while protein intake remained the same. One tablet of Unicap M containing vitamin and mineral supplements was given daily.

Water intake was ad libitum for the first four subjects. It was controlled for the last three subjects at volumes habitually taken.

Duration

Twelve weeks, or 84 days, for N balance response for all the subjects.

TABLE 3. Summary of Nitrogen Balance Data for Seven Female Subjects (mg/N/kg/day)a

Measurements Taken

Body weight was recorded daily.

Urine and faeces were collected daily except for three days during each menstrual period.

Total nitrogen in diet, urine, and faeces was analysed by the macro-Kjeldahl method.

Urine samples were also analysed for creatinine and urea.

Faecal samples were pooled at three- or four-day periods during the week, homogenized with water, and aliquots were taken for analysis. Formalin was used as a preservative.

Composites of an entire day's intake for each day of the five-day cycle menu for each subject were analysed for proximate analyses using AOAC methods.

Blood samples were drawn from the antecubital fossa every two weeks and analysed for haemoglobin, haematocrit, total serum proteins, serum albumin, and globulin.

The amino acid content of the five diets was analysed at the International Rice Research Center (IRRI).

SGOT and SGPT were analysed at the Philippine General Hospital.

In calculating the N balance, an allowance of 5 mg N per kg body weight was made for dermal losses.

Biological value (BV), net protein utilization (NPU), and true digestibilities were calculated using an obligatory urinary loss of 34.15 mg N per kg (average values of Kraisid, 34.9 and P.C. Huang, 33.4) and faecal metabolic N of 12.7 mg (average value from Kraisid, 12.6 mg, P.C. Huang, 13.1 mg and Inoue, 12.4 mg).

Statistical analyses: nitrogen balance data were computed for each two-week period. Analysis of variance was used to determine the linearity of changes in body weight and biochemical parameters.

TABLE 4. Body weight (kg) of Subjects During 84 Days of Study

Main Results

The actual nitrogen intake of the subjects showed a mean of 185 ± 4 mg N per kg body weight per day, or 1.16 9 protein. The nitrogen balance was 10 ± 3 mg (table 3).

All the subjects were in positive balance except one subject who was in negative balance on the eighth week of the study, but returned to adequacy for the next four weeks.

At the calculated energy intake of 40 kcal/kg body weight, most of the subjects were able to maintain their body-weight. One of the subjects who was given 42 kcal/kg body-weight gained 0.89 kg; another subject on 40 kcal (MJ) also gained 0.79 at the end of the study (table 4).

One subject (S.A.) who was placed on a calorie intake of 11.4 per cent less than 40 kcal/kg body weight (35 kcal) lost 0.70 kg at the end of four weeks. This subject, who was in positive nitrogen balance for eight weeks, showed zero balance after four weeks on the same level of nitrogen but at 35 kcal per kg body weight.

Values of BV, NPU, and digestibility remained essentially constant throughout the study (table 3).

TABLE 5. Summary of Weekly Nitrogen Balance Data of Four Adult Filipinos Consuming Local Diets Adequate in Protein but Limited in Calories by 15 Per Cent

At the start of the study the subjects had normal levels of haemoglobin (WHO, 1972). During the 12-week study haemoglobin concentrations decreased in one subject (P < 0.01 ) but increased in three (P < 0.01). Haematocrit values, which were also "normal," were maintained in six subjects but decreased in one (CU) (P < 0.01).

Initial serum albumin levels rated as "acceptable" in four subjects and as "low" in three (ICNND, 1963) did not change.

The amino-acid score of menus I, II, and V was 100. The limiting amino acid in menu III was tryptophan; that of IV was TSAA. The mean chemical score of the five-day menu cycle is 100.

The mild parasitic infestation of the subjects did not show any effect on the absorption of nitrogen.

Conclusions and Comments

A nitrogen balance of 10 ± 3 mg nitrogen at a mean intake of 185 ± 4 mg nitrogen per kg body weight (1.16 g protein) for a period of 12 weeks indicated that the current allowance recommended for protein (1.12 g) is adequate for Filipinos consuming local diets. At this level of protein intake, serum protein and its functions were maintained at initial levels.

TABLE 6. Mean Body Weights (kg) of Subjects During 42 Days of Study Low Calorie Intake)

From the amino-acid analysis and chemical scores of the five-day menu cycle, the 40:60 ratio of animal to vegetable protein in the Filipino diet apparently meets the FAO/WHO amino-acid scoring pattern.

At an intake of 40 kcal i 5 per cent, the subjects were shown to maintain their body weights.

Main Results of the Second Phase (15 per Cent Energy-Restricted Diet)

1. A summary of the weekly mean nitrogen balance data and body weights is shown in table 5. At the end of 42 days on a diet adequate in protein (1.12 g/kg body-weight) but limited in calories by 15 per cent, the subjects lost weight from 0.82 kg to 2.7 kg, or an average of 19 g to 64 9 per day. Data on mean body weights for each subject are presented in table 6. Two of the subjects lost more weight during the first two weeks; the other two in the third and fourth weeks. At the end of 42 days, subjects C.U. and S.A. lost more than 2 kg and were each given an additional 4 kcal/kg body weight.

2. The subjects were in negative nitrogen balance during the first two to three weeks of the study, which corresponds to the greater weight-loss of the subjects. After the third week or so, the subjects were all in positive nitrogen balance.

Under prevailing conditions in this study, it seems that the subjects could adapt and be in positive nitrogen balance despite exhibiting weight loss.

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