![]() | Protein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.) |
![]() | ![]() | Nitrogen absorption-adults |
![]() | ![]() | Absorptive capacity of adult Guatemalan rural males living under different conditions of sanitation |
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Objectives
Experimental
details
Summary of main
results
Conclusions
R.E. Schneider, B. Tor. Shiffman, C. Anderson, and R. Helms
Institute of Nutrition of Central America and Panama (INCAP), Guatemala
City, Guatemala, and Institute of Nutrition, University of North Carolina,
Chapel Hill, North Carolina, USA
This brief report summarizes the results of two studies carried out with healthy adult males from the rural Pacific lowlands of Guatemala consuming a diet qualitatively similar to that habitually eaten in that region. Some of these men lived for certain periods of time in environments with improved sanitary conditions, as described below.
1. To determine the apparent absorption of total energy, protein, and fat from the customary rural diet in: (a) military conscript males (soldiers) who were born and had lived all their life in rural Guatemala except for the two years before being studied, during which they lived in military installations with better sanitary conditions than those prevailing in their rural homes; and (b) men living in two rural communities.
2. To evaluate the effect of sanitation measures, such as the introduction of an intra-domiciliary water supply system and a sanitary education programme, on the absorptive capacity of men from one of the rural communities studied.
Hypothesis
Environmental sanitary conditions influence
the capacity of Guatemalan adults to absorb the major food nutrients present in
their habitual diet. if this is true, the soldiers should absorb the nutrients
better than men living in their rural homes.
Furthermore, the absorptive capacity of the rural men in the community where sanitary measures were introduced should also improve.
1. Absorption Studies in Soldiers
One hundred soldiers
who were born and had always lived in the lowlands of Guatemala and who had been
for two years at an army station (MZ) near Guatemala City were interviewed and
evaluated clinically. Besides being exposed during this period to improved
environmental sanitation, these men had been eating a better diet than the one
commonly eaten in rural areas. From this group 13 volunteers, 18 to 22 years
old, who fulfilled the following criteria were selected: (a) there was no
history of acute or chronic gastrointestinal diseases; (b) the result of the
physical check-up was normal; (c) there was normal urinary excretion of d-xylose
five hours after an oral dose of 25 9; and (d) two direct examinations of fresh
stools for ova and parasites proved negative. Table 1 gives the volunteers'
pertinent characteristics.
The soldiers lived for 21 days in a metabolic unit set up at the military post infirmary in Guatemala City (altitude 1,500 metres above sea level; temperature 19 to 22 C; low humidity). The experimental protocol followed was: Days 1 and 2: adaptation to the typical rural diet. Days 3 to 18: five consecutive three-day balance periods (Balances 1 to 5). Days 19 and 20 were used to complete faecal collections. A final physical check-up was done on day 21 before discharging the subjects from the unit.
2. Absorption Studies in Men from Two Rural Communities
In 1973, two villages, Guanagazapa (GU) and Florida Aceituno (FA), located in
the lowlands near the Pacific coast of Guatemala, were chosen in order to carry
out a study to evaluate the effect of introducing sanitation measures on the
absorptive capacity of their inhabitants. The villages were within one hour's
drive from Guatemala City, with a distance of 32 km between the two villages.
Their altitudes were 200 and 235 m above sea level, with an annual rainfall of
2,000 mm. Temperature was 20° C during the day and cooler at night. Their
populations of 973 for GU and 923 for FA were approximately 20 per cent Maya
Indian and 80 per cent Ladino (mixed Maya and Caucasian descent). Both
communities had water supplies of poor quality consisting of private wells and
some communal faucets.
Studies were carried out for four years in both villages, divided into three stages: (a) two years of basal studies were made (1973-1974); (b) sanitary measures were implemented in GU (test village). In December 1974 an intra-domiciliary water supply system became operative, and a sanitary education programme was started in early 1975-neither measure was implemented in FA (control village); (c) two years were spent evaluating the impact of the sanitary interventions (1975-1976).
TABLE 1. General Characteristics of the 13 Soldiers Studied
Age, years | 20.7 ± 1.2* |
Body weight, kg | 60.1 ± 4.5 |
Height, cm | 164.0 ± 4.6 |
Body surface, m2 | 1.66 ± 0.39 |
Weight/height (kg/m) | 37.0 ± 0.04 |
D -xylose, % excreted | 28.3 ± 4.6 |
Plasma proteins, g/dl | 8.1 ± 0.8 |
Haemoglobin, g/dl | 16.4 ± 1.5 |
Haematocrit, % | 49.0 ± 2.4 |
Urine analysis | Normal |
Two direct stool examinations | Negative for parasites |
Ethnic background | Maya Indian or Ladino (mixed Maya/Caucasian descent) |
* Mean ± S.D.
In 1973, 60 male volunteers aged 14 to 45 years were randomly chosen in each community among those men who had lived there at least ten years. By 1974 some had emigrated and were replaced by others of the same ages, also chosen at random, in order to study 120 men each year. The same procedure was followed in 1975 and 1976. Therefore, at the end of the four years there was a "longitudinal" group formed of men who participated one, two, or three times in the study. Table 2 gives the number of subjects in both groups each year. All were healthy at the time of the studies. Table 3 gives their characteristics. All men had mild or moderate infestations with one or more of the following intestinal parasites: Ascaris lumbricoides, Trichuris trichiura, hookworms.
Absorption studies were carried out between May and November in four consecutive years beginning in 1973. The men were housed in groups of 8 to 10 in a rural metabolic unit built adjoining the hospital of a nearby city (Escuintla) with the same climate as that of the study villages.
TABLE 2. Number of Subjects Included in the Statistical Analyses
Balance I |
Balance II | ||||||
1973 |
1974 |
1975 |
1976 |
1974 |
1975 |
1976 | |
Guanagazapa | |||||||
Longitudinal |
34 |
34 |
34 |
34 |
34 |
34 |
34 |
Non-longitudinal |
12 |
13 |
14 |
15 |
13 |
14 |
15 |
Whole sample |
46 |
47 |
48 |
49 |
47 |
48 |
49 |
Florida Aceituno | |||||||
Longitudinal |
28 |
28 |
28 |
27* |
28 |
28 |
28 |
Non-longitudinal |
18 |
23 |
23 |
26 |
23 |
23 |
26 |
Whole sample |
46 |
51 |
51 |
53* |
51 |
51 |
54 |
* One of the longitudinal subjects from FA was excluded from Balance I in 1976 due to diarrhoea.
TABLE 3. General Characteristics of the Men from Florida Aceituno (FA) and Guanagazapa (GU), 1973
FA |
GU | |
Number of men |
46 |
46 |
Body weight, kg |
50.2 ± 6.8* |
57.1 ± 9.5 |
Height, cm |
155.6 ± 6.8 |
162.5 ± 7.9 |
Body surface, m² |
1.47 ± 0.13 |
1.62 ± 0.42 |
Weight/height, kg/m |
32.0 ± 3.5 |
32.2 ± 3.1 |
D-xylose, % excreted |
18.5 ± 6.4 |
19.9 ± 5.8 |
Plasma proteins, g/dl |
6.8 ± 1.2 |
6.9 ±1.6 |
Haematocrit, % |
40.6 ± 7.7 |
44.0 ± 4.9 |
* Mean ± S.D.
The groups alternated between men of each village and they lived in the metabolic unit for five days in 1973 and for eight days in each of the following years. Metabolic-balance studies began on the day after admission; in 1973 only one three-day metabolic-balance study was performed, and in each of the following years two consecutive three-day balance studies were done (hereafter referred to as Balance I and Balance II). During the last two days, faecal collections were completed and d-xylose absorption tests were carried out.
3. Rural Diet Study
The same diets were used in the
absorption studies with soldiers and with men from GU and FA. The diet was
prepared with the foods and recipes used by the population from which these men
came, except it included certain amounts of commercial canned black beans and
more animal protein, since the men did not eat meat every day at home. Table 4
gives the amounts of food offered each day, divided into three meals. These
amounts provided 2,800 kcal (28 per cent of animal origin), 95 g protein (34 per
cent animal protein), and 35 g fat (22 per cent animal fat). The men were
encouraged, but not forced, to eat all the food served in the metabolic unit.
The maximum amount of food offered to each man from GU and FA in 1973, 1975, and 1976 provided 2,800 kcal/day, based on the mean intakes of 75 men from each village surveyed in 1972. In 1974, diets that provided 2,000, 2,400, or 2,800 kcal/day were offered during the first three days (Balance I ) to each man, depending on his personal dietary history; during the following five days (which included Balance II), food amounts equivalent to 2,800 kcal/day were offered to all men. This was done in an effort to assess the effect of the usual dietary intakes preceding admission to the metabolic unit. The proportions of nutrients offered were constant at all levels of energy intake, since the changes were achieved through proportional variations in the amounts of each food served.
4. Measurements
The amounts of each food eaten by each
man were weighed at every meal, and the nutrient intake was calculated from the
analyses of representative food aliquots. Complete urine and faecal collections
were also obtained, using carmine red as the faecal marker. Aliquots of the
foods and of the three-day stool collections from each balance period were
analysed, and their contents of total energy (bomb calorimetry), nitrogen
(macro-Kjeldahl), and fat (Van de Kamer) were used to calculate apparent
absorptions. Urinary nitrogen was also determined (macro-Kjeldahl) to calculate
apparent nitrogen
balance.
1. Soldiers
Table 5 summarizes the results of the five
consecutive three-day balance periods. One man's data were excluded from
Balances ill and IV because he had diarrhoea.
TABLE 4. Amount of Food Prepared and Offered Daily in the Metabolic Unit, in Grams
Cooked beans* | 307 |
Fried beans* | 40 |
Corn tortilla | 570 |
Rice | 200 |
Bread | 45 |
Sweet rolls | 66 |
Meat | 1 07 |
Cheese | 1 09 |
Chayote** | 100 |
Squash | 68 |
Carrots | 66 |
Sugar | 37 |
Total energy 2,800 kcal
Total protein 95 9 = 380 kcal (13.6% energy)
Total protein 95 9 = 380 kcal (13.6% energy)
Total fat 35 9 = 315 kcal (11.2 % energy)
* Black beans: Phaseolus vulgaris.
** Chayote: Sechium edule.
TABLE 5. Guatemalan Soldiers: Results of Metabolic-Balance Studies in Five Consecutive Three-Day Periods (Mean + S.D.)
Measurement |
Three-day balance periods | Average of balance periods II-V | Least significant difference** | ||||
I (13)* | II (13) | III (12) | IV (12) | V (13) | |||
Body weight, kga | 62.27 ± 3.08 | 62.77 ± 3.02 | 63.30 ± 2.91 | 62.47 ± 2.98 | 63.21 ± 2.94 | 62.94 ± 2.89 | 0.17 |
Stool weight, g/3 days | 789 ± 303c | 627 ± 291b | 633 ± 255b | 660 ± 273b | 630 ± 261b | 636 ± 261b | 60 |
Nitrogen, mg/kg/day | |||||||
Intake | 289 ± 14 | 285 ± 14 | 286 ± 13 | 286 ± 14 | 285 ± 13 | 285 ± 13 | |
Faecal | 60 ± 16C | 40 ± 20b | 43 ± 20b | 46 ± 20b | 37 ± 14b | 41 ± 18b | 11 |
Urinary | 200 ± 27 | 193 ± 21 | 213 ± 33 | 194 ± 29 | 216 ± 23 | 204 ± 28 | |
Apparent | 30 ± 20b | 52 ± 22c | 30 ± 31b | 47 ± 24c | 32 ± 25b | 40 ± 27 | 15 |
Apparent absorption, % | 79 ± 5b | 86 ± 6c | 85 ± 6c | 84 ± 6c | 88 ± 5c | 86 ± 6c | 3.8 |
Energy, kcal/kg/day | |||||||
Intake | 50 ± 3 | 50 ± 2 | 49 ± 2 | 50 ± 2 | 49 ± 2 | 49 ± 3 | |
Faecal | 6 ± 3c | 4 ± 2b | 4 ± 2 | 4 ± 1b | 4 ± 2b | 4 ± 2b | 1.4 |
Apparent absorption, % | 89 ± 5b | 93 ± 4c | 92 ± 3 | 92 ± 2c | 93 ± 5c | 92 ± 4c | 3.0 |
Fat, mg/kg/day | |||||||
Intake | 556 ± 27 | 583 ± 28 | 515 ± 23 | 586 ± 28 | 547 ± 25 | 558 ± 38 | |
Faecal | 87 ± 32 | 88 ± 34 | 80 ± 28 | 71 ± 27 | 68 ± 31 | 70 ± 32 | |
Apparent absorption,% | 84 ± 6 | 85± 3 | 84 ± 5 | 88 ± 5 | 88 ± 6 | 86 ± 6 |
* Number of men in parentheses. ** L.S.D. shown only when groups differed by
analysis of variance, p < 0.05.
a Linear tendency to gain weight with
time. b Lower than values with superscript c, P <0.05..
2. Rural Men
TABLE 6. Guatemalan Rural Men: Results of Metabolic-Balance Studies after Three Days in the Metabolic Unit (Balance I I, Longitudinal Group) and Comparison with Soldiersa
Measurement |
FA1974 |
GU1974 |
FA1976 |
GU1976 |
MZ11 |
Body weight, kg |
50.35 ± 5.67c |
58.86 ± 10.39 |
51.02 ± 5.51 |
60.69 ±10.53 |
62.77 ± 3.02 |
Stool weight, g/3 days |
1,056 ± 442 |
776 ± 238 |
928 ± 442 |
759 ± 229 |
627 ± 291 |
Nitrogen, mg/kg/day | |||||
Intake |
324 ± 46 |
300 ± 62 |
329 ± 42 |
303 ± 49 |
285 ± 14 |
Faecal |
83 ± 32 |
70 ± 29 |
71 ± 24 |
44 ± 20 |
40 ± 20 |
Urinary |
194 ± 40 |
171 ± 51 |
220 ± 37 |
225 ± 46 |
193 ± 21 |
Apparent balance |
59± 62 |
79 ± 25 |
34 ± 39 |
31 ± 26 |
52 ± 22 |
Apparent absorption, % |
75 ± 8 |
77 ± 8 |
78 ± 9 |
84 ± 6 |
86 ± 6 |
Energy, kcal/kg/day | |||||
Intake |
57 ± 8 |
53 ± 10 |
56 ± 6 |
49 ± 8 |
50 ± 2 |
Faecal |
7± 3 |
5± 2 |
6± 3 |
3± 1 |
4± 2 |
Apparent absorption, % |
88 ± 5 |
90 ± 3 |
89 ± 6 |
95 ± 2 |
93 ± 4 |
Fat, mg/kg/day | |||||
Intake |
702 ± 78 |
589 ± 106 |
574 ± 60 |
573 ± 89 |
583 ± 28 |
Faecal |
150 ± 51 |
115 ± 45 |
96 ± 46 |
54 ± 26 |
87 ± 34 |
Apparent absorption, % |
79± 6 |
81± 6 |
84± 7 |
91± 7 |
85±3 |
TABLE 7. Comparisons between the Second Metabolic-Balance Periods Rural Men (FA and GU,1974 and 1976) and Soldiers (Mz)a
FA-1974 Compared with |
GU-1974 Compared with |
GU-1976 Compared with | |||||||
GU | FA | GU | GU | FA | FA | ||||
1974 | MZ | 1976 | 1976 | MZ | 1976 | 1976 | MZ | 1976 | |
Stool weight, 9/3 days | **b | ** | - | ** | - | - | - | - | - |
Apparent absorption | |||||||||
Nitrogen | - | ¯ ** | - | ¯ ** | ¯ ** | ¯ ** | - | - | ** |
Total energy | - | ¯ ** | - | ¯ ** | ¯ ** | ¯ ** | - | - | ** |
Fat | - | ¯ ** | ¯ ** | ¯ ** | ¯ ** | ¯ ** | - | *** | ** |
Nitrogen balance, mg/kg/day | |||||||||
Intake | - | ** | - | - | - | - | ¯ * | - | ¯ * |
Faecal | - | ** | - | ** | ** | ** | - | - | ¯ * |
Urinary | - | - | ¯ ** | ¯ ** | - | ¯ ** | ¯ ** | * | - |
Balance | - | - | - | * | ** | ** | ** | ¯ * | - |
a From data shown in table 6.
b Mean values were higher ( ) or lower (
¯ ) based on student's grouped ''t" test with p < 0.05 (*) or 0.01
(**).
The results indicate that adult men from rural areas of a developing country who live under conditions of poor sanitation, without appropriate use of potable water, and who eat diets largely based on corn and black beans with some animal protein and low fat (about 11 per cent of total energy intake) have apparent absorptions of the order of 90 per cent of total energy, 75 to 80 per cent of protein, and 75 to 85 per cent of fat. It is also evident that these men's absorptive capacity improves after they have lived for two years in environments with better sanitation and have modified their hygiene habits through education. Their apparent absorptions become about 93 per cent of total energy, 85 per cent of protein, and 90 per cent of fat.
If we assume faecal obligatory losses of 12 to 14 mg N/kg/day, the "true" nitrogen digestibilities would be about 5 per cent higher than apparent digestibilities.
The diets used in this study were typical of the region, although their protein content (P% about 13.6 ) and the contribution made by protein of animal origin (about 34 per cent of total protein) were higher than those in the diets of most men of similar ethnic, cultural, and socioeconomic conditions in other parts of the country. It is conceivable that protein absorption may be somewhat lower in the latter, whose diets have a P% closer to 10 than 13, with animal proteins contributing only 20 to 25 per cent to the total.
The results obtained also indicate that future research studies involving measurements of absorptive capacity in rural subjects should allow about five days of dietary adaptation before starting the metabolic-balance studies.
Acknowledgements
These studies were done as part of a project carried out jointly by the University of North Carolina and INCAP with the economic support of the US Agency for International Development. The United Nations University contributed support for the last stages of data analysis.