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Seasonal Variation in the Nutritional Status of the Jarawas
by Ramesh Kumar Sahani
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Table of Contents
1. Abstract 2. Introduction 4. Bibliography |
Two of the four tribal groups living in the Andaman group of islands, the Great Andamanese and the Onges, came in contact with outsiders some time ago while the Jarawa did so only recently.
Contact with outsiders changed food habits. The Jarawas started consuming non-traditional food items, mostly coconut and banana, from 1974 onwards. More recently, they have started going to go the neighbouring settler villages. The reasons for such visits have been argued, but the most popularly held view among administrators and settlers was scarcity of food in the Jarawa habitat.To assess availability/scarcity of food, as well as to see the seasonal variation in nutritional status, a study was designed and conducted over one year year in six different locations.
Anthropometric measurements and indices related to nutritional assessment varied during different phases, but the differences were not significant. Though thinness (i.e. chronic energy deficiency) is observed, it is not due to shortage of ressources. When Jarawas were forced to live sedentary lives with a changing diet pattern for a few days, it resulted in drastic increase of body weight. Considering the overall leanness of the Jarawas, especially of males, and the physical activity level, the cut-off value for assessing under-nutrition can be considered lower for the Jarawas. If so, the findings suggest that there was no scarcity of food among the Jarawas during the study period.
Two of the four tribal groups living in the Andaman group of islands, the Great Andamanese came in contact with outsiders more than a century ago while the Onge did so less than half a century ago. The Jarawas came in contact with outsiders only very recently while the Sentinelese still keep themselves isolated even today.
Contact with outsiders changed the food habits of the Great Andamanese and the Onges to different degrees. The Jarawas started consuming non-traditional food items, mostly coconut and banana, which were given to them from 1974 onwards by visiting contact parties entering their territory. More recently the Jarawas have started going to the neighbouring settler villages. The reasons responsible for such visits have continuously been argued. The most popularly held view among the administrators and neighbouring settlers has been scarcity of food items in the Jarawa habitat. To assess availability/scarcity of food, a study was designed and conducted through one year in six different phases.
There were certain limitations to the study. We were not able to collect dietary information for twenty-four hours since we could not stay with the Jarawas during the night for certain reasons. We could stay with them for five to six hours a day on an average. We did not follow them to different parts of the forest or to coastal areas, but preferred to stay back at their camps. Weighing the foraged items, estimation along with recall methods were used. In addition, nutritional anthropometry was also used.
2.1. Subjects and methods
The subjects for the present study were some Jarawa males and females, who were measured in six different phases at an interval of more than two months. Due to the nomadic way of life of the Jarawas, despite all our efforts, the same individuals could not be measured during each phase. Table 1 shows the number of individuals measured in different phases. The largest number of individuals could be measured during the first phase in February 2000, when 17 adult males and 18 adult females were measured. Measuring efficiency was lowest during the fourth phaseduring September 2000, when 8 males and 9 females could be measured. Individuals who could be measured during the course of the study totalled 27 females and 20 males.
Anthropometric measurements were taken according to the method suggested by Martin and Saller (1957), Singh and Bhasin (1968). Body weight was measured using a portable weighing machine with a minimum reading of 0.5 kg and skin fold/fat fold measurements were taken with Holtain skin fold caliper having a minimum value of 0.1 mm. Steel tape having a minimum reading of 1 mm was used for circumferential measurements. The measurements considered here include body weight, stature, calf circumference, mid-upper-arm circumference (MUAC), fat-fold at triceps and sub-scapular region.
Considering the kind of activities that the Jarawa normally indulge in and the relationship of those activities with energy expenditure, the following indices were used to assess their nutritional status:
1. Body Mass Index (BMI)
2. Percentage body fat and fat free mass, which were predicted by using the prediction equation of Black et al (1983) and Hume & Wyre (1971)
3. Mid upper arm fat area and muscle area were calculated using the formulae of Gurney and Jelliffe (1973) and Heymsfield et al (1984).
4.Basal metabolic rate (BMR) was predicted by the equation of Schofield (1985) and the total energy requirement was estimated as per FAO/WHO (1957) recommendations (daily requirement of an individual in normal physiological condition is 152X (W) 0.73 kilocalorie of energy. As that is the requirement of an average sedentary person, we have added 15% value for the Jarawa males and 10% for the Jarawa females to compensate for the additional demand of energy due to their nomadic way of life.
5.The physical activity level was measured by dividing the total energy expenditure or requirement by the basal metabolic rate (since we are not able to measure total energy expenditure so it is considered that requirement is equal to expenditure).
Table 1. Number of individuals measured.
|
Phase and duration |
Male |
Female |
|
1 - February 10-20, 2000 |
17 |
18 |
|
2 - April 13-22, 2000 |
12 |
10 |
|
3 - July, 2000 |
12 |
11 |
|
4 - September, 2000 |
8 |
9 |
|
5 - November-December, 2000 |
15 |
12 |
|
6 - January 24-February 3, 2001 |
12 |
13 |
Table 2. Sample measured in different phases
|
Number of times |
Male |
Female |
|
1 |
0 |
4 |
|
2 |
1 |
10 |
|
3 |
8 |
9 |
|
4 |
8 |
1 |
|
5 |
2 |
4 |
|
6 |
1 |
0 |
|
Total |
20 |
28 |
The variables related to nutritional assessment were observed to vary during different phases due to values of the non inclusion of same individual in the sample as well as due to the sample size. Availability of resources also varied during the whole period of study. It is well known that populations dependent on hunting-gathering and pastoral economy experience greater variation in availability of food resources than agriculturalists (Ulizasjek 1992). However, differences in anthropometric measurements and indices from any two phases were not significant (Table 3 and the graphs). Body weight is the most important indicator of health and nutritional status of an individual or a population. The lowest mean bodyweight for males was found to be 44.50 kg (in January 2001) and the highest was 49.86 kg (in September 2000). In case of the females the lowest mean was 40.15 kg (in April 2000) and the highest value was 46.89 kg (in September 2000). The mean body weight showed maximum value in September 2000 for both sexes, while the minimum value was noted in November 2000 for the males and April 2000 for the females. Stature is the most important linear measurements for assessment of growth and nutrition. For the males the mean value of stature varied from 151.59 cm (November 2000) to 153.43 cm (April 2000). In case of the females it varied from 144.43 cm (April 2000) to 143.08 cm (September 2000). Minimum and maximum values for stature for the females were 134.1 cm and 150. 8 cm. The same for the males were 144.1 cm and 160.1 cm. The minimum body weight found among the males was 35 kg and that for the females was 32 kg. The maximum value among the males was 63 kg (recorded in April 2000), whereas it was 61 kg in case of the females (November 2000).
MUAC is another important indicator of nutritional status. Studies shows that MUAC show a slight increase up to the age of 40 years and then it starts decreasing. "From a regression of BMI versus MUAC, it was estimatedthat theaverageMUACis about24 cm in peoplewithBMI< 18.5 kg/m2. It is likely that, at a BMI of less than 18.5 kg/m2, individuals with MUAC greater than 24 cm &endash; a group that probably includes a large proportion of "thin but healthy people" &endash; will fare better than those with a smaller MUAC" (WHO1995: 367). The mean value of MUAC ranges from 24.15 cm to 25.07 cm among the males and 22.69 cm to 25.25 cm among the females. The minimum and maximum value for the males are 20.5 cm and 28.8 cm, while for the females the values are 18.5 cm and 29.7 cm.
Calf circumference also is an indicator of nutritional status. The mean value of calf circumference for the males was more than that of the females. The minimum value was 25.7 cm for the males and 25.1 cm for the females while the maximum value was 36.3 cm and 36.1 cm for the males and females respectively.
Skin fold measurements are used to assess thickness of subcutaneous tissues. Used independently, however, they are of limited value for assessing the degree of wasting because they fail to take into account change in muscle mass. But such measurements become more useful in combination with some other measurements like MUAC to estimate total body fat, arm muscle area and arm fat area. Use ofskin fold measurements, especially of triceps and arm fat area in assessment of nutritional status is based on the assumption that increased subcutaneous fat resulting from either high calorie intake or low energy expenditure or reflect a greater calorie reserve (Young and Sevenhuysen 1998; Pucciarelli et al 1993).
Generally a significant difference between skin fold measurement of males and females is expected. Among the Jarawas the mean values for fat fold have always been found to be significantly more in females than in the males; even the mean value for females is double than that of the males. The mean value of fat fold at triceps ranges in different phases from 6.85 mm to 7.76 mm, whereas in females it remained more or less constant (15.03 mm to 15.08 mm). The minimum value among the males and the females are 4.1 mm and 4.4 mm. While among the males the maximum value is 3 to 4 times more than the minimum value, it is about 7 to 8 times more in case of the females. The sub-scapular fat fold shows a similar trend with the triceps, only difference being the minimum mean value is more than that for the triceps and the difference between minimum and maximum values is not so wide. The minimum and maximum values for the females are 6.0 mm and 28.6 mm; that for the males are 5.8 mm and 15.0 mm. The mean value for the females ranges from 12.99 mm to 14.42 mm, for the males it was between 8.28 mm and 9.28 mm.
Total body fat was estimated from the percentage body fat. The mean value was found to vary between 6.51 kg and 8.68 kg for the males, between 9.30 kg and 12.81 kg for the females, with a minimum individual value of 3.91 kg among the males and 5.71 kg among the females. The mean value of percentage body fat was always more in females than in males. In females it was always more than 22%, whereas in males it was between 14.52% and 17.22%. The total body fat content found among the Jarawas suggests a balanced state of physique.
Body size, body composition, muscle mass and physical activity level are closely related (Malina 1994). Reduction in body size and wasting of muscle mass are the major factors causing low physical fitness (Benefice & Malina 1996). The measure of muscularity was employed as a general index of nutritional status and growth in developing countries (Frisancho & Tracer 1987; Strickland & Ulizasjek 1994). Himes et al (1980) stressed how fat areas can help to understand change with age or with sex difference in adiposity.
They have shown, fat areas may increase with age, while fat folds may decrease. The mean value of arm fat area ranges from 8.23 cm2 to 9.34 cm2 in males and 16.33 cm2 to 17.75 cm2 in females, with a minimum value of 4.86 cm2 for males and 4.29 cm2 for females. The mean value of arm fat area is more in females than in males.
Upper arm muscle is considered by some to be a good indicator of volume associated with the mass of skeletal muscle. MUAC and triceps skin fold are essential components for computing the same. Heymsfield (1984) has shown, if the bone corrected arm muscle area is reduced to 9-10 cm2 , it can be considered as a pointer of imminent death due to inanition. It is mostly used for clinical purposes. Upper arm muscle area was employed by several authors to evaluate organic protein pool (Frisancho 1974; Sann, Durand, Picard & Bethenod 1988; Driscoll & Bristrian 1994), which is based on the linear correlation between the body muscle mass and the organic protein pool (Heymsfield et al 1982; Friedman 1991). The mean value, as expected, is always more in males than in females. The mean value ranges from 41.26 cm2 to 42.58 cm2 in males and 28.86 cm2 to 33.48 cm2 in females, while the minimum value is 32.20 cm2 among the males and 21.89 cm2 for the females. So the minimum value of bone corrected upper arm muscle area is 22.20 cm2 in males and 11.89 cm2 in females, which does not show much critical condition; but the minimum value of upper arm muscle area for the females is close to the critical value. Similarly, the minimum value of upper arm fat area is 4.85 cm2 and 4.29 cm2 for the males and the females respectively.
Body mass index (BMI) is the most commonly used indicator of nutritional assessment and it is often considered to be independent of age. But it is evident that BMI increases slightly with increase of age even in adults.However, adult persons having different body shape, particularly those with legs shorter or longer than the expected value of height, may not follow the expected pattern of BMI. Nutritional status of athletes can not be assessed with the help of this index, as in their case the rate of energy expediture is very high. The mean value of BMI for the Jarawas ranges from 19.24 kg / m2 to 21.35 kg/m2 among the males and 20.04 kg/m2 to 21.84 kg/m2 for the females. The minimum value found among the males was 15.84 kg/m2 and the same among the females was 16.02 kg/m2, whereas the maximum value was 25.50 kg/m2 among the males and 27.04 kg/m2 among the females.
Table 4 shows the distribution of BMI in different categories according to WHO (1995). The BMI of only one male person was in the severe thinness category. The BMI of the Jarawas from 58% to 80% in males and from 50% to 90.90% in females come under the normal category. The overweight category was found during one phase among the males. In males it was 16.66% and in females it was between 5.55% and 22.22%. The remaining values were in the moderate to mild thinness categories.
It is necessary to estimate energy requirement and the physical activity level to assess nutritional status. The range of total energy requirement is from 2790.48 to 3030.6 k/cal for males and 2584.90 to 2894.19 k/cal for females. As has been mentioned, the value estimated here is in the excess of 15% for males and 10% for females from the actual value estimated by the equation.
"Measurements of Basal Metabolic Rate (BMR) is theoretically simple, but difficult in practice" (Ulizasjek 1992). Though it is not always possible to measure BMR, it can be predicted from body weight and some other physical characteristics like stature or surface area. Some of those equations for the prediction of BMR have some shortcomings. The Harris and Benedict (1919) equations are widely used in USA and have been found to over-predict the BMR of healthy adults below the age of 50 years by 9% to 15% (Clark & Hoffer, 1991; Daly et al 1985; Owen et al; 1987). The Schofield (1985) equation was adopted for international use (FAO/WHO/UNU 1985) and was seen to predict successfully BMR of Western subjects, but over-predicted BMR of a wide range of non-western population (between 1% and 22%) (Henry& Rees 1991).In case of African subjects the over-prediction value was 6.5%. The range of the mean value of BMR for the Jarawas was from 1254.94 to 1325.10 k/cal for males and 1034.00 to 1114.62 k/cal for females. The minimum and maximum value for males were 1144.55 and 1276.91 k/cal and for females it was 935.50 and 1111.14 k/ cal respectively.
"Physical activity level is generally considered to be an important indicator in assessing how an individual/population adapts to its environment. Physical activity can be quantified by measuring daily energy expenditure and qualified by determine daily time allocation. Studies of energy expenditure in free-living conditions have been conducted in many populations in developing countries across the world, but those conducted in subsistence societies remain limited" (Ferro-Luzzi & Martino 1996, cf Xamauchi, Umezarki & Ohtsuka 2000). Ferro-Luzzi & Waterlow (1988) have proposed a classification on the basis of two variables, BMI and Physical Activity Level (PAL) for assessment of under-nutrition. The mean value of PAL ranges from 2.22 to 2.59 in males and 2.49 to 2.59 in females and the values come under 'heavy' category. When PAL is calculated without adding the excess value of energy requirements, it indicates the same level of PAL. At individual level, however, the value for only one individual male comes under moderate level of PAL.
Table 3. Variables and indices related to nutritional assessment
(not supplied)
Table 4. Body Mass Index of the Jarawas
(not supplied)
Graphics based on Tables 3 and 4:
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