FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS	ESN:FAO/WHO/UNU EPR/81/42 August 1981
	WORLD HEALTH ORGANIZATION
	THE UNITED NATIONS UNIVERSITY

Provisional Agenda Item 4.1.5

Joint FAO/WHO/UNU Expert Consultation on
Energy and Protein Requirements

Rome, 5 to 17 October 1981

ADJUSTMENT OF REQUIREMENTS FOR OBSERVED GROWTH AND ANTHROPOMETRIC DATA

by

J.C. Waterlow
London School of Hygiene
and
Tropical Medicine
London

If children are underweight or underheight for their age, we have to consider, first, the effect on their individual requirements; secondly, the effect on recommendations for the intakes of groups, i.e. the effect on policy.

Everyone would accept that a child who is significantly underweight for his height (wasted) ought to be brought into the normal range of weight for height. Whether it is equally desirable that a stunted child should reach normal height for age is a more controversial question, since it may be argued that stunting is a successful biological adaptation (see working paper on Adaptation). For the purpose of the present paper I assume that it is desirable for the growth potential to be fully expressed; therefore we need to know the requirements to meet this objective.

1. Individual Requirements

To analyze the requirements of undersize children it is useful to distinguish separately the requirements for catch-up from wasting and from stunting, although the two conditions usually go together in varying degrees.

1.1 Catch-up from Wasting

We know from studies on malnourished children in hospital that once appetite is restored, if food is given ad libitum, very rapid rates of catch-up in weight are possible, up to 20g/kg/d (Waterlow et al.,1976 ). When normal weight for height is achieved food intake and rate of weight gain fall off (Ashworth, 1975). However, hospital conditions are artificial. It has been reported that rates of gain up to 5 times the normal for the age can be achieved in the home ( UNU, 1979). Since we are concerned here with the needs of moderately malnourished children, such as are found in the community, and whose home conditions are average rather than optimal, it might be reasonable to take 3 g/kg/d as a target for catch-up, and to consider the requirements for meeting it.

Table 1 shows the time needed for a moderately undernourished child ( -3 SD weight for age) to regain median weight at this rate, assuming (a) that the child's height is normal for his age - i.e. that he is wasted only; or (b) that he is moderately stunted as well ( -3 SD height for age). I assume further that the aim is to lay down balanced tissue containing 20% protein and 25% fat. In round figures the energy cost can be taken as 5 kcal /g gain ( see working paper on Energy Cost of Growth).

Table 2 shows the daily increments of energy and protein needed to meet the target, and the average P/E ratios. The increase in the requirement for protein is much greater than that for energy. I am aware of the criticisms of the use of P/E ratios for expressing relative protein and energy requirements; however, it is a con- venient way of making the point that relatively more protein than energy is needed for catch-up growth, and gives some indication of how much more.

Tables 1 and 2 are concerned with pre-school children from 1–3 years, since this is the age-range when significant deficits in attained weight and height are most common and obvious. However, it has been argued that faltering in the rate of growth may start much earlier, at 2–3 months, although it takes several months more to show up as a significant deficit (Waterlow et al., 1980). Table 3 shows the proportion of energy and protein requirements used for growth in young infants at two levels of weight gain, normal and 70% of normal. The extra intakes needed to prevent a mild degree of faltering are quite small. Such deficits could easily result from anorexia consequent on infection (Martorell et al., 1980 ).

2.2. Catch-up from stunting

It is difficult to discuss this subject adequately because it is possible that the requirements for ‘normal’ linear growth may not be fully met by the requirements for gain in weight, calculated in the conventional way. More protein may be needed, or more good quality protein (Graham et al., 1981 ). Fomon et al. ( 1977 ) found that in infants fed a skim milk formula growth in length was satisfactory even though energy intake was low. Lampl et al. (1978) reported that in New Guinea schoolchildren a protein supplement produced catch-up growth in height, whereas an energy supplement did not. The fact that the relative prevalences of wasting and stunting differ somewhat in different communities (Waterlow, 1978 ) suggests that the factors limiting tissue and skeletal growth may be to some extent independent. It is unknown whether the limiting factor for the former is protein or some other nutrient such as calcium or zinc.

In this situation all we can do is to assess the requirements for the gain in weight which should be associated with a given gain in height, if a normal weight-height relationship is main- tained. The first question then is: what rate of catch-up in height can reasonably be expected? Graham & Adrianzen (1972) reported that marasmic children, initially below the US 3rd centile for height, who were discharged from hospital to good homes, had after several years reached the 25th centile. Prader (1978) has published data on the rate of catch-up of children with coeliac disease after being put on a gluten-free diet. One child grew from 65 cm at 1.7 years to 93 cm at 3.2 years - a truly astonishing rate of catch-up. This represents moving from a position of - 6 SD below median almost to median height in 1½ years, or a gain of 4 SD units per year. Many of the children described by Prader gained in height at the rate of 2 SD units per year, under home conditions which were presumably good. This seems a reasonable rate of catch-up at which to aim.

Table 4 shows the weight gain appropriate for this rate of gain in height in children whose height was initially - 3 SD units below median (approximately equivalent to 85% of reference height for age). Because catch-up in height is slow, the corresponding daily gain in weight is small compared to that expected in children recovering from wasting. Nevertheless, for the 1 year old child the additional protein required for this extra growth represents an increment of some 20% above its requirement if it were not catching up.

1.3. Catch-up after infection

Recent studies have concentrated mainly on diarrhoeal disease as the commonest infection of young children. Other infections which have been less thoroughly studied from the nutritional point of view, e.g. malaria and measles, may have more profound and prolonged effects. As far as concerns diarrhoea, it is possible to make a rough estimate of the nutrient requirements for catch-up.

According to Rowland et al. ( 1977 ) each day infected produces on average a deficit in net weight gainof 3 g/kg body weight. In the Gambia during the rainy season children are reported as infected on average for 13% of the time; the figures from Guatemala are similar. If we take as a ‘worst case’ a child infected for 20 days out of 100, the growth deficit over 100 days is 20 × 3 = 60 g/kg. This has to be made up in 80 uninfected days, so there must be provision for catch-up at the rate of 60/80 = 0.75 g/kg/d. From the values given previously, this corresponds to an extra daily requirement of (0.75 × 5) = 3.75 kcal/kg/d, and (0.75 × 0.2 × 1.3) = approx. 0.2 g protein/kg/d. If the normal daily requirement is taken as 100 kcal and 1.25 g protein /kg, the extra needed for catch-up represents a negligible increase in energy but a 16% increase in protein.

One can make a similar calculation from the results of Martorell et al. (1980) on the effect of infection on food intake. Suppose that the child when not infected is receiving its ‘normal’ energy and protein requirements as above, but when infected its food intake drops by 40%; suppose also that, as before, it is infected 20% of the time: then, by the same kind of calculation as before, the extra requirement per day uninfected will be 10 kcal and 0.3 g protein /kg, equivalent to increases of 10% for energy and 24% for protein.

From the mean of these two estimates, the ratio of average protein to average energy requirement would rise from 5.0 to 5.6% - for what such a figure is worth.

2. Implications for Groups and for Policy

The figures I have given are a few examples out of an infinite possible range. It is therefore very difficult to draw any precise conclusions about policy. The question at issue in this paper is: what modifications should we propose to recommended protein and energy intakes to allow for the very large number of children in developing countries who are underweight for their age? I emphasize underweight because recommended intakes are conventionally based on weight. I suggest that three complemntary and overlapping policies are needed.

2.1. Growth faltering in the first year

Faltering in growth often begins early in the first year (Waterlow & Rutishauser, 1974; Waterlow et al., 1980). The danger period is when breast milk begins to be inadequate and supplementary feeding is first needed. It has been suggested that current estimates (FAO/WHO, 1973) of energy requirements during the first year may be too high by about 10 kcal/kg/d (Whitehead & Paul, 1981). The present estimate of the safe level of protein intake between 3 and 6 months, based on Fomon's findings in infants fed breast milk ad lib., is 1.85 g/kg/d. If a baby is getting 90 kcal/kg/d from breast milk, its daily protein intake will be about 1.45 g/kg (assuming that breast milk protein, calculated as N × 6.25, is about 1.1 g/100 ml). It is difficult, therefore, to argue that the present recommendation for this age group is too low. It may, indeed, be slightly too high, for protein as well as for energy.

However that may be, it is clear that infants who are faltering are not getting what they need, though whether the primary cause is inadequate food or infection, we do not know. I suggest that there is little to be gained by altering the recommendations for young infants. What is necessary is to find out why they are not met. Without this knowledge it is impossible to specify in a rational way what should be done to prevent faltering in the first year.

In what follows I assume that the prevention of faltering has not been successful, and that we have to deal with the consequences of it.

2.2. Rehabilitation of wasted children

In general, wasting is commonest towards the end of the first year and in the second year of life. From the available evidence, the prevalence of significant wasting (weight for height less than 80% of reference, or less than - 2SD from the median) is quite variable in different communities, and seldom rises above 20% even in those who are severely affected. Because a wasted child is at increased risk of death, action has to be taken directed towards that individual child. Since, however, such children are in a minority, it seems reasonable to suggest, as a second leg of policy, that their rehabilitation should be regarded as a therapeutic activity, based on primary health care centres. The requirements for such rehabilitation have already been discussed (section 1.1).

2.3. Provision for catch-up of stunted children

The position with stunting is rather different. In some communities 30–50% of children below 5 years are judged to be stunted (less than 90% of reference height for age or less than - 2 SD from the median). When such a large proportion are affected, it becomes appropriate to recommend measures directed towards the population as a whole.

From the figures in table 4 I am inclined to suggest that for such populations the requirements for this age-group (1–5 years) should be increased by 20% for protein and 10% for energy. This should meet the requirements for skeletal growth, if protein is indeed the limiting factor, and should also provide for catch- up after infections.

It is probable that in practice the major difficulty will not be specifically to provide the extra protein, but to ensure that the child's total food intake is adequate.

References

Ashworth, A. (1975). Regulation of weight and height during recovery from severe malnutrition. Proc. 9th Int. Cong. Nutr., Mexico, 1972. Vol. 2, pp. 280–285. Karger, Basel.

FAO/WHO (1973). Energy and protein requirements. Report of a Joint FAO/WHO Ad Hoc Expert Committee. FAO Nutrition Meetings, Rep. Ser. No. 52.

Fomon, S.J., Filer, L.J., Ziegler, E.E., Bergmann, K.E. and Bergmann, R.L. (1977). Skim milk in infant feeding. Acta Paediatrica Scand., 66, 17–30.

Graham, G.G., and Adrianzez, T.B. (1972). Late “catch-up” growth after severe infantile malnutrition. Johns Hopkins Med. J., 131, 204–211. Graham, G.G., Creed, H.M., MacLean, W.C., Kallman, C.H., Rabold, J. and Mellits, E.D. (1981). Determinants of growth among poor children nutrient intake-achieved growth relationships. Am. J. Clin. Nutr., 34, 539–554.

Lampl, M., Johnston, F.E. and Malcolm, L.A. (1978). The effects of protein supplementation on the growth and skeletal maturation of New Guinean school children. Ann. Human Biol., 5, 219–227. Martorell, R., Yarbrough, C., Yarbrough, S. and Klein, R.E. (1980). The impact of ordinary illness on the dietary intakes of malnourished children. Am. J. Clin. Nutr., 33, 345–354.

Prader, A. (1978). Catch-up Growth. Postgrad. Med. J., 54, Suppl. 133–143.

Rowland, M.G.M., Cole, T.J. and Whitehead, R.G. (1977). A quantitative study into the role of infection in determining nutritional status in Gambian village children. Br. J. Nutr., 37, 441–450.

United Nations University (1979). Protein-Energy Requirements under Conditions prevailing in Developing Countries: Current Knowledge and Research Needs. WHTR-1/UNUP-18. Tokyo.

Waterlow, J.C. (1978). Observations on the assessment of protein-energy malnutrtion with special reference to stunting. Courrier, 28, 455– 460.

Waterlow, J.C., Ashworth, A. and Griffiths, M. (1980). Faltering in infant growth in less developed countries. Lancet, ii, 1176–1178.

Waterlow, J.C., Hill, A. and Spady, D.W. (1976). Energy costs and protein requirements for catch-up growth in children. In: Early Nutrition and Later Development. Ed. A.W. Wilkinson. Pitman, Tunbridge Wells.

Waterlow, J.C. and Rutishauser, I.H.E. (1974). Malnutrition in man. In: Early Malnutrition and Mental Development. Eds. Cravioto, J., Hambraeus, L. and Vahlquist, Bo. Swedish Nutrition Foundation Symposia XII. Almqvist & Wiksell, Stockholm.

Table 1. Time (days) to achieve normal weight for height when catch-up is at the rate of 3 g/kg/d in: (A) children who are normal height for age; (B) children who are stunted.

It is assumed that height does not change significantly during the period of catch up.

Table 2. Extra protein and energy requirements for catch-up growth of a 1-year old child at the rate of 3 g/kg/d.

* Calculated as (3 × 0.2 × 1.3), when 0.2 is the fraction of protein in the tissue, and 1.3 is the ‘inefficiency factor’(FAO/WHO, 1973).

Table 3. Proportion of total protein and energy requirement needed for growth in a 3-month old child: (A) if growth (weight gain) is at normal rate; (B) if weight gain is at 70% of normal rate.

(1) Maintenance protein requirement taken as 0.7 g/kg/d.
(2) Maintenance energy requirement taken as 80 kcal/kg/d.

Table 4. Weight gain appropriate for catch-up in height of stunted children.

* Assuming that catch-up is occurring at the rate of 2 SD/year
+ Based on mean weight over period of catch-up.