Biomedical subjects
J C Waterlow
Publications and source records attributed to J C Waterlow.
A model for the measurement of whole-body protein turnover incorporating a protein pool with lifetime kinetics.
The hypothesis is proposed that the body contains a pool of protein turning over by lifetime rather than traditional first-order kinetics. The basis of the hypothesis is the observation of a step in the labelling curve or urinary ammonia during constant infusion of [15N]glycine. A four pool model has been constructed with different values for the rate of uptake of tracer into the lifetime pool; the calculated curves of tracer concentration show a step quite similar to that observed experimentally. It is concluded that it is possible, from an experimental curve, to derive an approximate estimate of the relative flux to the lifetime protein pool. Some suggestions are proposed for the physiological nature of this pool.
Basal metabolic rate, body composition and whole-body protein turnover in Indian men with differing nutritional status.
1. Three groups of adult men were studied in Bangalore, India: two groups were controls who had been receiving an adequate diet. Of these, one group, designated 'normal weight controls', had a mean body mass index of 22; the other group, 'underweight controls', had a mean body mass index of 16.7. The third group consisted of poor labourers, whose daily food intake had been less than 10 MJ and whose mean body mass index was 16.6. Previous studies had shown that such men had a lower basal metabolic rate than well-nourished Indian control subjects. 2. The object of the present study was to find out whether a reduced rate of protein turnover, measured after a single dose of [15N]glycine, contributed to a lower basal metabolic rate. It was found, however, that after adjusting for body weight and fat-free mass by analysis of co-variance there was no significant difference in basal metabolic rate between the three groups. Adjusted rates of protein synthesis were higher in the underweight controls and the undernourished labourers than in the normal weight controls, but not significantly so. 3. Estimates based on creatinine excretion showed that within the fat-free mass the underweight groups had a higher proportion of non-muscle to muscle mass. This may explain the somewhat higher rates of protein turnover in these groups. 4. Nitrogen flux (Q) was determined from 15N abundance in two end products, urea (QU) and ammonia (QA). In the underweight and undernourished groups the ratio QU/QA was increased compared with the normal weight group.(ABSTRACT TRUNCATED AT 250 WORDS)
Protein requirements of infants: an operational assessment.
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Nutritional adaptation in man: general introduction and concepts.
The aim of this paper is to clarify thinking on the subject of nutritional adaptation. A series of concepts and questions are proposed with, as examples, some of the responses that occur to low intakes of energy and protein. The main conclusions are first, that in dealing with human beings value judgements cannot be avoided, but to avoid sterile discussion they must be separated from objective descriptions of adaptive responses. Second, the way ahead lies in examining the shape of the responses of different functions to different degrees and kinds of stress. Objective studies of this kind do not require use of the word adaptation.
The duration for which exclusive breast-feeding is adequate. A study in Jordan.
The object of this study was to determine the length of time for which exclusive breast-feeding supported adequate growth in a cohort of infants from families in and around Amman, Jordan. The infants were described as "faltering" if their incremental growth over 4 weeks fell below -2 standard deviations of the increments reported by Fomon in the USA. The infants were examined every 2 weeks until they faltered, or, without faltering, were started on supplementary foods. In general, up to the time of faltering, growth was satisfactory by international standards. The median time of faltering was 6 months. The results support the view that, at least in this relatively well-nourished community, exclusive breast-feeding is satisfactory for 4-6 months. However, further examination is needed of the risk factors that lead to early faltering in some breast-fed children.
Diet of the classical period of Greece and Rome.
The diet of ordinary people in Greece and Rome was derived from cereals, pulses, vegetables, fruit, olive oil, milk, cheese and a little fish and meat. This pattern fits well with what we would not regard as a healthy diet. In both Greece and Rome the bulk of cereals had to be imported, with a good deal of government control. The available evidence suggests that the official rations, if fairly distributed, would have provided an adequate energy intake. The cost of luxury foods such as meat, in relation to that of flour, was much higher than in modern times. The expectation of life at birth was only 30-35 years, but it was long enough to allow for children to be born and for the populations to expand. No reliable information has been found about infant and child mortality. The reasons for life on average being so short were probably disease and war, rather than malnutrition. It is difficult to conceive how the Greeks and Romans could have achieved such remarkable feats, which involved far more than a small elite, if they had not in general had an adequate and nourishing diet.
Post-neonatal mortality in the Third World.
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Definition of chronic energy deficiency in adults. Report of a working party of the International Dietary Energy Consultative Group.
New criteria are proposed for classifying chronic energy deficiency (CED) in adults. A progressively more precise approach to identifying affected individuals involves measuring body weight and height, then energy intake (or expenditure) and finally the basal metabolic rate (BMR). Three cut-off points for body mass index (BMI) were identified: 18.5, 17.0 and 16.0. A BMI above 18.5 is classified as normal and below 16.0 as grade III CED. A diagnosis of grades I and II CED depends on finding the combination of a BMI of 16.0-16.9 or 17.0-18.4 with a ratio of energy turnover to predicted BMR of less than 1.4. Measuring the individual BMR avoids misclassification and confirms the diagnosis. In groups of African adults 38-63 per cent of each group had a BMI below 18.5 and the majority require studies of their energy turnover before specifying their degree of CED; 3 per cent of Ethiopian women and 24 per cent of a selected male African group had grade III CED. These guidelines can be used when assessing the input of aid programmes and for clinical and other studies.
European Journal of Clinical Nutrition.
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Effects of infection on growth in Sudanese children.
A cohort of 439 infants from poor districts of Greater Khartoum were examined at intervals of 2 weeks from birth to 1 year. At each visit symptoms suggesting infection were recorded--diarrhoea, fever, vomiting and cough or cold. On average 30 per cent of children had episodes of diarrhoea and 40 per cent had episodes of cold or cough in each 4-week period, the incidence being somewhat lower in the first 2 months of life. The average duration of an episode was 5 d. The effect of illness on weight gain was calculated by regressing weight gain against number of days ill. Diarrhoea produced a deficit in weight gain of 32 g per day ill, and cough/cold a deficit of 16.4g per day ill. From these data the overall impact of illness on weight gain was calculated. In the average child between 12 and 24 weeks diarrhoea produced a reduction in growth of 160g, and cough/cold a reduction of 95g. In most periods the frequency of episodes of diarrhoea was not significantly greater in supplemented than in exclusively breast-fed children. In the first 3 months of life episodes of diarrhoea had little effect on weight gain, but thereafter an episode of diarrhoea in any 2-week period reduced the gain in that period to less than 50 per cent of that found in uninfected children. 'Faltering' was defined as a weight increment below -2 s.d. of the reference mean. Diarrhoea did not always lead to faltering, but it seems to have been an initiating factor in some 50 per cent of those children who did falter.(ABSTRACT TRUNCATED AT 250 WORDS)
Faltering in infant growth in Khartoum province, Sudan.
Four hundred babies were recruited at birth and visited at intervals of 2 weeks. At each visit weight, length and morbidity were recorded. Growth in weight and length began to fall below the international reference by 5 months. 'Faltering' was defined as a weight gain less than the reference -1 s.d. for two consecutive 2-week periods. Fifty per cent of children had begun to falter by 16 weeks. Initially almost all the children were exclusively breast-fed. The mothers were neither encouraged nor discouraged from introducing supplementary food; 50 per cent had done so by 16 weeks. There were only minor differences in attained weight, length, weight gain and length gain between supplemented and unsupplemented children. The results emphasize the wide variability in this population both in feeding patterns and in growth from period to period. Although the average outcome was satisfactory, this average conceals a minority whose growth was unacceptably low.
Notes on the new international estimates of energy requirements.
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Metabolic adaptation to low intakes of energy and protein.
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Observations on the variability of creatinine excretion.
This paper reports the intra-individual variability of creatinine excretion under conditions of variable food intake and stress. Urine collections over 24 h were made by six subjects for 24 d in the course of an expedition to the Colombian Andes. The average coefficient of variation (CV) of day-to-day creatinine excretion was 11.4 per cent and of N excretion 28 per cent. When the outputs were averaged by 3-d period the mean CV of creatinine excretion was reduced to 5.7 per cent. It is concluded that in metabolic studies the 3-d creatinine excretion is a useful index even when food intakes and other conditions are not controlled.
Requirements for specialist training.
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The contribution of endogenous urea to faecal ammonia in man, determined by 15N labelling of plasma urea.
To establish the role of endogenous urea as a source of faecal ammonia, the plasma urea of two healthy men was labelled with 15N at a constant level for several days and its 15N enrichment was compared with that of faecal ammonia and total nitrogen. Faeces collected after one complete gastrointestinal transit from the onset of plasma labelling had ammonia 15N enrichments which were only 8.5 +/- 1.2% and total nitrogen enrichments which were 6.8 +/- 0.7% of the plasma urea 15N enrichment. These results show that endogenous urea is not the main precursor of faecal ammonia, which is probably derived by bacterial deamination from the protein of dietary residues, intestinal secretions and shed epithelial cells. The minor contribution of endogenous urea to faecal ammonia suggests that the lumen of the large bowel is not the main site of endogenous urea hydrolysis. The similar labelling of faecal total nitrogen and ammonia nitrogen supports other evidence that these faecal nitrogen fractions are in a constant state of exchange.