W. P. T. James

Adult malnutrition : simple assessment techniques for use in emergencies

The recent recognition of the problem of adult malnutrition requires methods for specifying the severity of undernutrition. The measurement of mid upper arm circumference (MUAC) can now be used as a screening method for underweight (normally assessed from the BMI) or as an additional criterion with the BMI to identify the preferential loss of peripheral tissue stores of fat and protein. By analysing and extrapolating anthropometric data from nine detailed adult surveys from Asia, Africa and the Pacific a series of MUAC cut-off points have now been identified to allow the screening of individual adults under extreme conditions, e.g. during famine. Grade 4 malnutrition is now specified for those with a MUAC < 200 mm for men and < 190 mm for women since these MUAC values correspond to the loss of fat stores at BMI of < 13. Food supplementation is clearly needed in these individuals. Extreme wasting (grade 5 malnutrition) corresponds to MUAC values of < 170 and < 160 mm for men and women respectively. These adults have extremely low BMI, i.e. about 10, have lost most, if not all, of their protein stores and are at a high risk of imminent death. These individuals will need immediate special feeding regimens to ensure their survival. The sex-specific MUAC values corresponding to BMI of 16, 13 and 10 can now therefore be used for rapid screening and the choice of remedial action.

Metabolic changes during the menstrual cycle

1. Eight women maintained on a constant diet throughout a single menstrual cycle were studied for cyclical changes in body-weight, carbohydrate, fat and protein metabolism. 2. A cyclical variation in weight occurred with two phases corresponding to the time of ovulation and menstruation. 3. Creatinine and nitrogen excretion in the urine also tended to be higher in the luteal phase. 4. Analysis of gas exchange in a respiratory chamber for 24 h periods at intervals during the cycle suggested that carbohydrate utilization tended to be less in the early follicular phase. 5. Feeding with a mixed diet produced marked increases in carbohydrate utilization during the day with little change in fat utilization from the fasting state. Carbohydrate utilization was less when fasting at night and tended to be less when fed during the day in the early follicular phase of the menstrual cycle. 6. Weight changes were not readily ascribed to changes in colonic function, or in glycogen or body protein storage.

Energy Needs of the Elderly

A discussion of human energy needs in the elderly as well as in other age groups raises the issue of what we mean by the term “needs.” A recent international report on energy and protein requirements (FAO/WHO/UNU, 1985) has dealt in some detail with this question, but the analysis warrants further emphasis because the question of needs is particularly relevant to the elderly. Indeed, most of the literature that purports to assess the adequacy of diets in the elderly ignores the principles of energy requirements. This chapter sets out a collection of some of the literature on energy requirements, supplemented where there are deficiencies by unpublished data collected as part of a current study of the nutritional status of elderly men and women in Italy (A. Ferro-Luzzi, unpublished data). The implications of these studies are then considered and set in the context of the new approach to assessing energy needs embodied in the recent FAO/WHO/UNU (1985) report.

Nutrition in Pregnancy

The study of carbohydrate metabolism in pregnancy dominates this Colloquium together with questions relating to the problems of pregnant diabetic women. This chapter deals with neither of these two themes but seeks to explore whether there are general principles of nutrition in pregnancy which might be applicable to the problems covered by other contributors. As with other studies involving a nutritional component, the effect of a diet depends not only on the amount of specific nutrients eaten but on the individual’s genetically determined response to that diet. Superimposed on this interaction is the physiological effect of pregnancy. Unfortunately we also have to recognize that a pregnant woman may deliberately change her diet and its effects are then modified by the different levels of the nutrient stores achieved in the prepregnant state. Only when one recognizes these different components of the problem will it be possible to assess the nutritional state of a pregnant woman in a meaningful way. This chapter illustrates some of these themes by reviewing evidence relating to protein needs, and vitamin and trace element metabolism in pregnancy.

Obesity: translating scientific research into therapeutic and preventive benefit

Obesity is an escalating problem in many countries. There is a need to reduce the average body weight of a population, not simply treat the extremes. This requires consideration of societal factors which affect body weight. Weight increases with age, the increase leading to a higher proportion of body fat to lean tissue. Causes include progressive inactivity and dietary fat which often accompany increasing affluence. A body mass index (BMI) of 20-25 is generally advised, but some suggest a BMI of 20-22 for lowest risk of disease. The risk of smoking when thin exceeds the risk of being overweight, so dietary advice is important on cessation of smoking. Genetic susceptibility to weight gain is strongly influenced by nutrient interactions at all stages of life. Foetal and neonatal nutrition may modify body weight in later life. Familial trends of reduced activity and low metabolic rate need to be addressed, as does the problem of lower metabolic rates and lower food needs after weight loss. Appetite control is poorly understood but dietary fat and energy density of food and exercise are important factors. For those who miss breakfast, the loss of a low fat meal of cereals and toast is significant. The strong influence of dietary fat on obesity and associated disease risks has led to expert committees to develop population nutrient goals which limit dietary fat. An energy discrepancy of only 2% a day can explain an increase in body weight of 5 kg/year. It is easier to understand why people become fat than to tackle the societal issues which affect the prevalence of obesity.

The Hypolipidaemic Effect of Different Diets

Saturated fatty acids are still accepted as stimulating and polyunsaturated fatty acids (PUFAs) as reducing total cholesterol and low density lipoprotein cholesterol levels; these changes seem to be mediated by modulating LDL receptor reactivity and therefore the uptake of cholesterol. Confusion remains on the role of individual fatty acids with stearic and medium chain fatty acids considered ineffective in raising cholesterol levels. Lauric and myristic acids dominate with palmitic acid traditionally linked to high cholesterol levels. New studies suggest a modest effect of palmitic but studies with formula feeding are probably flawed because of the absence of dietary fibre; these polysaccharides increase cholesterol catabolism, reduce its absorption and may promote the hypolipidaemic effects of PUFAs. The impact of hyperlipidaemia on coronary heart disease may be particularly dependent on the genetically controlled apoproteins in the lipoproteins but dietary effects on the turnover and reactivity of these proteins is unresolved; these proteins may have fibrinolytic and thrombotic effects.