Human nutrition. Clinical nutrition最新文献

Cooked dried legumes have been shown to stimulate low blood glucose responses, and their consumption by individuals with diabetes has been encouraged. However, canned beans are more convenient to use than dried beans. Since the glycaemic effects of canned beans have not been determined, we fed 50 g carbohydrate portions of five varieties of beans, both cooked dried and canned, to groups of diabetic patients and calculated their glycaemic indices (GI). All canned and dried beans tested had significantly lower GIs than that of white bread, which was ascribed a GI of 100. The mean GI of the five types of canned beans, 71 +/- 4, was less than that of bread, 100 (P less than 0.001), and greater than that of the same five varieties of cooked dried beans, 47 +/- 5 (P less than 0.001). It is concluded that the glycaemic effect of dried legumes is increased by the canning process. Nevertheless, canned beans give lower blood glucose responses than bread and may be of use in low glycaemic index diets.

In the past few years there has been a resurgence of interest in the protein composition of human milk. Up to now the influence of maternal diet and of the mothers' nutritional status on the protein composition of human milk have not been fully clarified. We have evaluated the relationship between the mothers' socioeconomic status and weight and the protein composition of human milk. Protein fractions were determined by a polyacrylamide gel electrophoresis method in 181 samples of human milk obtained from voluntary donors. Samples were classified according to the time of lactation and in relation to the socioeconomic status and to the weight of the lactating women. Total protein and non-protein nitrogen decreased with advancing lactation but there were no differences among the socioeconomic and weight groups of mothers who were considered. beta- and kappa-caseins fell during lactation and beta-casein was significantly increased in the milk of the upper socioeconomic class with respect to that of the low one. alpha-lactalbumin increased from transitional to mature milk (16-30 d) and then declined. The milk from the low socioeconomic group presented the lowest levels of this protein. Lysozyme increased during lactation, whereas lactoferrin decreased. Both proteins were significantly influenced by the mothers' socioeconomic status; the highest concentrations for these proteins were found in the milk of the low socioeconomic group. Deficit or excess of mothers' weight did not influence the levels of the different protein fractions of human milk.

Fatty acid composition of mature human milk from Curacao (Netherlands Antilles), Surinam and Tanzania was determined by capillary gas chromatography. In the Curacaoan samples the cholesterol and alpha- and gamma-tocopherol concentrations were also determined. Remarkable differences were found in the fatty acid composition of breastmilk fat from the three countries. The differences in the levels of medium chain fatty acids between Curacao and Tanzania, and between Curacao and Surinam were significant. The mean sum of the essential fatty acids linoleic acid and linolenic acid showed the highest values in Curacao (16.1 g per cent). Mean values for Tanzania and Surinam were 14.9 and 12.7, respectively. The mean level of the docosahexaenoic acid was higher in the Curacaoan and Surinam samples compared with that from Tanzania. In the Curacaoan breastmilk samples the concentrations of cholesterol and alpha- and gamma-tocopherol were about twice as high as those reported for Western countries.

The pattern of excretion of taurine was measured in four omnivore and four vegan/vegetarian women during pregnancy and lactation, and was compared with the changes in urinary excretion of other amino acids, including the precursors of endogenous taurine, observed in ten pregnant omnivores. The loss of taurine in breast milk was also determined in fourteen omnivore and fourteen vegan mothers. In contrast to the rise in excretion of all amino acids during pregnancy, including methionine and cysteine, taurine excretion fell dramatically from week 9 of pregnancy in all subjects, and, in the vegan/vegetarian subjects, fell still further during lactation. Although the concentration of taurine in breast milk was lower in vegan subjects, the mean value fell within the range found in omnivore subjects. Our findings indicate that the suppression of urinary taurine excretion, both during pregnancy and lactation, is a physiological response to reproduction that satisfies the needs of the fetus and the suckling infant for this amino acid. The data also suggest that taurine is stored in the maternal tissues in early pregnancy for later transfer to the fetus.

Knowledge of the vitamin D status of pregnant and lactating women in developing countries is very limited. An elective visit to the Transkei therefore provided us with the opportunity to study the relationship between the vitamin A and D status of dark-skinned mothers and babies resident in an environment of high sunshine exposure. 25-hydroxyvitamin D, retinol and retinol binding protein (RBP) were measured in serum samples collected from 43 black South African women and their babies, shortly after delivery. The results were compared with values obtained on sera from pregnant white and black women resident in the UK. The values for serum retinol in the Transkei mothers and babies were low. This accords with the poor nutrition and consequent high childhood mortality observed in this population. In contrast, the serum 25-OHD values were normal. This suggests that in these malnourished black South African mothers, normal vitamin D status is maintained by actinic synthesis.

Previous results of short-term diet studies of leucine kinetics have suggested that the currently accepted requirement value for the amino acid in adults is too low. In the present study the effects of a more prolonged diet period at low leucine intakes on leucine kinetics and nitrogen balance (NB) were explored in healthy young men. They (4 or 5 subjects per group) received an adequate leucine intake (80 mg/kg/d) for 1 or 2 weeks (Period 1) followed by either 7, 14 or 30 mg/kg/d for 3 weeks (Period 2) with a return to 80 mg/kg/d for 1 week (Period 3). Estimates of leucine fluxes (LF), oxidation (LO) and balance (LB) were based on a constant intravenous infusion of L-[1-13C]leucine, at end of Period 1, at 1 and 3 weeks of Period 2 and on days 1 and 3 of Period 3. At all three intakes LF and LO, during the fed state, fell between 1 and 3 weeks of Period 2. LB was negative at 1 week of Period 2 for all groups but had approached equilibrium by 3 weeks. N balance at 3 weeks was similar for all groups but during Period 3 was significantly higher (P less than 0.05) and markedly positive (+18 mgN/kg/d) for the 7 and 14 mg groups, compared with the 30 mg group (+4 mgN/kg/d), indicating that 'depletion' had occurred at the lower leucine intakes during Period 2. Our interpretation is that LB was approached by an adaptation in the 30 mg group whereas it was achieved in the 7 and 14 mg groups by an accommodation, associated with a reduced and low rate of leucine uptake into protein (LF minus LO). Thus, the leucine requirement was judged to be greater than 14 mg/kg/d, a level currently accepted as the upper range of the requirement for healthy adults. The significance of these findings for assessment of nutrient requirements is discussed, with emphasis on the limitation of NB measurements for evaluation of human amino acid requirements.

In the past, variations in the daily intake of an individual maintaining his weight and activity were considered negligible as it was assumed they arose from measurement errors. It was therefore believed that such variation could be eliminated by averaging over an appropriate period. This, however, is not borne out by the experimental data. The present study reports findings based on a longitudinal diet survey conducted on 43 adolescent schoolboys in a village, over a period of 1 year. A diet survey was carried out for 1 week every 3 months. Intake was estimated by recording the weights of all the food items actually consumed during the day by the students and analysing corresponding food samples in the laboratory. Intake data when analysed for the relative contributions of between- and within-subject variation showed that not only intra-individual variation contributes a substantial portion of the total variation but a significant part of it arises from changes in the mean intake from week to week. The daily intakes of a subsample of 5 students were observed for 49 consecutive d to study the short-term nature of the variation. The results obtained confirm those from the long-term study. Additionally there is an indication that daily intakes of an individual are serially correlated.

Eighty Italian adults (53 females, 18-69 years, and 27 males, 18-60 years) underwent double-blind tests involving the intake of increasing amounts (125, 250, 500, 1000 ml/d) of four types of milk with normal or low lactose and/or fat content. The tests were completed satisfactorily by 71 subjects. Forty were lactose malabsorbers (LMs) and 31 were absorbers (LAs), according to a standard oral lactose tolerance test. Each subject reported on a questionnaire whether he/she experienced symptoms during the 24 h after milk intake, and the intensity of the symptoms, adopting a score of 0 to 12, according to an already tested procedure. The aim of the study was to investigate the relationship between lactose malabsorption or absorption and intolerance to milk in Italian adults, relative to lactose and fat contents, dose of milk and individual sensitivity. LMs reported symptoms overall more frequently and with greater intensity than LAs (P less than 0.001). The amount of milk ingested was positively associated with the frequency of symptoms both in LMs and LAs. Contrary to earlier findings, fat seemed to contribute to milk intolerance in LMs rather than to reduce it. According to analysis of variance individual differences accounted for 40 per cent of total variation in symptom frequency.