Human nutrition. Clinical nutrition最新文献

Sixty rural Gambian children between 10 and 14 years of age with normal haematological status but generally poor riboflavin status and some evidence of poor ascorbic acid status were recruited for study at the beginning of the rainy season. Children were allocated to three treatment groups to receive, twice weekly, either a placebo or a supplement of riboflavin or ascorbic acid. Before receiving the supplement, and on two subsequent occasions 6 weeks apart children performed an exercise regimen on a bicycle ergometer during which expired air was collected, heart rate monitored and lactate accumulation measured. A modest but significant improvement in ascorbic acid status occurred in response to supplement and the riboflavin supplement enhanced the overall improvement in riboflavin status observed. There was no measurable change in bicycling performance during the study period in any of the treatment groups.

Human milk samples were collected from mothers on the third post-partum day with a manual breast-pump and pooled. They were divided into aliquots and stored at room temperature (24-25 degrees C), and at 4 degrees, 37 degrees and -20 degrees C. The creamatocrit (CR) values decreased significantly after storage at room temperature (P less than 0.03), or at 37 degrees C (P less than 0.001) for 45 min and 30 min, respectively. Creamatocrit remained stable for 14 d at 4 degrees C, and for up to 28 d at -20 degrees C. However, freezing and thawing samples twice significantly decreased creamatocrit values (P less than 0.001). The total energy concentration of the samples stored at -20 degrees C was stable for 28 d. These results indicate that strict precautions must be taken when handling and storing human milk samples for analysis of lipid content.

Plasma and breast milk vitamin A and plasma carotenoids were measured in groups of pregnant and lactating women in two neighbouring rural Gambian villages. One of the groups (Keneba) received a 650 micrograms daily vitamin A supplement. During pregnancy, plasma retinol values were significantly (19 per cent) higher in the supplemented group. During lactation, breast milk values were significantly (23 per cent) higher in the supplemented group. Changes in plasma and breast milk vitamin A levels during the cycle of pregnancy and lactation and with season are also described, and the value of a combined index of plasma retinol and plasma carotenoids is illustrated. The significant effect of a prolonged low level vitamin A supplement to pregnant and lactating women has important implications for nutrition intervention programmes.

The vitamin B6 status of women suffering from premenstrual symptoms (PMS, n = 19) and a group of matched controls (n = 19) has been investigated. The women volunteering in the study were selected on strictly defined criteria. Several biochemical parameters of the metabolism of vitamin B6 and tryptophan were studied in blood and urine samples during a full menstrual cycle. No significant differences in plasma pyridoxal and pyridoxal-5'-phosphate (PLP) concentrations, the holo and total EGOT activity, the erythrocyte pyridoxine kinase activity and the urinary 4-pyridoxic acid excretion between the two groups were observed. The excretion of the tryptophan metabolites xanthurenic acid (XA) and 8-methyl-xanthurenic acid (MXA), before as well as after an oral tryptophan load, tended to be higher for the PMS group. Each of the groups showed a significant cyclic variation during the menstrual cycle in the holo and total EGOT activities and in the excretion of XA and MXA before as well as after an oral tryptophan load. It is concluded that PMS is not related to a 'cyclic' vitamin B6 status. The slight differences observed for tryptophan metabolism between the PMS and the control group deserve further study.

The energy expenditure of 93 Colombian boys 6-16 years of age and 10 adult American males was measured while walking on a treadmill at 3 mph and 0, 4, 8 and 12 per cent grades without and with backpack loads of 3 (6-8 year), 6 (10-12 year) and 9 kg (14-16 year and adults). The boys were also divided into nutritionally normal and marginally malnourished, based on their weight-for-age and weight-for-height. The primary dependency of energy expenditure on body weight or body weight plus load was not affected by nutritional status, and the results of both adults and control and undernourished children fell on the same straight line at a given treadmill grade, indicating that the undernourished subjects would expend the same energy as nutritionally normal boys and adult subjects for a given load carried. The undernourished boys worked at a higher percentage VO2 max than control subjects when load carrying.

Longitudinal measurements of breast milk output were made using a 2H2O tracer technique over 24 months in 23 rural Papua New Guinean women. A small (n = 14) cross-sectional sample of women from a different area were also studied. Mean outputs of the longitudinal sample rose from 601 +/- 100 g/d at 1 month to a maximum of 901 +/- 211 g/d at 9 months and fell to 501 +/- 188 g/d at 24 months, values which are considerably higher than previously reported from Papua New Guinea. This is considered to be primarily due to the suitability of the method of measurement. The late and complementary nature of the introduction of additional foods to the infant diet is considered to be responsible for the maintenance of these high outputs over periods of up to 24 months in some cases. Multiple regression analysis performed on all data points up to 6 months or 6 kg infant weight showed that infant weight accounted for 55.8 per cent of the total variation in milk output. The additional effect of infant age, given weight, was not significant (t = 1.37). In cross-cultural comparisons infant size was also shown to be a more important determinant of milk output than infant age. These comparisons were made using the rate constant Fbm/Vb, the basic measurement of the estimation of milk output by the tracer method.

The effect of addition of pectin or wheat bran to a constant low-fibre diet on bile acid and cholesterol excretion from the small intestine has been studied in ileostomy patients. The study was designed to minimize bacterial alteration of ileostomy contents. An addition of 15 g of citrus pectin increased bile acid excretion by 35 per cent (P less than 0.05) and net cholesterol excretion by 14 per cent (P less than 0.05) in six patients, while 16 g of wheat bran to another six patients caused no consistent change. Ileostomy fat excretion increased on the diet with added pectin (P less than 0.05) but not on that with bran. The results support the concept of dietary fibre exerting its effects on lipid metabolism by altering intestinal excretion of sterols.

Vitamin C status was determined in schizophrenic subjects using fasting plasma levels and the urinary dose response after an oral load of 1.0 g ascorbic acid. The study was carried out in 20 schizophrenic patients and 15 controls with the diagnosis of neurosis who were on the same hospital diet for at least 2 months. The schizophrenic subjects had significantly lower fasting plasma vitamin C levels (P less than 0.05) and 6-h urinary vitamin C excretion after an ascorbic acid load test (P less than 0.01). Since urinary vitamin C excretion in both groups was significantly associated with differences in fasting vitamin C plasma levels (P less than 0.001), a new group of 15 schizophrenics and 15 controls was supplemented with 70 mg of ascorbic acid daily for 4 weeks in order to optimize and standardize their vitamin C plasma levels before the ascorbic acid loading test. The results showed that after 4 weeks of supplementation the average fasting plasma vitamin C levels were almost identical in both examined groups, but the urinary vitamin C excretion was again significantly lower in schizophrenic patients (P less than 0.05). These results are in agreement with the hypothesis that schizophrenia may be associated with impaired ascorbic acid metabolism.