During the Austral summer of 1992–3, two men, MS and RF, walked 2300 km across Antarctica in 96 d, unassisted by other men, animals or machines. During the journey they ate freeze-dried rations, towed on sledges, that contained an average of 21·3 MJ/d of which 56·7% was fat, 35·5% carbohydrate and 7·8% protein (98·8 g). Despite this high energy intake both men lost more than 20 kg in body weight due to their extremely high energy expenditures. Studies of protein turnover using [15N]glycine by the single-dose end-product method were made before, during and after the journey, and these demonstrated considerable differences in the metabolic responses of the two men to the combined stresses of exercise, cold and undernutrition. However, both men maintained high and relatively stable levels of protein synthesis during the expedition despite the great exertion and the onset of considerable debilitation. This stability indicates the vital physiological function of protein synthesis.

Abstract Body composition was measured by densitometry in a group of eighty-one healthy Chinese males and 124 healthy Chinese females, aged 18–67 years. Biceps, triceps, subscapular and suprailiac skinfolds were measured as well as total body bioelectrical impedance at 50 kHz. Mean heights were 1·71 (SD 0·05) and 1·61 (SD 0·06) m, body weights 66·1 (SD 9·1) and 57·2 (SD 9·4) kg and BMI 22·7 (SD 3·0) and 22·0 (SD 3·3) kg/m2 in males and females respectively. Body fat values from body density were 20·1 (SD 6·2) and 29·7 (SD 7·5)% in males and females respectively. Mean predicted body-fat values from skinfolds, bioelectrical impedance and BMI, using prediction formulas developed in Western populations, did not differ or differed only slightly from body-fat values estimated from body density. The SD of the difference for each method was 5% body fat or 3·3 kg fat-free mass (CV 6%), which is approximately equal to the accuracy level of each predictive method. Compared with densitometry the predictive methods overestimated body fat at the lower levels of body fatness, whereas at the higher levels of body fat the predictive methods tended to underestimate body fatness. It is concluded that prediction formulas for estimating body fat from skinfolds, impedance or BMI developed in Western populations are applicable and valid in the adult Chinese population. However, in very lean subjects the predictive methods overestimate body fat compared with values obtained from body density

Detailed anthropometric measurements were made on 169 healthy children aged between 4 and 40 months during a comprehensive study of the diet and nutritional status of Asian children (of Pakistani and Bangladeshi origin) living in Sheffield. These measurements were used to describe the growth profile of these apparently healthy children and to compare this with both international and UK reference data. The distribution of values for most anthropometric measurements was close to the UK reference data although both boys and girls tended to be slight of build, and girls tended to have relatively smaller head circumferences. Nevertheless, it was concluded that their growth and nutritional status over this age range can be evaluated using standard (UK) growth charts

Urea kinetics were measured using prime/lintermittent oral doses of [15N15N]urea, on five separate protocols in thirteen normal young women. Each woman underwent either two or three study protocols.Measurements were made at day 12 and day 22 of the menstrual cycle, whilst consuming their habitual protein intake in seven women not taking the contraceptive pill and in six women taking the contraceptive pill. In three woman taking the pill, and three not taking the pill, urea kinetics were measured whilst taking a diet in which the intakewas restricted to 55 g protein/d. There was no difference in the rate of urea production, urea excretion or urea hydrolysis between the women taking the pill and those not taking the pill at day 22. In the women not taking the pill there was no difference in any measure between day 12 and day 22. In the women taking the pill there was a significant difference in the disposal of urea N to excretion or hydrolysis on day 12 compared with day 22, with a relative decrease in excretion and enhancement of hydrolysis at day 12 compared with day 22. On the restricted diet, an intake of 55 g protein/d represented 77% of the habitual intake and urea production, excretion and hydrolysis were reduced to about 84% of the rate found on the habitual intake. In paired studies the reduction in urea production was statistically significant, and there was a statistically significant linear relationship between urea production and either intake or the sum of intake plus hydrolysis. The within-individual variability for urea production was about 10% for excretion 15% and for hydrolysis 44% The between-individual variability for intake was about 17% on the habitual intake. The variability for production, excretion and hydrolysis (14, 13, 36%) was less in the women not taking the contraceptive pill than in those taking the pill (23,32,42% respectively). The variability was reduced on the controlled low intake of 55 g protein compared with the habitual intake.These results confirm the wide variability in aspects of urea kinetics between individuals. In women this variability is not, to any large extent, accounted for by changes associated with themenstrual cycle

There is a need for studies on colonic fermentation in order to learn more abouthealth and diseases of the colon. The aim of the present study was to evaluate the fate of twodifferent doses of fructo-oligosaccharides (5 and 15 g/d) v. glucose in the intestine of healthy men. Twenty-four volunteers participated in a 5-weekstudy. The study was a completely balanced multiple crossover trial using an orthogonal Latin-square design for three periods, with supplement periods of 7 d and two 7 d wash-out periods. Breath samples and faecal samples were collected. There was a clear gaseous response to the consumption of fructo-oligosaccharides. The highest dose significantly increased 24 h integratedexcretion of breath H2 (P < 0·05). Breath H2 excretion after ingestion of 5 g fructo-oligosaccharides was higher than control, but did not reach significance. No effects on the total concentration of short-chain fatty acids in faeces were observed, no modification of the molar proportions of the various short-chain fatty acids was observed. The faecal pH did not change. No changes in faecal weight were observed. No fructo-oligosaccharides were recovered in faeces. We conclude that fructo-oligosaccharides added to the diet of young Western subjects are fully metabolized in the large intestine. The level of fermentation seems to be dose-dependent.

The human vitamin K requirement is not known precisely, but the minimal requirement is often assumed to be between 0·5 and 1 x 10−6g/kg body weight. In the present study we addressed the question to what extent circulating vitamin K concentrations are influenced by the form in which the vitamer is consumed. The experimental group consisted of five healthy volunteers who received phylloquinone after an overnight fast. On the first day of three successive weeks the participants consumed 1 mg (2·2 µmol) phylloquinone, either in the form of a pharmaceutical preparation (Konakion®), or in the form of spinach + butter, or as spinach without added fat. Circulating phylloquinone levels after spinach with and without butter were substantially lower (7·5- and 24·3-fold respectively) than those after taking the pharmaceutical concentrate. Moreover, the absorption of phylloquinone from the vegetables was 1·5 times slower than from Konakion. In a second experiment in the same five volunteers it was shown that relatively high amounts of menaquinone-4 enter the circulation after the consumption of butter enriched with this vitamer. It is concluded that the bioavailability of membrane-bound phylloquinone is extremely poor and may depend on other food components, notably fat. The bioavailability of dietary vitamin K (phylloquinone+menaquinones) is lower than generally assumed, and depends on the form in which the vitamin is ingested. These new insights may lead to a revision of the recommended daily intake for vitamin K.

Changes in splanchnic energy and N metabolism were studied in sheep, prepared with vascular catheters across the portal-drained viscera (PDV) and the Liver, and maintained on supramaintenance intakes of either grass or grass + barley pellets. The animals were challenged, on both diets, with 4 d intra- mesenteric vein infusions of NH4CI (25 µmol/min) plus NH4HCO3 (at either 0 or 125 µmol/min). On the final day of each treatment the natural abundance NH4Cl was replaced with 15NH4Cl over a 10 h infusion while over the same period [l-13C]leucine was infused via a jugular vein. Measurements were made of blood flow plus mass transfers of NH3, urea, free amino acids and O2, across the PDV and liver. Enrichments of [14N15N]urea and [15N15N]urea plus [15N]glutamine, aspartate and glutamate were also monitored. Whole-body urea flux was determined by infusion of [14C]urea. At the end of the study the animals were infused for 3 h with 15NH4CI, killed and liver samples assayed for intracellular free amino acid enrichments and concentrations. Blood flows across the splanchnic region were unaffected by either diet or level of ammonium salt infusion. At the lower ammonium salt infusion there was a trend for greater absorption of NH3 across the PDV (P<0·10) with grass + barley than with the grass diet, while removal of urea was unaltered. At the higher ammonium salt infusions there was a significantly greater appearance of NH, across the PDV and this exceeded the extra infused. Urea-N removal, however, was also elevated and by more than that required to account for the additional NH3. The PDV contributed 19–28% to whole-body O2 consumption and the liver 23–32%. Hepatic extraction of absorbed NH3 was complete on all treatments and systemic pH remained constant. The fractions of urea-N apparently derived from NH3, were similar on the grass (0·59–0·64) and grass + barley (0·64–0·67) diets. Hepatic production of urea agreed well with urea flux measurements. Between the two levels of ammonium salt infusion and within diets the additional NH3 removed across the PDV was accounted for by the increased urea-N production. The [14N15N]: [15N15N] ratio of the urea produced was 97:3, while the enrichment of hepatic intracellular free aspartate was lower than that of [14N15N]urea. Glutamine enrichments were 0·23–0·37 those of [14N15N]urea, indicating a minor role for those hepatocytes (probably perivenous) which contain glutamine synthetase (EC 6.3.1.2). Leucine kinetics, either for the whole body or splanchnic tissues, were not different between diets or level of ammonium salt infusion, except for oxidation which was less on the grassfbarley ration. Amino acid concentrations were lower on the grass + barley diet but net PDV absorptions were similar. The pattern of essential amino acids absorbed into the PDV showed good agreement with the published composition of mixed rumen microbial protein. Fractional disappearances of absorbed free essential amino acids across the liver varied from 0·4 (branched chains) to near unity (histidine, phenylalanine)

Two suggested modes of action of yeast in stimulating rumen fermentation were investigated. The first, that yeast respiratory activity protects anaerobic rumen bacteria from damage by O2, was tested using different strains of yeast that had previously been shown to have differing abilities to increase the viable count of rumen bacteria. Saccharomyces cerevisiae NCYC 240, NCYC 1026, and the commercial product Yea-Sacc®, added to rumen fluid in vitro at 1·3 mg/ml, increased the rate of O2 disappearance by between 46 and 89%. The same three preparations also stimulated bacterial numbers in an in vitro fermenter (Rusitec).S. cerevisiae NCYC 694 and NCYC 1088, which had no influence on the viable count in Rusitec, also had no effect on O2 uptake. Respiration-deficient (RD) mutants of S. cerevisiae NCYC 240 and NCYC 1026 were enriched by repeated culturing in the presence of ethidium bromide. S. cerevisiae NCYC 240 and NCYC 1026 stimulated the total and cellulolytic bacterial populations in Rusitec, while the corresponding RD mutants did not. Rigorous precautions to exclude air from Rusitec resulted i“n S. cevevisiae NCYC 240 no longer stimulating total bacterial numbers, although it still increased numbers of cellulolytic bacteria. The second hypothesis, that yeast provides malic and other dicarboxylic acids which stimulate the growth of some rumen bacteria, was examined by comparing the effects of yeast and malic acid on rumen fermentation in sheep. Three mature sheep were given 0·85 kg barley/d plus 0·55 kg chopped ryegrass hay/d either unsupplemented, or supplemented with 4 g S. cerevisiae NCYC 240/d or 100 mg l-malic acid/d either mixed with the diet or in aqueous solution infused continuously into the rumen. Yeast increased the total viable count of bacteria (P < 0·05)whereas malic acid did not, and no other effect of the treatments reached statistical significance. It was concluded, therefore, that the stimulation of rumen bacteria by S.cerevisiae is at least partly dependent on its respiratory activity, and is not mediated by malic acid.

Tibial traits were investigated for turkey poults fed on soyabean-meal-based semi-purified diets high in phytate P (2·2 g/kg) with added phytase and inorganic P. Dietary treatments were: (1) 2·7 g non-phytate P (nP)/kg; (2) diet 1 + 1000 U phytase/kg diet; (3) 36 g nP/kg; (4) diet 3+800 U phytase; (5) 4·5 g nP/kg; (6) diet 5+600 U phytase; (7) 6·0 g nP/kg. Added phytase and nP increased (P < 0·006) tibial dry matter, ash weight and content, body-weight gain, feed intake and gain:feed. The Mg and Zn concentrations in the tibial ash were also increased (P < 0·001 and P < 0·09 respectively) by added phytase or nP; tibial P and Ca concentrations tended to be increased. Hypertrophy zone width of the tibial proximal end decreased (P < 0·001), while proliferating zone width, tibial length, and widths at the long and short axes increased (P < 0·003) as phytase and nP were added. The addition of phytase also tended to enlarge the cartilaginous zone width, which was linearly increased (P < 0·05) by added nP. Disorganization scores of the hypertrophy zone and trabecular bone were low, approaching normal (P < 0·05), for turkey poults fed on diets with phytase supplementation, and tibial abnormality scores were linearly decreased (P < 0·001) as nP levels increased (zero score is considered normal). Adding phytase and nP improved the orderliness of development, mineralization and arrangement of cartilage and bone cells, and alleviated the effects of P deficiency on the histological and gross structure of the tibias. Tibial shear stress increased (P < 0·04) as phytase and nP were added. In summary, similar improvements in bone characteristics were achieved for turkey poults fed on a P-deficient diet supplemented with either phytase or nP.

The present study was designed to test the hypothesis that increasing short-chain fatty acid (SCFA)production in the large bowel increases gut epithelial proliferation rate (EPR). Two experiments were carried out in which rats were fed on bread (wholemeal or white)-based diets containing graded amounts of cooked haricot (Phaseofus vulgaris) beans; the latter are a rich source of fermentable carbohydrates. Consumption of beans was associated with several-fold increases in SCFA production with the greatest relative increase being for butyrate. Despite the very large increase in SCFA production, there was no evidence that this had any effect on EPR in the duodenum. Where the basal diet contained wholemeal bread (Expt 1) there was no effect of enhanced SCFA supply on EPR in either the caecum or colon, but with the white bread-based diet (Expt 2) adding beans produced increments in both SCFA supply and EPR in the caecum. Evidence that SCFA are responsible for enhanced EPR above normal levels is not convincing. In those instances where enhanced SCFA supply is associated with increased EPR, the increase may be (1) from a hypoproliferative state towards normal, (2) a transient phenomenon accompanying tissue hypertrophy or (3) a homeostatic response to increased cell loss by cell sloughing or apoptosis. It is not likely that there is any direct link with risk of colon cancer

It has increasingly been suggested that the short-chain fatty acids (SCFA) acetic, propionic and butyric acids, derived from colonic fermentation of dietary fibre and other indigestible carbohydrates, exert different physiological effects. Formation of propionic acid is discussed in terms of beneficial effects on glucose and cholesterol metabolism. The aim of the present study was to evaluate possible metabolic effects of propionic acid and to differentiate between effects mediated in the upper gastrointestinal tract and those mediated in the hind-gut. For this purpose, obese hyperinsulinaemic (fa/fa) rats were studied during a 19 d test period. Sodium propionate was either fed orally through the diet (1 g/d), or infused rectally (0·15 g/d) to animals given diets high in cholesterol (20 g/kg) and saturated fat (130g/kg). At the end of the test period total liver cholesterol pools were 20% lower (P < 0·01) in rats given dietary or rectally infused propionate (481 and 484 mg respectively) compared with the control group (614 mg). This was due to lower liver weights (P < 0·05) in propionate-treated animals, 15·5 and 15·3 g, v. 18·2 g in the control group, and no differences were noted in hepatic cholesterol concentrations. The urinary glucose excretion was measured during days 15–19 and was found to be lower (P < 0·05) in rats fed with propionate (23 mg) compared with the control group or the group infused rectally (39 and 38 mg respectively). In addition, fasting plasma glucose concentrations decreased significantly (P < 0·05) over the test period. It is concluded that orally supplied propionate affects both glucose and cholesterol metabolism as judged from lowered urinary glucose excretion, fasting blood glucose and liver cholesterol pools. On the other hand, propionate administered to the hind-gut at a physiologically relevant level reduces the hepatic cholesterol pool.

The properties of nuclear receptors belonging to the superfamily of receptors acting as transcription factors are modulated by nutritional and hormonal conditions. We showed recently that retinoic acid (RA) restored to normal the expression of receptors attenuated by hypothyroidism. The present study was designed to find out whether dietary vitamin A (as retinol) had the same effect. Propylthiouracil in drinking water induced both hypothyroidism and a vitamin A-deficient status in rats. The maximum binding capacity (Cmax) of triiodothyronine nuclear receptors (TR) was unchanged, while that of nuclear RA receptors (RAR) and nuclear glucocorticoid hormone receptors (GRn) was reduced in the liver of these hypothyroid rats. The reduced Cmax of RAR stemmed from a lower level of RAR mRNA, while the reduced Cmax of GRn was assumed to be due to reduced translocation of the receptor from the cytosol to the nucleus. Feeding the hypothyroid rats with a vitamin A-rich diet did not restore the Cmax of either RAR or GRn to normal. The lack of effect of dietary retinol on RAR expression may be attributed to either genomic (unoccupied TR block the expression of RAR genes) and/or extragenomic (hypothyroidism decreases the availability of retinol and/or its metabolism to RA) mechanisms. Triiodothyronine is thought to favour the translocation of glucocorticoid hormone receptors from cytosol to nucleus. These findings provide more information on the relationship between vitamin A and hormonal status, showing that a vitamin A-rich diet is without apparent effect on the expression of nuclear receptors in hypothyroid rats.

The ability of dietary supplementation with carotenoids to protect chick tissues against oxidative stress in vitro was examined. Male Leghorn chicks were fed on diets supplemented (100 mg supplement/kg diet) with either β-carotene, zeaxanthin (β,β-carotene-3,3'-diol), canthaxanthin (β,β-carotene-4,4'-dione) or α-tocopherol, or on a control diet, from 1 d old until 37 d of age. Tissues (liver, heart, skeletal muscle and plasma) were removed and assayed for total carotenoids and α-tocopherol content and portions subjected to oxidative stress by incubation of homogenates with cumene hydroperoxide and FeSO4. Animals receiving zeaxanthin and canthaxanthin had significantly greater carotenoid concentrations in liver, heart, muscle and plasma compared with untreated controls (P < 0·05); animals fed on diets supplemented with β-carotene or α-tocopherol did not have significantly different tissue carotenoid contents compared with untreated controls. α-Tocopherol supplementation elevated α-tocopherol levels in all tissues examined (P < 0·05). Supplementation with caroteuoids did not affect tissue α-tocopherol levels, but β-carotene lowered plasma α-tocopherol levels by 50% (P < 0·05). Incubation of plasma or tissue homogenates with oxidant stressors induced lipid peroxidation (production of thiobarbituric-acid reactive substances) in all tissues. Animals given α-tocopherol, β-carotene or zeaxanthin had a reduced susceptibility to oxidant stress in liver compared with unsupplemented controls (P < 0·05), and α-tocopherol-supplemented animals had reduced susceptibility in skeletal muscle compared with unsupplemented controls (P < 0·05). Canthaxanthin supplementation did not influence the susceptibility to oxidant stress in any tissue examined. These results suggest that zeaxanthin, a carotenoid present in animal and human diets, may have significant activity as an antioxidant against oxidative stress in tissues.