The aim of the present study was to establish whether the characteristics of members of a large national birth cohort study who submitted diet diaries with implausibly low-energy intake differed from those whose recorded energy intake was more plausible. Survey members (n 1898) recorded their diets in a 7d diary in household measures. Those whose reported energy intake (EI) as 'a fraction of their estimated BMR was less than 1·10, here termed low-energy reporters (LER) but often called under-reporters, constituted 20·6% of the study population. None of the variables describing dietary, smoking or exercise behaviour bore a significant relationship with low EI/BMR (<1·10), neither did those describing region of residence, subjective adequacy of income, current social class, social relations or the social environment of the subjects. Results of logistic regression analysis showed that the only independently significant characteristic for men was higher BMI. In women, in addition to higher BMI, having been overweight or obese as an adult independently, but less significantly, predicted low EI/BMR, while membership as a child of social class III (non-manual), having more children in the household and having a paid job marginally but independently decreased the probability of reporting low EI/BMR. Submission of a diary with EI/BMR < 1·10 7 years earlier in the same survey was an even more powerful predictor of current low EI/BMR than higher BMI in both sexes. The average reported diet-composition of LER was more micronutrient- and protein-rich than that of the others, indicating different dietary, or diet-recording, behaviour in this group of subjects. LER are not a random sample of the survey population, and their characteristics, definable to some extent, put them at risk for lower health status. Although EI/BMR cut-off points can be used to identify LER, the problem of how to use their data is still unresolved.

The use of oral contraceptive agents by women may be a factor that contributes to the observed inter-individual variability in the BMR. We, therefore, measured the BMR, body build and composition in two groups of young women and also assessed their self-reported level of physical activity. One group had been using oral contraceptive agents for a period of 6 months or more (OCA, n 24), while the other group had never used oral contraceptives (NOCA, n 22). There were no significant differences in age, body build or composition. The absolute BMR in the two groups were not significantly different when compared using an unpaired t test (OCA: 5841 (SD 471) v. NOCA: 5633 (SD 615)kJ/d). However, using an analysis of covariance, with either body weight or a combination of fat and fat free mass as covariates, the OCA group had a BMR almost 5% higher than that of the NOCA group (OCA: 5871 v. NOCA: 5601 kJ/d; P=0·002). When those subjects with high self-reported levels of physical activity were excluded, the difference in BMR between the two groups persisted (P = 0·001). An ANOVA of oral contraceptives use and phase of menstrual cycle showed significant differences in BMR with use of oral contraceptives (P=0·004) but no difference in BMR between phases of the menstrual cycle. In conclusion, the ose of oral contraceptive agents deserves consideration when conducting and analysing data from studies on energy metabolism in young women, as it results in a significantly higher BMR.

To investigate the chronological changes in conjunctival epithelium after supplementation with a massive oral dose of vitamin A, conjunctival impression cytology (CIC) with transfer was carried out repeatedly among 200 children aged 6–120 months in a randomized, double-blind, placebo-controlled study in Chandigarh (India). Significant conversion to normal CIC started 71–80 d after vitamin A supplementation and by 101–110d conversion had taken place in all children. Compared with the placebo group, plasma retinol concentration at 100d post-supplement was found to be significantly higher in the vitamin A-supplemented group P = 0·04. This study demonstrates that CIC responds to a massive oral dose of vitamin A 3–4 months after supplementation. These findings should guide future studies and evaluations in which CIC is used to assess response to vitamin A interventions.

We examined the effect of maternal chronic cold exposure, induced by winter-shearing ewes 4 weeks before their predicted lambing date, on brown adipose tissue (BAT) and liver development in lambs. Fetuses were sampled from under-fed (60% of energy requirements for maintenance and pregnancy of an unshorn ewe) shorn or unshorn ewes at 126,140 and 145 d of gestation. Lambs were sampled from ewes within 2 h of birth. Throughout gestation fetal body, BAT and liver weights were similar in shorn and unshorn groups. The level of GDP binding to mitochondrial uncoupling protein remained low throughout gestation, but increased dramatically after birth. Lambs born to shorn ewes possesd more mitochondrial protein and exhibited a significantly higher total thermogenic activity in BAT. Type I iodothyronine 5 deiodinas(EC 3.8.1.4) activity in BAT peaked at birth, as did hepatic iodothyronine Sdeiodinase activity and was significantly greater in lambs born to under-fed shorn ewes, which exhibited a higher plasma triiodothyronine concentration. Chronic maternal adaptations to prolonged cold exposure appear to enable pregnant ewes to compensate for the negative effects of under-feeding on fetal growth and development

The effect of a high dose of 3-hydroxy-3-methylbutyrate (HMB, a leucine catabolite) on protein metabolism was investigated in growing male lambs fed on hay and concentrate. Concentrate was supplemented with either Ca(HMB)2 (4g/kg) or Ca(C03)2 in experimental (HMB) and control groups respectively. Both groups consisted of six 2-month old lambs. Three complementary methods to study protein metabolism were carried out consecutively 2·5 months after beginning the dietary treatment: whole body phenylalanine fluxes, postprandial plasma free amino acid time course and fractional rates of protein synthesis in skeletal muscles. Feeding a high dose of HMB led to a significant increase in some plasma free amino acids compared with controls. Total, oxidative and non-oxidative phenylalanine fluxes were not modified by dietary HMB supplementation. Similarly, an acute infusion of HMB, in the control group, did not change these fluxes. In skeletal muscles, fractional rates of protein synthesis were not affected by long-term dietary supplementation with HMB. Taken together our results showed that administration of a high dose of HMB to lambs was able to modify plasma free amino acid pattern without any effect on whole-body protein turnover and skeletal muscle protein synthesis

The present experiments4 were undertaken to investigate the effects of environmental temperatures on growth, abdominal fat content, rate of muscle protein turnover, and heat production in tube-fed intact male broiler chickens. Plasma concentrations of thyroxine (T4), triiodothyronine (T3), and corticosterone (CTC) were also examined. Chicks (15d old) were kept at different environmental temperatures (16,19,22,25,28,31, and 34°) and given the experimental diet (200g crude protein/kg, 13·;57M/kg metabolizable energy) by tube three times daily throughout the 12d experimental period. In the hot conditions, except for 34°, body-weight gain was significantly higher than in the cold conditions. Thus, food conversion ratios (food: gain ratios) were lower when the birds were exposed to the hot conditions other than 34°. Likewise, abdominal fat content was significantly increased, and heat production was lower in the groups kept under the hot conditions other than 34°. The rate of skeletal muscle protein turnover and plasma concentration of CTC were decreased when the birds were exposed to hot conditions other than 34°. suggesting a role of CTC in the regulation of muscle protein turnover. Plasma concentrations of T4 and T3 were significantly decreased as environmental temperature increased. These results clearly show that plasma concentrations of thyroid hormones and CTC are associated with accelerated muscle protein turnover and heat production.

The relationship between in vitro gas production, concomitant in vitro apparent and true DM degradability has been examined in forty-two roughages. The partitioning of truly-degraded substrate between gas volume and microbial biomass yield and 15N incorporation into cells was also investigated. The relevance of this partitioning for the regulation of DM intake (DMI) was examined for fifty-four roughages. The results can be summarized as follows. In vitro gas production and in vitro apparent and true degradability are highly correlated (P<0.0001), r being 0.96 and 0.95 respectively. There is an inverse relationship between in vitro gas production and microbial biomass yield (r—0.67, (P<0.0001) and also 15N enrichment (P<0.001)when the variables were related to a given unit of substrate truly degraded. Selecting roughages by in vitro gas production may well be a selection against maximum microbial yield and a combination of in vitro gas volume measurements with a complementary determination of the substrate truly degraded is proposed, to calculate a partitioning factor (PF) reflecting the variation of short-chain fatty acid production per unit substrate degraded. PF is calculated as the ratio, substrate truly degraded: gas produced by it. PF was highly significant (P<0.0001) in DMI prediction when included in stepwise multiple correlations together with in vitro gas volume variables reflecting the extent and rate of gas production; 11 % of the variation in DMI was accounted for by the PF. The total model, including extent and rate of gas production and the PF, accounted for 84 % of the variation in DMI. Roughages producing proportionally less gas per unit substrate truly degraded had higher feed intakes.

The effect of policosanol, a mixture of high-molecular-weight aliphatic alcohols isolated from sugar-cane wax, on casein-induced hypercholesterolaemia in rabbits was studied. When policosanol was administered by the oral route once daily for 30 d (50mg/kg) the increases in plasma total cholesterol and LDL-cholesterol (LDC-C) were significantly reduced when compared with the control group. The incorporation of 3H2O into sterols in the liver was significantly depressed, suggesting inhibition of hepatic cholesterol biosynthesis. The oral administration of policosanol raised the rate of removal of 125l-labelled LDL from serum. Kinetic parameters calculated following injection of [125I]LDL showed than in casein-fed rabbits, the terminal half-life (t½) was significantly decreased after policosanol treatment. The hepatic LDL-binding activity was increased after policosanol administration which suggested that the enhanced clearance was due, at least in part, to increased receptor-mediated uptake of LDL by the liver. Considered together, these results suggest that policosanol can significantly reduce the increase of plasma LDL-C in rabbits fed on a wheat starch-casein diet by reducing cholesterol biosynthesis in the liver. Such an effect could account for the enhancement of LDL catabolism through the receptor-mediated pathway.

A diet-switching experiment, which aimed to improve the utilization of soyabean whey was carried out for 61 d with young rats. Feeding was arranged in such a way that after a few days on the soyabean diet, the rats were switched to a high-quality lactalbumin diet for a short period, after whicb the cycle was repeated several times. The weights of the rats at the end of the soyabean phases were significantly less than those of animals pair-fed on a high-quality diet throughout. However, the test group regained the weight loss after switching to the lactalbumin diet. After three cycles there were no significant differences between the weights of the test rats fed on a poor soyabean diet for over a third of the experiment and those fed on the lactalbumin diet throughout. Feed conversion was always significantly higher with test rats in the lactalbumin period than with continually pair-fed controls. Similarly, faecal N losses were significantly higher for test rats in the soyabean phase, but these differences disappeared after switching to the lactalbumin diet. At the end of the experiment there were no significant differences in body protein or lipids between the groups although the pancreas was significantly heavier while the liver was lighter in soyabean-fed rats. The high destruction of trypsin inhibitors in the gut suggests that they probably had little effect on protein digestion in the gut. In contrast, as selective depletion of the agglutinin from soyabean whey removed the nutritional benefit in the lactalbumin part of the cycle, the improved feed conversion in this period must have been the result mainly of the survival and functionality of soyabean agglutinin and the benefits due to the hyperplastic growth and faster renewal of the gut surface it induced. As processing is unnecessary, this novel method is cheap and can be easily adapted for the use of soyabean whey, regarded as a waste product.

Diets containing unheated casein (CD; control) or a casein-glucose mixture (CGD) previously heated at 140° for 2 h were fed to two groups of young rats for 21 d. Differences in body weight, feed consumption, thymus and spleen growth, protein metabolism and in vivo immune response were then determined. For this last experiment, animals were inoculated with sheep erythrocytes (SRBC) on day 15 to provide an immunological challenge. No changes were seen in body weight, feed consumption or feed conversion ratios. Neither were significant differences found in spleen weight, protein content, DNA content, DNase (EC 3.1.4.6) activity or lymphocyte count, suggesting that spleen cell growth remained similar in all the animals studied. The CGD induced marked increases in thymus DNA content whilst the protein:DNA ratio became lower. Spleen RNA content was similar in all rats, but thymus RNA content was 29% lower in the CGD group, although this difference did not reach statistical significance. This fact might be a consequence of the low RNase (EC 2.7.7.16) activity and RNase:RNA ratios in the thymus glands of CGD-fed animals. Further, the number of splenic plasma cells secreting anti-SRBC antibodies (direct plaque-forming cells) was significantly decreased in the same group. It might be concluded that both diets are adequate for rat growth and that the differences observed in the thymus of CGD-fed rats may be directed towards preserving tissue function. Nevertheless, the CGD did cause immunological disturbances affecting the humoral immune response.

The present work aimed to investigate the feasibility of using stable isotopes and inductively-coupled plasma mass spectrometry (ICP/MS) to study Mg absorption in rats. Male Wistar rats, aged 7 weeks and weighing 180g, were used. They were fed on a semi-purified diet containing 1070mg Mg/kg, and had free access to feed and distilled water. In the first experiment, after a 16d adaptation period, two doses of enriched 25Mg (6 and 12mg) were administered by oral intubation, faeces and urine were collected daily and blood was sampled. Isotope ratios were determined by ICP/;MS. ‘True’ absorption values, using the faecal isotope data, were 0.63 and 0.56 in rats receiving 6 and 12mg 25Mg respectively, while apparent absorption was 0.50 for two successive periods of metabolic balance studies. Moreover, the oral isotope administration resulted in a measurable isotopic enrichment in plasma within hours which was still detectable on the third day following the isotope administration. In the second experiment, investigating the double labelling technique, similar rats were dosed Simultaneously with 5mg 26Mg orally (premixed with diet) and 0.29mg 25Mg intravenously. The calculated Mg true absorption values were very similar when calculated from blood or urine data (0.38) but were lower than that obtained from faecal data (0.50). The possible causes of such an unexpected difference and limits of the double labelling technique for Mg absorption are discussed here. Together these results indicate that although 25Mg and 26Mg isotopes have high natural abundance, the described methodology permits meaningful investigations of Mg bioavailability and metabolism