Body composition was measured in twenty young females aged 19−27 years and eighteen elderly females, aged 65−78 years by densitometry (underwater weighing), deuterium oxide dilution and dual-energy X-ray absorptiometry (DXA). From body weight, bone-mineral content, total body water and body density, percentage body fat (BF%) was calculated using a four-compartment model. BF% abtained by this four-compartment model was regarded as a reference method and BF% obtained by the single methods were compared with this value. Differences in BF% from the four-compartment model minus the single methods were 2·1 (SD 1·2) for densitometry, 3·1 (SD 1·8) for DXA and -0·6 (SD 0·9) BF% for deuterium oxide dilution in the young women. In the elderly women these values were -0·6 (SD 2·3), 5·3 (SD 3·8) and 0·7 (SD 2·2) BF%. When a three-compartment model (calculated from body density and total body water) was compared with the four-compartment model, the bias was 0·4 (SD 0·3) BF% in the young and 0·0 (SD 0·3) BF% in the elderly women. From the mineral and water fractions in the fat-free mass the true density of the fat-free mass was calculated as 1·1070 (SD 0·0047) kg/l in the young females and 1·0970 (SD 0·0088) kg/l in the elderly women (P<0·001). This study shows that the single methods have considerable mean and individual biases compared with the four-compartment model, but that a three-compartment model calculated from density and total body water offers an acceptable alternative. The difference in calculated density of the fat-free mass between the young and the elderly women shows the need to adapt Siri's formula for specific groups.

Energy and nutrient intakes were assessed in 136 children, aged 7–8 years and living in and around Edinburgh, using the 7 d weighed inventory technique. The results were compared with UK dietary reference values (DRV) for energy, macronutrients and micronutrients. NSP intakes were compared with a calculated reference value (CRV). Mean energy intakes were close to the estimated average requirement for both boys and girls. Mean percentages of food energy derived from fat and saturated fat were high in relation to DRV (37 and 14 compared with 35 and 11 respectively). Mean percentage of food energy derived from total carbohydrate was close to the DRV of 50 but intakes of starch appeared to be low and intakes of total sugars high (23 and 26% food energy respectively). Superficially, this suggests that there is a need to alter the balance of carbohydrate in favour of increasing starch and lowering total sugar. There was, however, a clear ‘fat-sugar seesaw’, i.e. children with a high percentage energy from total sugars had a low percentage energy from fat, and vice versa. In view of this finding, it is possible that efforts to reduce total sugar intake in children may result in a further increase in percentage energy from fat. Mean intakes of NSP were only 50% of the CRV, but this guideline may be set too high. Mean intakes of most micronutrients were above reference nutrient intakes. Reported low intakes of Zn and Se were treated with caution due to the perceived incompleteness of the data for these in the nutrient database. The authors concluded that targeting high intakes of total fat and saturated fat should be the health priorities in this age-group.

The glycaemic index (GI) is an in vivo measurement based on the glycaemicresponse to carbohydrate-containing foods, and allows foods to be ranked on the basis of the rate of digestion and absorption of the carbohydrates that they contain. GI values are normalizedto a reference amount of available carbohydrate and do not reflect the amounts of carbohydrate normally present in foods; for example, a food with a low content of carbohydrates will have a high GI value if that carbohydrate is digested and absorbed rapidly in the human small intestine. This is potentially confusing for a person wishing to control his or her blood glucoselevels by the choice of foods. The rate and extent of starch digestion in vitro has been measured using a technique that classifies starch into three major fractions: rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). In addition, thistechnique gives a value for rapidly available glucose (RAG), which includes RDS, free glucose and the glucose moiety of sucrose. When the values for thirty-nine foods were expressed on the basis ofthe available carbohydrate content of these foods, highly significant (P<0·001) positive correlations were observed between GI and both RDS and RAG. The measurement of RAGin vitro provides values for direct calculation of the amount of glucose likely to be rapidly absorbed in the human small intestine and,thus, to influence blood glucose and insulin levels. These values can be used to compare foods, as eaten,on an equal-weight basis. Food-table RAG values would allow simple calculation of the total amount of RAG provided by single foods, by whole meals and by whole diets. Studies are planned in which RAG and the glycaemic response in man will be measured for identical food products.

Using percentage body fat (BF%) from a three-compartment (3C) model (body density from underwater weighing (UWW) and bone-mineral mass from dual-energy X-ray absorptiometry (DXA)) as a criterion, we studied the accuracy of UWW, DXA, two skinfold equations, and two bioimpedance (BIA) equations. Thirty-four women (aged 16–20 years) with BF% 13·5–31·1 volunteered. UWW underestimated BF% by −0·5 BF% (95 % CI: −1·0; −0·02), whereas DXA overestimated it by 7·3 BF% (95% CI5.8;8·8). Skinfolds underestimated and BIA overpredicted BF%. The differences between 3C and UWW, skinfolds (Durnin & Womersley, 1974) and BIA (Deurenberg et al. 1990) were dependent (range of r values: −0.63 to −0.79; P < 0·0001) on BF%, causing an overestimation of lean subjects' (UWW, BIA) or an underestimation of normal-weight subjects' (UWW, skinfolds) BF%. The 3C model and UWW gave comparable body-composition results for healthy young women with BF% of approximately 20–25. Based on a significant mean difference from the 3C model, and a large standard error of the estimate, we do not regard DXA as superior to skinfolds or BIA to assess BF%.

In pre-industrial times, honey was the main source of concentrated sweetness in the diets of many peoples. There are no precise figures for per capita consumption during most periods in history because honey was part of either a hunter-gatherer or subsistence economy. Until now, historians and food writers have proposed that it was a scarce commodity available only to a wealthy few. We do know, however, that in a cash economy honey was sold in large units (gallons and even barrels) and it was present in such abundance that mead, made from honey, was a common alcoholic drink. A reappraisal of the evidence from the Stone Age, Antiquity, the Middle Ages and early Modern times suggests that ordinary people ate much larger quantities of honey than has previously been acknowledged. Intakes at various times during history may well have rivalled our current consumption of refined sugar. There are implications therefore for the role of sugar in modern diets. Refined sugar may not have displaced more nutrient-rich items from our present-day diets but only the nutritionally comparable food, honey.

Four pigs fitted with a gastric cannula were fed on a wheat-flour-based diet (WF) and three oat-based diets, consisting mainly of oat flour (OF), rolled oats (RO) or oat bran (OB), for 1 week each. The stomach contents were collected quantitatively daily at 0·5, 1, 2, 3 or 5 h after feeding. The viscosity (mPa. s) of the liquid fraction of stomach contents 1 h after feeding was 1·7 with diet WF, 15 with diet OF, 30 with diet RO and approximately 400 with diet OB. The viscosity and the concentration of β-glucan in the liquid phase was to some extent determined by the dietary level of β-glucan in the diet. However, there was a trend towards a lower viscosity after longer exposure to the gastric juices. The correlation between logarithmic values for viscosity and concentration of β-glucan in the liquid phase of digesta was r 0·45. On centrifugation of digesta there was a higher proportion present in the sediment phase when the pigs were fed on diets with a higher content of soluble dietary fibre (DF), suggesting that the digesta was more coherent. This possibility was supported by the higher water-holding capacity (WHC) of the sediment. Feeding diets with oats containing a higher soluble DF content led to lower recoveries of digesta, PEG 4000 (liquid-phase marker), and the DF components β-glucan and arabinoxylan in the first hour after feeding. No effect related to the DF content of the diet was seen in the gastric emptying of starch and Cr2O3 (solid-phase marker). In conclusion, soluble DF from oatsincreased the viscosity of stomach contents and increased the ability of the dry matter to retain water. Higher levels of soluble DF led to higher recoveries of digesta, the liquid phase and DF itself in the initial stage of gastric emptying, whereas no effect was seen on the gastric emptying of starch.

We investigated the relationships between BMR, fat-free mass (FFM) and fat mass in pregnancy. BMR was measured by indirect calorimetry and body composition was assessed by densitometry in seventeen non-pregnant women (79·9 (SD 26·3, range 505−151·4) kg) and sixteen pregnant women (75·7 (SD 20·6, range 545−115·9) kg). The pregnant women were evaluated during weeks 31−35 of gestation. Multiple regression analysis of BMR with FFM and fat mass in the non-pregnant women showed that FFM was a highly significant predictor of BMR (P < 0·0001), but fat mass was not (P = 0·09). In contrast, in the pregnant women, multiple regression analysis revealed that fat mass was a highly significant predictor (P < 0·001), while FFM was not (P = 0·69). Evaluation of the interaction terms in the combined data set confirmed that the relationships of BMR with FFM and fat mass differ significantly in non-pregnant and pregnant women. It is proposed that pregnancy represents a unique condition during which BMR is regulated by maternal adipose reserves. An augmented BMR in overweight pregnant women may be protective, given that excessive weight gain may be detrimental to neonatal and maternal health.

Current recommendations for energy requirements in the elderly are based on assumed levels of physical activity relative to BMR (1.5 x BMR). The main aim of the present study was to establish whether these recommendations might be applicable to a randomly-selected group of free-living elderly men (all over 75 years of age). BMR was measured by indirect calorimetry and total energy expenditure (TEE) by the doubly-labelled-water technique. Further aims included evaluating the applicability of a variety of BMR prediction equations and whether assessed quality of life reflected any measured indices of energy expenditure. The mean value for daily energy requirement was found to be 1.5 x BMR (89 J/kg per min) but with substantial inter-individual variation (SD 0-2 x BMR; 14 J/kg per min). The bias between measured TEE and TEE estimated (1.5 x BMR) from the various BMR predictions varied according to which equation was used (-10-+ 8% of the mean) with substantial 95 YO limits of agreement (28-30%of the mean). TEE and physical activity plus thermogenesis (TEE -BMR) were positively related to activities of daily living, but no relationships were apparent between these and perceived quality of life. It is concluded that, despite considerable inter-individual variability, national recommendations for energy requirements of elderly people are applicable to this randomly-selected group of free-living men over 75 years of age but that substantial variation exists when attempts are made to estimate TEE from measurements or predictions of BMR.

Dual-energy X-ray absorptiometry (DXA) is a novel, non-invasive technique for the measurement of gross body composition in small animals. In the present study the absolute accuracy of the Hologic QDR-lOOOW scanner was assessed by comparison with direct analysis in twelve rats with a range of body fat and bone mineral content (BMC) values. Fat masses measured by DXA and petroleumether extraction were significantly different (P<0·0023). The DXA technique consistently overestimated fat mass by approximately one third of the measured fatcontent. BMC derived from the measurement of Ca in asb gave a mean of 8·26 (range 1·57–15·71)g. BMC measured by DXA was not significantly different for the group as a whole. However, there was a trend for DXA to overestimate BMC in animals with low BMC and underestimate in those with higher BMC, compared with direct analysis, such that the 95% limits of agreement for the two techniques were +2·73 to −2·58g. These results suggest that the present small-animal software developed for use with currently available Hologic machines does not give an accurate measure of gross body composition compared with the results from classical direct analysis.

The aim of the work was to compare the faecal output and digestibility estimated by two mathematical approaches with the actual amount of faeces excreted or feed digested by Siental cows. Experimental data (intakes and digestibility measured over 5 d) and faecal Cr concentrations (measured at 0, 4, 8, 12, 16, 24, 32, 48, 56, 72, 96, 120 and 144 h after a pulse dose of Cr-mordanted forage) were collected from published experiments and fitted to a multicompartmental (MC) model and a γ age-dependent (AD) model. From a statistical point of view, the MC model was very satisfactory while the AD model produced lower r2 and higher SE values and reached satisfactory statistical values only for higher DM intakes (lactating animals). The MC model produced higher correlations with the digestibility values while the AD model generated better correlations with the intake data; DM intake and digestibilities were more highly correlated with the model's parameters than neutral-detergent fibre terms. The regression between the estimated faecal outputs obtained with the two models showed an intercept closeto 0 (P>0·05) and angular coefficients near 1; there was a good correspondence of the estimates especially for the lowest values of output. The r2 values of the regressions were 0·800 and 0·829 for the MC and AD models respectively and their SE were 2·93 and 2·63. The ability of the two models to predict faecal output and digestibility was very similar, independent of the statistical accuracy of fitting the Cr- concentration data. The results indicate that variation of Cr concentration is the result of the entire digestive process, i.e. dilution and passage, which interact in a competitive or associative way.

It has been reported that loss of ovarian oestrogen after menopause or by ovariectomy causes osteoporosis. In order to elucidate the effect of dietary protein restriction on bone metabolism after ovariectomy, we fed ovariectomized young female rats on a casein-based diet (50g/kg diet (protein restriction) or 200g/kg diet (control)) for 3 weeks and measured mRNA contents of bone-matrix proteins such as osteocalcin, osteopontin and α1 type I collagen, insulin-like growth factors (IGF) and IGF-binding proteins (IGFBP) in femur. Ovariectomy decreased the weight of fat-free dry bone and increased urinary excretion of pyridinium cross-links significantly, although dietary protein restriction did not affect them. Neither ovariectomy nor protein restriction affected the content of mRNA of osteopontin and osteocalcin; however, ovariectomy increased and protein restriction extensively decreased the α1 type I collagen mRNA content in bone tissues. Ovariectomy increased IGF-I mRNA only in the rats fed on the control diet. Conversely, protein rest riction increased and ovariectomy decreased the IGF-II mRNA content in femur. Furthermore, the contents of IGFBP-2, IGFBP-4 and IGFBP-5 mRNA increased, but the content of IGFBP-3 mRNA decreased in femur of the rats fed on the protein-restricted diet. In particular, ovariectomy decreased the IGFBP-2 mRNA content in the protein-restricted rats and the IGFBP-6 mRNA content in the rats fed on the control diet. These results clearly show that the mRNA for some of the proteins which have been shown to be involved in bone formation are regulated by both quantity of dietary proteins and ovarian hormones.

An experiment was conducted in the pig to determine the consequences of deprivation of exocrine pancreatic secretion on the composition and quantity of nutrients absorbed after intake of a balanced diet. Five growing pigs (53·8 kg body weight) were fitted with permanent catheters in the portal vein and the carotid artery and with an electromagnetic flow probe around the portal vein to measure the exchanges between the blood and the intestinal lumen. They were also fitted with a permanent catheter in the duct of Wirsung to educe the exocrine pancreatic secretion and another one in the duodenum in order to reintroduce it. In each animal, glucose, amino-N and amino acid absorption as well as insulin and glucagon production were measured over a period of 10 h after the meal (semi-purified diet based on purified starch and containing 180 g fish meal/kg, DM content of the meal 731 g), either in the presence of pancreatic juice (group C : immediate reintroduction), or in the absence of pancreatic juice (group D: deprivation). The deprivation of pancreatic juice provoked a marked depression in the absorption of glucose (D 67·9 (SEM 27·9) g/10 h, C 437·7 (SEM 39·5) g/10 h, P < 0·00l), and of amino-N (D 7·55 (SEM 0·54) g/10 h, C 15·80 (SEM 0·79) g/10 h, P < 0·001). The composition of the mixture of amino acids in the portal blood was only slightly modified: only the levels of histidine (P < 0·05) and of valine (P < 0·06, NS) decreased in the absence of pancreatic juice. Insulin production was much lower (by 64%, P < 0·05) in the absence of pancreatic juice whereas that of glucagon was not affected.

The purpose of the present study was to assess whether rats are capable of selecting the right proportions of two diets that are individually inappropriate in terms of essential amino acid composition to satisfy their amino acid requirements. Rats were offered a choice of one protein-free regimen and another devoid of only one essential amino acid (either threonine or isoleucine) set up in such a way as to provide amino acid balance if they were consumed in 1/3 and 2/3 proportions respectively. Preliminary experiments had established that all our diets were aversive by themselves except for the 60 g casein/kg diet. Rats did reach almost the necessary proportion with, according to published standards (National Research Council, 1978), some excess in isoleucine intake. In addition, given access to two aversive diets that were each nutritionally inadequate, rats showed no aversion and gained body weight when they had the opportunity to consume both of them. Beyond the capacity that rats have of rebalancing their micronutrient intake, the present experiment brings out the idea that the imbalance-induced aversion: preference ratio may be completely upset when this omnivore has access to more than one feed.

There is a lack of information concerning the diet of vegetarian children. The present study compared the dietary intake of fifty vegetarian children, aged 7–11 years, with fifty matched omnivores. Three 3 d food records were completed by each child at intervals of 6 months. The day after completing the record each child was interviewed to clarify food items and assess portion sizes. Food records were analysed using Microdiet (University of Salford). Finger-prick cholesterol and haemoglobin measurements were taken from a subsample of the group. Only one child's family was a member of the Vegetarian Society and almost one-third of vegetarian children had omnivorous parents (seventeen of fifty subjects). The energy intake (MJ) of the vegetarians was significantly lower than that of the omnivores, 7·6 (SD 1·05) and 8·0 (SD 1·36) respectively; there were no significant differences in Fe or fat intakes. For the vegetarians polyunsatnrated:saturated fat ratio (P:S 0·7 (SD 0·04)) and NSP intake (13·8 (SD 0·7) g/d) were significantly higher than those of the omnivores (P:S 0·5 (SD 0·02), NSP 10·3 (SD 0·4) g/d). There was no significant difference in cholesterol measurements (mmol/I) between the two groups: vegetarian 3·5 (SD 0·12), omnivores 3·7 (SD 0·15). The haemoglobin level (g/I) of the vegetarians (11·8 (SD 0·2)) was significantly below that of the omnivores (12·4 (SD 0·2)); 47·5% of the vegetarian children fell below the third percentile of the Dallman reference curves (Dallman & Siimes, 1979). The intake of the vegetarians more closely resembled current recommendations (Department of Health, 1991), although they need to be as aware as omnivores of the need to reduce fat intake. The haemoglobin levels of vegetarian children suggest that they need dietary advice to ensure optimal absorption of Fe.

The present work was undertaken to study in vivo fibre degradation, rate of passage and caecal fermentation activity (CFA) in the young rabbit (7 weeks old) receiving ad lib. a control (C) or a lowfibre (LF) diet (400 and 220 g neutral-detergent fibre (NDF)/kg respectively). As a consequence of the 50% reduction in the dietary fibre level, the voluntary food intake of the rabbits decreased by 25%, and the daily fibre intake was reduced by 60% (26·7 and 10·8 g NDF/d for groups C and LF, respectively).In spite of a longer mean retention time of the fibre particles, the quantity of fibre digested daily was significantly lower (P<0·01) for the LF than for the C group (4·0 and 7·8 g NDF/d respectively). The circadian distribution of the faecal excretion (as a percentage of the total DM output) did not differ between diets (P = 0·52) and no interaction was found (P = 0·96) between diet and time of excretion. Also, variables describing the CFA showed no interactions between diet (C or LF) and time of sampling (during caecotrophy or during hard faeces excretion). Our results indicated no direct relationship between the quantity of fibre digested and the total short-chain fatty acid concentration in the caecum, but the fermentation pattern indicated lower proportions of acetate for the LF diet. Higher levels of diaminopimelic acid (DAPA) and ATP were found for the LF diet associated with an improved dietary fibre digestibility, suggesting a higher microbial activity. However, this effect was balanced by a lower caecal digesta turnover rate and the microbial biomass output estimated through the faecal DAPA output did not vary significantly

Threonine oxidation to glycine was investigated in vivo in twelve growing pigs (27·4 kg live weight) fed on one of the following three diets with graded levels of threonine supply: a low-threonine diet (LT), a control well-balanced diet (C) or a high-threonine diet (HT), during 10h constant infusion of L-[1-13C]threonine and [2-3H]glycine in the cranial vena cava and [l-14C]glycine in the portal vein.13C-threonine and glycine enrichments and [3H]glycine and [14C]glycine specific radioactivities (SR) were determined at plateau in peripheral venous plasma, liver and pancreas. Glycine praduction rates calculated from plasma [2-3H]glycine or [1-14C]glycine SR gave similar values suggesting that [l-14C]glycine SR could be used in order to estimate whole-body glycine flux. The high pancreas [1-13C]glycine enrichment provided evidence that the pancreas may be, with the liver, a major site of threonine oxidation to glycine. Moreover, the present findings suggest that threonine transport into the Liver could be the limiting step of threonine oxidation in this tissue when dietary threonine supply is low. Total threonine oxidation to glycine, calculated from plasma values of enrichment and specific radioactivity, was low and constant when the estimated absorbed threonine was lower than 4 g/d and increased for higher amounts of absorbed threonine.

The present study was undertaken to provide detailed information about the effect of dietary fibre (DF)level on the development of the digestive tract, on nutrient digestibility and on energy and protein metabolism of pigs housed in low (13°) or high (23°) thermal environments. Low- and high-fibre diets (59 v. 268 g DF/kg DM) were studied in three balance periods with fistulated pigs in the weight range 45-120 kg. Heat production was measured using open-circuit respiration chambers. Pea fibre and pectin were used to adjust theDF level in the high-fibre diet. Per kg empty body weight the stomach, caecum and colon and the length of colon were significantly greater in pigs consuming the high-fibre diet than in those on the low-fibre diet. Pigs kept at low temperature had significantly heavier caecums than those kept at the high temperature. Digestibilities of protein, DM and energy were lowest for the high-fibre diet. Only minor amounts of NSP and its constituent sugars were degraded anterior to the ileum, whereas in the hind-gut the fermentation of the total NSP fraction was high, being 0·77 for the high-fibre diet and 0·59 for the low-fibre diet. Feeding the high-fibre diet increased the flow of digesta through the terminal ileum 5-6-fold and an extra 460 g organic matter was fermented daily in the hind-gut compared with pigs fed on the low-fibre diet. The amount of retained energy as a proportion of metabolizable energy decreased in relation to the amount of energy fermented in the hind-gut. Based on the present data it was estimated that the relative value of energy derived from hind-gut fermentation was 0·73 in comparison with energy enzymically digested in the small intestine. There was negligible effect of the temperature –fibre interaction on energy metabolism. However, it could be calculated that the decrease in temperature from 23° to 13° was associated with an increase in heat production by 2.9 MJ/pig per d.