1. Metabolic balance studies (5 d) for Se were conducted in twenty-four apparently healthy elderly people (age 69·6–85·4 years), and twenty housebound subjects (age 69·9–85·1 years) with chronic disease. During the study the subjects lived in their own homes, ate self-selected diets and continued their normal daily activities.

2. Geometric mean daily dietary intakes of the two groups were significantly different (P < 0·01), being 819 (range 310–1631) nmol for the healthy and 475 (range 233–1136) nmol for the housebound elderly.

3. Daily intake of Se significantly correlated with balance in both groups. Solution of the regression equations gave theoretical daily requirements of 447 nmol for the healthy and 419 nmol for the housebound subjects. The healthy elderly were in positive balance of 148 nmol/d for Se and the housebound were in equilibrium with an overall mean retention of 43 nmol/d.

4. Mean levels of Se in blood fractions for the healthy and housebound subjects were significantly different, being 1·65 and 1·40 μmol/l whole blood, 1·45 and 1·21 μmol/l plasma and 5·72 and 5·30 nmol/g haemoglobin in erythrocytes respectively. There was no difference in the whole-blood glutathione peroxidase (EC 1.11.1.9) activities between the two groups.

5. There were clear differences in Se status between the two groups of elderly people. The cause of the positive balance in the healthy subjects remains unexplained.

1. Twenty-five northern Thai mothers, breast-feeding their infants on demand, were studied in their homes for 24 h. All breast-feeds were test-weighed and pre- and post-feed expressed breast-milk samples (0·5 ml) taken at each feed.

2. The fat concentration of milk taken during a feed showed significant circadian variation, with maximum values between 16.00 and 20.00 hours and minimum values between 04.00 and 08.00 hours. Fat concentration at the start and at the end of a feed also varied significantly over 24 h.

3. Multiple regression analysis showed that the most important predictor of fat concentration at a feed was the length of time elapsed since the previous feed – the longer this interval, the lower the subsequent fat concentration. Other significant predictors were the fat concentration at the end of the previous feed, and the milk intake at the previous and at the current feed.

4. Fat concentration declined between feeds in proportion to the length of time between feeds, but the decline was less between sleep feeds than between waking feeds. This would appear to be a reflection of the lower post-feed fat concentration and higher pre-feed fat concentration of sleep feeds compared with waking feeds, when other variables relating to feeding pattern are taken into account.

5. The larger the milk intake at a feed, the greater was the increase in fat concentration from the start to the end of the feed. The change in fat concentration was less in feeds taking place during the sleep period than in daytime feeds.

1. The glycaemic response of healthy males to potato, bread, rice and green gram (Phaseoh aureus Roxb.) was compared with that to meals equivalent to these foods in terms of carbohydrate, protein, fat and fibre content, but made up of maize flour, casein, maize oil and ispaghula husk.

2. Natural foods led to a higher postprandial glycaemia than their respective equivalents, but the difference was significant only in the case of potato at 0.5 h (P < 0.05).

3. The insulin response, studied only in the case of rice and green gram, followed a trend similar to the glycaemic response but the differences between natural foods and equivalents were even more marked.

4. A food is more than the sum of its major nutrients. Several poorly understood factors may contribute to the glycaemic response to a food. In addition to the quantity of nutrients, the response may be the result of the specific type of nutrients, non-nutrient chemicals and anti-nutrients composing the food, and their unique physical arrangement within the food.

1. Duplicate diet analysis for energy, protein, zinc and copper with estimates of biochemical status for Zn and Cu were undertaken in twenty-one elderly long-stay inpatients (mean age 82 (range 63–89) years) consuming their customary hospital diet and in a stable medical condition. Fourteen patients had a long-standing and significant healing problem, either a leg ulcer or pressure sore.

2. Mean daily intakes of energy (5·2 MJ), protein (45 g), Zn (85 μmol) and Cu (14 μmol) were low in comparison with both official recommendations and levels of intake at which metabolic equilibrium was observed in healthy elderly people studied by the same methods (Bunker et al. 1984a).

3. Mean leucocyte Zn (9 pmol/106 cells) and Cu (7·5 pmol/106cells) were low in comparison with results from healthy elderly people (Bunker et al. 1984a), implying suboptimal status for these elements. Those patients with healing problems tended to have the lower values within the range.

4. Recommendations are made with respect to improving nutritional status in this disadvantaged group of people.

1. Zinc metabolism has been studied in a group of undernourished, slum-dwelling, lactating women in Manaus, Brazil, by means of modified metabolic balance techniques and the stable isotope 67Zn.

2. The subjects were found to be consuming a diet which provided an average of 34% of the recommended dietary allowance for lactating women, but six of the seven appeared to achieve Zn balance. In five of the subjects use of 67Zn in a stable isotope dilution manner demonstrated that they were absorbing a high proportion of the dietary Zn (proportional absorption ranged from 0·59 to 0·84), suggesting an adaptation to the chronically low intake.

3. Two subjects had marginally low plasma Zn concentrations, although hair, urine and milk Zn contents were all within accepted normal values.

4. Preliminary findings on the rate of plasma Zn turnover and the size of the exchangeable body Zn pool obtained using 67Zn suggest that these subjects may have a reduction in both.

1. The present study assesses the accuracy with which mean 24 h breast-milk composition can be estimated if milk samples can only be collected during the daytime.

2. Twenty-five northern Thai mothers, feeding their infants on demand, were studied in their homes for 24 h. All feeds were test-weighed and 0·5 ml pre- and post-feed expressed milk samples taken at each feed.

3. If daytime sampling was restricted to two breast-feeds, it was found that the best estimate of 24 h fat concentration was given by two randomly chosen daytime feeds, predicting 24 h fat concentration with 95% confidence limits of ±7·0 g/l (equivalent to 21% of mean 24 h fat concentration).

4. Alternative sampling methods using the mean fat concentration of the feed after 08·00 hours and after 18·00 hours, or the first two feeds after 12·00 hours, predicted fat concentration with 95% confidence limits of ±9·7 g/l and ±8·9 g/l (28 and 26% of mean 24 h fat concentration) respectively.

5. If well-tolerated by mothers, it would be preferable to sample all daytime feeds, since this reduces the 95% confidence limits to ±3·3 g/l, equivalent to 10% of the mean 24 h fat concentration.

1. Selenate uptake by human placental brush-border-membrane vesicles was studied in order to establish whether this anion shares a pathway with sulphate.

2. Selenate uptake was found to be saturable with respect to medium selenate and was inhibited by the anion exchange inhibitor 4,4′-diisothiocyano-stilbene-2,2′-disulphonate (DIDS).

3. Anions which have a similar tetrahedral shape to selenate, e.g. chromate, molybdate, tungstate and sulphate, were effective inhibitors of selenate uptake when added to the incubation medium.

4. Sulphate inhibited selenate influx in a dose-dependent fashion; moreover sulphate was found to be a competitive inhibitor of selenate uptake.

5. It is concluded that selenate and sulphate share a pathway for transport in the human placental microvillus membrane.

1. Five healthy volunteers (usual fat intake 103) (SE 9) g/d and energy intake 9855 (SE 937) kJ/d were given on two separate occasions (a) 100 g oral glucose and (b) sufficient intravenous (IV) glucose to obtain similar arterialized plasma glucose levels to those after oral glucose.

2. Subjects increased their fat intake by 68 (SE 9·6) % for 28 d by supplementing their diet with 146 ml double cream/d (fat intake on high-fat diet (HFD) 170 (SE 8) g/d; energy intake 12347 (SE 770)).

3. The 100 g oral glucose load was repeated and IV glucose again given in quantities sufficient to obtain similar arterialized blood glucose levels. Immunoreactive plasma insulin, C-peptide and gastric inhibitory polypeptide (GIP) were measured.

4. Plasma GIP levels were higher following oral glucose after the HFD (area under plasma GIP curve 0–180 min 1660 (SE 592) v. 2642 (SE 750) ng/l.h for control and HFD respectively; P < 0·05). Both insulin and C-peptide levels were significantly higher after oral than after IV glucose (P < 0·01) but neither were affected by the HFD. Glucose levels were lower following the HFD after both oral and IV glucose (area under plasma glucose curve 0–180 min, following oral glucose 6·7 (SE 0·3) mmol/l.h for control and 4·2 (SE 0·6) mmol/l.h for HFD; P < 0·01).

5. Glucose-stimulated GIP secretion was thus enhanced by the HFD. Insulin secretion in response to oral glucose was unchanged, in spite of an improvement in glucose tolerance.

6. The improvement in glucose tolerance post-HFD could possibly be due to a GIP-mediated inhibition of hepatic glycogenolysis, or a decreased rate of glucose uptake from the small intestine.

1. Adult male rats were maintained on diets containing 80 g methylcellulose/kg of low (25 cP), medium (400 cP) and high (1500 cP) viscosity.

2. After 10 d, the viscosity of stomach and caecal contents was found to have increased in proportion to that of the dietary fibre. Concentrations of volatile fatty acids in caecal digesta were lowest with the high-viscosity fibre but acetate was the major acid present with all three diets. Acetate was the only acid found in significant quantities in hepatic portal venous plasma and concentrations of this acid were unaffected by diet.

3. Concentrations of glucose in arterial blood were low with the medium-and high-viscosity diets while the content of liver glycogen was high. These effects of fibre were not directly on glucose absorption as the intestines were net removers of the hexose at the time of sampling.

4. Hepatic lipogenesis and plasma triacylglycerol concentrations were both higher in rats fed on the low-viscosity fibre. Plasma cholesterol concentrations, hepatic cholesterol synthesis and faecal bile acid excretion were not altered by dietary fibre viscosity.

5. We conclude that the effects of dietary fibre on carbohydrate absorption and storage and fatty acid synthesis are a function of the viscosity of the fibre in solution, high viscosity slowing the digestion and absorption of nutrients in the small intestine. Large-bowel microbial fermentation is not of direct significance to these events. In contrast, effects of fibre polysaccharides on sterol metabolism seem not to be related to their rheological properties.

1. Radio-iron absorption measurements were performed in healthy volunteer subjects to assess the availability of fortification Fe added to various bread products.

2. When ferrous sulphate was used as a fortifier, Fe absorption from a traditional Egyptian flat bread (Baladi) averaged only 16% of that observed with European bread. This difference was attributed to the high extraction flour used to prepare Baladi bread.

3. The inhibiting effect of Baladi bread was largely eliminated by adding EDTA to the flour before baking.

1. Riboflavin may play a part in the transport of iron across the gastrointestinal mucosa. Fe absorption was measured in the rat by monitoring whole-body retention of a dose of 59Fe using a small-animal γ-counter.

2. Female Norwegian Hooded rats were fed on a diet deficient in riboflavin (B2−) from 5 weeks of age. Control animals, fed on a complete diet (B2+), were weight-matched to rats fed on the B2− diet. After 7 weeks all rats were fed on a test meal extrinsically labelled with 59Fe and whole-body radioactivity measured for 15 d.

3. Riboflavin deficiency was associated with a reduction in the percentage of the dose absorbed and an increase in the rate of loss of Fe post absorption.

4. A smaller percentage of the absorbed dose was present in the livers of the riboflavin-deficient animals.

1. The present work was undertaken to study the effects of cooking, pH and polyphenol level on carbohydrate composition and nutritional quality of sorghum (Sorghum bicolor (L.) Moench). Three different sorghum varieties; Dabar, Feterita and Argentine containing zero, intermediate to low and high levels of polyphenols respectively were used in the study. From these varieties uncooked, uncooked acidified, cooked, and cooked acidified diets were prepared. Diets were characterized with regard to resistant starch (RS), dietary fibre (DF), acid-detergent fibre (ADF) and amino acid content. Raw materials were further analysed for content and composition of non-starch polysaccharides and Klason lignin. The nutritional properties were studied in balance trials with rats. True protein digestibility (TD), biological value (BV), net protein utilization, digestible amino acids, digestible energy (DE) and digestible DF were used as criteria in the nutritional study.

2. Cooking at neutral and acid pH resulted in significantly higher assayed values for DF. Increase in DF could be accounted for by formation of RS. Approximately 50% of RS was recovered in the faeces.

3. In vitro values for protein associated with ADF and in vivo balance values using rats suggest that an endosperm protein fraction, kafirins, was made unavailable during cooking. This resulted in reduced TD and increased BV. It is assumed that unavailable kafirins serve as a nitrogen source for microflora in the hind-gut.

4. Dietary polyphenols changed the excretory route for N from urine to faeces. This resulted in lower TD and higher BV in Argentine (high in polyphenols) than in Dabar and Feterita (low in polyphenols), although dietary lysine (first limiting amino acid) was the same in the three varieties.

5. Variation in DE of the diets was attributed to DF, RS and the amount of faecal protein, which in turn were influenced by undigested kafirins and polyphenols.

1. The effect of partial replacement of meat protein with three different soya-bean-protein products on bile acid and cholesterol excretion was studied in seven ileostomy subjects. Four different test diets containing 60 g meat, rice and bread protein, or a replacement of 250 g protein/kg total dietary protein by soya-bean protein from soya-bean flour, soya-bean concentrate or soya-bean isolate, were randomly assigned to the subjects in 2-d periods.

2. Ileostomy contents were collected at 2-h intervals during the day and in one portion during the night, and immediately deep-frozen to avoid bacteriological degradation. Bile acids and cholesterol were quantified by gas-liquid chromatography.

3. No difference in daily excretion of bile acids and cholesterol was noted between test diets. Ileostomy sterol concentrations were lower when soya-bean products were fed.

4. Incorporation of moderate amounts of soya-bean products in solid diets does not seem to affect short-term sterol balance in man.

1. Immature, male Wistar rats were allocated to one of six groups and caged individually. The first group was given a semi-synthetic diet containing 38 mg iron and 55 mg zinc/kg (basal group). The second and third groups were given a diet containing 10 mg Zn and 12 mg Fe/kg respectively (low-Zn and low-Fe groups). Groups four, five and six were given similar diets containing 20 g Gypsophila saponins/kg. After 21 d the Fe and Zn status of the rats was estimated and plasma cholesterol concentration determined.

2. Measurements of whole blood haemoglobin concentration, packed cell volume and liver Fe stores indicated that rats in the basal + saponin and low-Fe + saponin groups had a significantly reduced Fe status when compared with their controls. Rats in the low-Zn + saponin group also showed a trend toward reduced Fe stores.

3. Zn status, as judged by femur Zn concentration, was not adversely affected by the inclusion of Gypsophila saponins in the diet.

4. Consumption of the saponins resulted in a significant reduction in blood cholesterol concentration, with rats in both the low-Fe groups having significantly lower concentrations than their basal and low-Zn counterparts.

5. In view of suggestions that the consumption of saponins should be encouraged because of their ability to lower blood cholesterol, possible effects on Fe metabolism should be investigated further, particularly with respect to the levels and sources of saponin in the human diet.

1. The effect of addition of guar gum (5 and 10 g/l) to a radiolabelled, homogenized, baked-bean test meal on the distribution of that meal in the gastrointestinal tract was investigated in groups of male rats killed at 25, 50, 100, 200, 300 and 400 min after gavage.

2. Addition of 5 and 10 g guar gum/l significantly increased the proportion of the meal remaining in the stomach at 25 and 50 min after gavage (P <0·01).

3. The heads of the control meal and meals containing guar gum reached the distal small intestine within 25 min after gavage but radioactivity was not observed in the caecum until 100 min after administration of each of the meals. Addition of guar gum (5 and 10 g/l) delayed caecal filling even though the head of each meal reached the caecum at the same time after gavage.

4. The geometric centres of guar-gum-containing meals were proximal to that of the control meal at all times after gavage.

5. The observed delay in the passage of a guar-gum-containing meal through the stomach and small intestine is probably due to the viscous nature of the meal resisting the propulsive and mixing effects of the gastrointestinal contractions, thereby reducing access of the glucose to the absorptive epithelium. This could contribute to the observed reductions in postprandial glycaemia seen in previous studies after incorporating guar gum into a meal.