1. Longitudinal changes in nutritional habits were studied in Dutch adolescents from 12 to 17 years of age (131 girls and 102 boys). The dietary differences on schooldays and weekend days are reported.

2. In girls only small changes in nutritional habits were seen as they grew older. In boys there was a gradual increase in food intake with age.

3. Overall, higher nutrient intakes could be seen on weekend days. The energy intake on weekend days was consistently higher for girls and boys in all age-groups. The proportional intakes of fat and sugar were rather high, especially on weekend days. The alcohol consumption increased with age for girls as well as boys, and was for some individuals extremely high (boys) on weekend days.

4. The observed levels of intake compared with the recommendations showed a rather low intake of polyunsaturated fatty acids, polysaccharides and iron.

1. The effect of a high-fibre bread mixed with guar-gum (75 g/kg flour) on serum glucose, connecting peptide (C-peptide), haemoglobin A1 (HbAI), high-density-lipoprotein-cholesterol (HDL-cholesterol) and triglycerides was examined in fourteen elderly patients with diabetes mellitus type II.

2. The mean daily consumption of guar gum was 8.1 g. Gastrointestinal disorders were not observed.

3. Consumption of guar-gum bread resulted in a significant decrease in C-peptide values on the 1st day and blood glucose values after 3 weeks (both measured 90 min after breakfast). C-peptide values remained low, while an unaccountable ‘rebound’ phenomenon was seen in the blood glucose values 90 min after breakfast at the end of the study.

4. No significant change was seen in respect to HDL-cholesterol and triglycerides. However, a small significant increase in HbAl was noted.

1. Rat pups were artificially reared (AR) from post-natal day 5 by intermittent gastric infusion. Mother-reared (MR) siblings served as controls. Fourteen measures of body and organ growth were taken at the end of each experiment.

2. In Expt 1, two batches of pups were given rats' milk only, obtained by manual expression from anaesthetized dams.

3. The first batch, reared to 12 d, grew less well than the MR group, probably because they received too little milk. However, relative to body-weight, organ weights were as great or greater than those of MR pups, except for heart weight. The second batch, given more milk and reared to 20 d, showed no deficits in organ or body-weights, but excesses in kidney, gastrocnemius muscle, stomach and caecum weights. There were no losses from ‘bloat’, a condition of gastrointestinal distention often encountered in artificial rearing with milk substitutes.

4. Obtaining rats' milk is extremely labour-intensive and in Expt 2, more economical regimens were devised in which pups were started off on expressed rats' milk and then changed to a milk substitute resembling rats' milk in composition, either abruptly at 12 d or gradually between 8 and 17 d.

5. Both regimens were successful, in that there were no losses from bloat and most measures of growth were at least as great as in the MR group. Only heart weight was lower in both AR groups and adrenal weight in the abruptly changed AR group. The weights of the stomach and caecum and the length of the small intestine were all high in both AR groups.

6. It is concluded that giving rat pups expressed rats' milk for the first few days of artificial rearing largely avoids the problem of bloat and results in satisfactory growth.

1. An assessment of iron and folic acid status, blood thick film and haemoglobin (Hb) electrophoresis was performed on 126 pregnant women (and their newborn infants) and in ninety-five menstruating women in Cotonou (Benin).

2. Anaemia (according to the World Health Organization (1972)) was observed in 55% of pregnant women and in 39% of menstruating women.

3. Fe-deficiency was defined as a low serum ferritin concentration (12μg/l or less), combined with a low transferrin saturation (less than 16%) or a high erythrocyte protoporphyrin level (more than 3 μg/g Hb), or both. A moderate elevation in the serum ferritin concentration (between 13 and 50 μg/l), associated with a low transferrin saturation or a high erythrocyte protoporphyrin level, or both, indicated Fe-deficiency in an inflammatory context. Fe-deficiency was present in 73% of pregnant women and in 41% of menstruating women.

4. Folate deficiency (defined as erythrocyte folate below 160 μg/l) was observed in 45% of pregnant women.

5. In pregnant women, anaemia was associated with Fe-deficiency in 83% of cases and with folate deficiency in 48% of cases.

6. Haemoglobinopathies were mainly heterozygous and did not seem to contribute significantly to anaemia. Intensity of malaria was not related to Hb level, but Plasmodium falcipurum was found in 99% of subjects.

7. Hb concentration and mean corpuscular volume were significantly lower in babies born of Fe-deficient mothers than in babies born of Fe-sufficient mothers. Hb concentration in newborn infants was positively correlated with maternal serum ferritin.

1. A competitive protein-binding assay for 25-hydroxy vitamin D (25-OHD) in saliva has been established by adaptation of that previously described for 25-OHD in serum (Fairney et al. 1979).

2. Random values of salivary 25-OHD in patients attending hospital for venesection showed a wide range of results (105–1000 pg/ml, n 55). These values corresponded to 1.2% of the total serum values with which they showed a significant relation (r 0.45, P < 0.001).

3. There was no relation between salivary 25-OHD and measured serum free 25-OHD in eighteen pairs of saliva and serum studied.

4. Studies in two individuals showed that salivary 25-OHD values varied throughout the day and that a vitamin D load (19.5 μg), given as pickled herrings at lunch, produced a marked rise in 25-OHD values 5–8 h later.

5. Diurnal profile studies of salivary 25-OHD in Caucasian and Asian 11-year-old male schoolchildren showed lower values in Asian children eating a vegetarian diet, and a significant variation with time and ethnic group(P < 0.001).

6. It is concluded that 25-OHD is present in saliva and that the values vary throughout the day. The values obtained may relate to dietary intake of vitamin D and the subject's ethnic origin.

1. Twenty apparently healthy and normal Nigerian female students, resident at the University of Ibadan campus, were studied for seven consecutive days to assess their food energy intake and energy expenditure during sedentary and physical activities.

2. The mean age (years) of the group was 20.05 (SD 3.44, range 16–29), mean height (m) 1.62 (SD 0.07, range 1.47–1.74) and body-weight (kg) 51.28 (SD 3.21, range 46–58).

3. The food intake of each subject was obtained by direct weighing, and the energy value determined using a ballistic bomb calorimeter. Daily activities were recorded and the energy cost of representative activities was determined by indirect calorimetry.

4. Activities mainly involved sitting, mean (min/d) 354 (SD 84, range 253–475). Personal domestic activities took a mean of 162 (SD 73) min/d. Sleeping took a mean of 451 (SD 62) min/d.

5. The mean energy intake of the group was 8480 (SD 1316) kJ/d or 167 (SD 30.6) kJ/kg body-weight per d. This value is lower than that recommended by the Food and Agriculture Organization/World Health Organization (FAO/WHO) (1973) as the energy requirement for adult women engaged in light activities (9205 kJ/d), but it is higher than the FAO/WHO/United Nations University (UNU) (1985) recommended value of 8326 kJ (1990 kcal)/d for a housewife in an affluent society. It is lower than the recommended intake of 9350 kJ/d for rural women in developing countries (FAO/WHO/UNU, 1985).

6. The mean energy expenditure (kJ/d) of the female subjects was 6865 (SD 214, range 6519–7222). Mean energy expenditure was lower than mean energy intake.

7. The energy intake and expenditure values indicated that the subjects participating in the present study were not physically very active. It is suggested, for health reasons, that they might undertake more physical activity.

1. To characterize further the effect of protein-mineral interaction on plasma cholesterol, four groups of rabbits were placed on cholesterol-free, semi-purified diets for 12 weeks. The diets were similar in proximate composition with either casein or soya-bean protein isolate as the protein source (250 g/kg).

2. The dietary zinc content of the casein diets was increased to 22 mg/kg to equal that of the soya-bean diets. The copper content was set at 2 and 6 mg/kg. There were no differences in weight gain; all animals grew at a similar rate.

3. When the dietary Zn content was equalized, the plasma and liver cholesterol responses were similar regardless of the source of protein.

4. Differences in liver Cu and Zn were observed. As dietary Cu increased, Cu decreased and Zn increased in the liver. Hepatic Zn was also higher in soya-bean-fed than in casein-fed animals.

5. No effects on plasma Cu and Zn were seen.

6. The addition of Zn to the casein diet resulted in a similar plasma cholesterol to that of animals fed on the soya-bean diet, suggesting that casein-induced hypercholesterolaemia is due to a marginal Zn intake.

1. A Finnish national programme to fertilize crops with sodium selenate led us to compare the nutritional availability to rats of selenium in two Finnish spring wheats (Triticum aestivum L.), either fertilized or sprayed with sodium selenate, with that in an American winter bread wheat naturally high in Se.

2. Weanling male rats were given a Se-deficient Torula yeast diet for 4 weeks followed by either continued depletion or repletion for 4 weeks with graded levels of Se as sodium selenite (standard) or wheat (test food). Plasma and liver Se levels and plasma and liver glutathione peroxidase (EC 1.11.1.9; GSH-Px) activities were used as criteria of body Se status.

3. The availability of Se under these conditions was calculated with the point-slope technique at two dietary levels of Se (Expt 1) and with the slope-ratio method (Expt 2).

4. In the point-slope assay, the level of dietary Se fed had a considerable effect on the apparent availability values obtained which made interpretation of the results difficult. In the slope-ratio assay, no difference in the availability of Se from the various wheats was observed when plasma or liver Se levels were used as the response criteria.

5. The Se in the fertilized wheat was somewhat more available than that in the sprayed wheat when plasma or liver GSH-Px activities were the response criteria. Overall, availability values (% ) derived by averaging all four response criteria were 86, 77 and 73 for the fertilized and sprayed Finnish wheats and the American wheat respectively (sodium selenite 100).

6. These results show that wheat is a relatively available source of Se to rats regardless of whether its Se content is naturally high or is increased by fertilization or spraying.

1. In the first part of the study, the absorption of lactitol, a new disaccharide analogue of lactose, was studied using an in vivo jejunal perfusion technique in man. Intestinal uptake of lactitol from isotonic solutions containing 10, 30, 60, and 100 mmol lactitol/l was insignificant.

2. In the second part of the study the laxative threshold of lactitol was determined and compared with that of sorbitol in a double-blind, randomized, cross-over study on twenty-one normal subjects. Laxative threshold was considered to be either the maximum dose tolerated without unacceptable diarrhoea or gastrointestinal side effects, or when the maximum dose in the study was reached. Increasing amounts of lactitol, sorbitol or placebo were administered in two divided doses each day until subjects developed diarrhoea or severe gastrointestinal side effects. The laxative threshold of lactitol (74 (SE 5) g/d) was similar to that of sorbitol (71 (SE 5) g/d).

3. These findings indicate that lactitol is not absorbed by the human small intestine. Although diarrhoea or other gastrointestinal side effects occurred as the dose was increased, 40 g lactitol/d was well tolerated.

1. Ten female subjects completed two similar experimental procedures (periods 1 and 2) to obtain values of reproducibility of energy intake and 24 h energy expenditure (24hEE) measurements in a whole body indirect calorimeter. The periods consisted of consumption of a provided weight-maintenance diet for 6–8 d, faeces and urine collection during the last 4 d and occupation of the calorimeter during the last 3 d. The daily routine inside the calorimeter simulated a sedentary day in normal life with some physical activity: 8 h sleep, 75 min bicycling and the remaining time spent on sedentary activities. The metabolizable energy (ME) content of the diet (14% energy as protein, 46% energy as carbohydrate, 40% energy as fat) was calculated using food tables. The actual ME intake as well as digestibility and metabolizability of the diet were obtained later by analyses of food, faeces and urine for energy. Three consecutive 24hEE measurements were performed during the stay in the calorimeter in each period. The time interval between the two periods varied from 2 to 24 months. Reproducibility was assessed at group and individual level.

2. Mean digestibility and metabolizability of the diet showed no significant difference between periods. The within-subject coefficient of variation of metabolizability between periods was 1.7%.

3. Mean 24hEE (MJ) over 3 d did not differ between period 1 (8.78 (SD 0.63)) and period 2 (8.73 (SD 0.66)). The within-subject coefficient of variation in mean 24hEE over three successive days between periods was 3.1% but decreased, after deletion of values for subjects who were less adapted to the calorimeter, to 1.9%.

4. The results are discussed with regard to length of trial and the number of subjects required to test a difference in energy metabolism using whole body indirect calorimeters.

1. The effects of the chemical composition of fruit juices and fruit on the absorption of iron from a rice (Oryza sativa) meal were measured in 234 parous Indian women, using the erythrocyte utilization of radioactive Fe method.

2. The corrected geometric mean Fe absorptions with different juices varied between 0.040 and 0.129, with the variation correlating closely with the ascorbic acid contents of the juices (rs 0.838, P < 0.01).

3. Ascorbic acid was not the only organic acid responsible for the promoting effects of citrus fruit juices on Fe absorption. Fe absorption from laboratory ‘orange juice’ (100 ml water, 33 mg ascorbic acid and 750 mg citric acid) was significantly better than that from 100 ml water and 33 mg ascorbic acid alone (0.097 and 0.059 respectively), while Fe absorption from 100 ml orange juice (28 mg ascorbic acid) was better than that from 100 ml water containing the same amount of ascorbic acid (0.139 and 0.098 respectively). Finally, Fe absorption from laboratory ‘lemon juice’ (100 ml orange juice and 4 g citric acid) was significantly better than that from 100 ml orange juice (0.226 and 0,166 respectively).

4. The corrected geometric mean Fe absorption from the rice meal was 0.025. Several fruits had little or no effect on Fe absorption from the meal (0.013–0.024). These included grape (Vitis vinifera), peach (Prunuspersica), apple (Malus sylvestris) and avocado pear (Persea americana). Fruit with a mild to moderate enhancing effect on Fe absorption (0.03 1–0.088) included strawberry (Fragaria sp.) (uncorrected values), plum (Prunus domestica), rhubarb (Rheum rhaponticum), banana (Musa cavendishii), mango (Mangifera indica), pear (Pyrus cornmunis), cantaloup (Cucumis melo) and pineapple (Ananas comosus) (uncorrected values). Guava (Psidium guajava) and pawpaw (Carica papaya) markedly increased Fe absorption (0.126–0.293).

5. There was a close correlation between Fe absorption and the ascorbic acid content of the fruits tested (rs 0.738, P < 0.0001). There was also a weaker but significant correlation with the citric acid content (rs 0.55, P < 0.03). Although this may have reflected a direct effect of citric acid on Fe absorption, it should be noted that fruits containing citric acid also contained ascorbic acid (rs 0.70, P < 0.002). Similarly, the negative correlation (rs –0.62, P < 0,008) between Fe absorption and the malic acid content of fruits may have been due to the fact that fruits with a high malic acid content tended to have low levels of ascorbic acid (rs–0.45, P < 0.06).

6. These various results suggested that most fruits have only a limited effect on overall Fe nutrition. However, the presence of citrus fruit, guava or pawpaw would be expected to increase Fe absorption markedly from diets of low Fe availability.

1. Weanling male rats were maintained on diets containing 5, 10, 20, 40, 80 or 160 mg zinc/kg for 14 d. On day 15 they received 65Zn either by intraperitoneal injection or in a test meal containing 20 mg Zn/kg. After dosing, the rats were again maintained on the diets they had received previously.

2. Whole-body 65Zn retention was measured immediately after dosing and daily for a further 9 d. From regression analysis of the semi-logarithmic plots of 65Zn retention from 0 to 192 h after 65Zn administration, the true extent of 65Zn absorption and the biological half-life (t1/2) of body 65Zn stores were calculated.

3. At the end of the experiment, the rats were killed and the entire small intestines of some rats from each group were rapidly flushed out to remove food and faecal residues, frozen in liquid nitrogen and stored under an atmosphere of N2 at –20° before separation of cytosolic Zn-binding fractions by gel filtration on Sephadex G–75.

4. The results suggest that rats which received diets that were either deficient(5 mg Zn/kg), marginal (10 mg Zn/kg) or adequate (20–80 mg Zn/kg) in Zn achieved homeostatic regulation of body Zn by changes in both the extent of Zn absorption and excretion. However, when Zn supply was excessive, increasing from 80 to 160 mg Zn/kg, no further changes were seen in Zn absorption, and homeostatic control appeared to be effected entirely by changes in rates of body Zn loss.

5. Gel chromatography of intestinal cytosol on Sephadex G-75 revealed that Zn was associated with two major fractions. The first (peak 1) had a molecular weight (MW) > 75 kdaltons and the second (peak 2), a MW of approximately 10 kdaltons and was assumed to be metallothionein.

6. There was no obvious relation between the amount of Zn bound to peak 1 and dietary Zn content. In contrast, the amount of Zn recovered in peak 2 increased linearly with increasing dietary Zn content.

7. Comparisons between the effect of dietary Zn content on Zn bound to peak 2 and 65Zn retention may, depending on the range of Zn intakes, indicate possible roles for intestinal metallothionein in the control of Zn absorption or excretion.

8. A study of the effects of dietary dose of 65Zn on the extent of 65Zn absorption in rats of normal Zn status indicated a possible biphasic relation. At low doses (5–40 mg Zn/kg) 65Zn absorption appeared to exhibit a curvilinear response to increasing 65Zn dose, indicating possibly a saturable process. At higher doses (40–160 mg Zn/kg) the capacity of this process appeared to be exceeded and 65Zn absorption increased in a linear fashion.

1. Brush-border-membrane vesicles were prepared from piglet small intestines and the uptake of 65Zn was studied using a rapid filtration assay. The mechanism of 65Zn uptake was complex and two processes were identified.

2. In the first process, 65Zn uptake was rapid, reached equilibrium in 5–15 min and had an optimum pH of 7.5. The uptake was saturable and involved both binding to, and transport across, the membrane. The initial phase of 65Zn uptake (1 min incubation) approached saturation at high levels of substrate 65Zn and a Michaelis-Menten constant (Km) of 67.0 µM was calculated. Maximum uptake at equilibrium was approximately 100 nmol/mg protein. Cupric, ferrous and ferric ions had no effect on the uptake, but cadmium ions inhibited it competitively. The results are consistent with a carrier-mediated process, possibly involving a protein receptor in the membrane which is specific for Zn and elements close to it in the periodic table. Lactoferrin stimulated 65Zn uptake by approximately 20% when pre-incubated with 65Zn at a concentration of 0.01 µg/ml. It had no significant effect on 65Zn uptake at higher concentrations or when pre-incubated with brush-border-membrane vesicles.

3. The second mechanism of 65Zn uptake was linear with respect to time and involved binding to the membrane only. It was inhibited by all divalent and trivalent metal ions tested and is probably a passive binding process.

4. The results are discussed with respect to the use of brush-border-membrane vesicles in examining the role of nutrient interactions and their effect on the biological availability of nutrients.

1. The absorption of iron from soya-bean (Glycine hispida)-based and milk-based infant formulas was assessed in 138 multiparous Indian women, using the erythrocyte utilization of radioactive Fe method.

2. Fe absorption was significantly greater from the basal milk formula (1.5 g protein) than it was from the basal soya-bean formula (2.3 g protein), with geometric mean values of 0.083 and 0.044 respectively.

3. Ascorbic acid markedly increased Fe absorption from the milk-based formula in a dose-dependent fashion. The increase was fivefold when the ascorbic acid: Fe ratio on a weight-for-weight basis was 6: 1 and over tenfold when it was 20:1. In contrast, ascorbic acid had a less-marked effect on the absorption of Fe from the soya-bean-based formula, with only a two- to threefold increase at an ascorbic acid: Fe ratio of 20: 1.

4. The geometric mean Fe absorption from the soya-bean formula (1.27 mg Fe, 2.3 g isolated soya-bean protein (ISP)) was somewhat less than that from the same amounts of ISP and ascorbic acid made up in milk (0.075 and 0.1 13 respectively). However, a direct comparison between the soya-bean formula in milk and in water showed no significant difference (0.043 and 0.060 respectively).

5. Fe absorption from a drink containing 10 g ISP and 30 mg ascorbic acid was significantly better than that from a similar drink containing the soya-bean flour from which ISP is extracted (0.044 and 0.027 respectively).

6. Heating ISP to 200° for 2 h before its use had no effect on Fe availability. When 2.3 g heated ISP (10 mg ascorbic acid) was compared with a similar formulation of untreated ISP, Fe absorption values were 0.135 and 0.099 respectively. Comparable values with 25 g ISP (no ascorbic acid) were 0.067 and 0.058.

7. Citric acid in amounts of 1 4 g had a dose related but limited enhancing effect on Fe absorption from 10 g ISP, with a rise from 0.01 1 (no citric acid) to 0.068 (4 g citric acid).

8. There was appreciable variability in the levels of Fe absorption in different studies, which suggested that unidentified manufacturing or preparative differences might be influencing the overall results.