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. 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. 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. Metabolic balance studies (5 d) for nitrogen were carried out in twenty-four apparently healthy elderly people (age 69.7–85.6 years) and a heterogeneous group of twenty housebound elderly people (age 69.9–85.1 years) with chronic diseases. During the study all subjects ate self-selected diets, lived in their own homes and continued their normal daily activities. Seven of the housebound received meals-on-wheels 5 d/week.

2. Healthy men and women had mean metabolizable energy intakes of 8.7 and 6.6 MJ/d respectively compared with 6.3 and 4.8 MJ/d in the housebound. The average energy content of the meals-on-wheels as delivered was 2.4 MJ per meal, of which 2.1 MJ were consumed.

3. The healthy men and women had average daily protein intakes of 69.4 and 59.7 g respectively compared with 46.3 and 39.1 g in the housebound. Meals-on-wheels as supplied provided 19.4 g protein per meal, of which 16.2 g were consumed.

4. Healthy subjects were in equilibrium for N balance (0 mmol/d) with a daily intake of 733 mmol, which was equivalent to 11.04 mmol N (0.97 g mixed protein)/kg body-weight per d. Housebound individuals were in negative N balance (–95 mmol/d) with an intake of 475 mmol/d, corresponding to 7.59 mmol N (0.67 g mixed protein)/kg body-weight per d.

5. We were unable to determine in the present study whether the negative N balance observed in the housebound people was due to the relatively low N intake or the underlying disease condition.

1. Plant foods were digested in vitro and the proportion of iron which diffused across a ssemi-permeable membrane was used as an index of Fe availability.

2. The mean (with SEM) Fe diffusibility from a group of eighteen cereals, legumes and nuts was very low, 2.1 (0.25)%, whereas from a group of sixteen fruits and vegetables it was high, 13.7 (1.09)%. The difference between the two food groups was highly significant (P < 0.001).

3. The results for Fe diffusibility correlated well with literature values for the in vivo absorption of Fe from similar foods (r0.84, P < 0.01).

4. When phytate, citrate and ascorbate were added to selected foods in amounts corresponding to endogenous levels, only phytate and citrate gave the expected effects on Fe diffusibility. Ascorbate only enhanced Fe diffusibility to the expected extent when it was added in much larger amounts, not normally found in foods.

5. When added to cereal foods, orange juice was found to enhance greatly Fe diffusibility even when its content of ascorbate was completely destroyed by boiling followed by prolonged storage. When citrate and ascorbate were added to cereal foods in amounts equivalent to those found in fresh orange juice, both enhanced Fe diffusibility but citrate was far more effective.

6. It is concluded that phytate is a major inhibitor of Fe diffusibility in cereals, legumes and nuts. However, citrate rather than ascorbate would appear to be the major enhancer of Fe diffusibility from many fruits and vegetables.

7. The implications of the present results are discussed in relation to the relative influence of phytate, citrate and ascorbate on dietary Fe availability.

1. The digestible energy (DE) and metabolizable energy (ME) values of a commercial Polydextrose® product and the polymer that it contained were determined by metabolic energy balance in male Wistar rats and compared with values obtained by radiochemical balance using a radiochemical analogue. The energy values of the whole preparations and of the polymer fractions were estimated.

2. In the energy-balance study of 6 d duration, 100 g maize starch/kg control diet were replaced by Polydextrose® to provide a test diet. Polydextrose® had no significant effects on food intake, body-weight gain, digestibility of nitrogen and N retention but significantly increased the water consumption to 143% of the control value (P < 0.05) and the water content of fresh faecal pellets from 548 (SE 10) to 646 (SE 15) g/kg wet weight (P < 0.01).

3. By energy balance the DE in the Polydextrose® product and in the polymer that it contained were 13.5 and 12.8 (SE 1.9) kJ/g respectively. The corresponding ME values were 12.7 and 12.1 (SE 1.8) kJ/g respectively. These values were higher (P < 0.05) than the corresponding values obtained by the radiochemical balance procedure: DE 8.8 and 8.6 (SE 0.4) kJ/g polymer respectively and ME 8.0 and 7.8 (SE 0.5)kJ/g polymer respectively.

4. These findings indicate relatively high energy values for Polydextrose® by comparison with previously published values and illustrate a potential difficulty when using energy values obtained by certain radiochemical methods to estimate the energy values of a mixed diet given to rats. Several alternative explanations of the discrepancies are advanced.

1. The effect of prolonged consumption of guar gum on iron absorption and Fe status was investigated in rats. Experiments with closed loops of duodenum, isolated in siru, were designed to reveal changes in the short-term regulation of duodenal Fe uptake, induced by challenge with low- and high-Fe meals. In separate experiments, the effect of guar gum on the capacity of intact rats to maintain Fe status and to absorb Fe from a test-meal was investigated.

2. Male Wistar rats were given either a control, semi-synthetic diet (C) for 21 d or a similar diet containing 100 g guar gum (G)/kg for 27 d. Both diets contained 36 mg Fe/kg. Two subgroups were then challenged with meals containing low-Fe (8 mg/kg) or high-Fe (566 mg/kg), while a third subgroup received a meal of the control diet (36 mg Fe/kg). At intervals of 12, 36, 60 and 84 h after the dietary challenge, the uptake of [59Fe] ferric citrate was measured using closed duodenal loops in situ. All G-supplemented animals absorbed less Fe than their C-fed counterparts. Within group C, animals given the high-Fe challenge had lower absorptions 12, 36 and 60 h later, compared with those given the maintenance diet, whilst those given the low-Fe meal showed much increased uptake 12 and 36 h later. The latter effect was virtually abolished by guar gum.

3. In the second experiment, male Wistar rats were fed on the C or G diets containing 8, 15, 20, 26 or 36 mg Fe/kg for approximately 10 weeks ad lib. Fe retention from a starch-sucrose test meal extrinsically labelled with 59Fe was then measured, together with packed cell volume and Fe content of the liver as indices of Fe status. No effect of feeding guar gum on Fe retention nor Fe status at any level of Fe intake was observed.

4. It was concluded that feeding guar gum leads to a small reduction in the rate of uptake of Fe in the rat duodenum and to an impairment of the regulation of uptake in response to brief episodes of dietary Fe depletion. However, these changes do not apparently lead to any nutritionally significant reduction in the capacity of the intact animals to absorb Fe and maintain their Fe status.

1. It was demonstrated that the development of experimental avitaminosis A in chicks led to secondary zinc deficiency. The balance of Zn in the chick became negative, while the Zn content of various tissues decreased. Thus in vitamin-A-deficient chicks the serum Zn content was 1258 (SD 26.3) μg/l which was considerably lower than 1652 (SD 97.8) μg/l in controls.

2. Zn absorption was considerably reduced throughout the entire small intestine of vitamin-A-deficient chicks and most markedly in the ileal region. Within 72 h after retinyl acetate administration Zn absorption was fully restored in this region of the intestine.

3. The 65Zn-binding capacity of soluble proteins, present in the supernatant fraction of ileal-mucosa homogenates of vitamin-A-deficient chicks, was found to increase 2.6 times by 72 h after the administration of a single dose of retinyl acetate.

4. A vitamin-A-dependent Zn-binding protein (ZnBP), absent in vitamin-A-deficient chicks, was isolated from the ileal mucosa after their repletion with vitamin A. Competitive-binding studies (calcium, cadmium, copper) showed the protein to be highly specific for Zn ions.

5. The molecular weight of ZnBP wa5 83 kDa. The association constant of the protein-Zn complex was 0.8 x 106/mol. The protein was acidic with approximately 20% of its amino acid residues belonging to dicarboxylic acids. ZnBP was found to be a glycoprotein, and it contained hexose as a carbohydrate component.

6. It is suggested that ZnBP is involved in the binding of Zn in the ileal mucosa of chicks.

1. The effect of starvation on whole-body protein synthesis and on the contribution of protein synthesis to basal metabolic rate was investigated in young chickens (Expt 1). Strain differences between layer and broiler chickens in whole-body protein synthesis and degradation rates were examined when the birds were starved (Expt 2).

2. In Expt 1, 15-d-old White Leghorn male chickens were used, while in Expt 2 Hubbard (broiler) and White Leghorn (layer) male chickens at 14 d of age were used. They were starved for 4 d, and heat production was determined by carcass analysis after 2 and 4 d of starvation. Whole-body protein synthesis rates were measured on 0, 2 and 4 d of starvation (Expt 1), and on 0 and 4 d of starvation (Expt 2).

3. The results showed that starving reduced whole-body protein synthesis in terms of fractional synthesis rate and the amount synthesized. Whole-body protein degradation was increased by starvation both in terms of fractional synthesis rate and the amount degraded on a per kg body-weight basis.

4. Reduced fractional synthesis rate of protein in the whole body was accounted for by reductions in both protein synthesis per unit RNA and RNA:protein ratio.

5. In the fed state, whole-body protein synthesis and degradation rates, whether expressed as fractional rates or amounts per unit body-weight, tended to be higher in layer than in broiler chickens. In the starved state, the difference in the rate of protein synthesis between the two strains virtually disappeared, while the degradation rates were higher in layer than in broiler birds.

6. Based on the assumed value of 3.56 kJ/g protein synthesized (Waterlow et al. 1978), the heat associated with whole-body protein synthesis in the starved state was calculated to range from 14 to 17% of the basal metabolic rate with no strain difference between layer and broiler chickens.

1. A continuous culture technique was used to study the phosphorus requirements of rumen micro-organisms. Solutions of artificial saliva containing 120, 80, 40 and 0 mg inorganic phosphorus (Pi)/1 were infused into the reaction vessels previously inoculated with rumen contents, resulting in Pi concentrations in the vessel contents of 48, 28, 4 and < 1 mg/l respectively. Various fermentative and synthetic characteristics were examined.

2. In the vessel contents, concentrations of protozoa (about 0.9 x 105/ml) were not significantly affected by pi concentration. Total volatile fatty acids (VFA) produced averaged about 6.83 mmol/h with Pi levels of 48 and 28 mg/l. Reduction in Pi concentrations to 4 and < 1 mg/l resulted in significant reductions in total VFA to approximately 6.25 and 3.75 mmol/h respectively, accompanied by a rise in pH from 6.5 to 7.3. Ammonia-nitrogen values, which averaged about 131 mg/l at the higher Pi concentrations, also increased with the lowest level of Pi to about 240 mg/l. ATP concentrations averaged about 14 μmol/l at the highest Pi concentration and fell progressively with each reduction in Pi concentration to a final value of 2.5μmol/1 with the Pi level < 1 mg/1.

3. At Pi concentrations of 48 and 28 mg/l, the digestibilities of xylose, arabinose and cellulose-glucose were maintained at about 0.90, 0.62 and 0.70 g/g input respectively. At lower Pi, concentrations these digestibilities fell significantly and corresponding values at Pi < 1 mg/l were 0.73, 0.41 and 0.31 respectively. Starch digestion was unaffected by Pi concentrations and remained at about 0.90 g/g input.

4. The amount of microbial-N synthesized averaged 0.48 g/d and was maintained with Pi concentrations down to 4 mg/l. There was, however, a significant reduction to 0.26 g/d with Pi concentrations of < l mg/l. The effiency of microbial protein synthesis was variable but averaged approximately 25 g N/kg total carbothdrate fermented.

5. It was estimated that the minimum Pi concentrations required in rumen fluid in vivo to maintain maximum degradative and synthetic microbial activities was in the range 75–100 mg/l and that the over-all P requirement of the microbes was of the order of 5.1 g/kg apparently digested organic matter intake.

1. The amylase (EC 3.4.21.4) and trypsin (EC 3.2.1.1) activities in the pancreas in rats during pregnancy, lactation and after the weaning period, and the secretory responses to a secretagogue (caerulein) in the exocrine pancreas of lactating rats were measured.

2. Trypsin activity increased as lactation progressed and reached twice that of unmated rats in the second half of the lactation period. The amylase activity fell before parturition and failed to recover even after the start of lactation and was significantly decreased throughout the lactation period.

3. The total amount of pancreatic juice produced in the lactating rats was significantly greater than that of unmated rats; the amylase output was significantly less than that of unmated rats.

4. When the pups were removed, amylase activity in the pancreas returned to the value in unmated rats. Furthermore, the amylase activity in lactating rats receiving a daily injection of insulin significantly exceeded that of normal lactating rats.

5 These results indicate that the decrease in amylase activity in lactating rats is due to the reduction of amylase synthesis and there is a possibility that insulin is required for normal or elevated rates of amylase synthesis in lactating rats.