1. Serum folate level, packed cell volume and haemoglobin concentration of apparently healthy rural Sri Lankan women, between 20 and 45 years and earning up to Rs. 500 (Sri Lankan Rs. 35 ⋍ £1 Sterling) per month, were estimated during pregnancy and when on oral contraceptive (OC) treatment with Ovulen 50 (ethinyl oestradiol 0·05 mg,ethinodiol diacetate 1 mg).

2. Ovulen 50 administration led to a fall in serum folate levels which occurred very rapidly during the first 6 months and more slowly thereafter, stabilizing at 2·2 ng/ml in women of very low economic status and at 2·9 ng/ml in the more privileged.

3. There was a steady fall in serum folate concentrations during pregnancy, the levels at the end of pregnancy being higher than those in women under OC treatment for 9 months.

4. The need for folate supplementation during OC treatment is stressed.

1. Randomized cross-over studies were undertaken to determine the effects of daily dietary supplements of pectin (12 g/d), cellulose (15 g/d) and lignin (12 g/d) on stool characteristics of healthy volunteers.

2. Detailed dietary records were kept throughout the study. Stool collections over 48 h were used to determine mean stool pH and weight. The single stool transit time was measured using radio-opaque markers.

3. Pectin did not significantly alter the mean stool pH, transit time or 24 h wet weight.

4. Cellulose lowered the mean stool pH from 6·38 to 6·12, decreased mean stool transit time by 27% and increased mean wet stool weight by 57%.

5. Lignin lowered the mean pH from 6·34 to 6·25, decreased the stool transit time by 20% and increased stool weight by 27% but these changes were not statisticallysignificant.

6. These findings have shown that individual fibre components have different colonic metabolic effects and support the view that associations between dietary fibre intakes anddiseases such as colorectal cancer should be evaluated with regard to the type of fibrecomponents consumed.

1. The capacity of wheat bran to impair mineral absorption independent of its phytate content was studied by metabolic balance studies in man.

2. Three breads were prepared, equivalent to white, brown and wholemeal, by adding bran in different quantities to white flour. Calcium, iron, zinc and sodium phytate were added to the loaves to make the amounts equal in all breads.

3. Six healthy volunteers were studied for three consecutive 24-d-periods during which they ate a controlled diet, typical of that normally consumed in the UK but with 200 g bread/d. Only the type of bread changed between each dietary period.

4. The phytate contents (mmol) of 200 g of each of the breads after baking were: white 2·3, brown 2·1 and wholemeal 2·2; non-starch polysaccharide contents (9) were: white 3·3, brown 10·9 and wholemeal 18·7

5 . The increased amount of bran in the breads increased stool output in the expected way but no change was seen in Ca, Zn and Fe balance. Blood levels of these minerals remained unchanged.

6. It is concluded that wheat bran and, in particular, the cell-wall polysaccharides of bran, are unlikely to exert a significant effect on mineral absorption in man, in amounts customarily eaten, independently of the effect of phytate present in the bran.

1. The influence of the nutrient composition of food on energy expenditure during a 24 h period was investigated in adult volunteers. The maximum probable effect was determined using iso-energetic diets high in either protein or in glucose.

2. Two men and four women took part in the study. Their body-weights and body composition were within the normal range. Each subject lived for 28 h in a whole-body calorimeterset at 26°, on two separate occasions. During each session they ate one of the following iso-energetic diets: high-protein–low-carbohydrate or high-glucose–low-protein.Energy expenditure was determined while the subject followed a pre-set pattern of activity. A 24 h collection of urine was made and total nitrogen, creatinine and urea excretions were determined, so that heat production could be corrected for protein metabolism.

3. Two independent measures of energy expenditure were made: direct calorimetry was used to obtain heat loss partitioned into its sensible and evaporative components, while indirect calorimetry was used to estimate heat production from oxygen consumption, carbon dioxide production and N excretion. There was good agreement between the two estimates of 24 h energy expenditure: for the twelve sessions in the calorimeter the mean difference between heat production and heat loss was only 0·4 (SEM 0·39)%.

4. The results showed that nutrient composition can have a marked influence on 24 h energy expenditure in adult humans. Mean values of 8659 (SEM 230) kJ and 7735 (SEM 250) kJ were obtained for the high-protein and high-glucose diets respectively. This 12% increasein energy expenditure on the high-protein intake was significant (P < 0·001). On the high-glucose intake, total heat loss comprised 22 and 78% evaporative and sensible heat losses respectively. The increase in heat loss onthe high-protein intake was accounted for by a 39% increase in evaporative heat loss and a 7% increase in sensible heat loss.

5. It is concluded that the composition of the nutrient intake has a greater influenceon the metabolic rate of adult humans than has been suggested by some groups of workers in recent years.

1. Two series of balance experiments were performed with growing rats to test the effect of black tea, green tea, coffee and cocoa on protein and energy utilization. In Expt 1 soya-bean meal was fed as a basal diet and supplemented with freeze-dried materials from 11 black tea, green tea or coffee/500 g dry matter. Cocoa powder, corresponding to 11 of the beverage, was also added to the basal diet. In Expt 2 the procedure was repeated with a barley-based diet.

2. In both experiments both tea varieties and coffee had significantly negative effects on true protein digestibility and biological value, while digestible energy was only slightly affected in the barley-based diet. Cocoa had no effect on protein or energy utilization in either soya-bean meal or barley diets, although the protein in cocoa powder was completely indigestible.

3. As the tannin concentration in both tea varieties and coffee was very high it is assumed that the observed deleterious effects might, in part, be explained by anti-nutritional effects of tannin.

4. The strongest deleterious effect was recorded for black tea.

1. Iron availability in potatoes and ferrous sulphate was measured in rats in a 10 d balance study and from a single meal using 59Fe and 55Fe as extrinsic labels.

2. Dried potato samples were incubated in gastric juice in vitro and the amount solubilized was compared with other foods. The relationship between ascorbic acid content of dried potato and Fe solubilization was examined in vitro.

3. In the balance study, the rats absorbed (mean with SE) 15·2 (2·7)% Fe from the diet containing 660 g dried potato/kg and 32·1 (2·8)% Fe from the semi-synthetic diet containing FeSO4. Absorption was higher from the extrinsically-labelled single meal: 49·6 (1·1)% Fe from 59Fe-labelled potato and 62·4 (1·2)% Fe from 59FeSO4.

4. The in vitro experiments showed a much greater solubilization of Fe from potato than from the other foods examined. There was a correlation between Fe solubilization and ascorbic acid content of potatoes (rs 0·76, P < 0·00).

5. It appears that potatoes contain Fe of moderate availability, possibly higher than most vegetables. They also provide ascorbic acid which may enhance Fe absorption from a meal if present in sufficient quantities. Thus potatoes may make a useful contribution towards the Fe nutriture of the UK population.

1. Eighty-five samples from fifteen different legume seed lines generally available inthe UK were examined by measurements of their net protein utilization by rats and by haemagglutination tests with erythrocytes from a number of different animal species. From these results the seeds were classified into four broad groups.

2. Group a seeds from most varieties of kidney (Phaseolus vulgaris), runner (Phaseolus coccineus) and tepary (Phaseolus acutifolius) beans showed high reactivity with all cell types and were also highly toxic.

3. Group b, which contained seeds from lima or butter beans (Phaseolus lunatus) and winged bean (Psophocarpus tetragonolobus), agglutinated only human and pronase-treated rat erythrocytes. These seeds did not support proper growth of the ratsalthough the animals survived the 10 d experimental period.

4. Group c consisted of seeds from lentils (Lens culinaris), peas (Pisum sativum), chick-peas (Cicer arietinum), blackeyed peas (Vigna sinensis), pigeon peas (Cajanus cajan), mung beans (Phaseolus aureus), field orbroad beans (Vicia faba) and aduki beans (Phaseolus angularis). These generally had low reactivity with all cells and were non-toxic.

5. Group d, represented by soya (Glycine max) and pinto (Phaseolus vulgaris) beans, generally had low reactivity with all cells but caused growth depression atcertain dietary concentrations. This growth depression was probably mainly due to antinutritional factors other than lectins.

6. Lectins from group a seeds showed many structural and immunological similarities. However the subunit composition of the lectin from the tepary bean samples was different from that of the other bean lectins in this or any other groups.

1. The concentration and distribution of iron in 59Fe-labelled chicken leg and breast meat and liver were determined by gel filtration. In all samples approximately 50% of the Fe was insoluble (haemosiderin) and the haemoproteins (haemoglobin and myoglobin) constituted from 15% (liver) to 25% (leg meat) of the total Fe. Ferritin accounted for from 12% (leg meat) to 27% (liver) of the total Fe.

2. A technique was developed which enabled the time-course of the passage of 59Fe-labelled whole and fractionated meat and liver through the gastrointestinal tract of Fe-replete and Fe-deficient rats to be followed and it was found that the rate of stomach emptying appeared to be a function of the viscosity of the meal. In Fe-replete rats approximately 71% of a meal of raw chicken meat had left the stomach within 1 h of administration and by 2 h the stomach was almost empty and much of the unabsorbed 59Fe was in the ileum. By 4 h the ileum and colon contained almost equal amounts of 59Fe. Between different test meals there were only slight differences in gastrointestinal distribution and these reflected the different rates of stomach emptying.

3. Stomach emptying was slower in Fe-deficient compared with Fe-replete rats.

4. In Fe-replete, but not Fe-deficient, rats it was found that the amount of 59Fe lost (absorbed) from the gastrointestinal tract 2 h after administration of a test meal was not significantly different from the value found using a 7 d faecal collection technique.

5. Comparison of the 2 h absorption values for several test meals indicated that 59Fe absorption from raw whole meat was significantly higher than from the soluble extract and the residue after extraction (haemosiderin).

6. Heat treatment caused a significant decrease in the absorption of Fe in whole meat and the soluble meat extract but a significant increase in the liver absorption values. It is suggested that denatured haemoproteins are less available for absorption than their native forms but that heating increases the availability of the Fe of haemosiderin or ferritin or both.

7. Isolated muscle ferritin was poorly absorbed but on the addition of excess bovine serum albumin the absorption of the Fe was markedly increased.

8. It is concluded that, to estimate the Fe availability of a food such as chicken meat or liver one must not only take account of the concentration and type of each Fe-containing compound present but also such factors as their possible synergistic effects, the presence of chelating agents, the extent of cooking and the concentration and type of proteinaceous digestion products.

1. In order to investigate the mechanism of the pellagragenic action of excess dietary leucine, rats were fed on diets providing a minimally-adequate amount of tryptophan, with no preformed niacin, with and without the addition of 15 g leucine/kg diet. This amount of leucine in the diet has been demonstrated previously to lead to depletion of blood and liver nicotinamide nucleotides. The metabolism of tryptophan was assessed by measurement of the production of 14CO2 after the administration of [methylene-14C]tryptophan to estimate the activity of kynureninase (L-kynurenine hydrolase, EC 3.7.1.3) and [benzene ring U-14C]tryptophan to estimate the activity of picolinate carboxylase (aminocarboxymuconate semialdehyde decarboxylase, EC 4.1.1.45).

2. A dietary excess of leucine led to inhibition of kynureninase and increased the activity of picolinate carboxylase. Both of these effects would result in a reduction in the rate of metabolism of acroleylaminofumarate (aminocarboxymuconate semialdehyde) to quinolinic acid and hence to nicotinamide nucleotides. These two effects provide an explanation for the pellagragenic effect of a dietary excess of leucine in animals that are wholly or partly reliant on endogenous synthesis from tryptophan to meet their requirements for nicotinamide nucleotides, and presumably also explain the pellagragenic effect of a dietary excess of leucine in man.

1. A randomized double-blind crossover trial was carried out to compare the influence on plasma lipid concentrations, platelet thromboxane B2 production and platelet aggregation induced by ADP, collagen and U46619 (a prostaglandin endoperoxide analogue), of a daily 10 g supplement of a fish-oil concentrate (MaxEPA), which provided (g): 1·7 20:5ω3, 0·3 22:5ω3 and 1·2 22:6ω3, taken for 2 weeks by ten healthy subjects, with one of vegetable oil providing 3·4 18:2ω6.

2. A lower response to platelet aggregation induced by 0·5 μg collagen/ml but not by other aggregating agents was observed following both types of supplement. Platelet thromboxane B2 production induced by collagen also tended to be lower following the supplements.

3. Plasma total cholesterol concentrations were unaffected by the supplements. The MaxEPA but not the vegetable-oil supplement lowered the concentration of plasma triglycerides and increased that of high-density-lipoprotein-cholesterol.

1. Everted sacs of rat proximal small intestine were used to determine the effect of guar gum (5 g/l) on the uptake of cholesterol (0·1 mM) from a solution of micelles.

2. The uptake of cholesterol was found to be linear both in the presence and absence of guar gum. When guar was present throughout the whole of the incubation medium, the uptake of cholesterol was reduced to approximately 40% of control values. Sacs which had been pre-incubated in guar gum before exposure to cholesterol in a guar-free medium also showed a reduction in cholesterol uptake but this was less pronounced.

3. A two-stage perfusion technique, previously described (Blackburn & Johnson, 1981), was used to determine the effect of a guar layer adsorbed to the mucosal surface on cholesterol absorption in vivo. Such a layer leads to a reduction of approximately 36%: itwas concluded that guar slows the absorption of cholesterol from micelles by a mechanism, or mechanisms, involving an increased resistance to diffusion in the aqueous medium.

4. Groups of rats were meal-fed for at least 30 d on semi-synthetic diets with or without the inclusion of guar gum (20 g/kg). Rates of intestinal absorption of cholesterol, glucose and fluid were then determined by the perfusion technique in vivo. There was no reduction in absorption in the test animals compared with the controls.

5. It is proposed that guar gum is able to slow the intestinal transport of cholesterol from a suspension of pre-formed micelles, but only when both are present in the lumen together. No evidence was obtained to suggest that the consumption by rats of a diet containing guar gum, at a level similar to that used in human studies, leads to any adaptive reduction in their rates of cholesterol or glucose absorption.

1. The effects of the administration of oestradiol and vitamin B6 on tryptophan metabolism in the rat have been assessed by measurement of the release of 14CO2 from [14C]tryptophan, in vivo, in order to determine whether, and to what extent, the abnormalities of tryptophan metabolism that are associated with oestrogen administration can be attributed to drug-induced vitamin B6 deficiency or depletion. Two positional isomers of [14C]tryptophan have been used; [ring-2-14C]tryptophan as an index of the activity of tryptophan oxygenase (L-tryptophan: oxygen oxidoreductase (decyclizing), EC 1.13.11.11) and [methylene-14C]trytophan as an index of the activity of kynureninase (L-kynurenine hydrolase, EC 3.7.1.3).

2. The administration of 500 μg oestradiol/kg body-weight led to a reduction in the release of 14CO2 from both positional isomers of tryptophan, suggesting that the activities of both tryptophan oxygenase and kynureninase are reduced following oestrogen treatment. The kinetics of the release of 14CO2 from [methylene-14C]tryptophan after the administration of oestradiol were compatible with competitive inhibition of kynureninase by oestradiol or a metabolite.

3. The administration of 10 mg pyridoxine hydrochloride/kg body-weight also reduced the production of 14CO2 from both positional isomers of 14C]tryptophan, suggesting some toxicity of such a high dose of the vitamin.

4. In animals which had received the supplementary dose of vitamin B6, the administration of oestradiol led to further reduction in the production of 14CO2 from [ring-2-14C]tryptophan, suggesting a further reduction in the activity of tryptophan oxygenase, and an increase in the production of 14CO2 from [methylen-14C]tryptophan, but with a delay in the peak of production.

5. These results confirm that there is no induction of tryptophan oxygenase by oestradiol, but rather reduced activity of the enzyme after the administration of a relatively high dose of the hormone. They also confirm that the inhibition of kynureninase by oestrogen metabolites that has been reported previously in partially-purified enzyme preparations also occurs in vivo.

6. It is suggested that the abnormal results of the tryptophan load test that have been reported in women receiving oestrogens, and which have been interpreted as indicating some extent of drug-induced vitamin B6 deficiency, can be accounted for by the inhibition of tryptophan metabolism by oestrogens or their metabolites. Therefore it seems likely that the practice of administering supplements of vitamin B6 to women receiving oestrogens may not be appropriate, and indeed may exacerbate the changes in tryptophan metabolism that result from the administration of oestrogens. The tryptophan load test would appear to be unreliable as an index of vitamin B6 nutritional status in women receiving oestrogens.

1. Tissue composition and skeletal muscle cathepsin D (EC 3.4.23.5) activity weremeasured in wether lambs treated with trenbolone acetate (TBA) and oestradiol-17β (Oe) in combination and female lambs treated with TBA or zeranol. Muscle and liver protein fractional synthesis rates and plasma leucine flux were measured in the female lambs.

2. Male castrate lambs treated with TBA plus Oe showed increased growth rate, improvedfood conversion efficiency, decreased muscle RNA concentration and decreased total cathepsin D activity in muscle.

3. Female lambs treated with TBA or zeranol showed increased weight gain, improved food conversion efficiency, decreased muscle RNA and DNA concentrations and decreased free cathepsin D activity in muscle. Mixed muscle protein fractional synthesis rate was decreasedafter TBA treatment. Plasma leucine flux, not corrected for oxidation or food intake, wasnot increased by TBA or zeranol treatment.

4. Treatment of female lambs with TBA or zeranol caused increased growth rate. This increased growth rate is probably due in part to decreased muscle protein degradation, since evidence was obtained that muscle protein synthesis is decreased by TBA and zeranol treatment.

1. Lipid-lowering diets enriched in polyunsaturated fat decrease the serum cholesterol in hyperlipoproteinaemia, usually by reducing both the low-density-lipoprotein (LDL) and high-density-lipoprotein (HDL) cholesterol concentrations. The aim of the present study was to investigate whether the effects on LDL could be maintained but those on HDL cholesterol be diminished by reducing the ratio, polyunsaturated: saturated fat (P:S) of the diet.

2. Twenty hyperlipoproteinaemic patients (six with type IIa, eight with type IIb and six with type IV) in a metabolic ward were given two fat-modified diets during two consecutive 3–week periods in a randomized order. The diets were identical with regard to nutrient composition but differed with regard to the P:S values, which were 2.0 and 1.3 respectively.

3. The lipoprotein-lipid composition and serum apolipoprotein concentrations were similar at the end of the two dietary periods in type IIa and type IV patients but in type IIb patients a more pronounced reduction of the LDL-cholesterol concentration by 9% (P < 0·05) was achieved on the diet with the higher P:S value. The HDL-cholesterol did not differ significantly.

4. The results indicate that increasing the P:S value of lipid-lowering diets from 1.3 to 2·0 does not offer a great advantage with regard to the lipoprotein-lipid reductions achieved in moderate hyperlipoproteinaemia.

1. Experiments to measure the effect of a fibre source in the diet on stool bulk are difficult and lack precision. In vitro methods which would identify fibre sources that are effective for clinical and epidemiologic use would be valuable. One important property of fibre which influences the ability of fibre to increase stool weight is its water-holding capacity (WHC).

2. WHC was measured using centrifugation, filtration, suction pressure and water flow-rate techniques using fibre concentrates of potato, cereal bran and gum arabic.

3. Dietary supplementation of three preparations of potato fibre (20 g/d) had no significant effect on stool weight but 16 g bran/d increased stool weight from 107 (SE 44) g/d to 174 (SE 51) g/d.

4. The effects of these fibres on stool weight can be related to the nature of the water-holding properties of fibre rather than absolute WHC.

1. Four groups of lambs were fed on a low-carotene basal diet. One group received no supplemental vitamin A (mildly deficient). Remaining groups were supplemented daily with vitamin A acetate equivalent to 100 (control) 9000 (mildly intoxicated) and 18000 (severely intoxicated) μg retinol/kg body-weight. After 16 weeks lambs received a bolus of[15−3H]retinol intravenously; blood, urine and faeces were sampled for 48 h.

2. Plasma retinol was complexed to a protein of 20000 molecular weight (MW), which in turn was complexed to a protein of 65000 MW; these proteins correspond respectively to retinol-binding protein and prealbumin. Plasma retinol concentration reached plateau values in intoxicated lambs, but plasma retinyl ester concentrations increased rapidly when liver contents of both retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded 30 μg. Labelled compounds, more polar than retinol, were found in plasma; their concentration increased tenfold in intoxicated lambs within 48 h.

3. Plasma retinol transport rates were 0·1, 10·5 and 11·8 times control values, and clearance rates were 0·3, 14·1 and 14·3 times control values in mildly-deficient, and mildly- or severely-intoxicated lambs respectively. Turnover of retinol increased rapidly when liver contents of retinol and retinyl esters exceeded approximately 10 and 100 mg respectively and kidney contents of both retinol and retinyl esters exceeded approximately 30 μg. Plasma clearance of retinyl esters was unchanged with intake. Faecal excretion of tracer increased linearly with plasma retinol clearance.

4. Our findings identify, several variables that appear to be involved in retinol homeostasis, including plasma retinol clearance and excretion.

1. A triple stable-isotope method was used to estimat simultaneously selenium absorption from poultry meat intrinsically labelled with 74Se and from an extrinsic tracer of 76SeO32− in four young adult men. The subjects received an experimental diet based on chicken meat as the source of protein. Two diet periods, lasting from 5 to 10 d, depending on the frequency of stool output for each subject, were conducted to allow duplicate determinations within each subject of Se absorption from both sources.

2. Absorption of Se was determined by the faecal isotope balance procedure through monitoring the stable isotopes 74Se, 76Se and 80Se by means of radiochemical neutron activation analysis.

3. For the separate periods, mean (with SEM) absorption of 74Se from the intrinsically-labelled poultry meat was 70·9 (1·5)% and 72·0 (2·5)%. The absorption of Se from 76SeO32− was 34·7 (5·5)% and 37·6 (3·2)% during the same periods.

4. From these results it is concluded that, under the present experimental conditions, the intrinsic and extrinsic Se isotopes did not form a common pool before absorption. Possible reasons for this are discussed.

1. Rates of lipogenesis de novo have been studied in liver and epididymal fat pads of male rats chronically treated with ethanol. A solution of ethanol (150 ml/l) was administered as the only drinking fluid for 3 months with a standard solid diet; both food and drink were available ad lib.

2. Lipogenesis in vivo was measured by the incorporation of tritiated water into lipid fractions: non-saponifiable lipid and fatty acids. Non-saponifiable lipid, both in liver and in adipose tissue, was unaffected by ethanol treatment. However, fatty acid synthesis de novo was significantly enhanced in both liver and adipose tissue, by 150 and 300% respectively.

3. Plasma triacylglycerol and non-esterified fatty acid levels were unchanged and plasma glucose concentration slightly increased by ethanol administration.

4. The rate of lipogenesis increased when insulin: glucagon increased twofold due to the effect of ethanol.

1. The potential use of an extrinsic label to measure iron absorption from a ferric orthophosphate-fortified malted cocoa drink was examined by measuring the solubility of the FePO4 in 0·1 M-hydrochloric acid.

2. The validity of using the stable isotope 58Fe as an extrinsic label was tested by comparing Fe absorption by rats from wheat flour extrinsically-labelled with 58Fe or 59Fe.

3. Fe absorption from a malted cocoa drink (20 g powder made up with hot water) fortified with FePO4 (0·5 mg Fe/g powder) was measured in human subjects using 58Fe as an extrinsic label. Absorption was calculated by measuring unabsorbed 58Fe in faeces. Absorptions of Fe from the drink fortified with either FePO4 or ferrous sulphate were compared. The effect of the addition of ascorbic acid to the drink (1 mg/g powder) on Fe availability was also examined.

4. The effect of fasting on Fe absorption from the drink was determined in rats by giving the drink to fasting animals or shortly after they had consumed a small meal.

5. The FePO4 was totally soluble in 0·1 M-HCl and there were no differences in absorption between 58Fe- and 59Fe-labelled wheat flour. In the human experiment the proportion of Fe absorbed from the drink plus FePO4 and ascorbic acid was (mean with SE) 0·25 (0·02), from the drink plus FePO4 0·24 (0·02) and from the drink plus FeSO4 0·23 (0·03). Fasting had a significant effect on Fe availability; rats given the drink shortly after a small meal absorbed less than half as much Fe as those given the drink on a fasted stomach.

6. It was concluded that the FePO4 used to fortify the malted cocoa drink was as well absorbed as FeSO4 but that the high levels of absorption were a reflection of the fasting condition of the subjects. The level of ascorbic acid was not great enough to enhance the availability of the FePO4 any further.