1. The influence of dietary meat and meat stock intake on urinary excretion of 3-methylhistidine (3MH) was examined in human adults.

2. In the absence of 3MH ingestion for 48 h, the study subjects adjusted to an intrinsic urinary 3MH: creatinine value. If the meat and meat stock-free diet was maintained on subsequent days, only minute diurnal variations occurred, and the values of random urine samples during the day were representative of the 24 h 3MH: creatinine value.

3. The mean 3MH: creatinine value (SD) for a group of adults (n 7) was 0·105 ± 0·023 (μmol of 3MH/mg creatinine), which is approximately 35% lower than the corresponding value in healthy growing infants (0·148 ± 0·039) (Seashore et al. 1981).

4. Ingestion of meat soup and meat causes different patterns of urinary excretion of 3MH which are consistent with the finding that meat extracts, such as soup and stock, contain considerable amounts of 3MH. The 3MH contents of beef, chicken and turkey were 3·8 ± 0·15, 3·0 ± 0·09 and 2·3 ± 0·29 μmol/g dry wt meat respectively. All three meats contained a water-soluble 3MH-fraction (% total 3MH: beef 8, chicken 21, turkey 23). Amino acid analysis of the soluble fraction with or without hydrochloric acid hydrolysis demonstrated free 3MH in chicken and turkey (5·2 and 2·8% of the total respectively) but not in beef.

5. Patients undergoing urinary 3MH measurements should maintain a diet that is free not only of solid meats, but also of meat stock. The ingestion of commercial food products (e.g. frozen or canned meals, sauces, pizza, etc.) may impair the validity of such measurements because of their meat-stock content.

6. A dietary regimen is presented which is based on a shorter 12 h urine collection. The shorter collection time is satisfactory in the light of the steady rate of 3MH-excretion after 2 d of a diet free of meat and meat stock.

1. Total heat loss was measured by 24 h direct calorimetry in five obese and five lean women who were maintained throughout the study on a diet supplying 3·3 MJ/d. Each subject was measured five times to assess the effect of temperature, exercise and food on energy expenditure. Within each weight group a Latin-square design was used to balance sequence effects on the thermogenic responses to temperature, exercise and food.

2. Compared with the control day, on which no thermogenic stimulus was given, the increase in 24 h heat production by the lean and obese women caused by 30 min exercise on a bicycle ergometer against a load of 20 N was 10·1 and 10·3 W for obese and lean groups respectively. There was no evidence in either group of a measurable long-term increase in metabolism which would increase the energy cost of the exercise above that predicted from indirect calorimetry during the exercise.

3. The increase in heat production associated with ingesting an extra 4·4 MJ (obese group) or 4·0 MJ (lean group) was 3·4 and 3·0 W respectively. This response was similar to that predicted from indirect calorimetry for a few hours after the meal.

4. The obese and lean groups differed in metabolic response to calorimetry at the upper or lower limits of the thermal comfort zone, which was determined individually for each subject. The difference from control values in the obese group was an increase of 3·8 W on the ‘warm’ run, and a decrease of 2·0 W on the ‘cool’ run. Among subjects the change was an increase of 0·4 W on the ‘warm’ run, and an increase of 4·8 W on the ‘cool’ run. The differences between the groups did not achieve statistical significance. The lower and upper temperature limits were similar in the two groups: 23·2–26·4° for the obese group, and 23·3–26·2° for the lean group.

5. The most striking difference between lean and obese subjects in the present study was the much higher resting metabolic rate, and total energy expenditure, of the obese group. During the control run the obese group had a mean energy expenditure of 96·1 W, compared with 61·7 W in the lean group. There was no overlap: the lowest energy expenditure for an obese subject was 81·4 W and the highest for a lean subject was 76·1 W. In comparison to this large difference in baseline the magnitude of the thermogenic responses was small.

6. Under the conditions of this study there was nothing to support the view that a failure of thermogenic response is an important factor in the causation of human obesity. To support that view it would be necessary to show differences in thermogenesis in lean and obese subjects which were at least an order of magnitude greater than those which we have observed.

1. Fluoride content in ninety-three individual food items from a hospital in a fluoridated area was determined by ashing (total fluoride) v. unashing (inorganic fluoride) analysis.

2. No discrepancy between the two methods was found by food group but two dry cereals and black pepper did show significantly more fluoride after ashing. The reason for the unavailability before ashing was not determined.

3. Daily fluoride intake was estimated at 1·783 mg which is midway between the 1·211 and 2·201 mg reported from studies in which composite diets were analysed.

4. Daily intake from food at 0·4 mg was one-quarter of the daily total intake of 1·8 mg; a ratio consistent with those previously reported in serum, urine and bone between residents from a non-fluoridated v. fluoridated community.

1. Japanese sumo wrestlers have a diet rich in energy, which results in marked obesity. Their plasma urate and triglyceride levels were significantly elevated.

2. Erythrocyte phosphoribosylpyrophosphate (PRPP) and ATP concentrations in sumo wrestlers were significantly elevated when compared to the levels in control subjects.

3. There were no significant differences in erythrocyte PRPP synthetase (EC 2.7.6.1), purine nucleoside phosphorylase (EC 2.4.2.1) and hypoxanthine guanine phosphoribosyl transferase (EC 2.4.2.8) activities between sumo wrestlers and control subjects.

4. Erythrocyte adenosine kinase (EC 2.7.1.20), adenosine deaminase (EC 3.5.4.4) and adenine phosphoribosyl transferase (EC 2.4.2.7) activities in sumo wrestlers were significantly elevated.

5. It seems that sumo wrestlers have an increased turnover of adenine nucleotides which may contribute to hyperuricaemia.

1. Male Wistar rats were fed on semi-synthetic diets containing cooked white kidney beans (Phaseolus vulgaris) or equivalent levels of protein and carbohydrate.

2. No change was observed in over-all nitrogen balance in animals fed on the bean diet, but there was a two-to three-fold increase in their faecal excretion, compared with control rats. This was compensated by a decrease in urinary-N excretion.

3. Homogenized small intestinal mucosa, prepared from bean-fed animals, showed at 28%increase in protein content compared with control material.

4. Measurements of 3H-labelled thymidine turnover indicated that mucosal cell exfoliation was increased by approximately 35% in the small intestines of bean-fed rats compared with controls.

5. It is concluded that though a diet rich in cooked P. vulgaris leads to someincrease in mucosal cell turnover in the small intestine of rats, the consequent increasein mucosal protein loss could not account for the increased faecal-N excretion seen in these animals.

1. Folate was measured microbiologically with Lactobacillus casei in extracts from a range of different foods at two incubation pH values, 6·2 and 6·8.

2. The values for folate content obtained at pH 6·2 were, in several instances, considerably higher than at pH 6·8. The ‘positive drift’ seen in the values for dilutions incubated at pH 6·8 were absent from results at pH 6·2.

3. A comparison was made of the ability of the two main sources (hog kidney and chicken pancreas) of deconjugase enzyme to produce measurable folate and the hog-kidney enzyme was shown to produce consistently higher values.

4. The results presented here will have significance for studies of folate intake using calculations from food composition tables, in the light of the apparent discrepancy between calculated folate intake and the recommended daily allowances for the UK.

1. A group of rats were given ad lib. a diet with a protein-energy: total energy (P:E) value of 0·03. Other animals received the same protein intake (g/kg body-weight per d) as this group, but had their energy consumption reduced to either 90, 80. 70, 60 or 50% of the ad lib. value.

2. The restricted growth rate of rats fed on the P:E – 0·03 diet ad lib. has been shown to be due entirely to their insufficient protein consumption. In contrast, energy intake was far in excess of that required for maintenance and the limited amount of growth.

3. Carcass analysis demonstrated that some of the excess energy intake was stored as fat, but a greater part had been dissipated, presumably by diet-induced thermogenesis.

4. The plasma concentration of triiodothyronine (T3) was elevated in all animals consuming excess energy and was significantly related to both the total surplus and the amount of energy dissipated.

5. In the group of animals restricted to 50% of the ad lib. intake, energy rather than protein appeared to be the factor limiting growth. Energy intake was below estimated requirements for maintenance and was associated with values for plasma T3 that were lower than those found in well-fed control rats.

6. Although all the animals had similar protein intakes, plasma albumin concentration differed between the groups and was found to be inversely proportional to the energy intake. Thus it was lowest in animals receiving food ad lib. and rose to near normal values in the most-severely-restricted rats.

7. It is suggested that hypoalbuminaemia, and perhaps other features of protein deficiency, seen in animals fed on low-P:E diets may occur as an undesirable consequence of the metabolic response required to deal with excess energy consumption.

1. Four groups of rats were fed for 49 d on one of four semi-purified diets, without added cholesterol and containing 230 g/kg of the following isolated proteins: casein, whey, soya-bean or sunflower.

2. Whey, soya-bean and sunflower proteins, when compared with casein, decreased the level of serum high-density-lipoprotein (HDL)-cholesterol. These low cholesterol levels were accompanied by an increase in the daily faecal excretion of neutral sterols and bile acids in the case of soya-bean protein, and by a decrease in the liver cholesterol content, when rats were fed on whey protein.

3. Considering the amino acid composition of the four purified proteins, we observed that serum total and HDL-cholesterol levels had a significant positive correlation with tyrosine and glutamic acid, and a negative correlation with cystine and alanine.

4. The present study showed that the hypocholesterolaemic effect of dietary proteins was not related to their animal or vegetable origin.

1. The effect of the nature and amount of dietary energy on the lipid composition of rat gingival tissue was studied. Male weanling rats were given one of three iso-energetic diets: high-carbohydrate, high-protein and extremely high-protein, or a fourth high-fat diet, for 49 d.

2. The high-carbohydrate, extremely high-protein and high-fat diets caused significant increases in the gingival levels of total lipids compared with the normal-protein diet. These increases in total lipids were due primarily to increases in the levels of triglycerides and cholesterol esters. There were no significant differences in the fatty acid compositions of either non-polar or polar lipids among rats given the high-carbohydrate diet and those given the high-protein diet.

3. A comparison of the fatty acid composition of lipids of rats given the extremely high-protein diet and the other two iso-energetic diets revealed that the proportion of palmitic acid was higher and the proportion of oleic acid was lower in animals given the extremely high-protein diet than in animals given the other two diets. Compared with the three iso-energetic low-fat diets, the high-fat diet caused decreases in the proportion of palmitic and palmitoleic acids and increases in the proportion of linoleic, arachidonic and docosapentaenoic acids in total fatty acids of both non-polar and polar lipids. It should be noted that the high-fat diet contained a high proportion of linoleic acid and it is expected that this diet would raise the 18:2 fatty acid content of the lipids and also would raise the 20:4 and 22:5 levels as 18:2 is an essential fatty acid and will, with its metabolites, be directly incorporated into tissue lipids.

1. Male and female mice, 4 weeks old, were fed ad lib. diets containing various amounts of lard (0–300 g/kg) or various kinds of dietary fats (300 g/kg) for 13 weeks. Fat cell number and size were determined by a histological method in three different adipose sites.

2. Lard at 200 g/kg diet (43% energy from lipids) was sufficient to promote fat cell hyperplasia in the parametrial fat. Hyperplasia was also observed in the subcutaneous fat in males. The relationship between fat cell hypertrophy and the level of lard in the diet was dependent on site and sex.

3. Obesity was produced whatever the kind of dietary fat eaten: lard, beef tallow, sunflower oil or soya-bean oil. In the subcutaneous depot of males given lard, fat cell size and number were increased, but only cell hypertrophy was observed in those given soya-bean oil. In the female groups of mice fat cell hyperplasia or hypertrophy or both were related to the adipose site but not the kind of dietary fat.

4. It is concluded that dietary fats of different origin can induce obesity in mice. The effects on adipose tissue cellularity depend on the levels and kind of fat eaten, the adipose site and sex.

1. The effects of overfeeding by gastric intubation on the body composition and energy metabolism of adult female rats were studied in three experiments.

2. In Expt 1 there were significant (P < 0·001) linear increases in carcass dry matter, fat and energy during a 10 d period as metabolizable energy (ME) intake was increased from 160 to 300 kJ/d.

3. In Expt 2 rats were fed to maintain weight (130 kJ/d) or given approximately 270 kJ/d for 120 d. Measurements of fed and fasting heat production (FHP) were made at intervals. FHP (kJ/d per kg metabolic weight (W0·75)) decreased by 15% over the 120 d period on both treatments. The mean carcass weight of the overfed rats increased from 216 to 465 g, over 90% of the increase being due to fat.

4. In Expt 3 rats were fed to maintain weight (137 kJ/d) or given approximately 300 kJ/d for 6, 12, 18, 24 or 30 d. There were significant linear increases (P < 0·001) with time in carcass weight, dry matter, fat and energy. FHP, measured before slaughter, increased from 118 to 160 kJ/d but remained constant at 334 kJ/d per kg W0·75.

5. In all three experiments there were significant (P < 0·01) increases in carcass crude protein (nitrogen × 6·25) in response to overfeeding.

6. The efficiency of utilization of energy for production (Expt 1) or for maintenance and production (Expts 2 and 3) averaged 0·92, 0·86, 0·88 respectively.

7. It is concluded that FHP per kg W0·75 may be regarded as constant over a wide range of body compositions in adult rats made obese by gastric intubation, and that energy utilization conforms to classical concepts.

1. In order to test the suggestion that a dietary excess of leucine may be a precipitating factor in pellagra, rats were fed on diets that provided 15 g leucine/kg in excess of requirements for 7 weeks from weaning. This led to a significant reduction in the concentrations of nicotinamide nucleotides in liver and blood. The effect was only apparent when the diets provided less than a minimally adequate amount of nicotinamide, so that the animals were dependent on the synthesis of nicotinamide nucleotides from tryptophan to meet all or part of their requirements.

2. Urinary excretion of N1-methyl nicotinamide was not a useful indicator of tissue concentrations of nicotinamide nucleotides, and seemed not to be adequately sensitive to differentiate between minimal adequacy and marginal deficiency, as demonstrated by changes in concentrations of nicotinamide nucleotides in liver and blood.

3. The addition of leucine to incubation media for the measurement of enzyme activity in tissue homogenates at concentrations within the physiological range, led to a significant activation of tryptophan oxygenase (L-tryptophan: oxygen oxidoreductase (decyclizing), EC 1.13.11.11) and significant inhibition of kynureninase (L-kynurenine hydrolase, EC 3.7.1.3). The effect on tryptophan oxygenase may not be physiologically significant, in view of the considerable range of activity of this enzyme under normal conditions. However, the inhibition of kynureninase, which was primarily competitive with respect to the substrate, probably is physiologically significant, and was enough for this enzyme to become a probable rate-limiting step in tryptophan metabolism and nicotinamide nucleotide synthesis. Other enzymes of the tryptophan – nicotinamide nucleotide pathway were not affected by the addition of leucine to the incubation medium.

4. Feeding 15 g leucine/kg diet in excess of minimum requirements had no effect on the activities of tryptophan oxygenase or kynureninase in liver homogenates. This may reflect the reversible competitive nature of the inhibition of kynureninase by leucine, and hence be an artefact of the incubation procedure. Rats fed on the high-leucine diets excreted significantly more kynurenine than did control animals, which is evidence of inhibition of kynureninase in vivo.

5. It appears that a dietary excess of leucine, of the order of 15 g/kg above requirements, may be a precipitating factor in pellagra when there is reliance on the synthesis of nicotinamide nucleotides from tryptophan to meet a part or all of the requirements, but not when minimally adequate niacin is available from the diet.

1. Non-haem iron absorption from a variety of vegetable meals was studied in parous Indian Women, using the erythrocyte utilization of radioactive Fe method.

2. The studies were undertaken to establish whether Fe absorption could be correlatedwith the chemical composition of the foodstuff.

3. Addition of the following organic acids commonly found in vegetables, improved the geometric mean Fe absorption from a basic rice meal as follows: from 0·028 to 0·085 with 1 g citric acid, from 0·031 to 0·081 with 15 mg ascorbic acid, from 0·048 to 0·095 with 1 g L-malic acid, from 0·041 to 0·096 with 1 g tartaric acid. The only exception was oxalic acid; the addition of 1 g calciumoxalate to cabbage (Brassica oleraceae) was associated with some depression in Fe absorption from 0·320 to 0·195.

4. There was a marked inhibition of the geometric mean absorption when 500 mg tannic acid was added to a broccoli (Brassica oleraceae) meal (0·015 v. 0·297). Sodium phytate (2 g) caused a similar, though less profound inhibition (0·035 to 0·152).

5. When 3 mg ferrous sulphate was added to different vegetables the geometric mean absorption varied widely. Vegetables of low Fe bioavailability were wheat germ (Triticum aestivum) 0·007, aubergine (Solanum melongena) 0·007, butter beans (Phaseolus lunatus) 0·012, spinach (Spinacea oleraceae) 0·014, brown lentils (Lens culinaris) 0·024, beetroot greens (Beta vulgaris) 0·024 and green lentils (Lens culinaris) 0·032. In contrast, bioavailability was moderate or good with carrot (Daucus carota) 0·098, potato (Solanum tuberosum) 0·115, beetroot (Beta vulgaris) 0·185, pumpkin (Cucurbita mixta) 0·206, broccoli 0·260, tomato (Lycopersicon esculentum) 0·224, cauliflower (Brassica oleraceae) 0·263, cabbage 0·320, turnip (Brassica rapa) 0·327 and sauerkraut 0·327.

6. All the vegetables associated with moderate or good Fe bioavailability contained appreciable amounts of one or more of the organic acids, malic, citric and ascorbic acids.

7. Poor Fe bioavailability was noted in vegetables with high phytate contents (e.g. wheat germ 0·007, butter beans 0·012, brown lentils 0·024 and green lentils 0·032).

8. The fact that a number of vegetables associated with low Fe-absorption turned bluish-black when Fe was added to them, suggested that the total polyphenol content in them was high. The vegetables included aubergine spinach, brown lentils, green lentils and beetroot greens. When the total polyphenol content in all the vegetables tested was formally measured, there was a significant inverse correlation (r 0·859, P < 0·001) between it and Fe absorption. The inverse correlation between the non-hydrolysable polyphenol content and Fe absorption was r 0·901 (P < 0·001).

9. The major relevance of these findings is the fact that the total absorption of non-haem-Fe from a mixed diet may be profoundly influenced by the presence of single vegetables with either marked enhancing or inhibiting effects on Fe bioavailability.

1. Ascorbic acid deficiency results in a reduction in the activity of the hepatic mixed function oxidase systems in the guinea-pig. In this study, male Dunkin-Hartley guinea-pigs were given 0, 50, 100, 200 or 300 mg ascorbic acid/d in two equal doses in buffered sucrose solution (200 g/l) for 4 d. Controls received an equal volume of sucrose solution.

2. A dose of 50 mg ascorbic acid/d resulted in a significant rise in the specific activities of both cytochromes P-450 and b5. At doses of 200 and 300 mg ascorbic acid/d the concentration of both haemoproteins was significantly lower than the control values. These effects were mirrored by total microsomal haem concentration.

3. These results suggest that when given in large doses, ascorbic acid ceases to act simply as a vitamin and should be considered a drug competing for substrates and cofactors with co-administered drugs and endogenous substrates such as cholesterol.

1. We measured erythrocyte folic acid and riboflavin, serum folic acid and leucocyte vitamin C in women at high risk for neural tube defect (NTD) recurrence who were receiving periconceptional vitamin supplementation, before they received extra vitamins, after 28 d of supplementation and at the 8th week of pregnancy. Blood vitamin concentrations in unsupplemented high-risk women were also compared with the values found in unsupplemented low-risk women.

2. Vitamin supplementation with Pregnavite Forte F (Bencard®) raised the mean values for all vitamins measured by the 8th week of pregnancy. Mean erythrocyte folic acid rose from 250 to 478 ng/ml; plasma folic acid from 8·4 to 26·1 ng/ml; leucocyte vitamin C from 1·82 to 3·21 μg/ml blood; erythrocyte riboflavin (glutathione reductase (EC 1.6.4.2) activation ratio) from 1·08 to 1·04. All women receiving supplements had increased their serum and erythrocyte folic acid levels above the highest values found in women in an earlier study, who subsequently gave birth to children with NTD. Not all women, however, increased their leucocyte ascorbic acid or erythrocyte ribflavin levels above the highest values.

3. When vitamin concentrations in unsupplemented high-risk women were compared with levels in unsupplemented women at low risk for NTD, no significant differences were found in the mean values. However, a significantly higher proportion of high-risk compared with low-risk women had erythrocyte folic acid and leucocyte vitamin C values on or below the 5th percentile of the adult normal range.

4. The effectiveness of Pregnavite Forte F (Bencard®) for increasing maternal vitamin reserves is discussed with a view to preventing NTD and the possibility of identifying groups at risk for NTD because of low blood vitamin levels is considered.

1. Transport of L-homocitrulline, an amino acid which occurs in milk products, was studied with rat small intestine in vitro and from the human mouth in vivo. Absorption was partially dependent, in both systems, on the presence of sodium ions.

2. Metabolic inhibitors decreased L-homocitrulline uptake across the small intestine. Transport across the intestine did not occur against the concentration gradient but did show saturation kinetics.

3. The barbiturate, amytal, did not inhibit buccal absorption. Saturation kinetics were demonstrated.

4. Experiments were conducted with L-citrulline, or other amino acids, as possible inhibitors of L-homocitrulline transport. Results were compatible with Na+-dependent carrier-mediated uptake across the buccal mucosa. Active transport could be involved with the small intestine assuming that L-homocitrulline has a low affinity for the carrier system.

1. The plasma disappearance of 3H-labelled 25-hydroxyvitamin D3 (25(OH)D3) was studied in healthy volunteers on normal and high-fibre diets, using 3H-labelled tracer doses given intravenously.

2. The mean (±SEM) plasma half-life in the high-fibre-diet group was 19·2±1·7d, which was significantly shorter than in the group on normal diets (27·5±2·1 d, P < 0·02).

3. This finding suggests that a high-fibre diet leads to enhanced elimination of 25(OH)D3 by an action within the intestinal lumen. This may involve interference with an enterohepatic circulation of the metabolite, perhaps by binding of 25(OH)D3 to dietary fibre.

4. The reduced plasma half-life of 3H-labelled 25(OH)D3 associated with a high-fibre diet may explain the development of vitamin D deficiency in Asian immigrants with normal exposure to u.v. light.