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. 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. 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. 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. 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. 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.

1. A questionnaire inquiring about food intolerance was sent to a random sample of the electorate in a small South Wales town. Replies were received from 170 men and 305 women, the response rates being 87 and 93% respectively.

2. Adverse effects of some food were reported by 19% of men and 26% of women, or 14 and 18% respectively if minor digestive symptoms are excluded. Certain foods were thought to cause non-abdominal symptoms by 4% of men and 10% of women, and vomiting, diarrhoea or abdominal pain by 11% of men and 10% of women.

3. Plasma IgE was measured in a random subset of ninety-nine women and found to be significantly lower in those with major symptoms than in the rest. This suggests that allergy is probably not a common cause of food intolerance.

1. The effects of level of feeding of either a protein-adequate or a protein-deficient diet on nitrogen retention (NR), growth performance, body composition and some aspects of energy utilization in pigs growing from 1·8 to 6·5 kg live weight (LW) were investigated in two experiments.

2. In Expts 1 and 2 piglets were given a protein-adequate diet at four levels of intake (0·93, 1·44, 1·83 and 2·30 MJ gross energy (GE)/kg LW0·75 per d) and a protein-deficient diet at five levels of intake (1·14, 1·38, 1·68, 1·95 and 2·30 MJ GE/kg LW0·75 per d) respectively.

3. For pigs given the protein-adequate diet (Expt 1) NR was linearly (P < 0·001) related to energy intake (EI) and independent of N intake (NI). NR in pigs given the protein-deficient diet (Expt 2) was linearly (P < 0·001) related to NI and independent of EI.

4. Average daily LW gain responded linearly to increases in EI in both experiments. However, at equivalent levels of EI pigs given the protein-adequate diet exhibited more rapid and efficient growth than those given the protein-deficient diet. The results also indicated an interaction between the effects of EI and dietary protein content for feed conversion efficiency.

5. Body fat at 6·5 kg LW increased in a curvilinear fashion with increasing EI in both experiments. However, over the range of EI tested (from approximately 1·8 to 4·6 times energy for maintenance) body fat increased by 153% in Expt 1 and by only 27% in Expt 2. Pigs given the protein-deficient diet were also markedly fatter than those given the protein-adequate diet. Body protein at 6·5 kg LW decreased (P < 0·01) with increasing EI in Expt 1 but was unaffected by EI in Expt 2.

6. As estimated by multiple regression analysis, the values for the efficiency of energy utilization for protein (kp) and fat (kf) deposition were 0·76 and 0·78 respectively in Expt 1 and 0·42 and 0·89 resepctively in Expt 2. The estimates of metabolizable energy required for maintenance were 445 and 532 kJ/kg LW0·75 per d for Expts 1 and 2 respectively.

1. The influence of trace-nutrient-binding proteins on the growth of coliforms, streptococci and lactobacilli in the gastrointestinal tract was examined in neonatal rabbits delivered germ-free and dosed with an artificial flora (ESL), or born conventionally and dosed with ESL or rabbit faeces.

2. In the stomach and small intestine of both gnotobiotic and conventional animals the counts of coliforms were usually atypically high and those of streptococci were always low. In the colon the counts of coliforms and streptococci were high. Lactobacilli usually became established in the gut of the gnotobiotic animals but were not found in the conventional rabbits.

3. Sterilization (freeze-drying followed by γ-irradiation) of the milk decreased its capacity to bind added iron by 45% and vitamin B12 by 30%. When compared with raw milk, feeding of radiation-sterilized milk did not affect the viable count of coliforms and streptococci in the gut of gnotobiotic animals.

4. Saturating the nutrient-binding proteins in milk with Fe, folic acid and vitamin B12 had no effect on the numbers of coliforms, streptococci and lactobacilli recovered from the intestine.

1. Kale (Brassica oleracea) and ryegrass (Lolium perenne)–clover (Trifolium repens) pasture, grown under similar soil conditions, were grazed in the vegetative state by growing lambs of 23·6 kg initial live weight for 24 weeks. The kale and pasture contained respectively 20 and 270 μg iodine/kg dry matter (DM). The kale also contained 8 μmol total glucosinolates/g DM and 11·5 g S-methyl-L-cysteine sulphoxide (SMCO)/kg DM, both of which were nondetectable in the pasture diet.

2. Intramuscular injections of 1 (475 mg) were given during weeks 1 and 12 to half the forty-eight lambs grazing each forage. Wool growth, live-weight gain and cytochrome oxidase (EC 1.9.3.1) activity of biopsied hind-limb muscle were measured at 6-week intervals. Jugular blood samples were removed every 6 weeks for the determination of haematological factors and serum thyroid hormone concentrations. All animals were slaughtered at the end of the experiment and thyroid weight, thyroid I content, and the weight and cytochrome oxidase activity of heart muscle determined.

3. Serum concentrations of thyroxine (T4) increased from 20 to 48 nmol/l during the 24 weeks that control lambs grazed ryegrass-clover pasture. I supplementation increased the concentration and total amount of I in the thyroid gland and increased serum T4 concentration, but did not affect any other values measured in the lambs grazing the pasture herbage. Serum concentrations of triiodothyronine (T3) were stable at 2 nmol/l for both groups.

4. Control lambs grazing kale for 24 weeks showed marked thyroid enlargement and depletion of thyroid I. By week 6, serum T4 and T3 concentrations had declined to 2–5 nmol/l and 1 nmol/l respectively and were stable at these values for the remainder of the experiment. I supplementation eliminated the thyroid depletion of this element, caused serum T4 concentration to rise and stabilize at 90 nmol/l by week 18, and T3 concentration to stabilize at 2 nmol/l by week 6. From week 6 onwards, wool growth was increased 13% by I supplementation, whereas empty body growth was unaffected.

5. Lambs grazing kale developed haemolytic anaemia, due to rumen fermentation of SMCO. I supplementation enabled the lambs to resist the anaemia better by increasing erythrocyte reduced gluthathione (GSH) content. Relative to pasture-fed animals, lambs grazing kale and supplemented with I showed increased heart muscle weight and cytochrome oxidase activity. This represented a compensatory mechanism for the reduced blood oxygen-carrying capacity caused by the anaemia. I-deficient (i.e. control) lambs grazing kale showed reduced cytochrome oxidase activity in both heart and hind-limb muscle.

6. The findings are in accord with T3 having a greater biological potency than T4 for regulating rates of body and wool growth. Increases in heart weight, heart cytochrome oxidase content and erythrocyte GSH content of kale-fed lambs were, however, associated with elevation in serum T4 and not T3 concentration.

7. I requirements of growing sheep and cattle consuming the pasture diets are discussed. Because of its better relationship to production traits, it is considered that requirements should be based on the ability to maintain T3 rather than T4 concentrations. On this basis, requirements could be met by diets containing 180–270 μg I/kg DM.

1. The heat losses and energy and nitrogen balances of thirty-six individually-housed, entire male pigs (initial body-weight 18–30 kg) were measured over 7 d periods, when they were fed on rations containing 153, 201 and 258 g crude protein (nitrogen × 6·25; CP)/kg dry matter (DM). The rations also contained 16·29, 16·96 and 17·24 MJ metabolizable energy (ME)/kg DM so that the CP:ME values were 9·4, 11·8 and 15·0 g CP/MJ ME respectively. Each ration was given at three levels, 20, 35 and 50 g feed/kg body-weight per d, thus giving nine dietary treatments. The experiments were carried out at an environmental temperature of 22 (±1)°.

2. Heat loss (H) increased significantly (P < 0·01) with increase in ME intake. The rate of increase in H was not, however, influenced by the protein content of the ration. Thus, energy retention (ER) at any given level of ME intake was independent of the ration offered. From the relationship between ER and ME, estimates of the maintenance energy requirement (MEm) and the partial efficiency of energy utilization (k) were determined. MEm varied within the range 494–568 kJ/kg body-weight0·75 per d, while k varied from 0·70 to 0·76.

3. Both energy and protein intakes had a significant influence upon the rates of protein (P) and fat (F) deposition, and hence body-weight gain. At any given level of feed intake P was higher and F lower the higher the protein content of the ration. However, when compared at similar levels of protein intake, both P and F were reduced the higher the protein content of the ration.

4. From the multiple regression equations relating P and F to ME, individual estimates of MEm and the energetic efficiencies of protein (kp) and fat (kF) depositions were determined. Using an overall mean kF value of 0·86, it was calculated that MEm ranged from 462 to 525 kJ/kg body-weight0·75 per d while kp varied from 0·48 to 0·55. The significance of these estimates of kp are discussed in the light of their derivations and in relation to theoretical values.

1. The nitrogen balances of thirty-six individually-housed, entire male pigs (body-weight range 19–50 kg) were measured over 7 d periods when the animals were kept initially at an environmental temperature of 22° and then at 10° while fed on rations containing 153, 201 and 258 g crude protein (N × 6·25; CP)/kg dry matter (DM). The respective metabolizable energy (ME) contents were 16·29, 16·96 and 17·24 MJ/kg DM. Each ration was given at three levels, 20, 35 and 50 g feed/kg body-weight per d. The animals fed on the 20 and 35 g/kg feeding level were catheterized and blood samples withdrawn on two consecutive days within the N-balance periods for the determination of blood urea (BU) concentration both before and at hourly intervals for 7 h following the morning feed.

2. An increase in feed intake resulted in a significant increase in N retention (NR) at each environmental temperature. However, NR as a proportion of N intake was higher the lower the protein content of the ration. With the exception of the animals fed on the low-protein ration, NR at any given feed intake was lower at 10° than at 22° and these differences were reflected in the animal's body-weight gain.

3. Values for the fasting N metabolism (Nf), calculated from the relationship between NR and intake of digestible N (IDN), were temperature-dependent. At 22°, a constant Nf value of 0·255 g N/kg body-weight0·75 per d was found appropriate, while at 10° Nf increased with increase in protein content of the ration from 0·380 on the low protein ration to 0·533 and 0·753 g N/kg body-weight0·75 per d on the medium- and high-protein rations respectively.

4. The efficiency of N utilization (kN) reflected the differences in the relationships between NR and IDN. At 22° the relationship was curvilinear so that kN decreased with increase in both the level of feed intake and the protein content of the ration. At 10° the relationship was linear, hence kN was independent of feed intake within rations. However, it decreased from 0·909 to 0·679 as the protein content of the ration was increased.

5. The concentration of BU attained a maximal value some 3–5 h after the ingestion of the feed, with the values at 10° being higher than those at 22°. BU increased as the level of protein in the ration increased but decreased with the level of feed intake when dietary protein concentration was held constant. There was a significant correlation between BU and kN, indicating that BU is a useful criterion for assessing the efficiency of N utilization.