In order to study the influence of pancreatic enzyme secretion on the intestinal absorption of mediumchain fatty acids (MCFA), three growing pigs (mean body-weight 61 kg) with ligated and severed pancreatic ducts were fitted with a permanent fistula in the duodenum and with two catheters in the portal vein and carotid artery respectively. An electromagnetic flow probe was also set up around the portal vein. A mixture of octanoic and decanoic acids, esterified as medium-chain triacylglycerols, together with maltose dextrine and a nitrogenous fraction was continuously infused for 1 h into the duodenum. Samples of blood were withdrawn from the two vessels at regular intervals of time for 8 h and further analysed for their non-esterified octanoic and decanoic acid contents. The concentrations of non-esterified octanoic and decanoic acid in the portal blood increased slowly after the beginning of each infusion, reaching about 10 times higher values than the basal level. Only 26% of octanoic acid infused in the duodenum and 27% of decanoic acid were recovered in the portal flow throughout each experiment. The possible mechanisms underlying the appearance of MCFA in the portal blood in the absence of pancreatic enzyme secretions and the importance of duodenal absorption of MCT in such physiological conditions have been discussed.

Two growth experiments were conducted to determine the effect of heat on the utilization of ileal-digestible lysine from field peas (Pisum sativum cultivar Dundale) fed to growing pigs. Five lysine-deficient diets (0.36 g ileal-digestible lysine/MJ digestible energy (DE)) were formulated using raw field peas, and field peas heated to either 110°, 135°, 150°, or 165° for 15 min respectively in a forced-air dehydrator. Additional diets were formulated with supplements of free lysine to verify that lysine was limiting in the diets containing the raw peas, and peas heated to 150° or 165°. The growth performance and retention of ileal-digestible lysine by pigs given the diets was determined over the 20–45 kg growth phase. Heat had a significant quadratic effect (P < 0.01) on growth rate, with responses declining from 543 g/d with pigs given the raw peas, to 407 g/d for those given the peas heated to 165°. Similarly, crude protein deposition declined in a quadratic manner (P < 0.001) from 76 to 36 g/d for pigs fed on raw peas and peas heated to 165° respectively. Retention of ileal-digestible lysine was 0.85 in the pigs given the raw field peas and declined in a quadratic manner (P < 0.001) with the application of heat to 0.48 in those pigs given the peas heated to 165°. Pigs fed on field peas heated to 165° had increased (P < 0.05) liver weights. The results indicate that heat applied to protein concentrates, even at mild temperatures, renders lysine in a form that is apparently absorbed but inefficiently utilized by the growing pig. Consequently, ileal digestibility values for lysine in heat-processed meals are unsuitable for diet formulations.

The effect of dietary protein content (25, 60, 95, 130, 165 and 200 g crude protein (N × 6.25)/kg diet) on the apparent and true ileal digestibilities of N and amino acids in meat-and-bone meal given to the growing rat was investigated. Semi-synthetic diets in which meat-and-bone meal was the sole protein source were given to 180 g body-weight rats for 14 d. On the fourteenth day the rats were fed and then killed 4 h after the start of feeding and digesta were sampled from the terminal 200 mm ileum. Endogenous amino acid excretion was determined for eighteen rats given an enzymically hydrolysed casein (EHC)-based diet and with subsequent treatment of the digesta using ultrafiltration. The EHC-fed rats were killed 3 h after the start of feeding and digesta were collected from the terminal 200 mm ileum. True ileal digestibility values determined with reference to Cr as a marker were higher than the corresponding apparent estimates. Apparent digestibility values of N and amino acids increased significantly (P < 0.001) with increasing dietary protein level; however, dietary protein content had no significant (P > 0.05) effect on the true ileal digestibilities of N and amino acids. The mean apparent ileal digestibility of N in meat-and-bone meal ranged from 65.6 to 75.3%. The corresponding range for the true ileal digestibility of N was 76.9 to 78.2%. True ileal digestibility, unlike apparent digestibility, appears to be independent of dietary protein level and may allow feed ingredients to be compared accurately even if they are ingested in different quantities.

The effect of heat on the availability of lysine in field peas (Pisum sativum cultivar Dundale) was determined using the slope–ratio assay with growing pigs. The field peas were heated to 110°, 135°, 150°, or 165° for 15 min using a forced-air dehydrator. Lysine availability was significantly depressed (P < 0.05) with the application of heat, even at mild temperatures of 110°. Lysine availability values of 0.96, 0.71, 0.77, 0.56, and 0.47 were determined for the raw peas and peas heated to 110°, 135°, 150° or 165° respectively. The effect of dietary protein level on the ileal digestibility of lysine in raw field peas was determined in a second experiment to estimate true ileal digestibility. Five diets were formulated to contain 85, 105, 125, 145 and 165 g protein/kg. Increasing dietary protein from 85 to 105 g/kg resulted in a significant increase in the estimate of apparent ileal digestibility from 0.84 to 0.93. Comparisons were then able to be drawn between the ileal digestibility, availability and utilization of lysine from raw and heat-treated field peas. The results indicate that unlike ileal digestibility values, estimates of lysine availability are sensitive to heat treatment and are a close reflection of lysine utilization in heated protein concentrates. Thus, lysine availability values would be more suitable for use in diet formulations than ileal digestibility estimates when dealing with heat-processed protein concentrates.

The absorption of Zn from a lupin (Lupinus angustifolius) milk fortified with Ca, a bread containing lupin flour (230 g/kg), a sauce containing lupin flour and a sauce containing a lupin-protein isolate was determined in humans by measuring the whole-body retention of radioisotope from meals labelled with 0·02 MBq 65Zn, allowing for endogenous excretion of Zn, after 14 d. The absorption of Zn from the Ca-enriched milk (16·2%) and the bread made with lupin flour (27·0%) was similar to literature figures for comparable soya-bean products. The absorption from composite meals made with lupin flour (28·2%) and protein isolate (32·7%) was significantly higher than that reported for comparable soya-bean products. In a second experiment the absorption of Zn from a lupin-milk base and a soya-bean-milk base was compared with that from Ca-supplemented bases. The absorption of Zn from the lupin-milk base (26·3%) was significantly higher than from the soya-bean-milk base (17·6%), and neither was significantly altered by the addition of Ca. Overall the absorption of Zn from lupin-protein foods was found to be higher than from comparable soya-bean products. Lupin milk could be an attractive alternative to soya-bean milk for infant formulas.

In a controlled clinical trial we have recently shown that patients with rheumatoid arthritis (RA) improved after fasting for 7–10 d and that the improvement could be sustained through 3.5 months with a vegan, diet and 9 months with a lactovegetarian diet. Other studies have indicated that the inflammatory process in R A can be reduced through manipulation of dietary fatty acids. A switch to a vegetarian diet significantly alters the intake of fatty acids. Therefore, we have analysed the changes in fatty acid profiles of the plasma phospholipid fraction and related these changes to disease activity. The concentrations of the fatty acids 20: 3n-6 and 20: 4n-6 were significantly reduced after 3.5 months with a vegan diet (P < 0.0001 and P < 0.01 respectively), but the concentration increased to baseline values with a lactovegetarian diet. The concentration of 20: 5n-3 was significantly reduced after the vegan diet (P < 0.0001) and the lactovegetarian diet periods (P < 0.01). There was no significant difference in fatty acid concentrations between diet responders and diet non-responders after the vegan or lactovegetarian diet periods. Our results indicate that the changes in the fatty acid profiles cannot explain the clinical improvement.

One hundred and fourteen 11–14-year-old schoolgirls from Wembley, Middlesex, were assessed for Fe status (haemoglobin (Hb), packed cell volume and mean corpuscular Hb concentration, height, weight eating habits, and ethnic origin, and undertook a step test to assess physical performance. Overall, 20% of girls had Hb less than 120 g/l, ranging from 11 % in White girls to 22–25% in girls of Asian origin. Prevalence of low Hb was 20% in vegetarians, higher in White vegetarians compared with non-vegetarians (23 v. 4%), but lower in the Indian vegetarians compared with non-vegetarians (17 v. 32%). Low Hb was present in 25 % of girls who had tried to lose weight in the previous year, and was more common in girls from manual social class backgrounds than non-manual (24 v. 10%). At the start of the step test the twenty-three girls with low Hb had heart rates similar to those with normal Hb, but hear rates in the low Hb group were significantly elevated immediately after the step test, and still significantly elevated 1 min later. The present results confirm the findings of a previous study in White girls, and suggest that physical performance may be compromised at mild levels of anaemia.

An extract from oats known as oat gum (OG) is composed mainly of the polysaccharide (1→3) (1→4)-β-D-glucan, which is highly viscous in aqueous solution. Viscous polysaccharides are known to attenuate postprandial plasma glucose and insulin responses. The purposes of this study were to determine the dose–response to OG and establish quantitatively the effect of viscosity on plasma glucose and insulin levels of healthy humans consuming 50 g glucose. Increasing the dose of OG successively reduced the plasma glucose and insulin responses relative to a control without gum. Reduction of the viscosity of OG by acid hydrolysis reduced or eliminated the capacity to decrease postprandial glucose and insulin levels. The ability of OG to modify glycaemic response was unchanged following agglomeration in the presence of maltodextrin. Agglomerated gum dispersed smoothly in a drink without formation of lumps, and development of maximum viscosity was delayed. These properties improve palatability. There was a highly significant linear relationship between log[viscosity] of the mixtures consumed and the glucose and insulin responses. The relationship shows that 79–96% of the changes in plasma glucose and insulin are attributable to viscosity, and that changes occur at relatively low doses and viscosities.

The present study examined whether different proteins have different effects on whole-body protein turnover in adult rats. The rats were either starved, given a protein-free but energy-sufficient diet (1 MJ/kg body weight (BW) per d) or a diet containing intact casein, hydrolysed casein, or hydrolysed soya-bean protein at a level of 9.1 g/kg BW per d. The diets, which were isoenergetic with the same carbohydrate: fat ratio, were given as a continuous intragastric infusion for at least 4 d. During the last 19 h 15N-glycine (a primed continuous infusion) was given intragastrically and 15N was recovered from urinary ammonia and urea during isotope steady state for measurement of protein synthesis and protein degradation. Compared with starvation the protein-free diet decreased N excretion by 75%, probably by increasing the rate of reutilization of amino acids from endogenous proteins for protein synthesis. The protein diets produced a positive N balance which was independent of the protein source. Intact and hydrolysed casein increased protein synthesis 2.6- and 2.0-fold respectively, compared with the protein- free diet. Protein degradation increased 1.4- and 1.2-fold respectively. Hydrolysed soya-bean protein did not increase protein synthesis but decreased protein degradation by 35% compared with the protein-free diet. Compared with the hydrolysed soya-bean protein, intact casein resulted in 2.2- and 2.8-fold higher rates of protein synthesis and degradation respectively. These results are not easily explained by known sources of misinterpretation associated with the 15N-glycine method. Hydrolysed casein and hydrolysed soya-bean protein produced similar concentrations of insulin-like growth factor-1, insulin, glucagon, and corticosterone. The difference in amino acid composition between the dietary proteins was reflected in plasma amino acid composition and this is suggested to be responsible for the different effect on protein turnover. Preliminary results from this study have previously been published in abstract form (Nielsen et al. 1991).

The bioavailability of Se from ground beef has been previously found in this laboratory to be greater than that of selenite or selenate when fed to female Fischer 344 rats. In the present study we examined the bioavailability of Se from various commercial portions of beef, the liver, striploin, round, shoulder and brisket. All beef was cooked, freeze-dried, finely powdered and mixed with the other dietary ingredients. The experimental diets were fed to the weanling Fischer 344 rats which had been subjected to dietary depletion of Se for 6 weeks. The bioavailability of Se from the beef diets was compared with that of Se as selenite or L-selenomethionine (SeMet) added to torula-yeast diets. Each experimental diet contained 0·10 mg Se/kg. After 8 weeks of dietary Se repletion, relative activity of liver glutathione peroxidase (EC 1·11·1·9; GSHPx) from the different dietary groups compared with that of control animals (100%) was (%): selenite 91, SeMet 122 (P < 0·05), liver 108, striploin 105, round 106, shoulder 106, brisket 103. Se recovery for liver GSHPx was generally highest from SeMet beef muscle = beef liver selenite. Muscle tissue deposition of Se was highest from SeMet beef muscle selenite = beef liver. In addition, the faecal excretion of Se was lowest from the SeMet dietary group and highest from the selenite dietary group. The experimental results suggest that all cuts of beef appear to be highly bioavailable sources of dietary Se when compared with selenite or L-SeMet. Selenjum bioavailability: Beef: Selenite: Selenomethionine

To investigate the sensitivity of guinea pig tissues to ascorbic acid depletion, as distinct from inanition, young male guinea pigs were maintained with either ascorbic acid restriction or total diet restriction for 8 weeks. One group (A) received no ascorbic acid for 3 weeks, then 0·5 mg/d for 5 weeks; one group (B) was weight-matched by restricted food intake to the first group; a third (marginally deficient) group (C) received 1 mg ascorbic acid/d throughout; a fourth was weight-matched to this group (D); and a fifth group received the control diet ad lib. (E). Both of the groups with restricted ascorbic acid intakes (A and C) developed very low tissue ascorbic acid contents, but only the first group (severely deficient group A) also exhibited a severely reduced growth rate. This group also exhibited reduced femur calcium and hydroxyproline contents and reduced skin hydroxyproline content. These changes were not seen in the corresponding weight-matched group (B). Neither plasma alkaline phosphatase (EC 3.1.3.1) activity, nor a variety of indices of vitamin D status exhibited changes which could be attributed specifically to reduced ascorbic acid intake and hence to lowered tissue ascorbic acid content. It is concluded that low tissue ascorbic acid levels in guinea pigs clearly alter the connective tissue composition of growing femur and skin, but do not necessarily produce a major, specific effect on vitamin D status. Moreover, the control of inanition is crucial to permit interpretation of the changes in metabolism that are caused by ascorbic acid deficiency.

Apparent Mg absorption, that is Mg intake minus faecal excretion, was found to be greater in rats fed on diets containing fructose instead of glucose. This effect of fructose was accompanied by enhanced urinary excretion and diminished retention of Mg. True Mg absorption was then determined with the use of oral and intraperitoneal administration of tracer doses of 28Mg. True Mg absorption was significantly greater in rats fed on fructose. There was no significant effect of fructose v. glucose on faecal excretion of endogenous Mg. It was hypothesized that fructose enhances the solubility of Mg in the ileal lumen and thereby facilitates its absorption. The distribution of Mg between the solid and liquid phases of the ileum was determined in rats fed on either glucose or fructose. Fructose reduced the amount of Mg in the solid phase but raised both the amount and the concentration of Mg in the liquid phase. We conclude that the dietary-fructose-induced stimulation of Mg absorption in rats is caused by a raised solubility of ileal Mg. but the mechanism by which fructose exerts this effect and why it was not associated with a decrease in faecal excretion of endogenous Mg remain unknown. Dietary fructose v. glucose did not systematically affect the apparent absorption of Ca and P.

Broiler chickens were fed on a control diet based on maize and maize starch or diets containing chitin, or 94, 82 or 76% deacetylated chitin (chitosans) with different viscosities (360, 590 and 620 m Pa.s respectively) at an inclusion level of 30 g/kg. Animals had free access to feed and water for the whole experimental period. On days 10 and 18 of the experiment chickens given the control and chitin-containing diets weighed more, had consumed more feed and had lower feed conversion ratios (g feed/g weight gain) than chitosan-fed birds. Feeding of chitosan-containing diets generally reduced total plasma cholesterol and high-density-lipoprotein (HDL)-cholesterol concentrations and gave an increased HDL:total cholesterol ratio in comparison with chickens given the control and chitin-containing diets. However, no significant reductions in plasma triacylglycerol concentrations resulting from feeding of the chitosan-containing diets were observed. The reduction in total cholesterol concentration and increased HDL: total cholesterol ratio were probably caused by enhanced reverse cholesterol transport in response to intestinal losses of dietary fats. The suggestion that dietary fat absorption was impeded by the chitosans was strengthened by the observation that ileal fat digestibility was reduced by 26% in comparison with control and chitin-fed animals. In a plasma triacylglycerol response study on day 21, feeding of 94 and 76%-chitosan-containing diets generally reduced postprandial triacylglycerol concentrations compared with chickens given the chitin-containing diet. Duodenal digestibilities of nutrients amongst chickens given the chitin-containing diet were generally lower than those of control and chitosan-fed birds indicating decreased intestinal transit time. The reduced caecal short-chain fatty acid concentrations of chickens given chitosan diets compared with the control diet illustrates the antimicrobial nature of chitosan. The fact that the three chitosan-containing diets affected the registered variables similarly indicated that the level of inclusion of chitosans in the diet exceeded the level at which the effect of the different viscosities could be significant.

Levels of I were determined in selected foods and dietary supplements, and in samples of the British ‘Total Diet’. The average concentration of I in British milk collected in thirteen areas on four occasions during 1990 and 1991 was 150 μg/kg (range 40–310 μg/kg), compared with 230 μg/kg in 1977–79. No difference was found between skimmed and whole milk. Winter milk contained 210 μg/kg while summer milk contained 90 μg/kg. Regional differences were less pronounced than seasonal differences. Levels in fish and fish products were between 110 and 3280 μg/kg. Edible seaweed contained I levels of between 4300 and 2660000 μg/kg. Kelp-based dietary supplements contained I at levels that would result in a median intake of 1000 μg if the manufacturers' recommended maximum daily dose of the supplement was taken, while other I-containing supplements contained a median level of 104 μg in the manufacturers' maximum recommended daily dose. Intake of I, as estimated from the Total Diet Study, was 173 μg/d in 1985 (277 μg if samples with very high I contents were included) and 166 μg/d in 1991. These levels are above the UK reference nutrient intake of 140 μg/d for adults but well below the Joint Expert Committee on Food Additives provisional maximum tolerable intake of 1000 μg/d.

True fractional Ca absorption (TFCA) was compared in children with different habitual Ca intakes using a double-label stable-isotope technique. Chinese children aged 7 years from Hongkong (n 22) and Jiangmen (n 12) participated in the study. An oral administration of 8 mg 44Ca in 100 g chocolate milk was given shortly after an intravenous injection of 0·75 mg 42Ca. Ca isotopic ratios were determined in urine samples collected 24 h later using thermal-ionization mass spectrometry. There was no significant difference in TFCA between Jiangmen and Hongkong children (P=0·16). TFCA of a lower-Ca-intake group (Ca > 500 mg/d, n 19) with mean Ca intake 359 mg/d was 63·1 (SD 10·7)%; and that of a higher-Ca-intake group (Ca > 500 mg/d, n 15) with mean Ca intake 862 mg/d was 54·8 (SD 7·3)%; the difference in TFCA was significant (P=0·016). Serum levels of 25-hydroxycholecalciferol of the children were adequate (33·7 (SD 7·7) ng/ml). The present study indicates that growing children accustomed to a low-Ca diet appear to be able to enhance their absorptive capacity. If it is assumed that dietary Ca absorption by Chinese children resembles their TFCA from a single meal of chocolate milk, then the recommended dietary allowance (RDA) for Ca for Chinese children would be lower than the US RDA (800 mg/d), which is based on an estimated 40% Ca absorption as reported for Caucasian children. A comparative absorption study is necessary to determine whether there is any difference in TFCA between Caucasian and Chinese children.

An experiment was performed to examine the interaction between Zn deficiency and lipid intake in carp. The carp were given a high-lipid diet that was either Zn-deficient (ZD) or Zn-supplemented (ZS), or were pair-fed (PF) the ZS diet to the intake of the ZD group. After 8 weeks the carp were killed and measurements were made of intestinal glucose uptake, levels of DNA, RNA and triacylglycerol, and alkaline phosphatase (EC 3.1.3.1) activity in liver and intestine samples. A further group of similar carp were given the same diets but at week 8 were transferred to low-lipid diets, with the exception of half the ZD group. After a further 8 weeks of treatment, carps were killed for biochemical studies. Intestinal [14C]glucose uptake, levels of DNA, RNA and alkaline phosphatase activity in intestine and liver were significantly (P < 0·05) lower in the high-lipid ZD group than in the high-lipid ZS and PF diet groups. The triacylglycerol concentration in the intestine was higher in the high-lipid ZD group than in the other two groups. When the carp were given the corresponding low-lipid diets, the variables measured in intestine and liver of the ZD group were close to those of the other groups. The results of this study demonstrate that lipid, when present in excess in the diet, accumulates in the intestine under Zn-deficient conditions and may reduce the absorption of glucose in carp. The reduced RNA and DNA levels and alkaline phosphatase activity in liver and intestine of ZD fish compared with those of ZS fish given high- lipid diets is proposed to be due to the malabsorption of nutrients linked with lipid deposition in the intestine, rather than their dependence on the level of Zn in the diet.

Fibre-mediated physiological effects of raw and processed carrots were investigated in twenty-four young women under strict dietary control in two randomized crossover studies. For 3 weeks between 405 and 688 g of either raw frozen, blanched or canned carrots (first study), or raw or raw frozen carrots (second study) were consumed in addition to a low-fibre basal diet. Carrots provided 15 g dietary fibre (DF)/d. Total DF intake was 16.0 to 1.90 g (control periods) and 31 to 34 g (experimental periods). Faecal bulking effects of raw and processed carrots were similar (between 2.4 and 3.7 g additional stool/g carrot fibre in the diet). Faecal excretion of dry matter, fibre, and protein also increased significantly during carrot consumption. Fermentability of carrot fibre constituents was high (91–94%) and independent of processing, in spite of differences in the distribution of soluble and insoluble fibre and in the texture of raw and processed carrots. There was no effect of either type of carrot on serum total and high-density-lipoprotein-cholesterol or on faecal bile acid excretion.

A variety of compounds which bind to Fe have substantial reductions in absorption when co-administered with Fe compounds. The binding of both Fe2+ and Fe3+ ions to pteroylmonoglutamic acid and the pteroylmonoglutamate dianion was examined in vitro. In dimethylsulphoxide (DMSO) alone, pteroylmonoglutamate formed a 2:1 (pteroylmonoglutamate: Fe3+ ion) complex. However, in DMSO–aqueous Bis-Tris buffer (4:1, v/v; pH 6.0) no evidence of complex formation could be seen. Likewise spectroscopic evidence was obtained for complex formation with Fe2+ ion and pteroylmonoglutamate in DMSO alone but not in the aqueous DMSO buffer. In vivo studies examined the effect of FeSO4 on pteroylmonoglutamic acid absorption in an isolated perfused rat jejunal model of nutrient absorption. The dose of pteroylmonoglutamic acid approximated a human dose of 1 mg for the rat, while the FeSO4 doses were chosen to represent 6.4 mg, 64 mg and 300 mg human doses. There was no significant effect of FeSO4 on pteroylmonoglutamic acid absorption or instability of pteroylmonoglutamic acid in vivo in the presence of FeSO4 in the rat. Although 2:1 binding of pteroylmonoglutamic acid to Fe ions could be demonstrated in DMSO alone, no binding could be demonstrated in DMSO–Bis-Tris buffer (4:1, v/v; pH 6.0). It is unlikely that there will be a significant reduction in pteroylmonoglutamic acid absorption during concurrent ingestion of Fe preparations.

The effects of wheat bran and pectin on the gastrointestinal distribution of a radiolabelled, homogenized baked-bean meal were investigated in the rat. These fibres were chosen because of their very different physical characteristics; wheat bran is a coarse, particulate, mainly insoluble fibre whilst pectin is a soluble viscous polysaccharide. Sixty male rats were administered orally with control or test meals and five from each group were killed after 50, 100, 200 and 300 min. The gut was removed and the distribution of the meal established scintigraphically. Addition of the fibres altered the distribution of the meal with faster accumulation at the distal and caecal areas. Wheat bran delayed gastric emptying whilst pectin promoted gastric emptying and had a pronounced effect on increasing the distal accumulation of the meal. These alterations in the distribution of a homogenized baked bean meal show that dietary fibres with different physical characteristics may alter gastrointestinal motility in different ways and these differences may have implications for meal absorption and clinical treatments of gastrointestinal disorders.

In three experiments [amide-15N]glutamine was infused intravenously in male volunteers. After 4–8 h of infusion acidosis was achieved by an oral dose of CaCl2 (1 mmol/kg). In one subject acidosis was maintained for 5 d. The acid load produced an approximately 3-fold increase in urinary NH3 excretion, with a small (approximately 20%) and transient increase in the isotope abundance of urinary NH3 Estimates of glutamine production rate (flux) were obtained in two experiments. There was no evidence that it was increased in acidosis. The extra NH3 production by the kidney represented only a very small part, about 3%, of the total glutamine production rate.