Rates of protein synthesis for the liver, plasma albumin and total plasma protein were quantified in sheep either offered a supra-maintenance intake or fasted for 3 d. The technique of continuous infusion over a 12 h period was employed with the simultaneous infusion of [1-13C]glycine, [1-13C]leucine and [2H5]phenylalanine. Blood and plasma samples were removed at timed intervals from the hepatic portal and hepatic veins plus the aorta. Enrichments of the free amino acids (AA) were determined in all blood and plasma samples as was the protein-bound AA in an apolipoprotein B100 extract. Protein-bound phenylalanine enrichments were also measured in albumin and total protein from plasma plus samples from liver biopsies. The apolipoprotein B100 enrichments agreed well with those of the free AA in hepatic (and hepatic portal) plasma but were lower than for arterial free AA and greater than liver homogenate free AA. This adds support to the concept that export proteins may preferentially use AA directly from extracellular sources. Intake had no significant effect on constitutive liver protein synthesis and the values agreed well with those obtained by other isotopic approaches. There were, however, signicant declines, based on hepatic venous free phenylalanine enrichment, at the lower intake in both the fractional (3·4v. 4·7 % per d; P=0·024) and absolute (2·4 v. 4·2 g/d; P=0·011) synthesis rates of albumin, which matched the estimated decrease in total plasma albumin content (52 v. 67 g, P <0·01). In contrast, there was a smaller reduction in total plasma protein mass (145 v. 151 g, P=0·035) with no observed significant difference in kinetic parameters. Albumin synthesis was calculated to account for a maximum of 17 % of total liver protein synthesis in the fed condition and this may fall to 8 % during moderate fasts.

The relationship between in vitro gas production, concomitant in vitro apparent and true DM degradability has been examined in forty-two roughages. The partitioning of truly-degraded substrate between gas volume and microbial biomass yield and 15N incorporation into cells was also investigated. The relevance of this partitioning for the regulation of DM intake (DMI) was examined for fifty-four roughages. The results can be summarized as follows. In vitro gas production and in vitro apparent and true degradability are highly correlated (P<0.0001), r being 0.96 and 0.95 respectively. There is an inverse relationship between in vitro gas production and microbial biomass yield (r—0.67, (P<0.0001) and also 15N enrichment (P<0.001)when the variables were related to a given unit of substrate truly degraded. Selecting roughages by in vitro gas production may well be a selection against maximum microbial yield and a combination of in vitro gas volume measurements with a complementary determination of the substrate truly degraded is proposed, to calculate a partitioning factor (PF) reflecting the variation of short-chain fatty acid production per unit substrate degraded. PF is calculated as the ratio, substrate truly degraded: gas produced by it. PF was highly significant (P<0.0001) in DMI prediction when included in stepwise multiple correlations together with in vitro gas volume variables reflecting the extent and rate of gas production; 11 % of the variation in DMI was accounted for by the PF. The total model, including extent and rate of gas production and the PF, accounted for 84 % of the variation in DMI. Roughages producing proportionally less gas per unit substrate truly degraded had higher feed intakes.

Two experiments were designed to determine the tissue distribution of threonine oxidation through the threonine dehydrogenase (EC 1.1.1.103) pathway in pigs. The first experiment was conducted on eleven Piétrain x Large White piglets. The piglets were slaughtered at 5, 12 or 20 kg after 1 h of infusion with L-[U-14C]threonine (55 kBq/kg) mixed with unlabelled threonine (100 mg/kg). In the second experiment, four Piétrain x Large White and four Large White piglets (10 kg body weight) were infused with L-[1-13C]threonine (50 mg'kg) mixed with 50 mg'kg unlabelled threonine for 1 h, then killed for tissue sampling. In the two experiments, threonine dehydrogenase specific activity and threonine and glycine specific radioactivities and enrichments were measured in several tissues and in plasma. The higher level of labelling of threonine in the pancreas than in the liver suggested either a lower protein degradation rate or a faster rate of threonine transport in the liver than in the pancreas. Threonine dehydrogenase activity was found only in the liver and the pancreas. Whereas liver and pancreas threonine dehydrogenase specific activities were similar, glycine specific radioactivity and enrichment were 12- to 14-fold higher in the pancreas than in the liver. This is probably the consequence of a higher production rate of glycine from sources other than threonine (protein degradation, de novo synthesis from serine) in the liver than in the pancreas. Our results showed that Large White pigs could oxidize more threonine than Piétrain x Large White pigs. This could be related to the difference in growth performance and dietary N efficiency for protein deposition between these two genotypes.

In the present study we examined the immune-enhancing effect of a nucleoside-nucleotide mixture on the non-specific T-cell immune functions of senescence-accelerated mice (SAM) fed on a low-protein diet. The immune functions studied were in vitro thymic and splenic cell lymphoproliferative responses to phytohaemagglutinin, lipopolysaccharide and concanavalin A and their production of interleukin-2 (IL-2) and interferon-γ (INF-γ) in response to mitogen stimulation. SAMP8 mice aged 3 and 6 months were used. In each age group, mice were fed on diets containing either 50g casein/kg, 50 g casein/kg supplemented with 5 g nucleoside-nucleotide mixture/kg or 200 g casein/kg for 3 weeks. The supplemented 3- and 6-month-old mice had higher (P<O·O5) thymic and splenic cell counts compared with the low-protein group. In both age groups of mice, concanavalin A induced higher (P<0·05) total thymic and splenic lymphoproliferative responses for the nucleoside-nucleotide mixture-supplemented group compared with the 50 g casein/kg dietary groups. Thymic and splenic production of IL-2 was higher for the 3-month-old mice in both the supplemented and the 200 g casein/kg dietary groups. INF-γ production in the supplemented 3-month-old group and the 6-month-old 200 g casein/kg dietary group was higher (P<0·05) compared with the other groups. Overall the supplemented 3-month-old mice exhibited both higher lymphoproliferative responses and production of cytokines compared with the supplemented 6-month-old mice. The results indicate that early nucleoside-nucleotide mixture supplementation may enhance the immune response in protein-deprived SAMP8 mice

In the present study energy balance and liver respiratory activity were studied in rats fed on either a control diet or an energy-dense diet. Liver respiration was assessed both without added substrates and after the addition of hexanoate, glycerol, or sorbitol. The effect of ouabain on hexanoate-supported respiration was also determined. Metabolizable energy intake and energy expenditure increased in rats fed on an energy dense diet, but body-weight gain, as well as lipid and protein content, remained unchanged. When net energy expenditure, obtained excluding the total cost of storage, was expressed as a percentage of metabolizable energy, significant differences were found between the two groups of rats. This finding supports the presence of regulatory mechanisms in rats fed on an energy-dense diet, which are useful to counteract development of obesity. In addition, a significant increase in liver respiratory activity was found in rats fed on an energy-dense diet, both in the basal state and in that stimulated by added substrates. Na/K-pump-dependent O2 consumption also increased in rats fed on an energy-dense diet. The results indicate that a greater production of metabolic heat by the liver can contribute to the increased energy expenditure found in rats fed on an energy-dense diet.

The effect of policosanol, a mixture of high-molecular-weight aliphatic alcohols isolated from sugar-cane wax, on casein-induced hypercholesterolaemia in rabbits was studied. When policosanol was administered by the oral route once daily for 30 d (50mg/kg) the increases in plasma total cholesterol and LDL-cholesterol (LDC-C) were significantly reduced when compared with the control group. The incorporation of 3H2O into sterols in the liver was significantly depressed, suggesting inhibition of hepatic cholesterol biosynthesis. The oral administration of policosanol raised the rate of removal of 125l-labelled LDL from serum. Kinetic parameters calculated following injection of [125I]LDL showed than in casein-fed rabbits, the terminal half-life (t½) was significantly decreased after policosanol treatment. The hepatic LDL-binding activity was increased after policosanol administration which suggested that the enhanced clearance was due, at least in part, to increased receptor-mediated uptake of LDL by the liver. Considered together, these results suggest that policosanol can significantly reduce the increase of plasma LDL-C in rabbits fed on a wheat starch-casein diet by reducing cholesterol biosynthesis in the liver. Such an effect could account for the enhancement of LDL catabolism through the receptor-mediated pathway.

Sheep fitted with a PVC cannula in the dorsal rumen, a silastic infusion tube in the abomasum, and single ‘T’-shape PVC cannulas in the proximal duodenum (D1), distal duodenum (D2), mid-jejunum (J), and terminal ileum (I), were fed on diets varying in crude protein (Nx6·25) and fibre contents. 15N was administered to the sheep as a 15N-labelled grass meal-beer yeast suspension which was continuously infused into the abomasum over a period of 1 week. Subsequently, over a period of 4 d, 15N excess in the D1, D2, J and I digesta and faeces was measured and related to 15N excess in blood plasma TCA-soluble N. Average daily intakes of DM and N were 1·12 kg and 26·3 g respectively. Average daily endogenous N (g) amounted to 3·1 at D1, 10·2 at D2, 6·1 at J, 5·0 at I, and 5·1 in the faeces (F). Corresponding percentage values for total N were: D1 12·4, D2 32·9, J 46-4, I 48.4 and F 50.7. The secretion, particularly of pancreatic juice and/or bile, varied. The apparent re-absorption of endogenous protein varied among experimental diets, on average by 50·4% between D2 and I. Along the small intestine the percentage of 15N in the TCA-precipitable fraction gradually changed, on average by 66·0, 63·0, 46·3 and 55·7 at D1, D2, J and I respectively. Because of differential rates of enrichment and turnover among protein pools which contribute towards endogenous secretion, care should be taken in interpreting these data as absolute values.

The effects of raw sweet lupin (Lupinus angustifolius) meal and its fractions on the growth and N utilization of rats were determined in two NPU and five N balance experiments. Sweet lupinseed grown in Western Australia, obtained as meal, unsupplemented (LMU), or fully supplemented with required amino acids (360 g/kg diet) (LMFS) was tested. In addition, six fractions were tested: aqueous non-dialysed extract at pH 7·0 (LPAND), dialysed extracts soluble (LPAD) and insoluble at pH 7·0 (LPADI), buffer-soluble extract at pH 7·0 (BUSOL), buffer-insoluble extract after dialysis at pH 7·0 (BUDI) and the residue (LMR) containing most of the material from meal insoluble in water and phosphate-citrate buffer. All diets based on fractions contained the same amounts of energy and protein and were supplemented with amino acids, vitamins and minerals to target requirements. Body N and lipid contents of rats fed on LMU and LMFS were reduced significantly in comparison with rats fed on positive lactalbumin (LACT) and non-protein diets (NPC) as negative controls. This wasdue in part to the lower retention of the absorbed N. As a result, the NPU and the biological value (BV) of sweet lupinseed proteins were less than expected. Urea-N outputs of the LMU- and LMFS-fed rats were also elevated. In contrast, true N and DM digestibilities of rats fed on LMU and LMFS were not significantly affected by the difference in the energy content of the diet. The replacement of lactalbumin in thediet with LPAND (196 g/kg), LPAD (148 g/kg), LPADI (124 g/kg), BUSOL (136 g/kg) or BUDI (119 g/kg) reduced dry body weight, N and lipid contents, NPU and BV compared with those obtained from the LACT control, even though the N and DM digestibilitieswere not significantly different. Inclusion of the residue fraction (170 g LMR/kg) had no apparent effect on any of the variables studied. Since sweet lupinseed had asmall amount of non-reactive lectin and LMR had some undesirable side-effects in these rats, it appears that the low nutritional value of LMFS for rats (NPU 0·62) despite the very high level of digestibility of its N, results from disturbances in N metabolism, and particularly from the low retention value of the absorbed N

Effects of different dietary fats on plasma, hepatic and biliary lipids were determined in male golden Syrian hamsters (Mesocricetus auratus) fed on purified diets for 7 weeks. Diets were made by blending different fats containing characteristic fatty acids: butter (14:0 + 16:0), palm stearin (16:0), coconut oil (12:0 + 14:0), rapeseed oil (18:1), olive oil (18:l) and sunflowerseed oil (18:2). In all diets except the sunflowerseed oil diet dietary 18:2 was held constant at 2% energy. Total fat supplied 12% of energy and cholesterol was added at 4 g/kg diet. Plasma cholesterol and triacyglycerol concentrations were increased by dietary cholesterol. After 7 weeks, plasma cholesterol concentrations were highest with the palm Stearin, coconut oil and olive oil diets (8·9, 8·9 and 9·2 mmol/l) and lowest with the rapeseed oil and sdowerseed oil diets (6·7 and 5·5 mmol/l) while the butter diet was intermediate (8·5 mmol/l). Hepatic cholesterol concentration was highest in hamsters fed on the olive oil diet and lowest with the palm stearin diet (228 v. 144 µmol/g liver). Biliary lipids, lithogenic index and bile acid profile of the gall-bladder bile did not differ significantly among the six diets. Although the gallstone incidence was generally low in this study, three out of 10 hamsters fed on the palm stearin diet developed cholesterol gallstones. In contrast, no cholesterol gallstones were found with the other diets. Rapeseed and dowerseed oils caused the lowest plasma cholesterol and triacyglycerol concentrations whereas olive oil failed to demonstrate a cholesterol-lowering effect compared with diets rich in saturated fatty acids. Since 18:2 was kept constant at 2% of energy in all diets, the different responses to rapeseed and olive oils could possibly be attributed to their different contents of 16:0 (5·6 % v. 12·8% respectively). Other possible explanations are discussed.

Two areas of sports nutrition in which the periodicity of eating has been studied relate to: (1) the habitually high energy intakes of many athletes, and (2) the optimization of carbohydrate(CHO) availability to enhance performance. The present paper examines how the timing and frequency of food and fluid intake can assist the athlete and physically-active person to improve their exercise performance in these areas. Frequent eating occasions provide a practical strategy allowing athletes to increase energy intake while concomitantly reducing the gastric discomfort of infrequent large meals. The optimization of CHO stores is a special challenge for athletes undertaking prolonged training or competition sessions. This is a cyclical process with post-exercise CHO ingestion promoting muscle and liver glycogen re-synthesis; pre-exercise feedings being practised to optimize substrate availability and feedings during exercise providing a readily-available source of exogenous fuel as endogenous stores become depleted. The timing and frequency of CHO intake at these various stages are crucial determinants for optimizing fuel availability to enhance exercise capacity.

To obtain further information about the immunomodulatory effects of specific dietary fatty acids, weanling male rats were fed for 6 weeks on high-fat (178 g/kg) diets which differed according to the principal fatty acids present. The nine diets used differed in their contents of palmitic, oleic, linoleic and α-linolenic acids; as a result the total polyunsaturated fatty acid (PUFA) content and the PUFA: saturated fatty acid ratio varied (from 17·8 to 58·5 g/lW g fatty acids and from 0·28 to 5·56 respectively). The n−6 PUFA: n−3 PUFA ratio was kept constant in all diets at approximately 7·0.The fatty acid compositions of the serum and of spleen lymphocytes were significantly influenced by that of the diet fed. The ex vivo proliferation of spleen lymphocytes decreased as the levelof oleic acid in the diet increased. Spleen natural killer cell activity decreased as the oleic acid content of the diet increased and increased as the palmitic acid content of the diet increased. The extent of the effects of these fatty acids on lymphocyte functions was modified by the nature of the background fatty acid composition of the diet.

The effects of diet on the composition and properties of adipose tissue in relation to lymph nodes were studied in adult guinea-pigs. The proportions of monoenoic triacylglycerol fatty acids were constant in all sites in adipose tissue of similarly fed guinea-pigs, but were substantially greater in samples from guinea-pigs fed on suet-enriched chow. Triacylglycerols in adipose tissue from near nodes contained significantly fewer saturated fatty acids, and significantly more 18:2n−6 and 18:3n−3 than those in samples from sites remote from nodes within the same depot. Depots that interact most strongly with lymphoid cells in vitro had the largest and most consistent within-depot differences. The gradients of triacylgiycerol fatty acid composition with distance from lymph nodes in two small intermuscular depots were similar in guinea-pigs fed on plain or suet-enriched chow. These findings are consistent with the hypothesis that adipose tissue around lymph nodes is specialized for local interactions with the lymphoid cells therein, and help to explain the variability of serial or duplicate measurements of adipose tissue composition. When cultured alone, lipopolysaccharide-stimulated lymph node lymphoid cells from suet-fed guinea-pigs incorporated as much labelled thymidine as the controls. Adipose tissue explants from suet-fed guinea-pigs inhibited lymphocyte proliferation much less than those of the controls, although the site-specific differences were similar. The pattern of site-specific differences in glycerol released from explants incubated alone was generally similar for both dietary groups, but except in the popliteal depot, the increases following co-culturing with lymphoid cells were smaller for samples from suet-fed guinea-pigs. These experiments show that minor changes in the fatty acid composition of the diet can substantially alter the interactions between adipose tissue and lymphoid cells.

Over the past two decades, substantial research has been conducted to investigate the idea that alterations in short-term nutritional intake play a role in influencing cognitive behaviour and mood. A portion of this research has examined specifically the effect of meal intake on the performance of mental tasks and subjective feelings of mood. Results of this research indicate that a number of variables including the timing and nutritional composition of the meal, nutritional status, habitual patterns of feeding behaviour, beliefs about food, and the nature of the mental tasks, can influence the effects of meals on cognitive behaviour. For example, studies have demonstrated that breakfast intake generally is associated with an improvement in cognitive performance later in the morning, while lunch intake is associated with an impairment in mid-afternoon performance on mental tasks and more negative reports of mood. Intake of nutrients late in the afternoon appears to have a positive effect on subsequent performance on tasks involving sustained attention or memory. Although research has provided insights into the role of meal intake on cognitive behaviour and mood, there are a number of factors which remain to be studied. These include the interaction of age, gender, activity level, meal composition, personality factors, stress with the effects of meals on cognitive behaviour. Additionally, more work is needed on the time-course of short-term nutrient effects, and the effects of chronic changes in meal intake on behaviour.

A diet-switching experiment, which aimed to improve the utilization of soyabean whey was carried out for 61 d with young rats. Feeding was arranged in such a way that after a few days on the soyabean diet, the rats were switched to a high-quality lactalbumin diet for a short period, after whicb the cycle was repeated several times. The weights of the rats at the end of the soyabean phases were significantly less than those of animals pair-fed on a high-quality diet throughout. However, the test group regained the weight loss after switching to the lactalbumin diet. After three cycles there were no significant differences between the weights of the test rats fed on a poor soyabean diet for over a third of the experiment and those fed on the lactalbumin diet throughout. Feed conversion was always significantly higher with test rats in the lactalbumin period than with continually pair-fed controls. Similarly, faecal N losses were significantly higher for test rats in the soyabean phase, but these differences disappeared after switching to the lactalbumin diet. At the end of the experiment there were no significant differences in body protein or lipids between the groups although the pancreas was significantly heavier while the liver was lighter in soyabean-fed rats. The high destruction of trypsin inhibitors in the gut suggests that they probably had little effect on protein digestion in the gut. In contrast, as selective depletion of the agglutinin from soyabean whey removed the nutritional benefit in the lactalbumin part of the cycle, the improved feed conversion in this period must have been the result mainly of the survival and functionality of soyabean agglutinin and the benefits due to the hyperplastic growth and faster renewal of the gut surface it induced. As processing is unnecessary, this novel method is cheap and can be easily adapted for the use of soyabean whey, regarded as a waste product.

We hypothesized that feed preference depends on the interplay between flavour and postingestive effects, and we tested two predictions based on this hypothesis: (1) lambs acquire preferences for poorly nutritious feeds paired with starch; and (2) preferences persist when starch is no longer administered. Twenty lambs were randomly allocated to two groups and conditioned as follows: on odd-numbered days, lambs in group 1 received onion-flavoured wheat straw and lambs in group 2 received oregano-flavoured wheat straw. On even-numbered days, the flavours were switched and starch (2-5-9.4% of the digestible energy received/d) was infused into the rumen of aU animals during straw consumption. Four periods of 8 d of conditioning were performed and on the 9th day of each period all animals were offered a choice between onion- and oregano-flavoured straw. After conditioning, starch administration was suspended and lambs were offered onion- and oregano- flavoured straw at weekly intervals for 8 weeks (extinction). Lambs strongly preferred the flavoured straw paired with starch, and this preference persisted during extinction. Thus, these results suggest that the postingestive effects of energy play an important role in the development of feed preferences of ruminants

The effect of hypoxic exposure on in vitro duodenal Fe uptake kinetics was studied in tissue fragments from rats that were fed or fasted overnight before study. Hypoxic exposure was for 3 d at 0·5 atm and fasting was for the last 18-24 h before Fe uptake determinations. The non-permeable Fe2+ chelator 3-(2-pyridyl)-5,6-bis-(4-phenyl-sulphonic acid)-l,2,4-triazine (ferrozine), and medium deoxygenation inhibited uptake in all experimental groups. Ferrozine sensitivity and mucosal Fe3+ reductase activity were greatest in hypoxic animals. Fe uptake was inhibited by membrane depolarization only after fasting or hypoxic exposure of the rats. The data demonstrated that Fe uptake by rat duodenal fragments involves at least two mechanisms: a membrane-potentialindependent mechanism which is not responsive to hypoxia and a second mechanism, induced by fasting or hypoxia, which is inhibited by membrane depolarization. Uptake is partially dependent on reduction of Fe3+ to Fe2+ and this is primarily associated with the second mechanism for uptake. These properties have been reported also in mouse and human Fe uptake, suggesting that the rat is a useful model for the study of basic mechanisms of Fe absorption

The activities of hepatic enzymes of fatty acid synthesis and oxidation were compared in rats fed on diacylglycerol and triacylglycerol. In the first trial, rats were fed on diacylglycerol or triacylglycerol (rapeseed oil) for 14 d. The diacylglycerol preparation contained 65·2 g and 32·6 g fatty acids/100 g total fatty acids as 1,3-species and 1,2-species respectively. Fatty acid compositions of these dietary lipids were similar. Dietary acylglycerols were added to experimental diets to provide the same amounts of fatty acids (93·9 g/kg diet). Dietary diacylglycerol compared with triacylglycerol significantly reduced the concentrations of serum and liver triacylglycerol. The activities of enzymes of fatty acid synthesis (fatty acid synthetase, glucose 6-phosphate dehydrogenase (EC 1.1.1.49) and malic enzyme (EC 1.1.1.40)) were significantly lower in rats fed on diacylglycerol than in those fed on triacylglycerol. In contrast, the rates of mitochondrial and peroxisomal oxidation of palmitoyl-CoA in liver homogenates were higher in rats fed on diacylglycerol than in those fed on triacylglycerol. In the second trial, varying amounts of dietary triacylglycerol were replaced by diacylglycerol while the dietary fatty acid content was maintained (93·9 g/kg diet). After 21 d of the feeding period the significant reductions in serum and liver triacylglycerol levels were confirmed in groups of rats fed on the diets in which diacylglycerol supplied more than 65·8 g fatty acids/kg diet (65·8 and 93·9 g/kg). Reductions in the activities of enzymes of fatty acid synthesis and increases in palmitoyl-CoA oxidation rates by both mitochondrial and peroxisomal pathways were also apparent when diacylglycerol replaced triacylglycerol in diets to supply more than 65·8 g fatty acid/kg. Increasing dietary levels of diacylglycerol also progressively increased the activities of enzymes involved in the β-oxidation pathway (carnitine palmitoyltransferase (EC 2.3.1.21), acyl-CoA dehydrogenase (EC 1.3.99.3), acyl-CoA oxidase (EC 1.3.3.6), enoyl-CoA hydratase (EC 4.2.1.17), 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35), 2,4-dienoyl-CoA reductase (EC 1.3.1.34) and Δ3,Δ2-enoyl-CoA isomerase (EC 5.3.3.8)) in the liver. These results suggest that alteration of fatty acid metabolism in the liver is a factor responsible for the serum triacylglycerol-lowering effect of dietary diacylglycerol.

In the last 20 years, mainly due to optimum fluoride exposure, and practice of good oral hygiene procedures, an important reduction in caries has been observed, despite the fact that sugar consumption was maintained and/or was increasing during the same lapse of time. A sugar-caries relationship cannot be established in most of the industrialized countries and the dietary factor is not as preponderant in the caries process as it used to be two decades ago. The factors which seem to contribute the most significantly to the cariogenicity of the diet are the frequency of carbohydrate ingestion and eating patterns. The relative cariogenicity of food is not correlated with the amount of carbohydrate it contains. Even if sucrose remains the most important sugar consumed in sweets, beverages and confectionery products, all fermentable-carbohydrate foods can be involved in the caries process. The use of chewing gum and other xylitol-containing products have resulted in defined reduction in caries and represent interesting alternatives for high-caries-risk populations. Caries risk and oral health assessments as well as the evaluation of oral hygiene procedures and fluoride exposure should become essential tools in dietary counselling. People who receive optimum fluoride exposure and follow regular oral hygiene measures can safely use dietary carbohydrates, preferably during meals and two to three times daily in snacks or drinks.

We studied Fe absorption from FeSO4 in rats with Fe deficiency-induced anaemia that were given an Fe-sufficient purified diet without or with ascorbic acid (10·4 g/kg diet). Attention was focused on mucosal Fe uptake as measured in vivo by a double-isotope technique. Haemoglobin repletion and liver Fe levels were not affected when the ascorbic acid-supplemented diet was given, but apparent Fe absorption and retention of orally administered 59Fe were significantly enhanced. The distribution of Fe between liquid and solid phases of contents of both the stomach and the proximal intestine was not affected by the feeding of the ascorbic acid, but ascorbic acid significantly enhanced mucosal Fe uptake. It is concluded that ascorbic acid in the diet raises mucosal Fe uptake through a mechanism independent of the intestinal Fe solubility.

To investigate the mechanism of tissue Fe accumulation in graded Mg deficiency rats were fed on diets of different Mg contents (70, 110, 208, 330, and 850 mg Mg/kg) for 10, 20, and 30 d during rapid growth. There was no significant impact of Mg deficiency or high luminal Mg concentrations on intestinal 59Fe transfer in vitro or in vivo. Plasma Mg concentrations and body weight started to decrease after 10 d. Significant haemolytic anaemia was observed after 20 d with siderosis in liver and spleen developing in parallel. Anaemia showed no features of Fe deficiency or infiammation. Comparison between the 70 mg Mg/kg group and animals that received the same quantity of a Mg-adequate diet (850 mg Mg/kg) permitted estimation of quantities of Fe liberated by haemolysis and the increased Fe content in liver and spleen. Both variables showed a high degree of correlation, indicating that the excess of liberated haemoglobin Fe was stored in the tissue. The erythropoietic activity was high during rapid growth, i.e. at days 10 and 20 and decreased significantly after 30 d in all except the most Mg-deficient groups. However, haemolytic anaemia developed because even the high erythropoietic activity in the 70 and 110 mg Mg/kg groups was not sutlicient to recycle all haemoglobin Fe liberated by haemolysis. After 30 d of Mg-deficient feeding the erythrocyte Mg content had decreased to 40% of control values. According to the literature Mg-deficient erythrocytes have a decreased survival time which is likely to be the cause of the observed haemolysis.