The metabolic response to a 150 or 400 g 13C-labelled pasta meal was studied for 8 h following rest or exercise at low or moderate workload (n 6). Following rest, the 400 g meal totally suppressed fat oxidation (v. 14.1 g following the 150 g meal) and a small amount of glucose was converted into fat (4.6 g), but fat oxidation remained high in subjects who had exercised following both the small (21.8 and 34.1 g) and large meal (14.1 and 32.3 g). Exogenous glucose oxidation was significantly higher in subjects who had remained at rest both following the small (67.6 g v. 60.4 and 51.3 g in subjects who exercised at low and moderate workloads) and large meal (152.2 v. 123.0 and 127.2 g). Endogenous glucose oxidation was similar in the three groups following the 150 g meal (42.3–58.0 g), but was significantly lower following the 400 g meal in subjects who had exercised at low workload (24.2 v. 72.2 g following rest; P<0.05), and was totally suppressed in those who had exercised at moderate workload. As a consequence, a larger positive glycogen balance was observed in subjects who exercised before the large meal (182.8–205.1 g v. 92.4 g following rest; P<0.05). Total fat oxidation calculated from 08.00 hours to 20.00 hours was similar in subjects who exercised at low and moderate workloads. These results indicate that: (1) de novo lipogenesis, which plays only a minor role for the disposal of an acute dietary carbohydrate load, is totally suppressed following exercise, even when a very large carbohydrate load is ingested; (2) the reduction in glycogen turnover as well as a preferential conversion of glucose into glycogen are responsible for the increase in glycogen stores following exercise; (3) for a similar energy expenditure, exercise at low workload for a longer period does not favour fat oxidation when the post-exercise period is taken into account.

Nearly 600 000 women die every year from pregnancy related conditions and the maternal mortality rates (MMR = deaths per 100 000 live births) in developing countries may be as high as 1000 compared with less than ten in industrialised countries. In the light of the striking impact of deficiencies of micronutrients such as vitamin A and zinc on immune function, morbidity and mortality in children it seems reasonable to suggest that such deficiencies might play a contributing role in the high rates of morbidity and mortality in mothers. Hitherto, there has been rather little published on the contribution of malnutrition to maternal morbidity or mortality but recent results of micronutrient supplementation show a major effect of vitamin A or beta carotene supplementation on maternal mortality in Nepal and an impressive effect of a multiple micronutrient mixture on pregnancy outcome in Tanzania. There is now data showing that subclinical mastitis, a potential risk factor for mother to child transmission of HIV by increasing levels of virus in breast milk, is influenced by maternal diet in Tanzania and feeding patterns in South Africa. Considering the massive tragedy of maternal mortality the recent data provides opportunities for new, innovative nutritional interventions for the reduction of the global burden of maternal morbidity and mortality.

The dose-dependent bone-sparing effects of dietary isoflavones (IF) were investigated in adult (7-month-old) Wistar rats. Forty animals were ovariectomised, allocated into four groups of ten rats each, and immediately treated orally with IF at 0 (OVX), 20 (IF20), 40 (IF40) or 80 (IF80) μg/g body weight per d for 91 d; ten sham-operated (SH) controls received the same diet without added IF. Animals were killed on day 91. Both femoral failure load and total femoral, diaphyseal or metaphyseal bone mineral densities (BMD) were lower in OVX animals than in SH animals. Urinary deoxypyridinoline (DPD) excretion, a marker of bone resorption, and plasma osteocalcin (OC) levels, a marker of osteoblast activity, were higher in OVX animals than in SH animals. Total femoral and diaphyseal BMD and femoral failure load were similar in IF-treated rats and SH rats. Although metaphyseal BMD in IF40 or IF80 rats was similar to that in SH rats, its value was lower in IF20 rats than in controls. The day 91 urinary DPD excretion in IF40 and IF80 rats, but not in IF20 rats, was similar to that in SH rats. Day 91 plasma OC concentrations in IF-treated rats were similar to day 45 values, but were decreased in OVX and SH rats. Thus, daily IF consumption prevented ovariectomy-induced bone loss, both by depressing bone resorption and stimulating osteoblast activity. Moreover, as only the highest IF level induced a weak uterotrophic activity, the optimal IF dose which preserves both cancellous and cortical bone, but exhibits no oestrogen-like effects on the uterus, was 40 μg/g body weight per d.

The present study was aimed at evaluating in patients with type 2 diabetes: (1) the glycaemic response to four starchy foods based on wheat, typical of the Italian diet; (2) the importance of some food characteristics in relation to their effects on postprandial glucose response. Seventeen patients with type 2 diabetes (eleven men and six women) participated in the study. All patients consumed, in random order and on alternate days, 50 g available carbohydrate provided by 90 g white bread and, according to a randomised procedure, an equivalent amount of carbohydrate provided by one (n 8) or two (n 9) of three other different test foods (g): pizza 85, potato dumplings 165, hard toasted bread 60. Foods had a similar nutrient composition. Plasma glucose response, measured for 180 min, was significantly lower after the potato dumplings than after white bread at 90 (P<0·05), 120 (P<0·01) and 150 (P<0·05) min. No difference was observed in postprandial plasma insulin response after the various test foods. The percentage of starch hydrolysed after 5 h in vitro hydrolysis with α-amylase was about 30 % lower for potato dumplings than for the other foods. However, no differences in the resistant starch content, the rate of diffusion of simple sugars added to a dialysis tube containing the food, and the viscosity of digesta were observed among the test foods. Scanning electron microscopy of potato dumplings showed a compact structure compatible with impaired accessibility of starch to digestive enzymes. In conclusion, carbohydrate-rich foods typical of the Italian diet which are often consumed as an alternative to pasta dishes are not equivalent in terms of metabolic impact in diabetic patients. Due to their low blood glucose response, potato dumplings represent a valid alternative to other starchy foods in the diabetic diet. Food structure plays an important role in determining starch accessibility to digestion, thus influencing the postprandial blood glucose response.

The aim of the present study was to examine the effect of consumption of a high-fruit and vegetable diet, or a spray-dried extract of selected fruits and vegetables of high antioxidant content, on indices of antioxidant status of individuals consuming a background diet with minimal antioxidant intake. Plasma antioxidant concentrations were determined in twenty-five men following a 2-week depletion period during which they consumed self-selected low-antioxidant diets (less than three servings of fruit and vegetables with no tea, coffee, red wine or fruit juice). Following this period the volunteers consumed either a self-selected diet containing five to seven servings of fruit and vegetables/d, or 30 g of a spray-dried supplement designed to provide the equivalent antioxidant activity of five to seven servings of fruit and vegetables for 2 weeks in a crossover trial. Following consumption of a high-antioxidant diet for 2 weeks, plasma concentrations of ascorbic acid, α- and β-carotene and lutein+zeaxanthin were all significantly increased (P<0.05) over the depletion period. However, concentrations of lycopene, retinol and tocopherol were not affected. Consumption of the supplement also raised the concentrations of these same antioxidants in plasma. Despite the increases in the concentrations of measured antioxidant nutrients, the 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid-equivalent antioxidant capacity of plasma, as estimated by inhibition of metmyoglobin activity, was not significantly affected by any of the dietary treatments.

The hypothesis that hepatic lipase mediates the differential hepatic uptake of chylomicron remnants of different fatty acid composition, demonstrated in previous work from our laboratory, was tested by investigating the effect of antibodies to the enzyme on the uptake of remnants enriched with saturated or n-3 polyunsaturated fatty acids by the perfused rat liver. After perfusion of rat livers with polyclonal antibodies to rat hepatic lipase raised in rabbits or with rabbit non-immune serum for 15 min, [3H]oleate-labelled chylomicron remnants, derived from chylomicrons of rats given a bolus of either palm (rich in saturated fatty acids) oil or fish (rich in n-3 polyunsaturated fatty acids) oil, were added. The disappearance of radioactivity from the perfusate during 120 min and its recovery in the liver at the end of the experiments were then measured. Although the rabbit anti-rat hepatic lipase antiserum was shown to inhibit hepatic lipase activity by up to 90 %, and to bind extensively to hepatic sinusoidal surfaces when added to the perfusate, radioactivity from remnants of chylomicrons from rats given a bolus of fish oil as compared with palm oil disappeared from the perfusate and appeared in the liver more rapidly in the presence both the antiserum and the non-immune serum, and the differences between the uptake of the two types of remnants were similar. We conclude, therefore, that differential interaction with hepatic lipase is not responsible for the differences in the rate of removal of chylomicron remnants of different fatty acid composition from the blood.

The present study was designed to determine the apparent absorption and retention of the inorganic Se compounds SeO32- and SeO42-, which are commonly used for Se fortification of clinical nutrition products and infant formulas. Ten healthy men were fed a milk-based formula labelled with 40 μg Se as 74SeO32- or 76SeO42- on two consecutive days using a randomised crossover design. Se stable-isotope analysis of 9 d complete collections of urine and faeces was used to calculate apparent Se absorption and retention. Se retention from 74SeO32- (41·0 (SD 8·4) %) AND FROM 76SEO42- (46·0 (sd 7·9) %) was not significantly different (P>0·05). However, Se absorption was significantly higher from SeO42- than from SeO32- (91·3 (sd 1·4) % v. 50·2 (sd 7·8) %, P<0·05). Urinary excretion of the administered dose was 9·2 (sd 1·8) % for 74SeO32- and 45y3 (sd 8·2) % for 76SeO42- (P<0·05). Urinary Se excretion kinetics differed significantly for the two Se compounds; 90 % of the total urinary Se was excreted after 121 h for 74SeO32- and after 40 h for 76SeO42- (P<0·05). These results suggest that although Se absorption and urinary excretion differ for SeO32- and SeO42-, both Se compounds are equally well retained when administered at a relatively low dose (40 μg Se). The nutritional impact of Se fortification of foods would thus be expected to be similar when SeO42- or SeO32- are used.

Polyol-containing confectionery offers considerable advantages over traditional sucrose-based confectionery in terms of reduced energy content and reduced cariogenicity. However, over-consumption of polyol confectionery may lead to gastrointestinal symptoms in some individuals. Rather than consider this as a distinct disadvantage to the consumer, this article discusses how careful consideration of the physico-chemical properties of polyols and advances in product development and formulation can provide suitable polyol-based products for the consumer. Furthermore, food legislation and ingredient pricing issues are just some of the factors that must be taken into account when designing new polyol-containing products if their functional benefits and good product quality are to be delivered to the consumer.

Large doses of ascorbic acid may mobilise Fe from Fe-binding proteins in vivo which in turn could catalyse lipid peroxidation, a process associated with degenerative diseases. This hypothesis was tested in vitro in the serum of Fe-loaded animals. Eighteen male guinea pigs weighing about 500 g on arrival were allocated to two groups of nine. Fe loading was induced in one group by two intraperitoneal injections of 200 mg iron dextran given on days 1 and 5. Blood (6 ml) was drawn from all animals on day 12 by cardiac puncture. Serum and LDL were separated. Serum was tested for loosely-bound Fe (bleomycin assay) and lipid peroxidation (thiobarbituric acid reactive substances (TBARS) assay) and LDL for susceptibility to in vitro oxidation (TBARS and conjugated diene assays). On day 12, another intraperitoneal injection of 200 mg iron dextran was given to the animals in the Fe-loaded group. On day 19, all animals were given 75 mg ascorbic acid by intraperitoneal injection. Blood (6 ml) was drawn 4 h later by cardiac puncture. Serum and LDL assays were repeated. Ascorbic acid increased loosely-bound Fe and in vitro oxidation in the serum from animals of the Fe-loaded group but not in the serum from animals of the control group. Susceptibility of LDL to in vitro oxidation increased after the ascorbic acid injection in the control group but there was no further increase in the Fe-loaded group. These data suggest that large doses of ascorbic acid promote Fe mobilisation and in vitro oxidation in the serum of Fe-loaded animals.

To evaluate some of the mechanisms involved in the plasma cholesterol lowering of sitostanol (SI), male Hartley guinea pigs were fed diets containing cholesterol (0.25 g/100 g) and four doses of SI: either 0 (control), 0.75, 1.5 or 2.25 g/100 g. In addition a negative control (-C) group with dietary cholesterol (0.04 g/100 g) was included. Corn oil was used as the source of fat and the contribution of fat energy was 35 %. Plasma total cholesterol was 43, 49 and 53 % (P<0.0001) lower after SI intake compared to the control. Plasma LDL concentrations were 47, 53 and 61 % lower with increasing doses of SI. In addition, intake of SI resulted in 26–42 % lower hepatic total cholesterol. Hepatic esterified cholesterol and triacylglycerols were 32–60 % and 55–61 % lower after SI intake. SI intake resulted in favourable plasma and hepatic cholesterol concentrations similar to those in guinea pigs fed low levels of dietary cholesterol (-C). The LDL obtained from the control group had a higher number of molecules of free and esterified cholesterol than the SI groups. SI intake resulted in 69–71 % higher cholesterol excretion compared to the control. SI treatment enhanced the total faecal neutral sterol excretion by 54–58 % compared to control and by 70–76 % compared to the (-C) group. These results suggest that SI might have its hypocholesterolaemic effect by reducing cholesterol absorption, which results in lower concentration of cholesterol in liver. This reduction in hepatic cholesterol might possibly alter hepatic cholesterol metabolism and affect lipoprotein concentration and composition.

The present study investigated the digestion and cholesterol-lowering effects of the water-soluble NSP guar gum (GG) and sodium alginate (SA) in laboratory animals. Groups of five male Wistar strain rats were fed semi-purified cholesterol-free diets containing 0, 50 or 100 g NSP source/kg for 21 d which comprised a 14-d adaptation period followed by a 7-d balance period. Weight gain over the balance period and food conversion ratio decreased linearly with increasing NSP intake (P=0.006 and P=0.07 respectively). DM digestibility decreased with increasing NSP intake (P=0.001) and this effect was greater for SA-containing diets compared with GG-containing diets (P=0.001). At the lower inclusion rate, 0.9–1.0 of the additional NSP was digested, but this value fell to 0.8 for both NSP sources at the 100 g/kg inclusion rate, implying that the capacity for near complete digestion of the test NSP had been exceeded. Intestinal tissue mass was increased in response to inclusion of both NSP sources. Caecal digesta pH decreased linearly with additional GG, but increased slightly with consumption of SA. Total caecal short-chain fatty acid concentrations (μmol/g caecal contents) increased markedly with 50 g GG/kg but did not increase further with 100 g GG/kg, and were slightly lower than control values in rats consuming SA. Plasma cholesterol concentration fell linearly (P=0.03) with increasing NSP in the diet and the effect was similar for both GG and SA. Total output of faecal bile acids rose in rats fed 50 g GG/kg and 50 g SA/kg (59 μmol/7 d v. 24 μmol/7 d for control rats) with no further increase at the higher inclusion rate. These results show that SA has a strong hypocholesterolaemic effect in rats which is similar to that of GG, and that this effect is most likely to be mediated through an interruption in the entero-hepatic circulation of bile acids and not through increased hepatic supply of propionate from fermentation of the NSP in the large bowel.

The aim of the present study was to examine the effect of reducing saturated fat in the diet, or partly replacing it with unsaturated fat, on the serum lipoprotein profile of human subjects. The study had two intervention periods, 8 weeks (phase 1) and 52 weeks (phase 2). In phase 1, total fat was reduced from 31 to 25 % energy (polyunsaturated fatty acids (PUFA):saturated fatty acids (SFA) ratio increased from 0.2 to 0.4) by reducing the quantity of coconut fat (CF) in the diet from 17.8 to 9.3 % energy intake. In phase 2, subjects were randomised to groups A and B. In group A total fat was reduced from 25 to 20 % energy (PUFA:SFA ratio increased from 0.4 to 0.7) by reducing the quantity of CF in the diet from 9.3 to 4.7 % total energy intake. In group B, the saturated fat content in the diet was similar to group A. In addition a test fat (a mixture of soyabean oil and sesame oil, PUFA:monosaturated fatty acids ratio 2) contributed 3.3 % total energy intake and total fat contributed 24 % energy intake (PUFA:SFA ratio increased from 0.7 to 1.1). At the end of phase 1, there was a 7.7 % reduction in cholesterol (95 % CI -3.6, -12.2) and 10.8 % reduction in LDL (95 % CI -4.9, -16.5) and no significant change in HDL and triacylglycerol. At the end of phase 2, the reduction in cholesterol in both groups was only about 4 % (95 % CI -12, 3.2) partly due the concomitant rise in HDL. The reduction in LDL at 52 weeks was significantly higher in group B (group A mean reduction 11 %, 95 % CI -20.1, -2.0 and group B mean reduction 16.2 % 95 % CI -23.5, -8.9). In phase 2, triacylglycerol levels showed a mean reduction of 6.5 % in group 2A and a mean increase of 8.2 % in group 2B. The reduction of saturated fat in the diet is associated with a lipoprotein profile that would be expected to reduce cardiovascular risk. The reduction of dietary saturated fat with partial replacement of unsaturated fat brings about changes in total cholesterol, HDL- and LDL-cholesterol that are associated with a lower cardiovascular risk.

Many LDCs currently on the market are not digested in the upper gastrointestinal tract and become fermented in the large intestine. They possess physiological benefits similar to those of dietary fibre. For some of these materials the fermentation process is highly specialised and leads to the selective stimulation and growth of beneficial gut bacteria, e.g. bifidobacteria. These materials are described as prebiotics, which are defined as nutrients fermented in the large bowel that favour the growth of desirable large bowel microflora. This activity has been demonstrated for inulin and oligofructose. Two other carbohydrates with low digestibility that offer desirable physiological properties are resistant starch (RS) and polydextrose (PD). These ‘functional’ benefits have led to considerable interest from the food industry leading to the use of these ingredients in the development of new ‘healthy’ products. This paper describes the use of these materials in the development of ‘healthy’ products, some of their functional properties, and the benefits they confer on different food systems.

The present paper compares the effects of two monounsaturated oils, extra virgin olive oil (EVOO) and high-oleic acid sunflower oil (HOSO), on serum and LDL peroxides, eicosanoid production and the thrombogenic ratio (thromboxane (TX) B2:6-keto-prostaglandin F1α) in fourteen non-obese post-menopausal women. The subjects, mean age 63 (SD 11) years, were assigned to two consecutive oleic acid-rich 28 d dietary periods. EVOO and HOSO represented 62 % of the total lipid intake and were used as the only culinary fat during the first and second dietary periods respectively. Serum peroxides, plasma α-tocopherol and TXB2 levels in stimulated platelet-rich plasma (PRP-TXB2) were significantly higher (P<0.01, P<0.001, and P<0.05 respectively) after the HOSO diet than after the EVOO diet. The relationship between the serum cholesterol level (<6.21 mmol/l or ≥6.21 mmol/l) and the type of dietary oil on eicosanoids, peroxides and α-tocopherol were evaluated by two-way ANOVA. Dietary oil significantly affected (P<0.05) the PRP-TXB2 level, whereas serum and LDL peroxides were significantly affected (P<0.001 and P<0.01 respectively) by the serum cholesterol level. The plasma α-tocopherol level was significantly affected by the serum cholesterol level and the type of dietary oil (both P<0.001). No significant relationships were found between serum cholesterol levels, serum peroxide or LDL peroxide levels, plasma α-tocopherol concentrations or α-tocopherol intakes with eicosanoid production or the thrombogenic ratio due to dietary changes. However, in spite of their higher α-tocopherol levels, hypercholesterolaemic subjects showed increased peroxidation in serum and LDL in comparison with normocholesterolaemic subjects on the HOSO diet in comparison with the EVOO diet. These findings suggest that differences in the type of minor compounds, as well as in the concentration of linoleic acid, in both these monounsaturated oils may play an important role in modulating eicosanoid production and lipoprotein peroxidation when they constitute a large proportion of the diet of post-menopausal women.

The lack of a valid indicator precludes a true estimate of zinc deficiency in pregnancy in various populations. However, it is possible that mild to moderate deficiency (as assessed by available indicators) may be common in the developing world. Animal experiments indicate that zinc deficiency can result in adverse maternal and fetal consequences. Human data, particularly from prenatal zinc supplementation trials, has failed to document a consistent maternal or infant benefit on evaluated outcome measures including pregnancy induced hypertension, preterm/post-term labour, premature rupture of membranes, maternal infection, postpartum haemorrhage, perinatal mortality, congenital malformations and fetal growth and gestation. Preliminary data suggest a beneficial effect of prenatal zinc supplementation on infants’ neurobehavioural development and immune function (evaluated by diarrhoeal and ARI morbidity incidence in the first year of life). Future research should focus on these functional consequences and congenital malformations (with adequate sample sizes), and simultaneously address the safety issue, particularly in relation to micronutrient interactions. In the light of the currently available information, routine zinc supplementation can not be advocated to improve pregnancy outcome.

The effect of dietary conjugated linoleic acid isomers (CLA) on growth performance, carcass composition, fatty acid composition of adipose and muscle tissues, and serum lipoproteins was investigated in broiler chickens. A total of 160 (eighty male and eighty female) chickens were allocated to four dietary treatments (0.0, 0.5, 1.0, and 1.5 % CLA) and fed a standard starter diet from 8 to 21 d, and a grower-finisher diet from 22–42 d. When determined for the total period 8–42 d, feed intake and body weight gains of broiler chickens were significantly reduced (from 3.31 to 3.12 kg and from 1615 to 1435 g respectively; P<0.05), particularly at the 1.5 % dietary CLA level. Feed conversion efficiency and carcass yield values showed no significant effects of dietary CLA. Abdominal fat deposition was significantly reduced (from 2.68 to 1.78 %; P<0.05), the relative proportion of breast muscles was unaffected, and that of leg muscles significantly increased (from 19.0 to 20.6 %; P<0.05). The concentration of CLA isomers (% of total methyl esters of fatty acids) increased linearly in tissue samples from broilers fed 0.5, 1.0, and 1.5 % dietary CLA. The relative proportions of saturated fatty acids (16:0, 18:0) were significantly (P<0.01) increased, and those of monounsaturated (16:1, 18:1) and polyunsaturated fatty acids (18:2, 20:4 in muscle tissues) significantly (P<0.05) reduced. Total serum cholesterol concentrations reached a maximum in broilers fed 1.0 % CLA and then decreased slightly (from 141.73 to 136.47 mg/dl; P<0.01). The same was true also for HDL-cholesterol (from 113.58 to 109.97 mg/dl; P<0.01). The HDL cholesterol:total cholesterol ratio and serum triacylglycerol concentration was unaffected. In conclusion, feeding CLA to broiler chickens resulted in substantial incorporation of CLA isomers into their tissue lipids, thus providing a potential CLA-rich source for human consumption.

This study presents the nutrient data collected from women who were being screened for premenstrual syndrome (PMS) for entry into an intervention study. Screening was by the Steiner self-rated questionnaire. One hundred and forty-four overweight women completed the screening process and eighty-eight met the criteria for PMS. All women kept 4 d diet diaries pre- and postmenstrually over two menstrual cycles. The mean energy and macronutrient intakes were compared between the pre- and postmenstrual phases. Energy and macronutrient intake was also calculated according to food categories. Goldberg's cut-off limit for the ratio of energy intake to estimated basal metabolic rate was used to exclude data that was incompatible with predicted energy requirements. The diet diaries were also used to determine the mean number of meals or snacks eaten pre- and postmenstrually. Nutrient analysis of the diet diaries of the women with PMS showed a significant increase (P<0.001) in total energy and all macronutrients premenstrually when compared to nutrient intake postmenstrually. Women who did not meet the criteria for PMS showed a significant increase in energy and fat intake (P<0.05) but not in the other macronutrients. When adjusted for energy, data collected from women with PMS showed a premenstrual significant increase in fat, carbohydrate (P<0.05) and simple sugars (P<0.001). There was a significant decrease (P<0.001) in protein premenstrually. Women not meeting the PMS criteria showed no significant difference between pre- and postmenstrual intakes when adjusted for energy. Analysis according to food categories in women with PMS showed a significantly greater intake premenstrually of energy and all macronutrients for cereals, cakes and desserts and high-sugar foods (P<0.001). In women with PMS there was a significantly greater number of ‘episodes of eating’ premenstrually (P<0.001). This study provides further evidence, to support the very limited number of earlier studies, that there is a group of women with PMS who increase their nutrient intake during the premenstrual phase. This could potentially be a contributing factor for some women experiencing difficulties adhering to suggested dietary modification and should be considered when counselling premenopausal women.

Under conditions of chronic supply the liver removes most amino acids (AA) in excess of net anabolic needs. Little information is available, however, on how acute alterations in AA supply (as might occur with once-daily feeding regimens) are controlled by the liver. Are these also extracted completely in a ‘first-pass’ manner or are there limitations to hepatic uptake? Furthermore, is the rate of removal ‘saturable’ (by Michaelis–Menten kinetics) over the range of supply experienced under normal feeding conditions? These questions have been addressed in a study that involved acute (4.5 h) increases in AA supply. Four sheep were prepared with trans-hepatic vascular catheters and were offered a basal diet (equivalent to 1.6×energy maintenance) throughout. On four occasions, at 7 d intervals, they were infused with various amounts of an AA mixture into the mesenteric vein over a 4.5 h period. The mixture contained fourteen AA in the proportions present in rumen microbial protein. The amounts infused were calculated to provide an additional one, two, three and four times that absorbed from the basal diet. Continuous blood collections were removed over 2 h intervals before (basal diet only) and at 0.5–2.5 and 2.5–4.5 h of AA infusion. Transfers of AA, from the digestive tract and to the liver, were calculated for both plasma and total blood. The recovery of the infused AA across the portal-drained viscera (PDV) was quantitative (100%) only for histidine and proline, the remaining AA were recovered at 56–83 %. These losses correlated (P <0.001) with the arterial concentrations and were probably due to removal of AA from the systemic circulation by the tissues of the digestive tract. Despite the wide range of net PDV appearances (i.e. absorbed plus infused), the percentage of most AA removed by the liver remained constant, but the percentage varied with AA (from 34 for proline to 78 for tryptophan for blood transfers). Thus, even when supply was increased 5-fold over baseline there was no indication that the transport into the liver declined, indeed the absolute removals continued to increase. In contrast, the branched-chain AA (isoleucine, leucine and valine) did not exhibit constant percentage extractions. Their percentage extractions were always the lowest (16, 10 and 25 respectively) and tended to decline at the highest infusion rates, indicative of saturation in hepatic transport and/or metabolism. The arterial concentrations of all infused AA increased (P <0.001) with rate of infusion, again indicative that the liver did not extract all the net AA available across the PDV. Absolute amounts removed were similar between plasma and blood, indicating that most of the hepatic transfers occurred from plasma. The fractional rates of transfer from total inflow to the liver (i.e. with re-circulated AA included) were 3- to 4-fold lower than rates based on the amounts absorbed plus infused. The highest percentage extraction for total blood inflows was for serine (27), but most were between 6 and 16, except for the branched-chain AA, which were all <1. Use of percentage extractions based on total inflows are probably more appropriate for development of mathematical models of liver metabolism, and the current data suggest that constant values may be applied. The needs of the liver for specific mechanisms involving phenylalanine and histidine (plasma protein synthesis), glycine (detoxification of xenobiotics) and alanine (gluconeogenesis) probably also require to be included in such models.

Whole-blood free amino acids were measured in a control group made up of eight healthy women fasted for 12 h and also in eight patients with acute pancreatitis, five patients with acute cholecystitis and seven patients with acute appendicitis. Blood was withdrawn immediately on admission to hospital and again 3 d later following a controlled peripheral parenteral nutrition diet; this is with the exception of the appendicitis group. L-CYSTATHIONINE AND l-methionine concentrations were significantly higher in pancreatitis and appendicitis patients when compared with controls. In the pancreatitis and cholecystitis patients, l-serine concentration was also significantly higher when compared with controls. The l-homocysteine concentration was significantly higher only in the appendicitis group when compared with the control group. l-Cystine concentration was unchanged in all the patients studied when compared with control subjects. The l-methionine : l-cystine ratio was significantly higher and the l-glutamine : l-cystine ratio was significantly lower in all the patients when compared with controls. The blood S-amino acid pattern reflects an impairment in liver transsulfuration pathway during acute abdominal processes. This work supports the idea that the l-methionine : l-cystine and l-glutamine : l-cystine ratios can be taken as good markers to evaluate the S-amino acid metabolism and suggests the importance of using N-acetylcysteine as a required nutrient in these situations.

Evidence of the impact of maternal nutritional status on pregnancy outcome is increasing. However, reference values for vitamin and homocysteine concentrations in maternal blood during normal pregnancy are scarce, and are lacking for the preconceptional period and early pregnancy. Thus, in a longitudinal study we evaluated vitamin and homocysteine concentrations in 102 nulliparous women with an uneventful singleton pregnancy and normal outcome not using supplements. The physiological changes in vitamin and homocysteine concentrations in blood were determined from the preconceptional period throughout pregnancy until 6 weeks post-partum. The vitamins evaluated comprised retinol, thiamin, riboflavin, pyridoxal 5′-phosphate, folate in serum and erythrocytes, vitamin B12 and α-tocopherol. The plasma homocysteine concentration was also measured, considering the essential roles of folate, vitamin B6 and vitamin B12 in homocysteine metabolism. The concentrations of retinol, thiamin, pyridoxal 5′-phosphate serum folate and vitamin B12 decreased during pregnancy. In contrast, the concentrations of riboflavin, α-tocopherol, and folate in erythrocytes increased or showed only minor changes. Homocysteine concentrations also remained approximately constant during pregnancy. These observations emphasize the importance of preconceptional and post-partum concentrations of vitamins in the evaluation of pregnancy-induced changes. These data have provided valuable reference values for vitamins and homocysteine before, during and after pregnancy in order to contribute to better diagnosis of maternal deficiencies and to study further the relationship between maternal vitamin status and adverse course and outcome of pregnancy.