We investigated the effect of wheat bran on biochemical indicators of Ca and bone metabolism in nineteen healthy women, aged 25·5 (se 0·9) years. Subjects received six wheat bran biscuits or six white flour biscuits per day for a period of 4 weeks (crossover). Wheat bran consumption increased fibre intake from 17·7 (se 1·3) to 29·6 (se 1·3) g/d (7 d food record) and enhanced P intake from 1225 (se 59) mg/d to 1663 (se 65) mg/d; P < 0·001. Mean daily Ca intake during wheat bran consumption (1110 (se 82) mg/d) significantly (P = 0·008) exceeded Ca ingestion during the white flour period (955 (se 67) mg/d). Wheat bran increased the number of defecations per week from 7·9 (se 0·8) to 12·2 (se 1·4) (P = 0·0018). Urinary Ca excretion over 24 h significantly (P = 0·021) decreased from 473 (se 53) μmol/mmol creatinine (control period) to 339 (se 37) μmol/mmol creatinine (wheat bran period). Serum 25-hydroxyvitamin D, 2 h fasting urinary Ca/creatinine excretions and 24 h urinary P excretion remained constant. No differences in serum levels of carboxy-terminal propeptide of type I procollagen (biomarker of bone formation) or in 2 h fasting urinary hydroxyproline/creatinine excretions (biomarker of bone resorption) were observed at the end of the two cycles of dietary supplementation. We conclude that a high fibre intake of approximately 30 g/d has no significant adverse effects on bone turnover in subjects with Ca intakes above 1000 mg/d and that the reduction in 24 h urinary Ca excretion is most probably the result of an adaptation process, induced by a decrease in net absorbed Ca.

In a study of the impact of aspartame, fat, and carbohydrate on appetite, we monitored blood glucose continuously for 431 (se 16) min. Ten healthy males (19–31 years) participated in three time-blinded visits. As blood glucose was monitored, appetite ratings were scored at randomized times. On the first meal initiation, volunteers consumed one of three isovolumetric drinks (aspartame, 1 MJ simple carbohydrate, and 1 MJ high-fat; randomized order). High-fat and high-carbohydrate foods were available ad libitum subsequently. Blood glucose patterns following the carbohydrate drink (+1·78 (se 0·28) mmol/l in 38 (se 3) min) and high-fat drink (+0·83 (se 0·28) mmol/l in 49 (se 6) min) were predictive of the next intermeal interval (R 0·64 and R 0·97 respectively). Aspartame ingestion was followed by blood glucose declines (40 % of subjects), increases (20 %), or stability (40 %). These patterns were related to the volunteers' perception of sweetness of the drink (R 0·81, P = 0·014), and were predictive of subsequent intakes (R -0·71, P = 0·048). For all drinks combined, declines in blood glucose and meal initiation were significantly associated (χ2 16·8, P < 0·001), the duration of blood glucose responses and intermeal intervals correlated significantly (R 0·715, P = 0·0001), and sweetness perception correlated negatively with hunger suppression (R -0·471, P = 0·015). Effects of fat, carbohydrate, and aspartame on meal initiation, meal size, and intermeal interval relate to blood glucose patterns. Varied blood glucose responses after aspartame support the controversy over its effects, and may relate to sweetness perception.

The effects of sucrose and oil preloads were explicitly compared in a single-blind controlled trial using a between-subjects design. Eighty adult subjects (forty-three male, thirty-seven female) aged 18–50 years received at 11.00 hours one of four yoghurt preloads. All were 80 g low-fat, unsweetened yoghurt (188 kJ), containing additionally (1) saccharin (control, 23 kJ), or (2) 40 g sucrose (859 kJ), (3) 40 g maize oil (1569 kJ), (4) 20 g sucrose, 20 g maize oil (1213 kJ). Subjects were normal eaters and of normal weight (male mean weight: 68·8 (sd 3·2) kg, BMI 21·8 (sd 1·6) kg/m2; female mean weight: 53·7 (sd 5·1) kg, BMI 20·4 (sd 1·2) kg/m2). Food intake was measured with a food diary and mood with ten single Likert scales. ANOVA was conducted using preload type (saccharin, sucrose, oil, sucrose + oil), sex (male, female) and early v. late breakfast times as factors. Mood was analysed using the same design, with time of rating (immediate, 60 min, 120 min) as an additional factor. Men ate more after the saccharin preload than after the other preloads, but did not vary the time of their next solid food. Women increased the intermeal interval only after the oil preload, which also had the highest energy content value, but did not vary the energy content of their next solid food. The saccharin preload decreased rated tiredness at 2 h compared with the sucrose preload, possibly due to its lower energy content. The preloads containing sucrose or sucrose + oil increased calmness between 1 and 2 h afterwards, compared with the saccharin preload. It is concluded that both sucrose and oil increase the intermeal interval in men, but that women are less sensitive to preloading. The mood effects suggest that tiredness after carbohydrate at 2 h may in part be a decrease in rated energy compared with the increased rated energy found after a preload with low energy content. Carbohydrate may genuinely increase calmness. These effects apply to non-restrained eaters of normal weight.

Cognitive performance has been found to decline after exposure to stress, particularly in stress-prone subjects. The present study investigated whether a carbohydrate-rich, protein-poor (CR/PP) diet, which may enhance cerebral serotonin function in stress-prone subjects due to increases in the available tryptophan, improves the performance of stress-prone subjects after exposure to acute laboratory stress. Twenty-two high-stress-prone (HS) subjects and twenty-one low-stress-prone (LS) subjects aged between 19 and 26 years performed a memory scanning task after controllable and uncontrollable stress, following either a CR/PP diet or a protein-rich, carbohydrate-poor (PR/CP) isoenergetic diet. Uncontrollable stress reduced feelings of control (F(1,38) 9·30; P = 0·004), whereas pulse rate and skin conductance increased after both stress tasks (F(1,38) 78·34; P = 0·0005 and F(1,37) 83·16; P = 0·0004). Diet, stress-proneness and stress-controllability interacted (F(1,36) 9·46; P = 0·004) in such a way that performance in HS subjects was better with the CR/PP diet than with the PR/CP diet, but only after controllable stress. As the CR/PP diet has been found to increase the plasma tryptophan: large neutral amino acids ratio, indicating an increased availability of cerebral tryptophan and, thus, higher serotonin levels, it appears that there may be an increased availability of brain serotonin in HS subjects after controllable laboratory stress.

Only a few studies have been published on the postprandial effects of different fatty acids in obese subjects. Therefore, the present study investigated the effects of three test meals containing palm oil (PO), lard (LD), or puff-pastry margarine (PPM), all normal dietary ingredients, on postprandial lipid and hormone responses in normal-weight and obese young women. The study was performed as a randomized, crossover design. The fats differed in the content of palmitic acid, stearic acid, and trans monounsaturated fatty acids allowing a dietary comparison of different ‘solid’ fatty acids. The obese women had significantly higher fasting concentrations and postprandial responses of plasma total triacylglycerol (TAG), chylomicron-TAG, and insulin compared with the normal-weight women but there was no significant difference in the postprandial responses between the three test meals. The obese women had fasting concentrations of leptin four times greater than the normal-weight women. There were no postprandial changes in the concentrations of leptin. The fasting concentrations of HDL-cholesterol were significantly lower in the obese women than in the normal-weight women, whereas there was no significant difference between the two groups in the concentrations of total cholesterol or LDL-cholesterol. These results provide evidence that obese women have exaggerated lipid and hormone responses compared with normal-weight women but the different contents of saturated and trans monounsaturated fatty acids provided by PO, LD, and PPM have no effect in either group.

The aim of the present study was to quantify the incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into plasma lipids after oral administration of n-3 fatty acid ethyl esters, since little is known about the rate and pattern of incorporation into plasma lipid fractions. In addition, we aimed to obtain preliminary information regarding EPA half-life, which is needed to establish an optimal dosing schedule. Five healthy volunteers ingested two 8·5 g doses of n-3 fatty acid ethyl esters daily for 7 d, supplying 6·0 g EPA/d and 5·3 g DHA/d. The fatty acid compositions of plasma phospholipids (PL), cholesteryl esters (CE) and triacylglycerols (TAG) were determined during supplementation and during a washout period of 7 d. Half-lives of EPA and DHA were calculated. The proportion of EPA in PL showed a 15-fold increase after 7 d (P < 0·001), while DHA showed a smaller increase (P < 0·01). In CE, EPA also increased (P < 0·05), while DHA did not increase at all. Remarkably, incorporation of DHA into TAG was even higher than that of EPA. Half-life of EPA in PL ranged from 1·63 to 2·31 d (mean 1·97 (se 0·15) d), whereas mean half-life of EPA in CE was 3·27 (se 0·56) d. In three subjects, washout of EPA and DHA from TAG seemed to follow a bi-exponential pattern, with a short half-life (< 1 d) in the initial phase and a half-life of several days in the second phase. In conclusion, EPA ethyl esters are rapidly incorporated into plasma lipids, especially into PL. The relatively long half-life of EPA in plasma would permit a dosing schedule with intervals of ≥12 h in supplementation studies.

The Maillard reaction produces coloured, macromolecular materials (melanoidins) in a variety of foods, on heating. Significant quantities may enter the human gut on a daily basis, but there is little information on their metabolism in the human colon. As the large bowel contains a diverse population of bacteria involved in normal bowel function, it is possible that melanoidins are metabolized therein. Depending on the bacteria involved, there may be disease or health implications. The aim of the present study was to use in vitro models to determine the digestibility of melanoidins and the effect of melanoidins on colonic bacteria in the gastrointestinal tract. Melanoidins were prepared and the effects of simulated upper-gut secretions on their stability determined in a model system. The effects of faecal bacteria were also determined, in batch culture, with a combination of phenotypic and genotypic (probes) criteria being used to identify the microbial diversity involved. Simulation of peptic and pancreatic digestion showed that the melanoidins did not produce detectable amounts of low-molecular-mass degradation products. However, melanoidins affected the growth of gut bacteria during mixed culture growth. The effect was to cause a non-specific increase in the anaerobic bacteria enumerated. This in vitro study indicates that melanoidins can affect the growth of human large-bowel bacteria and serves to demonstrate possible effects that may occur in vivo. Given the large and varied number of food items that contain Maillard reaction products, this may have relevance for lower-gut health.

The present study was conducted to determine the role of α-lipoic acid (LA) in plasma metabolites, hepatic O2 consumption, and β-adrenergic response in broilers. In Expt 1, 12-d-old female broiler chicks were divided into three dietary groups and fed on diets with or without LA (5 or 50 mg/kg) until 4 or 6 weeks of age, as a 2 × 3 factorial arrangement. The dietary LA had no effect on growth rates (body weight, abdominal fat, breast muscle, and liver). The higher level of LA increased plasma non-esterified fatty acid and decreased plasma triacylglycerol concentrations only at 6 weeks of age. A 42 % increase in hepatic respiration was observed in the 4-week-old chickens given 50 mg LA/kg diet. In Expt 2, 3-d-old female broiler chicks were treated with or without dietary LA at 50 mg/kg. At 30 and 31 d old, isoproterenol (2 mg/kg body weight per h) was continuously infused into a wing vein for 2 h, and changes in plasma glucose, triacylglycerol, and non-esterified fatty acid concentrations were analysed. Isoproterenol increased plasma glucose over basal levels maximally at 60 min. Furthermore, the glucose increase in the LA-treated chickens was 35% greater than that of the controls at this time. Plasma non-esterified fatty acid and triacylglycerol concentrations were decreased by the isoproterenol infusion, regardless of LA administration. Therefore, the present study suggests that dietary LA has repartitioning effects on energy metabolism in chickens (although this depends on age-related metabolic state) and is a possible facilitator in the β-adrenergic response of plasma glucose to a β-agonist.