Glycaemic index methodology

The glycaemic index (GI) concept was originally introduced to classify different sources of carbohydrate (CHO)-rich foods, usually having an energy content of >80 % from CHO, to their effect on post-meal glycaemia. It was assumed to apply to foods that primarily deliver available CHO, causing hyperglycaemia. Low-GI foods were classified as being digested and absorbed slowly and high-GI foods as being rapidly digested and absorbed, resulting in different glycaemic responses. Low-GI foods were found to induce benefits on certain risk factors for CVD and diabetes. Accordingly it has been proposed that GI classification of foods and drinks could be useful to help consumers make 'healthy food choices' within specific food groups. Classification of foods according to their impact on blood glucose responses requires a standardised way of measuring such responses. The present review discusses the most relevant methodological considerations and highlights specific recommendations regarding number of subjects, sex, subject status, inclusion and exclusion criteria, pre-test conditions, CHO test dose, blood sampling procedures, sampling times, test randomisation and calculation of glycaemic response area under the curve. All together, these technical recommendations will help to implement or reinforce measurement of GI in laboratories and help to ensure quality of results. Since there is current international interest in alternative ways of expressing glycaemic responses to foods, some of these methods are discussed.

Impact of postprandial glycaemia on health and prevention of disease

Postprandial glucose, together with related hyperinsulinemia and lipidaemia, has been implicated in the development of chronic metabolic diseases like obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). In this review, available evidence is discussed on postprandial glucose in relation to body weight control, the development of oxidative stress, T2DM, and CVD and in maintaining optimal exercise and cognitive performance. There is mechanistic evidence linking postprandial glycaemia or glycaemic variability to the development of these conditions or in the impairment in cognitive and exercise performance. Nevertheless, postprandial glycaemia is interrelated with many other (risk) factors as well as to fasting glucose. In many studies, meal-related glycaemic response is not sufficiently characterized, or the methodology with respect to the description of food or meal composition, or the duration of the measurement of postprandial glycaemia is limited. It is evident that more randomized controlled dietary intervention trials using effective low vs. high glucose response diets are necessary in order to draw more definite conclusions on the role of postprandial glycaemia in relation to health and disease. Also of importance is the evaluation of the potential role of the time course of postprandial glycaemia.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions - and related biomarkers - implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon-like peptide, peptide tyrosin-tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

Quality of life and disability after ilio-inguinal lymphadenectomy

AIM

To examine and report the quality of life together with the level of disability of cancer patients who underwent therapeutic ilio-inguinal lymphadenectomy.

MATERIALS AND METHODS

The complete files of 62 patients who underwent 66 procedures between January 1990 and November 2006 were obtained and analysed retrospectively. Data concerning postoperative complications, presence and extent of lymphoedema, physical symptoms, duration of disability, daily life and social activities were collected through a specific questionnaire and reviewed.

RESULTS

Early postoperative complications occurred in 36% of cases. Sixty-five percent of patients developed some degree of postoperative lymphoedema. Twenty patients suffered at least one episode of erysipelas. Median postoperative disability was 4 months (range 1.5 to 24 months). Among the active population, 8 patients (18%) never returned to work. Postoperative quality of life was good or very good for most patients, with acceptable limitation in daily activities.

CONCLUSION

Ilio-inguinal lymphadenectomy is the only radical procedure able to provide long-term tumour control and maintain a good to very good quality of life, thus providing a real possibility of returning to work.

Gastrointestinal responses following acute and medium term intake of retrograded resistant maltodextrins, classified as type 3 resistant starch

DESIGN

Study part 1 was executed as a randomized double-blind placebo-controlled crossover study and study part 2 as a longitudinal study.

SUBJECTS

Forty-one healthy adult volunteers aged 18-24 years were recruited from the student population of the University of Salford. All subjects enrolled and completed study part 1 and 39 subjects enrolled and completed study part 2.

INTERVENTIONS

In study part 1, individuals consumed, in random order 0, 20, 40, 60, 80, 100 or 120 g of a RRM containing starch product incorporated in pre-prepared foods on individual test days. Assuming a minimum content of 50% RRM in the starch product this delivered respectively 0, 10, 20, 30, 40, 50 or 60 g of RRM. All foods were prepared and coded by personnel not involved in carrying out the tests. Test days were separated by 7 day washout periods. In study part 2, consumption of RRM was increased from 3.6 g at day 1 in incremental doses up to each subject's MNED as determined in study 1, to be achieved at day 14. Subsequently, RRM intake was from day 15-21 in a way that the final intake at day 21 was at least 10 g above the individual MNED. In both parts of the study, subjects reported the prevalence and magnitude of GI symptoms.

RESULTS

No significant change was observed in either defecation frequency and faecal consistency or the number of subjects experiencing any GI symptoms, following consumption of foods containing 0-60 g RRM. The individual MNED at which an increase in symptoms did not occur was determined as 60 g RRM for 71% of the subjects who participated in study part 1. Regression analysis showed that consumption of gradually increasing doses of RRM in food products over 21 days was associated with a significant increase in the mean symptom score for flatulence (P=1.5 x 10(-4)), total bowel movement frequency (P=0.023) and bowel movement frequency to pass watery faeces (P=0.0157). Increasing the ingested dose of RRM by 10 g above the predetermined MNED, however, did not provoke significant increases in GI symptoms. In both studies, the majority of symptom responses were classified by the subjects as 'little more than usual'.

CONCLUSIONS

Consumption of up to 60 g RRM is tolerated well by most individuals with no evidence of any significant dose-dependent increase in the magnitude of symptoms or the occurrence of multiple GI symptoms. However, a mild laxative effect when consuming >60 g RRM is suggested. Although there was no change in GI responses following consumption of increasing doses of RRM over 21 days, generally a dose of 10 g RRM above the MNED level was tolerated well during medium term intake.

Gastrointestinal tolerance of erythritol and xylitol ingested in a liquid

OBJECTIVES

To determine and compare the gastrointestinal (GI) responses of young adults following consumption of 45 g sucrose, 20, 35 and 50 g xylitol or erythritol given as a single oral, bolus dose in a liquid.

DESIGN

The study was a randomized, double-blind, placebo-controlled study.

SUBJECTS

Seventy healthy adult volunteers aged 18-24 years were recruited from the student population of the University of Salford. Sixty-four subjects completed the study.

INTERVENTIONS

Subjects consumed at home without supervision and in random order, either 45 g sucrose or 20, 35 and 50 g erythritol or xylitol in water on individual test days, while maintaining their normal diet. Test days were separated by 7-day washout periods. Subjects reported the prevalence and magnitude of flatulence, borborygmi, bloating, colic, bowel movements and the passage of faeces of an abnormally watery consistency.

RESULTS

Compared with 45 g sucrose, consumption of a single oral, bolus dose of 50 g xylitol in water significantly increased the number of subjects reporting nausea (P<0.01), bloating (P<0.05), borborygmi (P<0.005), colic (P<0.05), watery faeces (P<0.05) and total bowel movement frequency (P<0.01). Also 35 g of xylitol increased significantly bowel movement frequency to pass watery faeces (P<0.05). In contrast, 50 g erythritol only significantly increased the number of subjects reporting nausea (P<0.01) and borborygmi (P<0.05). Lower doses of 20 and 35 g erythritol did not provoke a significant increase in GI symptoms. At all levels of intake, xylitol produced significantly more watery faeces than erythritol: resp. 50 g xylitol vs 35 g erythritol (P<0.001), 50 g xylitol vs 20 g erythritol (P<0.001) and 35 g xylitol vs 20 g erythritol (P<0.05).

CONCLUSIONS

When consumed in water, 35 and 50 g xylitol was associated with significant intestinal symptom scores and watery faeces, compared to the sucrose control, whereas at all levels studied erythritol scored significantly less symptoms. Consumption of 20 and 35 g erythritol by healthy volunteers, in a liquid, is tolerated well, without any symptoms. At the highest level of erythritol intake (50 g), only a significant increase in borborygmi and nausea was observed, whereas xylitol intake at this level induced a significant increase in watery faeces.

Infection assessment of totally implanted long-term venous access devices

AIM

Comparison of catheter tip versus port content culture techniques to assess infection in totally implanted vascular access devices (TIVAD).

MATERIALS AND METHODS

Comparison of pocket swab, catheter-tip and port content cultures after removing the silicon puncture septum in a prospectively collected consecutive series of 102 TIVAD removed for clinical suspicion of infection, between May 2000 and March 2003.

RESULTS

102 totally implanted port-catheters in 98 patients, age ranging from 1 to 90 years (median 53 years), were removed 7 to 2616 days after insertion (median 210 days). Infection of the pocket surrounding the port was found in 21 cases, all proven by a positive culture of the pocket swab. Out of the remaining 81 cases without pocket infection, 32 had only a positive catheter tip culture, whereas 56 had a positive port content culture (p = 0.0002). Always the same microorganism was isolated in the 32 patients with positive catheter tip and port content cultures. The main organisms identified within TIVAD were Coagulase Negative Staphylococcus (CNS) (41 cases) and Candida sp (15 cases). Eight out of the 21 pocket infections were caused by Staphylococcus aureus.

CONCLUSION

In the presence of local signs of infection, taking cultures of the pocket surrounding the port is sufficient for diagnostic purposes. When infection is localized within the device only, port content cultures taken after removal of the silicon septum are more often positive than cultures of the catheter tip, and constitute therefore a more reliable tool for the assessment of TIVAD infection.

Low-carbohydrate diets: nutritional and physiological aspects

Recently, diets low in carbohydrate content have become a matter of international attention because of the WHO recommendations to reduce the overall consumption of sugars and rapidly digestible starches. One of the common metabolic changes assumed to take place when a person follows a low-carbohydrate diet is ketosis. Low-carbohydrate intakes result in a reduction of the circulating insulin level, which promotes high level of circulating fatty acids, used for oxidation and production of ketone bodies. It is assumed that when carbohydrate availability is reduced in short term to a significant amount, the body will be stimulated to maximize fat oxidation for energy needs. The currently available scientific literature shows that low-carbohydrate diets acutely induce a number of favourable effects, such as a rapid weight loss, decrease of fasting glucose and insulin levels, reduction of circulating triglyceride levels and improvement of blood pressure. On the other hand some less desirable immediate effects such as enhanced lean body mass loss, increased urinary calcium loss, increased plasma homocysteine levels, increased low-density lipoprotein-cholesterol have been reported. The long-term effect of the combination of these changes is at present not known. The role of prolonged elevated fat consumption along with low-carbohydrate diets should be addressed. However, these undesirable effects may be counteracted with consumption of a low-carbohydrate, high-protein, low-fat diet, because this type of diet has been shown to induce favourable effects on feelings of satiety and hunger, help preserve lean body mass, effectively reduce fat mass and beneficially impact on insulin sensitivity and on blood lipid status while supplying sufficient calcium for bone mass maintenance. The latter findings support the need to do more research on this type of hypocaloric low-carbohydrate diet.

The Effect of Two Sports Drinks and Water on GI Complaints and Performance During an 18-km Run

Gastrointestinal (GI) complaints are frequently experienced during running. Sports drinks to prevent dehydration and hypoglycemia during exercise are generally used. The aim was to investigate the effect of 3 different drinks on GI complaints and performance during competitive running in a controlled field study. Ninety-eight well-trained subjects (90 M, 8 F, age 41 +/- 8 y) performed a competitive 18-km run three times within 8 days. The study was a controlled, standardized field experiment following a randomized, crossover design. Three different drinks were compared: water, a sports drink (CES), and a sports drink with added 150 mg/l caffeine (CAF). The incidence of GI complaints and the effect of the drinks on performance was studied. Each subject consumed 4 times 150 ml as follows: at the start, after 4.5 km, 9 km, and 13.5 km. Fluid intake was controlled. Incidence and intensity of GI complaints during the run were determined using a 10 points scale questionnaire. There were no significant differences in performance between the 3 drinks. Run time (18 km, mean +/- SD): WAT 1 : 18 : 03 +/- 08 : 30, CES 1 : 18 : 23 +/- 08 : 47, CAF 1 : 18 : 03 +/- 08 : 42. The use of carbohydrate-containing sports drinks led to higher incidences of all types of GI complaints compared to water. Significant differences (p < 0.05) were reached for flatulence; incidence: WAT 17.9 %, CES 28.6 %, CAF 30.6 %, and reflux; incidence: WAT 55.7 %, CES 78.6 %, CAF 72.5 %. There were no significant differences in intensity of the GI complaints. Addition of caffeine to CES had no effect on GI complaints, compared to CES alone. We conclude that sports drinks used during an 18-km run in cool environmental conditions do not support the performance better than mineral water. The use of sports drinks during an 18-km run leads to a higher incidence of both upper and lower GI complaints compared to water. Addition of caffeine to the sports drink has no effect on either running performance or GI complaints.

Effects of short-chain fructo-oligosaccharides on glucose and lipid metabolism in mild hypercholesterolaemic individuals

BACKGROUND

The intake of 10 g/day of short-chain-fructo-oligosaccharides (sc-FOS) has been shown to increase significantly bifidus counts and to produce high amounts of short-chain fatty acids (SCFA), presumed to influence glucose and lipid metabolism.

AIM

To evaluate the effects of moderate intake of sc-FOS on glucose and lipid metabolism in individuals with mild hypercholesterolaemia.

DESIGN

A randomized double-blind sequential cross-over study.

SUBJECTS AND METHODS

Thirty subjects of both genders (20 M/10 F), mean age 45.5+/-9.9 years (M+/-SD), BMI 26.6+/-2.2 kg/m(2), with plasma cholesterol >5.17 and <7.76 mmol/l and plasma triglycerides <3.45 mmol/l, participated in the study. The study was performed after a wash-out period of 1 month and a run-in period of 1 month to stabilize patients on a standard diet (CHO 50%, fat 30%, protein 20%, fibre 20 g/day) plus placebo (maltodextrine plus aspartame 15 g/day). At the end of run-in, subjects were randomly assigned to receive sc-FOS (Actilight) (10.6g/day) or placebo (maltodextrine plus aspartame 15 g/day) with tea and/or coffee for a duration of 2 months and thereafter switched to the other treatment for additional 2 months. Plasma glucose, total and lipoprotein (VLDL, LDL, HDL) cholesterol and triglyceride concentrations were measured in the fasting state at the end of run-in and of each treatment period. At the end of the two treatment periods, patients consumed a standard test meal (protein 15%, carbohydrate 34%, fat 51%, kJ 3988) 1h after the administration of 5.3g of sc-FOS or placebo; plasma glucose, insulin, free fatty acid (FFA) and triglyceride responses to the test meal were evaluated.

RESULTS

No significant difference in fasting parameters was detected between the two treatments. After sc-FOS and placebo plasma cholesterol levels were, respectively, 6.47+/-0.70 and 6.44+/-0.78 mmol/l (n.s.) and plasma triglycerides were 1.53+/-0.71 and 1.56+/-0.53 mmol/l (n.s.). No significant differences were observed in cholesterol and triglyceride content of VLDL, LDL and HDL and in plasma Apo A1 levels; conversely, fasting plasma Lp(a) concentrations were significantly increased after sc-FOS (37+/-38 vs. 33+/-35 mg/dl; P<0.005). Postprandial responses of glucose, FFA and triglycerides were not significantly different between sc-FOS and placebo, while postprandial insulin response (incremental area) was significantly reduced after sc-FOS compared to placebo (14,490+/-7416 vs. 17,760+/-7710 pmol/l x 300 min; P<0.02).

CONCLUSIONS

A moderate intake of sc-FOS has no major effects on lipid metabolism, both in the fasting and in the postprandial period, in individuals with mild hypercholesterolaemia. A small but significant increase of Lp(a) concentrations was observed with sc-FOS consumption together with a reduction of the postprandial insulin response; however, the clinical relevance of these small effects is unclear.

Vitamin K1 supplementation retards bone loss in postmenopausal women between 50 and 60 years of age

Although several observational studies have demonstrated an association between vitamin K status and bone mineral density (BMD) in postmenopausal women, no placebo-controlled intervention trials of the effect of vitamin K1 supplementation on bone loss have been reported thus far. In the trial presented here we have investigated the potential complementary effect of vitamin K1 (1 mg/day) and a mineral + vitamin D supplement (8 microg/day) on postmenopausal bone loss. The design of our study was a randomized, double-blind, placebo-controlled intervention study; 181 healthy postmenopausal women between 50 and 60 years old were recruited, 155 of whom completed the study. During the 3-year treatment period, participants received a daily supplement containing either placebo, or calcium, magnesium, zinc, and vitamin D (MD group), or the same formulation with additional vitamin K1 (MDK group). The main outcome was the change in BMD of the femoral neck and lumbar spine after 3 years, as measured by DXA. The group receiving the supplement containing additional vitamin K1 showed reduced bone loss of the femoral neck: after 3 years the difference between the MDK and the placebo group was 1.7% (95% Cl: 0.35-3.44) and that between the MDK and MD group was 1.3% (95% Cl: 0.10-3.41). No significant differences were observed among the three groups with respect to change of BMD at the site of the lumbar spine. If co-administered with minerals and vitamin D, vitamin K1 may substantially contribute to reducing postmenopausal bone loss at the site of the femoral neck.

Delay in diagnosis of soft tissue sarcomas

AIM

We reviewed 100 patients referred with soft tissue sarcoma between May 1999 to determine doctor- and patient-related delay.

METHODS

Patient delay is defined as longer than one month from first symptoms till doctor's visit, doctor delay as longer than one month from first visit till definitive diagnosis. Sixty-eight patients had a multifactional delay.

RESULTS

Forty-seven patients showed patient delay, with a median patient delay of 4 months, ranging from 2 to 240 months. The main reason for this delay is a painless mass that is mostly ignored. When pain is present, median patient delay is shorter.Twenty-seven patients experienced doctor delay, ranging from 2 to 79 months, with a median of 6 months. The most frequent reason was a misdiagnosis from the outset, on a clinical basis only, or due to a wrong diagnosis on ultrasound. Only two of these 27 patients had a biopsy, showing a benign tumour. High grade tumours are diagnosed earlier, 85% within 6 months.

CONCLUSIONS

Delay in diagnosis of soft tissue sarcomas is still a problem requiring better patient and doctor education.

Safety of soy-derived phosphatidylserine in elderly people

Phosphatidylserine (PS) is a phospholipid which has been claimed to enhance neuronal membrane function, and can be derived from several sources. Earlier studies used brain cortex derived PS, of which the human tolerability of 300mg daily in 130 patients has been shown. The human tolerability of PS derived from soybean has not been reported, although it is widely sold as a nutritional supplement which may improve cognitive function in the elderly. We report the results of a study of the safety of two dosages of soy-phosphatidylserine (S-PS) in elderly. Subjects were 120 elderly of both sexes who fulfilled the more stringent criteria for age-associated memory impairment; some also fulfilled the criteria for age-associated cognitive decline. Subjects were allocated at random to one of the three treatment groups: placebo, 300 or 600 mg S-PS daily. Standard biochemical and hematological safety parameters, blood pressure, heart rate and adverse events were assessed at baseline, after 6 and 12 weeks of treatment. No significant differences were found in any of the outcome variables between the treatment groups after Bonferonni-Holme correction. In conclusion, soy derived PS is a safe nutritional supplement for older persons if taken up to a dosage of 200 mg three times daily.

Nutritional aspects of short-chain fructooligosaccharides: natural occurrence, chemistry, physiology and health implications

Short-chain fructooligosaccharides occur in a number of edible plants, such as chicory, onions, asparagus, wheat... They are a group of linear fructose oligomers with a degree of polymerisation ranging from n = 1 up to 5 (oligosaccharides). Short-chain fructooligosaccharides, to a large extent, escape digestion in the human upper intestine and reach the colon where they are totally fermented mostly to lactate, short chain fatty acids (acetate, propionate and butyrate), and gas, like dietary fibres. As a consequence of their fermentation, their caloric value is approximately 2 Kcal/g. A faecal bulking effect of fructooligosaccharides has been observed in humans. An important property of short-chain fructooligosaccharides is the stimulation of bifidobacterial growth specifically while suppressing the growth of potentially harmful species such as, for example, Clostridium perfringens in the colon. It is associated with a decrease in faecal pH, an increase in faecal or colonic organic acids, a decrease in the production of nitrogenous end products in urine and stools, a decrease in faecal bacterial enzymatic activities and a modification in faecal neutral sterols. The short-chain fructooligosaccharides enhance magnesium absorption in humans and have been shown, in animal models, to reduce colon tumour development by enhancing both colon butyrate concentrations and local immune system effectors.

The effect of guar gum addition to a semisolid meal on appetite related to blood glucose, in dieting men

OBJECTIVE

To investigate whether addition of modified guar gum (GG) to a low-energy semisolid meal might be effective on appetite by modifying the response of blood glucose and other blood parameters.

DESIGN

Three intervention periods of 2 weeks each, separated by washout periods of 4 weeks. Randomized and cross-over design.

SUBJECTS

Fifteen overweight male subjects (mean+/-s.d.; age, 44+/-9 y; body mass index, 28.6+/-1.8 kg/m(2)).

INTERVENTION

Subjects consumed a low-energy diet divided over three times a day, consisting of a semisolid meal with (SSM+) or without (SSM) addition of 2.5 g GG, or a solid meal (SM) with the same energy content (947 kJ) and macronutrient composition, plus a dinner of the subject's own choice. At the end of each intervention, time and number of meal initiations, dynamics of blood glucose and other blood parameters, and appetite ratings such as hunger and satiety were determined in a time-blinded situation.

RESULTS

The changes in blood glucose from meal initiation to blood glucose peak and from peak to nadir were smaller with SSM+ and SM compared to SSM. Satiety before the third meal was higher with SSM+ and SM compared to SSM (P<0.01). Meal pattern, general appetite and total energy intake were similar for all treatments.

CONCLUSIONS

We conclude that, similar to SM, SSM+ resulted in a more moderate change in blood glucose compared to SSM and positively affected satiety before the third meal, while general appetite, total energy intake and meal pattern did not differ.

The effects of rehydration on cycling performance after exercise-induced dehydration

The effects of 7.6% carbohydrate-electrolyte solution (CES) and placebos (P) on rehydration (R) after exercise-induced dehydration and on a subsequent time-trial (TT) of cycling performance were studied. Thirteen male subjects exercised in a thermally-controlled environment (28 degrees C, 63% RH) until 3% of their body weight was lost. After exercise, the subjects moved to a neutral environment (22 degrees C) and rested for 30 minutes prior to a 2-hour R period. During R, subjects were fed CES or P to a maximum volume of 120% of previous body mass loss at 0, 30, and 60 minutes, in bolus-doses of 50%, 40% and 30% respectively. After R, subjects performed a 1-hour TT with no further fluid intake. % R with CES was significantly higher than with P (70 +/- 3% vs 60 +/- 5%; p < 0.01). During the TT, blood glucose dropped in the CES group but not in the P group. It was found that, despite a more effective R with CES, the performance results did not differ between groups (65.1 +/- 2.2 minutes and 65.2 +/- 2.3 minutes for CES and P respectively). It is suggested that an insulin-mediated rebound effect on CHO metabolism during TT, in which no further CHO was supplied, nullified the benefits of rehydration.

The effect of ad libitum ingestion of a caffeinated carbohydrate-electrolyte solution on urinary caffeine concentration after 4 hours of endurance exercise

The purpose of the present study was to examine the effect of ad libitum ingestion of a carbohydrate-electrolyte solution (CES) with 150 mg x L (-1) caffeine (CAF) on urinary CAF concentration after 4 h of endurance exercise. Fifty-eight healthy and well-trained male subjects ingested ad libitum a 7 % CES with 150 mg x L (-1) CAF during 4 h cycling at 50 % of maximal work capacity. Total fluid consumption (mean +/- SE) was 2799 +/- 72 mL and CAF intake was 420 +/- 11 mg (5.7 +/- 0.2 mg x kg (-1) body weight). The post-exercise urinary CAF concentration (4.53 +/- 0.25 microg x mL (-1)) was below the doping level of the International Olympic Committee (12 microg x mL (-1)) in all subjects (range 1.20 - 10.84 microg x mL (-1)). A highly positive correlation was observed between CAF intake and post-exercise urinary CAF concentration (r = 0.68, p < 0.001). It is concluded that ad libitum ingestion of a CES with 150 mg x L (-1) CAF during 4 h cycling resulted in post-exercise urinary concentration below the doping level in all subjects.

No effects of oral ribose supplementation on repeated maximal exercise and de novo ATP resynthesis

A double-blind randomized study was performed to evaluate the effect of oral ribose supplementation on repeated maximal exercise and ATP recovery after intermittent maximal muscle contractions. Muscle power output was measured during dynamic knee extensions with the right leg on an isokinetic dynamometer before (pretest) and after (posttest) a 6-day training period in conjunction with ribose (R, 4 doses/day at 4 g/dose, n = 10) or placebo (P, n = 9) intake. The exercise protocol consisted of two bouts (A and B) of maximal contractions, separated by 15 s of rest. Bouts A and B consisted of 15 series of 12 contractions each, separated by a 60-min rest period. During the training period, the subjects performed the same exercise protocol twice per day, with 3-5 h of rest between exercise sessions. Blood samples were collected before and after bouts A and B and 24 h after bout B. Knee-extension power outputs were approximately 10% higher in the posttest than in the pretest but were similar between P and R for all contraction series. The exercise increased blood lactate and plasma ammonia concentrations (P < 0.05), with no significant differences between P and R at any time. After a 6-wk washout period, in a subgroup of subjects (n = 8), needle-biopsy samples were taken from the vastus lateralis before, immediately after, and 24 h after an exercise bout similar to the pretest. ATP and total adenine nucleotide content were decreased by approximately 25 and 20% immediately after and 24 h after exercise in P and R. Oral ribose supplementation with 4-g doses four times a day does not beneficially impact on postexercise muscle ATP recovery and maximal intermittent exercise performance.

Effects of 2-week ingestion of (-)-hydroxycitrate and (-)-hydroxycitrate combined with medium-chain triglycerides on satiety and food intake

The aim of this study was to assess the effects of 2 weeks of supplementation with (-)-hydroxycitrate (HCA) and HCA combined with medium-chain triglycerides (MCT) on satiety and energy intake. The experimental design consisted of three intervention periods of 2 weeks separated by washout periods of 2 or 6 weeks in a double-blind, placebo-controlled, randomized, and crossover design. Seven male and 14 female normal to moderately obese subjects (mean+/-S.D.; age, 43+/-10 years; body mass index, 27.6+/-2.0 kg/m(2)) participated in this study. Subjects consumed three self-selected meals and four isoenergetic snacks daily with either no supplementation (PLA), with 500 mg HCA (HCA), or 500 mg HCA and 3 g MCT (HCA+MCT). Each intervention period ended with a test day, consisting of a standardized breakfast and ad libitum a lunch and a dinner. There was a significant body weight (BW) loss during the 2 weeks of intervention (PLA, -0.5+/-0.3 kg, P<.05; HCA, -0.4+/-0.2 kg, P<.05; HCA+MCT, -0.7+/-0.2 kg, P<.01), but this reduction was not different between treatments. Twenty-four-hour energy intake (PLA, 8.1+/-0.3 MJ; HCA, 8.3+/-0.3 MJ; HCA+MCT, 8.4+/-0.3 MJ) and the area under the curve of the appetite-related parameters during the test day were similar for all treatments. Two weeks of supplementation with HCA and HCA combined with MCT did not result in increased satiety or decreased energy intake compared to placebo in subjects losing BW.

Five-week intake of short-chain fructo-oligosaccharides increases intestinal absorption and status of magnesium in postmenopausal women

Fermentable carbohydrates have been shown to be nondigestible by human enzymes in the small intestine but are fermented extensively in the large bowel to short-chain fatty acids (SCFAs), which can increase mineral absorption. It has been shown that feeding such carbohydrates including short-chain fructo-oligosaccharides (sc-FOSs) increases intestinal magnesium (Mg) absorption in animals, but their beneficial impact on Mg absorption in humans still remains to be established. Therefore, this work aimed to investigate the effect of moderate daily doses of sc-FOSs (10 g/day) on the intestinal absorption and status of Mg in postmenopausal women without hormone replacement therapy (HRT). Eleven healthy postmenopausal women aged 59 +/- 6 years (mean +/- SD) received for 5 weeks sc-FOS or sucrose (placebo) treatments according to a randomized, double-blind, crossover design separated by a washout period of at least 3 weeks. Subjects ingested 87.5 mg of stable isotope 25Mg together with a fecal marker. Subsequently, feces were collected for 5-7 days. An inductively coupled plasma mass spectrometer (ICP/MS) was used for 25Mg stable isotope measurements in feces, urine, and blood. Mg levels were assessed also at the beginning and at the end of each treatment in plasma, erythrocytes, and urine. These measurements allowed for the determination of net intestinal Mg absorption and Mg status. The results show that the addition of 10 g sc-FOS to the diet increased Mg absorption by 12.3%, from 30.2 +/- 5.0% (placebo treatment) to 33.9 +/- 7.2% (sc-FOS treatment; mean +/- SD; p < 0.02). This increase in intestinal Mg absorption was accompanied by an increase in plasma 25Mg level and led to a higher urinary 25Mg excretion. This is the first time that such an effect is shown in humans. The overall conclusion of this work is that the ingestion of moderate doses of sc-FOS did improve intestinal Mg absorption and status in postmenopausal women. Because of the important role of Mg in many cellular functions, such Mg absorption improvement may be particularly interesting when the dietary intake of Mg is limited.

The effect of addition of modified guar gum to a low-energy semisolid meal on appetite and body weight loss

OBJECTIVE

To investigate the effect of addition of modified guar gum (GG) to a low-energy semisolid meal on appetite and body weight (BW) loss.

SUBJECTS

Twenty eight mainly overweight male volunteers (age, 19-56 y; body mass index, 29+/-2 kg x m(-2); BW, 89.4+/-9.2 kg).

DESIGN

Baseline of one week with self-selected diet. Three treatments of 2 weeks with a low-energy diet divided over three times a day, consisting of a semisolid meal with (SSM+) or without GG (SSM) or a solid meal (SM) with the same energy content (947 kJ) and macronutrient composition, and a dinner of the subject's own choice. Washout periods lasted 4 weeks.

RESULTS

Compared to baseline values, reduction in energy intake and BW loss were similar for SSM+, SSM and SM. Appetite (hunger, desire to eat or estimation of how much one could eat) was increased in SSM and in SM compared to baseline, but not in SSM+. Satiety and fullness in SSM+, SSM and SM were similar to baseline. Any intervention was more effective on BW loss when it took place the first time compared to the second and third times (2.6+/-0.2 kg, 1.7+/-0.2 kg and 1.1+/-0.2 kg, respectively; P<0.001). The SM-SSM+-SSM sequence was more effective on BW loss compared to the SSM+-SSM-SM sequence (5.6+/-1.0 and 2.5+/-0.6 kg, respectively; P<0.05).

CONCLUSION

All the three treatments were equally effective with respect to BW loss. GG addition to a semisolid meal prevented an increase in appetite, hunger and desire to eat, which increase was present in the other treatments. However, differences between treatments were not statistically significant. The order effect shows that repeated 2-week bouts of dieting become increasingly ineffective. The sequence SM-SSM+-SSM was more effective than the sequence SSM+-SSM-SM, probably because compliance was relatively higher with the SSM+ or SSM diet, and compliance decreased towards the end of the complete experiment.

The effect of different dosages of guar gum on gastric emptying and small intestinal transit of a consumed semisolid meal

BACKGROUND

There is no consensus about the effect of guar gum supplementation on gastrointestinal transit. It has been suggested that guar gum slows gastric emptying and intestinal transit, thus inducing an increased feeling of satiety.

OBJECTIVE

To investigate whether addition of guar gum to a semisolid meal affects gastrointestinal transit.

DESIGN

Eight male subjects were randomly studied four times. They consumed a standard semisolid test meal containing either 0 g, 2.5 g, 3.5 g, or 4.5 g of guar gum. The test meals contained 1 mCi 99mTc-hepatate for scintigraphy and 5 g lactulose for the H2-breath test. Scintigraphic scanning was performed for at least two hours, and gastric half-emptying time (T1/2) was calculated. Breath samples were collected at 15 minute intervals and analyzed for H2-enrichment. The orocecal transit time (OCTT) was then determined. A parameter of intestinal transit (PIT) was obtained by subtracting the T1/2 from the OCTT.

RESULTS

There were no significant differences (in minutes) between the different tests in both T1/2 (0 g, t = 88.2 +/- 11, 2.5 g, t = 83.3 +/- 11.9, 3.5 g, t = 83.3 +/- 13.6, 4.5 g, t = 72.4 +/- 7.2, p = 0.86) and PIT (0 g, t = 149.9 +/- 26.6, 2.5 g, t = 145.5 +/- 25.6, t = 3.5 g, t = 175.3 +/- 17.6, t = 4.5 g, t = 152.6 +/- 22.4, p = 0.52).

CONCLUSION

Addition of guar gum to a semisolid meal up to a dosage of 4.5 g does not affect gastrointestinal transit. Other mechanisms than gastrointestinal motility are involved in a possible satiating effect of guar gum supplementation.

The influence of soy-derived phosphatidylserine on cognition in age-associated memory impairment

Phosphatidylserine (PS) is a phospholipid widely sold as a nutritional supplement. PS has been claimed to enhance neuronal membrane function and hence cognitive function, especially in the elderly. We report the results of a clinical trial of soybean-derived PS (S-PS) in aging subjects with memory complaints. Subjects were 120 elderly (> 57 years) of both sexes who fulfilled the more stringent criteria for age-associated memory impairment (AAMI); some also fulfilled the criteria for age-associated cognitive decline. Subjects were allocated at random to one of the three treatment groups: placebo, 300mg S-PS daily, or 600mg S-PS daily. Assessments were carried out at baseline, after 6 and 12 weeks of treatment, and after a wash-out period of 3 weeks. Tests of learning and memory, choice reaction time, planning and attentional functions were administered at each assessment. Delayed recall and recognition of a previously learned word list comprised the primary outcome measures. No significant differences were found in any of the outcome variables between the treatment groups. There were also no significant interactions between treatment and 'severity of memory complaints'. In conclusion, a daily supplement of S-PS does not affect memory or other cognitive functions in older individuals with memory complaints.

Effect of dehydration on gastrointestinal function at rest and during exercise in humans

Dehydration leads to the aggravation of gastrointestinal (GI) complaints during exercise. The aim of this study was to examine the effect of dehydration on various GI parameters during strenuous exercise. Ten healthy well-trained men were investigated in dehydrated and in euhydrated conditions. Dehydration took place before the experiments using a dehydration regimen in a sauna leading to a 3% loss of body mass. Each experiment consisted of 1 h pre-exercise rest, 1.5 h cycling at 70% maximal exercise intensity, and 3.5 h post-exercise rest. During cycling, liquid gastric emptying (GE), orocaecal transit time (OCTT) and intestinal permeability and glucose absorption were measured. The GI-symptoms were scored using a questionnaire. Body temperature, plasma volume and vasopressin were measured before and after cycling. The GE was significantly slower during dehydration [median time to peak 13C enrichment in the breath sample (13C-TTP) 23.6 min, range 13.7-50.0 min, P = 0.02] than in the control situation (median 13C-TTP 17.1 min, range 9.8-38.4 min). The OCTT was unchanged (median 173 min, range 98-263 min compared to median 128 min, range 98-195 min, P = 0.18). Dehydration did not change intestinal permeability, glucose absorption, plasma volume, rectal temperature or plasma vasopressin concentration. In the dehydration experiment, exercise induced a significant increase in nausea (P = 0.01) and epigastric cramps (P = 0.05), in contrast to the control situation. In both experiments, exercise led to a significant increase in rectal temperature and plasma vasopressin concentration, and a significant decrease in plasma volume. The increase in plasma vasopressin concentration was significantly higher in the dehydration experiment (P = 0.015). No significant differences in either the post-exercise rectal temperatures or in plasma volumes was observed. The difference in GE between the two experiments was significantly correlated with the difference in nausea score (r = 0.87, P = 0.002). We concluded that dehydration leads to a delayed GE but not to differences in OCTT, intestinal permeability or glucose uptake during intense cycling. The delay in GE is significantly associated with an increase in exercise-induced nausea.

Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine

Caffeine is suspected to affect gastrointestinal function. We therefore investigated whether supplementation of a carbohydrate-electrolyte solution (CES) sports drink with 150 mg/l caffeine leads to alterations in gastrointestinal variables compared with a normal CES and water using a standardized rest-exercise-rest protocol. Ten well-trained subjects underwent a rest-cycling-rest protocol three times. Esophageal motility, gastroesophageal reflux, and intragastric pH were measured by use of a transnasal catheter. Orocecal transit time was measured using breath-H(2) measurements. A sugar absorption test was applied to determine intestinal permeability and glucose absorption. Gastric emptying was measured via the (13)C-acetate breath test. In the postexercise episode, midesophageal pressure was significantly lower in the CES + caffeine trial compared with the water trial (P = 0.017). There were no significant differences between the three drinks for gastric pH and reflux during the preexercise, the cycling, and the postexercise episode, respectively. Gastric emptying, orocecal transit time, and intestinal permeability showed no significant differences between the three trials. However, glucose absorption was significantly increased in the CES + caffeine trial compared with the CES trial (P = 0.017). No significant differences in gastroesophageal reflux, gastric pH, or gastrointestinal transit could be observed between the CES, the CES + caffeine, and the water trials. However, intestinal glucose uptake was increased in the CES + caffeine trial.

Effects of pre- and post-absorptive factors on the lactulose/rhamnose gut permeability test

It is assumed that the outcome of the lactulose/rhamnose gut permeability test is not influenced by pre- or post-absorptive factors. The aim of our study was to investigate the role of a pre-absorptive factor, i.e. small-intestinal transit, and a post-absorptive factor, i.e. renal clearance. Ten healthy male subjects were studied. Urinary lactulose and rhamnose excretion was measured after intraduodenal administration of lactulose and rhamnose following induction of increased intestinal permeability using chenodeoxycholic acid (chenodiol), in the absence and in the presence of accelerated intestinal transit. Urinary sugar excretion was measured after intravenous administration of either a regular dose (50 mg/50 mg) or a high dose (250 mg/250 mg) of lactulose/rhamnose. The intraduodenal experiments showed that a combination of accelerated small-bowel transit and increased permeability did not lead to significant differences in the recovery of lactulose (P=0.647) or rhamnose (P=0.889), or in the lactulose/rhamnose ratio, compared with those under conditions of increased permeability alone (P=0.68). However, lactulose recovery was significantly lower (P=0.025) after intravenous administration of a high dose of the sugars. There was no significant difference in urinary rhamnose recovery (P=0.575) between the high and the regular doses. This resulted in a significantly lower lactulose/rhamnose ratio (P=0.021) after intravenous administration of a high dose, compared with a regular dose, of the sugars. In conclusion, the assumption that post-absorptive processes do not influence the outcome of the lactulose/rhamnose permeability test appears not to be valid.

The effect of physical exercise on parameters of gastrointestinal function

Exercise decreases splanchnic bloodflow. Therefore exercise may induce alterations in gastrointestinal (GI) function. In the present study we investigated the effect of high-intensity exercise on oesophageal motility, gastro-oesophageal reflux, gastric pH, gastric emptying, orocaecal transit time (OCTT), intestinal permeability and glucose absorption simultaneously, using an ambulatory protocol. Ten healthy well-trained male subjects underwent a rest-cycling-rest, and a rest-rest-rest protocol (60-90-210 min). Oesophageal motility, gastro-oesophageal reflux and intragastric pH was measured using a trans-nasal catheter. OCTT was measured via breath H2 measurement. A sugar absorption test was applied to determine intestinal permeability and glucose absorption. Gastric emptying was measured using the 13C-acetate breath test. Peristaltic velocity was increased during cycling, compared to rest (4.92 (2.86) vs. 4.03 (1. 48) cm s-1, P = 0.015). Peristaltic contraction pressure at the mid-oesophagus and the duration of the peristaltic contractions at the mid- and distal oesophagus was lower during cycling. There were no differences between the pre-exercise, the exercise and the post-exercise episodes for gastric pH or for both the number and duration of reflux episodes, in both the rest and cycling trials. Neither gastric emptying nor OCTT showed differences between rest and cycling. The lactulose/rhamnose ratio and intestinal glucose absorption were significantly decreased in the cycling trial. Our model enables multiple GI-measurements during exercise. Cycling at 70% Wmax does not lead to differences in reflux, gastric pH or gastrointestinal transit in healthy trained individuals. The distal oesophageal pressure decreases and peristaltic velocity increases. The lactulose/rhamnose ratio and jejunal glucose absorption are decreased during exercise.

Performance of the [13C]-acetate gastric emptying breath test during physical exercise

BACKGROUND

The gastric emptying rate of liquids can be determined non-invasively using the [13C]-acetate breath test at rest. The aims of our study were to validate this test during physical exercise against the double-sampling method and to evaluate the time needed for intestinal absorption and the delay between absorption and appearance of 13CO2 in breath, both at rest and during exercise.

DESIGN

Fifteen well-trained male subjects were investigated. Gastric emptying was determined simultaneously measuring the 13CO2 breath enrichment after intragastric administration of 0.5 L of carbohydrate solution with 150 mg of [13C]-acetate added and by the double-sampling technique (n = 9). In separate tests, 150 mg of [13C]-acetate was also applied intraduodenally and intravenously (n = 6), both at rest and during exercise. Time-to-peak (TTP) 13CO2 enrichment was determined using a curve fit and was considered as the parameter for gastric emptying.

RESULTS

TTP enrichment derived from the breath test significantly correlated with the gastric emptying half-time obtained from the gastric aspirates. During exercise, median TTP enrichment values after intragastric, intraduodenal (i.d.) and intravenous (i.v.) administration of [13C]-acetate were 22.3, 10.3 and 5.4 min respectively. During exercise, i.d. and i.v. values were reached significantly earlier than at rest.

CONCLUSION

The [13C]-acetate breath test can be used as a non-invasive method to determine relative gastric emptying rates of liquids during exercise, but the results are influenced by the rate of absorption and the time needed for subsequent oxidation of [13C]-acetate and exhalation of 13CO2.

Cognition-enhancing properties of subchronic phosphatidylserine (PS) treatment in middle-aged rats: comparison of bovine cortex PS with egg PS and soybean PS

There are various clinical and non-clinical studies that have indicated that phosphatidylserine (PS) treatment can improve cognitive functions in humans and other animals. However, treatment with PS derived from bovine cortex is not desirable because of possible transfer of infectious diseases. The present study investigated the cognition-enhancing properties of different types of PS in rats. Seventeen-month-old male Fischer 344 rats were treated daily with a dose of 15 mg/kg of PS derived from bovine cortex (BC-PS), soybean (S-PS), egg (E-PS), or vehicle (n = 9 for each group). The effects of treatment were evaluated in three different behavioral tests. An open field test was conducted to examine the effects of treatment on psychomotor behavior. Two other tests (Morris water escape task and two-way active avoidance) assessed treatment effects on the cognitive performance of rats. Treatment with the different forms of PS did not affect the psychomotor or spatial discrimination performance of the rats. In accordance with previous studies, the cognition-enhancing effects of BC-PS were observed in the two-way active avoidance task. It appeared that the cognition-enhancing effects of S-PS were not different from those of BC-PS. The performance of rats treated with E-PS did not deviate from that of vehicle-treated rats. On the basis of the present study, it was concluded that S-PS, but not E-PS, may have comparable effects on cognition when compared with BC-PS.

Caffeine improves cognitive performance after strenuous physical exercise

The effects of three carbohydrate electrolyte solutions (CES) containing different amounts of caffeine on cognitive function and the combined effects of these drinks and exercise on cognitive functions were investigated in a double-blind, cross-over study. On five separate occasions, fifteen endurance trained male athletes (23.3 years) received water placebo, CES placebo (68.8 g/l), and three CES drinks containing low, medium and high dosages of caffeine (150, 225 and 320 mg/l). Each occasion, 8 ml/kg of the drink was consumed before -- and 6 ml/kg of the drink was consumed during an all-out 1 hour time trial on a bicycle ergometer. Cognitive (attentional, psychomotor, and memory) tests were carried out immediately before and immediately after exercise. Before exercise, long term memory was improved by CES plus low dose caffeine compared to both placebos. Immediately after exercise, all cognitive functions were improved by CES plus low- and medium-dose caffeine compared to placebo. These results comprise the first practical demonstration of the cognition improving effects of low amounts of caffeine in CES after strenuous physical exercise.

Carbohydrate ingestion can completely suppress endogenous glucose production during exercise

The purposes of this study were 1) to investigate the effect of carbohydrate (CHO) ingestion on endogenous glucose production (EGP) during prolonged exercise, 2) to study whether glucose appearance in the circulation could be a limiting factor for exogenous CHO oxidation, and 3) to investigate whether large CHO feedings can reduce muscle glycogen oxidation during exercise. Six well-trained subjects exercised three times for 120 min at 50% maximum workload while ingesting water (FAST), a 4% glucose solution (LO-Glc), or a 22% glucose solution (HI-Glc). A primed continuous intravenous [6, 6-2H2]glucose infusion was given, and the ingested glucose was enriched with [U-13C]glucose. Glucose ingestion significantly elevated CHO oxidation as well as the rates of appearance (Ra) and disappearance. Ra glucose equaled Ra of glucose in gut (Ra gut) during HI-Glc, whereas EGP was completely suppressed. During LO-Glc, EGP was partially suppressed, whereas Ra gut provided most of the total glucose Ra. We conclude that 1) high rates of CHO ingestion can completely block EGP, 2) Ra gut may be a limiting factor for exogenous CHO oxidation, and 3) muscle glycogen oxidation was not reduced by large glucose feedings.

Glucose kinetics during prolonged exercise in highly trained human subjects: effect of glucose ingestion

1. The objectives of this study were (1) to investigate whether glucose ingestion during prolonged exercise reduces whole body muscle glycogen oxidation, (2) to determine the extent to which glucose disappearing from the plasma is oxidized during exercise with and without carbohydrate ingestion and (3) to obtain an estimate of gluconeogenesis. 2. After an overnight fast, six well-trained cyclists exercised on three occasions for 120 min on a bicycle ergometer at 50 % maximum velocity of O2 uptake and ingested either water (Fast), or a 4 % glucose solution (Lo-Glu) or a 22 % glucose solution (Hi-Glu) during exercise. 3. Dual tracer infusion of [U-13C]-glucose and [6,6-2H2]-glucose was given to measure the rate of appearance (Ra) of glucose, muscle glycogen oxidation, glucose carbon recycling, metabolic clearance rate (MCR) and non-oxidative disposal of glucose. 4. Glucose ingestion markedly increased total Ra especially with Hi-Glu. After 120 min Ra and rate of disappearance (Rd) of glucose were 51-52 micromol kg-1 min-1 during Fast, 73-74 micromol kg-1 min-1 during Lo-Glu and 117-119 micromol kg-1 min-1 during Hi-Glu. The percentage of Rd oxidized was between 96 and 100 % in all trials. 5. Glycogen oxidation during exercise was not reduced by glucose ingestion. The vast majority of glucose disappearing from the plasma is oxidized and MCR increased markedly with glucose ingestion. Glucose carbon recycling was minimal suggesting that gluconeogenesis in these conditions is negligible.

Urine color, osmolality and specific electrical conductance are not accurate measures of hydration status during postexercise rehydration

BACKGROUND

The aim of the study was to determine whether urine color, osmolality and specific electrical conductance (SEC) provide an accurate index of hydration status and of fluid requirements during the recovery phase after an acute exercise-induced dehydration.

METHODS

EXPERIMENTAL DESIGN

eight well-trained healthy males were dehydrated about 3% of body mass, 3 times, by cycling in the heat. To rehydrate after exercise, three types of drinks frequently consumed by athletes postexercise, i.e. a caffeinated soft drink (CC), a mineral water (MW), or a carbohydrate-electrolyte solution (CES) were ingested ad libitum and in randomized cross-over design during the first 2 hrs of an observation period lasting 6 hrs.

MEASURES

urine was sampled each hour for determination of color, osmolality and SEC. Net rehydration was calculated from fluid intake and fluid loss by sweat and urine.

RESULTS

Fluid intake amounted 2.6 +/- 0.2 kg for CC, 2.2 +/- 0.2 kg for MW and 2.8 +/- 0.3 kg for CES representing 116%, 96% and 127% of fluid lost by sweat. Urine output showed a negative correlation with color, osmolality and SEC (p < 0.001). These variables were highly interrelated (p < 0.001). However, the level of rehydration did not correlate with any of the measured urinary variables (p > 0.05).

CONCLUSIONS

Urine color, SEC and osmolality are poor indicators of hydration status measured from the balance between fluid intake and urine output up to 6 hrs postexercise.

The sensitivity of the lactulose/rhamnose gut permeability test

BACKGROUND

The lactulose/rhamnose (L/R) intestinal permeability test is widely used. However, different quantities and proportions of lactulose and rhamnose are used. The aim of this study was to determine whether a low dosage of lactulose is able to discriminate between normal and increased permeability.

MATERIALS AND METHODS

Two groups of 10 healthy subjects were studied. In group 1, three different iso-osmolar test solutions were administered on 3 days. The solutions consisted of 10 g of L with 1 g of R, 5 g of L with 0.5 g of R and 1 g of L with 0.1 g of R in 65 mL of water. Group 2 ingested these solutions 1 h after ingestion of 750 mg of chenodeoxycholeic acid (CDCA), which is known to increase permeability. The urinary L/R ratio was determined using high-performance liquid chromatography. Data are presented as medians (range).

RESULTS

In group 1, no differences were observed between the three solutions. In Group 2, there was a significant difference (P = 0.045) between the three solutions. The L/R ratios were 0.0079 (0.0024-0.0152) (1L to 0.1R), 0.0138 (0.0066-0.0192) (5L to 0.5R) and 0.0144 (0.0074-0.0374) (10L to 1R). The L/R ratio differed significantly between Groups 1 and 2 (P < 0.001) using the 5L to 0.5R and 10L to 1R solutions respectively.

CONCLUSION

If the permeability is increased, the urinary L/R ratio depends on the quantity of lactulose and rhamnose administered in equal proportion. 5L to 0.5R is sufficient to discriminate between a normal and a moderately increased permeability.

Improved bone metabolism in female elite athletes after vitamin K supplementation

In female elite athletes strenuous exercise may result in hypoestrogenism and amenorrhoea. As a consequence a low peak bone mass and rapid bone loss are often seen in relatively young athletes. In postmenopausal women, increased intake of vitamin K may result in an increase of serum markers for bone formation, a decrease of urinary markers for bone resorption, and a decrease in urinary calcium loss. In the present paper we report an intervention study among eight female athletes, four of whom had been amenorrhoeic for more than one year, whereas the others had been using oral contraceptives. All participants received vitamin K supplementation (10 mg/day) during one month, and various bone markers were measured before and after treatment. At baseline the athletes not using oral contraceptives were biochemically vitamin K-deficient as deduced from the calcium binding capacity of the circulating bone protein osteocalcin. In all subjects increased vitamin K was associated with an increased calcium-binding capacity of osteocalcin. In the low-estrogen group vitamin K supplementation induced a 15-20% increase of bone formation markers and a parallel 20-25% decrease of bone resorption markers. This shift is suggestive for an improved balance between bone formation and resorption.

Carbohydrate supplementation improves stroke performance in tennis

The effect of carbohydrate supplementation on stroke quality during prolonged simulated tennis match-play was investigated. Well-trained tennis palyers reported to the test center three times. At each occasion they performed a pretest, consisting of the leuven Tennis Performance Test (LTPT) and a shuttle run (SHR), which they repeated (posttest) after a 2-h strenuous training session. Throughout the test session, they received in a double blind random order either a placebo drink (P), a carbohydrate solution (0.7 gxkg(-1) BWxh(-1); CHO), or CHO plus a dose of caffeine (5 mg per kg BW). Stroke quality was evaluated during the LTPT by means of measurements of error rate, ball velocity, precision of ball placement, and a velocity-precision (VP) and a velocity-precision-error (VPE) index. Pretest scores were similar during P and CHO. During P, compared with the pretest, stroke quality during the posttest deteriorated (P < 0.05) both for the first service and strokes during defensive rallies and for SHR performance. However, compared with P, the increase in error rate and number of nonreached balls indefensive rallies was smaller (P < 0.05) during CHO. Similarily, CHO attenuated (P < 0.05) the increase in error rate and the decrease in both the VP (P < 0.1) and VPE (P < 0.05) indices for the first service upon fatigue. Furthermore, CHO improved posttest SHR performance. Stroke quality and SHR time were similar during CHO alone and during combined CHO plus caffeine administration, both for the pretest and for the pretest and for the posttest. It is concluded that CHO supplementation improves stroke quality during the final stages of prolonged tennis play. The data prove that CHO intake may facilitate the maintenance of physical quality during long-lasting intermittent exercise to fatigue.

Functional food science and substrate metabolism

The present review addresses the role of food constituents in the aetiology of metabolic conditions and chronic diseases, mostly related to energy metabolism and substrate regulation, such as obesity and non-insulin-dependent diabetes mellitus. Second, attention is paid to malnutrition, a major cause of mortality and morbidity in developing countries, which may be a cause of concern in Europe because of the increasing number of elderly people in the population. Finally, the role of diet during exercise, a condition of enormous substrate demands, is evaluated. Based on a critical evaluation of the existing knowledge in the literature, implications for future research in relation to functional foods are discussed.

Effect of caffeinated drinks on substrate metabolism, caffeine excretion, and performance

The effect of addition of different dosages of caffeine (Caf) to a carbohydrate-electrolyte solution (CES) on metabolism, Caf excretion, and performance was examined. Subjects (n = 15) ingested 8 ml/kg of water placebo (Pla-W), 7% CES (Pla-CES), or 7% CES with 150, 225, and 320 mg/l Caf (CES-150, CES-225, and CES-320, respectively) during a warm-up protocol (20 min) and 3 ml/kg at one-third and two-thirds of a 1-h time trial. Performance was improved with Caf supplementation: 62.5 +/- 1.3, 61.5 +/- 1.1, 60.4 +/- 1.0, 58.9 +/- 1.0, and 58.9 +/- 1.2 min for Pla-W, Pla-CES, CES-150, CES-225, and CES-320, respectively. The postexercise urinary Caf concentration (range 1.3-2.5 microg/ml) was dose dependent and always far below the doping level of the International Olympic Committee (12 microg/ml) in all subjects. Sweat Caf excretion during exercise exceeded postexercise early-void urinary Caf excretion. Caffeinated CES did not enhance free fatty acid availability, ruling out the fact that performance improvement resulted from enhanced fat oxidation. It is concluded that addition of relatively low amounts of Caf to CES improves performance and that postexercise urinary Caf concentration remained low.

Gastric emptying as a regulatory factor in fluid uptake

Since the last two decades substantial interest has been given to the effects of dehydration and rehydration in the exercising athlete. This has resulted in numerous studies which, to a large extent, have been reviewed in a number of excellent papers (5,10,12,18,24). In the present article we will give a brief summary of the major findings, while also discussing some new developments.

Aspects of food and fluid intake during labour. Policies of midwives and obstetricians in The Netherlands

OBJECTIVE

This study outlines the current policies on food and fluid intake during labour in The Netherlands and discusses the pro's and con's of food-restriction.

STUDY DESIGN

50 midwives and 30 obstetricians were asked about their actual policy on food and fluid-intake during labour.

RESULTS

A restrictive policy during normal labour is followed by 20% of the midwives and 14% of the obstetricians. About 75% leaves the decision on food and fluid-intake to the women themselves.

CONCLUSIONS

Despite the non-restrictive policy in The Netherlands, the mortality due to the Mendelson-syndrome is not higher than in countries where a restrictive policy is followed. During normal labour there are no conclusive reasons for food or fluid-restriction. From a metabolic point of view it is hypothesized that the intake of energy-rich substrates may have a positive influence on labour progression. Further study on the subject seems indicated.

Strategies to enhance fat utilisation during exercise

Compared with the limited capacity of the human body to store carbohydrate (CHO), endogenous fat depots are large and represent a vast source of fuel for exercise. However, fatty acid (FA) oxidation is limited, especially during intense exercise, and CHO remains the major fuel for oxidative metabolism. In the search for strategies to improve athletic performance, recent interest has focused on several nutritional procedures which may theoretically promote FA oxidation, attenuate the rate of muscle glycogen depletion and improve exercise capacity. In some individuals the ingestion of caffeine improves endurance capacity, but L-carnitine supplementation has no effect on either rates of FA oxidation, muscle glycogen utilisation or performance. Likewise, the ingestion of small amounts of medium-chain triglyceride (MCT) has no major effect on either fat metabolism or exercise performance. On the other hand, in endurance-trained individuals, substrate utilisation during submaximal [60% of peak oxygen uptake (VO2peak)] exercise can be altered substantially by the ingestion of a high fat (60 to 70% of energy intake), low CHO (15 to 20% of energy intake) diet for 7 to 10 days. Adaptation to such a diet, however, does not appear to alter the rate of working muscle glycogen utilisation during prolonged, moderate intensity exercise, nor consistently improve performance. At present, there is insufficient scientific evidence to recommend that athletes either ingest fat, in the form of MCTs, during exercise, or "fat-adapt" in the weeks prior to a major endurance event to improve athletic performance.

Effect of medium-chain triacylglycerol and carbohydrate ingestion during exercise on substrate utilization and subsequent cycling performance

The aim of this study was to investigate the effect of medium-chain triacylglycerol (MCT) ingestion during exercise on subsequent time-trial cycling performance. Seven well-trained cyclists performed four exercise trials consisting of 2 h at 60% of maximal oxygen uptake followed by a simulated time trial (ie, completion of a preset amount of work as fast as possible) of approximately 15 min duration. During the trials, subjects ingested 1) a 10% carbohydrate solution (CHO; 170 +/- 6 g glucose), 2) a 10% carbohydrate electrolyte with 5% MCT solution (CHO + MCT; 85 +/- 3 g MCT), 3) a 5% MCT solution, or 4) artificially colored and flavored water (placebo). Neither CHO nor CHO + MCT ingestion had any effect on performance compared with placebo ingestion, whereas ingestion of MCT had a negative effect on performance. Average work rates during the time trial were 314 +/- 19, 314 +/- 13, and 312 +/- 18 with CHO, CHO + MCT, and placebo, respectively, and was 17-18% lower in the MCT trial (263 +/- 22 W). In addition, compared with placebo ingestion, MCT ingestion had no effect on total rates of fat or carbohydrate oxidation, nor did it affect exogenous or endogenous carbohydrate utilization. The negative effect of MCT ingestion was associated with increased gastrointestinal complaints (ie, intestinal cramping). These data suggest that large amounts of MCTs (85 g) ingested during prolonged submaximal exercise may provoke gastrointestinal problems leading to decreased exercise performance.

Utilization of lipids during exercise in human subjects: metabolic and dietary constraints

During endurance exercise, skeletal muscle relies mainly on both carbohydrate (CHO) and fat oxidation to cover energy needs. Numerous scientific studies have shown that increasing the exercise intensity leads to a progressive utilization of CHO. The latter will induce a state of glycogen depletion which is generally recognized as being a limiting factor for the continuation of strenuous exercise. Different dietary interventions have been proposed to overcome this limitation. A high-CHO diet during periods of intense training and competition, as well as CHO intake during exercise, are known to maintain a high rate of CHO oxidation and to delay fatigue. However, it has been recognized also that enhancing fatty acid (FA) oxidation during exercise induces a reduced rate of glycogen degradation, resulting in an improved endurance capacity. This is most strikingly observed as a result of frequent endurance exercise which improves a number of factors known to govern the FA flux and the oxidative capacity of skeletal muscle. Such factors are: (1) blood flow and capillarization; (2) lipolysis of triacylglycerol (TAG) in adipose tissue and circulating TAG and transport of FA from blood plasma to the sarcoplasm; (3) availability and rate of hydrolysis of intramuscular TAG; (4) activation of the FA and transport across the mitochondrial membrane; (5) the activity of enzymes in the oxidative pathway; (6) hormonal adaptations, i.e. sensitivity to catecholamines and insulin. The observation that the plasma FA concentration is an important factor in determining the rate of FA oxidation, and that some dietary factors may influence the rate of FA supply to muscle as well as to the mitochondria, has led to a number of dietary interventions with the ultimate goal to enhance FA oxidation and endurance performance. It appears that experimental data are not equivocal that dietary interventions, such as a high-fat diet, medium-chain TAG-fat emulsions and caffeine intake during exercise, as well as L-carnitine supplementation, do significantly enhance FA oxidation during exercise. So far, only regular endurance exercise can be classified as successful in achieving adaptations which enhance FA mobilization and oxidation.

The effect of different rehydration drinks on post-exercise electrolyte excretion in trained athletes

Eight well-trained cyclists were dehydrated (median [P25-P75 percentiles]) 3.21 [2.97-3.56]% of body mass by cycling in the heat (28 C). During the first 2 h of recovery, the subjects randomly ingested ad libitum either a caffeinated soft drink (CC), a low Na+ mineral water (MW), or an isotonic carbohydrate-electrolyte solution (CES). Fluid intake and urine loss amounted respectively to 2.77 [2.34-2.85] kg, 1.00 [0.82-1.20] kg for CC, 2.15 [1.86-2.79] kg, 0.96 [0.40-1.49] kg for MW, and 2.86 [2.15-3.58] kg, 1.10 [0.86- 1.50] kg for CES. Electrolyte retention was calculated from electrolyte intake with the drink and loss with the urine. Consumption of CC and MW which were low in electrolytes resulted in marked loss of Na+, K+, Cl-, Mg2+ and Ca2+. Consumption of CES resulted in Na+, Mg2+ and Ca2+ retention while K+ and Cl- loss were not influenced. The significantly lower Na+, Mg2+ and Ca2+ loss with CES compared to both CC and MW may be explained by its higher electrolyte content in CES, compared to CC and MW, which only had minor amounts of these electrolytes. Furthermore, it was shown that CC potentiated urinary Mg2+ and Ca2+ excretion. It is concluded that: 1) Post-exercise MW or CC ingestion results in a negative electrolyte balance, 2) Caffeine containing beverages potentiate Mg2+ and Ca2+ excretion; 3) Consumption of CES containing moderate amounts of Na+, Mg2+ and Ca2+ results in sufficient replacement to compensate for urinary losses.