Influence of a carbohydrate drink on performance of military personnel in NBC protective clothing.

BACKGROUND: The increased threat of nuclear, biological and chemical (NBC) weapons underlines the need of protective clothing and gas masks, but this may impair performance. Thus, attention should be focused on the nutritional requirements. HYPOTHESIS: Optimal performance is guaranteed if the supply of water and energy is adequate. METHODS: Two groups of 20 trained military men (mean age 22 yr) received either an isotonic carbohydrate drink or a placebo drink (flavored water) for 24 h under simulated NBC conditions (wearing gas masks and protective clothing). Various physical and mental tests were performed at intervals and blood samples were collected three times. RESULTS: Five men of the placebo group had to be withdrawn during the experiment because of exhaustion. The decrease in physical performance (about 15%) and mental performance (about 20%) was most apparent for the group that had only water for consumption. CONCLUSIONS: When only water is consumed, physical performance of a group of military men decreases during 24 h of simulated NBC conditions. An isotonic carbohydrate drink is recommended with respect to maintaining performance under NBC conditions. Energy restriction prior to an NBC scenario has a negative influence on performance.

Thiamin, riboflavin and vitamin B6: impact of restricted intake on physical performance in man.

OBJECTIVE: A combined marginally deficient status of thiamin, riboflavin, vitamin B6 and vitamin C may affect physical performance, but the relative contribution of each vitamin can only be speculated. In a previous study we did not find any effect of restricted intake of vitamin C individually. Therefore, the functional effect of restriction of thiamin, riboflavin or vitamin B6, individually or in conjunction, was investigated. METHODS: A double-blind, 2 x 2 x 2 complete factorial experiment on the effects of thiamin, riboflavin and vitamin B6 restriction on physical performance was executed with 24 healthy men. During 11 weeks of low vitamin intake, the subjects were given a daily diet of regular food products providing no more than 55% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin and vitamin B6. Other vitamins were supplemented at twice the RDA level. RESULTS: In vitamin-restricted subjects, blood vitamin levels, erythrocytic enzyme activities and urinary vitamin excretion decreased and in vitro erythrocytic enzyme stimulation increased. Short-time vitamin restriction had no harmful effects on health. A significant overall decrease was observed in aerobic power (VO2-max; 11.6%), onset of blood lactate accumulation (OBLA; 7.0%) and oxygen consumption at this power output (VO2-OBLA; 12.0%), peak power (9.3%), mean power (6.9%) and related variables (p < 0.01). However, the observed performance decrements could not be attributed to marginal deficiency for any of the vitamins studied. CONCLUSION: The absence of vitamin-specific effects on performance decrements due to thiamin, riboflavin and vitamin B6 restriction suggests quantitatively similar but non-additive effects of these B-vitamins on mitochondrial metabolism.

Comparison of the inhibition of dietary fat absorption by full versus divided doses of orlistat.

Orlistat is a potent and selective inhibitor of gastrointestinal lipases. The drug is designed for the treatment of obesity. The effect on dietary fat absorption of orlistat after administration of divided doses spread over 2 hours from mid-meal, in comparison with that after administration of a full dose mid-meal, was investigated in a randomized, single-blind study including 16 hospitalized healthy males. After a 5-day run-in, to accustom the subjects to a diet of 2350 kcal and 76 g fat per day and to establish baseline fecal fat excretion, subjects received, in two parallel groups of eight over 8 days, three times a day 80 mg orlistat at mid-meal, and placebo at mid-meal and 0.5, 1, and 2 hr after mid-meal (group A), or placebo at mid-meal, and 20 mg orlistat at mid-meal and 0.5, 1, and 2 hr after mid-meal (group B). Feces were collected to measure total fat excretion. The mean (SD) of fecal fat in percent of dietary fat, after deduction of pretreatment fecal fat, was (%) 36.1 (4.2) and 37.0 (9.3) in groups A and B, respectively. Changing the mode of administration of orlistat, within the dose regimens investigated, does not affect its pharmacologic efficacy.

Combinations of low thiamin, riboflavin, vitamin B6 and vitamin C intake among Dutch adults. (Dutch Nutrition Surveillance System).

OBJECTIVE: Clustering of low vitamin intake may entail a greater functional and/or health risk than the summation of separate low intakes may suggest. Therefore, the prevalence of combined low thiamin, riboflavin, vitamin B6 and vitamin C intake in various adult sex-age groups in The Netherlands was estimated. METHODS: Nutritional risks were evaluated by comparing the calculated intakes with the recommendations for each vitamin. For this purpose the data of a subsample of 3353 adults of a nationwide food consumption survey were used, which had been collected in 1987-88 within the framework of the Dutch Nutrition Surveillance System. Food consumption data were obtained through 2-day dietary records. Respondents were segmented into tertiles based on their vitamin intake per 1000 kcal (4.2 MJ) to adjust for energy intake. RESULTS: As compared with the RDAs, mean overall intake was lowest for vitamin B6. Based on tertile analyses, the risk for inadequate intake was relatively high for vitamin C, small for riboflavin and intermediate for thiamin and vitamin B6. Low vitamin densities clustered somewhat since the prevalence of combined low intakes for all four vitamins was higher than expected from probability calculations. This interdependence was mainly the result of a higher consumption of alcoholic beverages and of other food products with a low vitamin density. CONCLUSION: In affluent societies nutritional risk assessment should not be based solely on single vitamins but should also be oriented at combined low intake levels.

Vitamin B-6 supplementation in elderly men: effects on mood, memory, performance and mental effort.

This study evaluates the effects of vitamin B-6 supplementation (20 mg pyridoxine HCL daily for 3 months) on mood and performance in 38 self-supporting healthy men, aged between 70-79 years. Effects were compared with 38 controls who received placebo and were matched for age, plasma pyridoxal-5'-phosphate (PLP) concentration and intelligence score. Before and after drug intervention vitamin B-6 status was determined, and mood and performance were measured by means of a computerized testing system. In addition, the phasic pupil response was measured in order to assess mental effort. Positive effects of vitamin B-6 supplementation were only found with respect to memory, especially concerning long-term memory. In view of the finding that mental performance improvement and delta PLP values were most strongly correlated within an intermediate range of delta PLP, it is suggested that cognitive effects are primarily associated with a certain range of vitamin B-6 status increment. The general conclusion is that vitamin B-6 supplementation improves storage of information modestly but significantly.

Dutch dietary guidelines: impact on blood lipids, blood pressure, body composition and urinary mineral excretion of Dutch middle-aged men.

In this study the impact of the Dutch dietary guidelines diet on various health status parameters was examined. Twelve apparently healthy men aged 35-52 years were given both the guidelines diet (G) and the 'average' Dutch diet (D) in a controlled eight-week study period with a cross-over design. Compared with the D diet, the G diet contained less fat (accounting for 35 per cent vs 44 per cent of total energy intake), about half the amounts of saturated and monounsaturated fatty acids and twice the amount of polyunsaturated fatty acids. The G diet was given either as a high-sugar or as a low-sugar variant (25 per cent and 15 per cent of total daily energy intake, respectively). Serum total, LDL- and HDL-cholesterol decreased during the four-week G diet from 5.76 to 4.99, from 3.95 to 3.35 and from 1.13 to 1.03 mmol/l respectively. Also the apo-lipoprotein A-I, A-II and B concentrations decreased in subjects on the G diet. Blood pressure and body composition did not change significantly. Urinary pH and the excretion of sodium and potassium were significantly lower for the G diet. It is concluded that the combined factors in the Dutch guidelines diet, irrespective of amount of sugar, has favourable effects on total and LDL-cholesterol levels, whereas the decrease of the concentrations of HDL-cholesterol and of apo-A-I and A-II is less desirable. The changes in urinary mineral excretion, in particular of sodium, during the G-diet is considered as a positive effect.

Biogenic amines in anorexia nervosa: circadian rhythm in urinary excretion and influence of posture and physical task load on plasma catecholamines.

To investigate the sympathetic response in anorexia nervosa (AN) patients to stimuli occurring in normal life, biogenic amines were studied in 10 female outpatients. As control groups 10 lean and 10 normal weight healthy female subjects were included. It was hypothesized that the lean control group would have intermediate values between the AN patients and the normal weight controls. The AN patients and the lean controls had a mean underweight of 33.1% and 13.7%, respectively. For the excretion in 24-hr urine, differences among the groups were observed for several compounds, unexpectedly the values being lowest for the patients and highest for the lean controls. Furthermore, the lean controls had a higher excretion of a number of compounds in diurnal than in nocturnal urine, whereas this effect was absent or reversed for the AN patients and intermediate for the normal weight controls. Plasma norepinephrine was highest in the patients and lowest in the lean controls. The catecholamine response to postural changes and physical exercise did not differ among the groups. The results obtained indicate neither a (linear) relationship between underweight and the metabolism of biogenic amines nor a disturbed response to sympathetic stimulation in AN, but suggest an altered metabolism of biogenic amines in patients suffering from AN.

Vitamin supplementation and physical exercise performance.

Vitamins, just as minerals and trace elements, meet with great interest in the world of sports because of their supposed role in enhancing physical performance. Of the 13 compounds now considered as vitamins, most water-soluble vitamins and vitamin E are involved in mitochondrial energy metabolism. The influence of vitamin supplementation on mitochondrial metabolism is largely unknown. The principal argument for vitamin supplementation is the assumed increased vitamin requirement of athletes. Theoretically, an increased requirement can be caused by decreased absorption by the gastrointestinal tract, increased excretion in sweat, urine and faeces, increased turnover, as well as biochemical adaptation to training. Of course, a marginal low vitamin status can simply be the consequence of a long-term inadequate intake. However, considering the RDAs there are no indications that long-term vitamin intake among athletes is insufficient. Neither are there indications that vitamin excretion or turnover is increased in athletes. However, it is very likely that the (apparently) increased requirement is the consequence of biochemical adaptation to training and does not indicate a decreased intake. Although a marginal vitamin status, induced by inadequate vitamin intake, may have a negative effect on performance, there is no evidence to support the view that this occurs in trained athletes. Moreover, vitamin supplementation in athletes with an adequate vitamin status has no effect on physical working capacity. Possibly, exceptions have to be made for the use of vitamin E at high altitudes and for the use of vitamin C and multiple B-vitamin supplements in hot climates.

Controlled vitamin C restriction and physical performance in volunteers.

A double-blind study on the effects of vitamin C restriction on physical performance was executed with 12 healthy men. During seven weeks of low vitamin C intake six subjects were on a daily diet of regular food products, providing 20% of the Dutch Recommended Dietary Allowances (RDA) for vitamin C (Dutch RDA is 50 mg/day). Other vitamins were supplemented at twice the RDA level. After three weeks of low vitamin intake an additional vitamin C dose of 15 mg/day was provided, resulting in a total intake of 25 mg/day (50% of the Dutch RDA). Six control subjects consumed the same diet supplemented with twice the RDA for all vitamins. In the restriction group blood vitamin C levels decreased significantly (p less than 0.01). Vitamin C restriction had no harmful effects on health, aerobic power (VO2-max), and onset of blood lactate accumulation (OBLA). However, an increased heart rate at OBLA level was observed during the period of low vitamin C intake (p less than 0.05), possibly by interference with either catecholamine or carnitine metabolism. These results suggest that short-term marginal vitamin C deficiency does not affect physical performance in single bouts of intensive exercise.

Fat patterning during weight reduction: a multimode investigation.

Changes in body composition during weight reduction of 20 obese women were quantified by anthropometry (weight, waist and hip circumferences, skinfold thicknesses determined with a skinfold caliper and ultrasonically), densitometry (hydrostatic weighing), tetrapolar bioelectrical impedance (TBI) and computed tomography (CT scan of abdomen and thorax). The average reduction in mean weight (92.7 kg), induced by an energy restricted diet over a period of 12 wk was 5.6 kg (5.8%). Fat areas were calculated from the CT scans of the thorax; intra-abdominal fat and subcutaneous fat were separately calculated from the abdominal CT scans. Anthropometric and CT fat values were found to decrease significantly during weight reduction, whereas the percentages of body fat as determined by densitometry and TBI did not. The relative deposition of intra-abdominal and subcutaneous fat of 19 women did not essentially change after weight reduction. One woman, who had a relatively large intra-abdominal fat accumulation, lost more subcutaneous fat than intra-abdominal fat. It is concluded that in general fat patterning does not change during weight reduction.

[Is vitamin intake by the elderly in The Netherlands precarious?]. / Is de vitaminevoorziening van ouderen in Nederland zorgwekkend?

The elderly are vulnerable to nutritional risks. The vitamin intake (assessed through dietary history) and vitamin status of 539 independently living persons aged 65-79 years and 44 lacto-(ovo)-vegetarian persons aged 65-97 years were evaluated. All respondents were apparently healthy. Compared with the Dutch recommended dietary allowances the intake of vitamins was assessed as adequate except for vitamin B6. The marginal intake of vitamin B6 is reflected in the vitamin B6 status. The prevalence of low 25-hydroxyvitamin D concentrations in plasma is high among elderly people as compared with younger adults (blood donors); the concentration is negatively correlated with age. The vegetarian elderly appeared to be at risk regarding the vitamin B12 status. In conclusion, the average intake of vitamins is assessed as adequate, whereas the intakes of vitamin B6 and vitamin D of Dutch apparently healthy elderly need more attention.

Thiamin, riboflavin, and vitamins B-6 and C: impact of combined restricted intake on functional performance in man.

A double-blind study of combined restriction of thiamin, riboflavin, and vitamins B-6 and C was carried out with 23 healthy males. During 8 wk of low vitamin intake, 12 deficient subjects consumed daily a diet of normal food products, providing maximally 32.5% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin, vitamins B-6 and C. Other vitamins were supplemented at twice the RDA. Eleven control subjects consumed the same diet but with a supplementation of twice the RDA of all vitamins. In deficient subjects blood vitamin levels, urinary vitamin excretion, and erythrocytic enzyme activities decreased; in vitro enzyme stimulation increased. Vitamin depletion had no ill effects on health, physical activity, and mental performance. A significant decrease was observed in aerobic power (VO2max) and onset of blood lactate accumulation (p less than 0.001) of 9.8 and 19.6%, respectively. A combined restricted intake of thiamin, riboflavin, and vitamins B-6 and C causes a decrease in physical performance within a few weeks.

Computed tomography measurement of abdominal fat deposition in relation to anthropometry.

In a study on the abdominal fat deposition measurements were carried out with computed tomography (CT) at the umbilical level in 130 patients (68 males and 62 females), submitted to the Department of Radiodiagnosis for routine CT of the abdomen. Weight, height, waist and hip circumference were measured. From a single CT scan at the umbilical level the subcutaneous and intra-abdominal fat areas were calculated. In men relatively more fat was found in the abdominal cavity than in women. Using all possible subset regression for both subcutaneous and intraabdominal fat areas, the best subsets of predictor variables were examined for males and females separately. Quetelet index and hip circumference were good predictor variables, explaining more than 70 per cent of the variance of the subcutaneous fat in both males and females. Waist and hip circumference explained about 74 per cent of the variance in intra-abdominal fat in males and 56 per cent in females. The results indicate that the single CT scan is fairly representative of overall abdominal fatness and that waist and hip circumference measurements can provide a useful indication of the abdominal fat deposition.

Type A behaviour, borderline hyperventilation and psychological, psychosomatic and neuroendocrine responses to mental task load.

Psychological, psychosomatic and neuroendocrine (in blood) responses to mental task load were investigated in relation to Type A behaviour and borderline hyperventilation. For this purpose 32 apparently healthy, male volunteers were classified on the basis of their scores on the Jenkins Activity Survey (JAS) and on a questionnaire assessing hyperventilation related symptoms (HRS). The subjects performed a memory search task in which a monetary bonus could be won or lost. At rest higher HRS scores were related to increased acute psychosomatic symptom scores and higher JAS scores to higher prolactin levels. Task performance caused an increase of state anxiety, acute psychosomatic symptoms, adrenaline and cortisol, whereas prolactin decreased. Higher JAS scores were related to greater cortisol responses and higher HRS scores to smaller adrenaline responses.

Effects of moderate alcohol consumption on platelet aggregation, fibrinolysis, and blood lipids.

To investigate the effect of moderate alcohol consumption on blood constituents related to cardiovascular disease, 12 male volunteers consumed (instead of their usual alcoholic drinks) four different standardized amounts of red wine in addition to their habitual diet. Each dose was given to the subjects during a period of 5 weeks in a randomized order, all subjects receiving the four doses. They consisted of 0, 2, and 4 glasses/d, providing 0, 23, and 46 g alcohol/d as well as in "binge drinking" (14 glasses in the weekend, comparable to an average of 2 glasses/d). The results showed a clear dose-related response to the drinking for several blood constituents. Most marked was a decrease in the tissue-type plasminogen activator activity and to a lesser degree an increase in plasminogen levels. Collagen-induced platelet aggregation was reduced, affecting all parameters measured. Levels of HDL3-cholesterol, gammaglutamyltransferase, and urate showed a small but significant increase. No change was noted in the levels of alkaline phosphatase, alanine-aminotransferase, aspartate-aminotransferase, bile acids, folate, fibrinogen, the ADP-induced platelet aggregation, platelet secretion, or in hematologic values. The results are only partially in accordance with the presumed protective action of moderate drinking on the cardiovascular system and show a stronger response to the consumption of alcohol in coagulation and fibrinolysis factors than in blood lipids.

Effect of work load on free and sulfate-conjugated plasma catecholamines, prolactin, and cortisol.

The effects of maximal performance capacity and different work load intensities on the response of free and sulfate-conjugated plasma catecholamines, prolactin (PRL), and cortisol were studied in six healthy male volunteers. In a first experiment, the volunteers had to perform a step-wise incremental bicycle ergometer test to determine the onset of blood lactate accumulation (OBLA) and aerobic capacity (VO2 max). The levels of free noradrenaline (NE), adrenaline (Epi), and dopamine (DA) increased considerably, whereas no significant changes for sulfate-conjugated catecholamines, PRL, and cortisol were observed. In a second series of experiments with the same volunteers, the effects of 30 min exercise were studied at a constant work load intensity on 3 different days. Three intensities were used for each of the volunteers: 45%, 60%, and 75% of their aerobic capacity (i.e., below, close to, and above their OBLA). The values obtained for all parameters showed an intensity-dependent rise. The most important changes occurred at work load intensities above the OBLA. At the highest intensity, all parameters except sulfate-conjugated Ne and cortisol showed a significant increase. Although the physiologic parameters reached a steady state during exercise, there were no indications that this was the case with the values of the neuroendocrine parameters. Ten minutes after the exercise, the levels of the free catecholamines had declined considerably, whereas the values of the other parameters were unchanged or showed a further increase.

Comparison of ultrasound and skinfold caliper measurement of subcutaneous fat tissue.

Subcutaneous fat thickness of 26 young males (aged 18-32 years) was measured at eight sites (biceps, triceps, subscapula, axillary, subcosta, paraumbilica, suprailiaca, quadriceps) using a commercial high-resolution B-scan ultrasound equipment with a 7.5-MHz transducer as well as a Holtain skinfold caliper. The aim of the study was to investigate the relationship between ultrasound and skinfold caliper measurements of subcutaneous fat and body density determined by the hydrostatic weighing technique. Correlations between ultrasound and caliper measurement were above 0.7. The variability of duplicate measurements with the skinfold caliper appeared to be somewhat lower than with ultrasound measurements. Using all possible subsets regression, for both techniques measuring subcutaneous fat thickness those multiple regression equations were chosen which predicted body density best. The best equations for the two techniques explained about 80 percent of the variance of body density in this group. These results indicate that in young men, body fat can be estimated with the same degree of accuracy using either the skinfold caliper or the ultrasound technique, but for estimates of actual subcutaneous fat thickness, ultrasound is to be preferred.

Vitamins and endurance training. Food for running or faddish claims?

The inter-relationship of food and physical performance, food is considered as a conglomerate of nutrients and man is depicted as a kind of organic pudding. This 'machine' concept of human performance in combination with the mysticism surrounding vitamins, has led to the faddish belief that additional vitamins are necessary to improve physical performance by means of supercharging the metabolic processes in the body. Various vitamins and their dietary recommendations as well as the indicators for vitamin status are discussed. It is concluded that a marginal or subclinical deficiency state can be defined as an intermediate between optimal vitamin status and frank clinical deficiency. Marginal deficiency is characterised by biochemical values deviating from statistically derived reference limits as well as the absence of clinical signs and symptoms of vitamin deficiency. Besides the static, mostly biochemical, indicators of vitamin status, more functional indicators are considered, among them work capacity. An extensive historical review on depletion studies, epidemiological surveys and supplementation studies is presented. It is concluded that a restricted intake of some B-complex vitamins-individually and in combination-of approximately less than 35 to 45% of the recommended dietary allowance may lead to decreased endurance capacity within a few weeks. Studies on ascorbic acid (vitamin C) depletion and fat-soluble vitamin A deficiency have noted no decrease of endurance capacity. However, in a few recent epidemiological surveys, biochemical vitamin C deficiency was actually shown to decrease aerobic power. Although the general conclusion is that a reduced water-soluble vitamin intake decreases endurance capacity, it is believed that further controlled experimentation is needed with B-complex vitamins and vitamin C individually. Furthermore, usually employed reference limits for vitamins need reappraisal translating them into impairment limits. With respect to the available evidence, it can be concluded that supplementation of diet with either single or multivitamin preparations containing B-complex vitamins, vitamin C or E does not improve physical performance in athletes with a normal biochemical vitamin balance resulting from a well-balanced diet. Although vitamin supplementation does not seem to produce any effect when the diet is adequate, it is possible that vitamin B-complex supplementation is useful in sports with a high energy expenditure, because of the unavoidable consumption of 'empty calories' i.e. food products with a low nutrient density. The side effects of megavitamin supplementation are discussed briefly.