Glycyrrhizic acid: the assessment of a no effect level.

Because from earlier experiments in rats and a pilot study in humans a no-effect level of glycyrrhizic acid could not be established, a second experiment was performed in healthy volunteers. The experiment was performed in females only, because the effects were most marked in females in the pilot study. Doses of 0, 1, 2 and 4 mg glycyrrhizic acid/kg body weight were administered orally for 8 weeks to 39 healthy female volunteers aged 19-40 years. The experiment lasted 12 weeks including an adaptation and a "wash-out" period. A no-effect level of 2 mg/kg is proposed from the results of this study, from which an acceptable daily intake (ADI) of 0.2 mg/kg body weight can be extrapolated with a safety factor of 10. This means consumption of 12 mg glycyrrhizic acid/day for a person with a body weight of 60 kg. This would be equal to 6 g licorice a day, assuming that licorice contains 0.2% of glycyrrhizic acid. The proposed ADI is below the limit advised by the Dutch Nutrition Council of 200 mg glycyrrhizic acid/day. This reflects the relatively mild acute toxicity of glycyrrhizic acid, which is also emphasised by the "generally recognised as safe" (GRAS) status of glycyrrhizic acid in the USA in 1983. However, the long-term effects of a mild chronic intoxication (causing, for example, a mild hypertension), although not immediately lethal, justify special attention to the amount of glycyrrhizic acid used daily.

Lactulose stimulates calcium absorption in postmenopausal women.

Animal studies have indicated that calcium absorption is increased by lactulose, a synthetic disaccharide. Therefore, the influence of lactulose on calcium absorption was measured in postmenopausal women who may benefit from the possible enhancing effect of lactulose on calcium absorption. Twelve postmenopausal women drank 100 ml of water containing 5 or 10 g of lactulose or a reference substance at breakfast for 9 days. The three treatments were given according to a randomized, double-blind, cross-over design, separated by two 19-day wash-out periods. On the 8th day of each treatment period, 44Ca dissolved in orange juice was drunk immediately after the solution with the study substance and just before a standard breakfast with 162 mg of carrier calcium. Within half an hour, 48Ca was given intravenously. Based on isotope ratios measured in urine collected before and until 36 h after isotope administration, true fractional calcium absorption was calculated. Calcium absorption during the treatments with the reference substance, 5 g and 10 g of lactulose was (mean +/- SD) 27.7 +/- 7.7, 30.0 +/- 7.6, and 32.2 +/- 7.0, respectively. A significant difference in calcium absorption was found between the highest dose of lactulose and the reference treatment (p < 0.01). A significant linear trend was found between the dose of lactulose and its positive effect on calcium absorption. In conclusion, in postmenopausal women a 9-day consumption of lactulose increases calcium absorption in a dose-response way. More research is warranted to explore how lactulose stimulates calcium absorption and whether it is able to improve calcium balance and/or to attenuate the rate of aging bone loss.

Oligofructose stimulates calcium absorption in adolescents.

BACKGROUND: In rats, nondigestible oligosaccharides stimulate calcium absorption. Recently, this effect was also found in human subjects. OBJECTIVE: The objective of the study was to investigate whether consumption of 15 g oligofructose/d stimulates calcium absorption in male adolescents. DESIGN: Twelve healthy, male adolescents aged 14-16 y received, for 9 d, 15 g oligofructose or sucrose (control treatment) daily over 3 main meals. The treatments were given according to a randomized, double-blind, crossover design, separated by a 19-d washout period. On the 8th day of each treatment period, 44Ca was given orally with a standard breakfast containing approximately 200 mg Ca. Within half an hour after administration of 44Ca, 48Ca was administered intravenously. Fractional calcium absorption was computed from the enrichment of 44Ca:43Ca and 48Ca:43Ca in 36-h urine samples, which was measured by inductively coupled plasma mass spectrometry. RESULTS: An increase in true fractional calcium absorption (%) was found after consumption of oligofructose (mean difference +/- SE of difference: 10.8+/-5.6; P < 0.05, one sided). The results are discussed in relation to the methods used. CONCLUSION: Fifteen grams of oligofructose per day stimulates fractional calcium absorption in male adolescents.

Effect of nondigestible oligosaccharides on large-bowel functions, blood lipid concentrations and glucose absorption in young healthy male subjects.

OBJECTIVE: To study the effect of the intake of 15 g nondigestible oligosaccharides per day on various parameters of large-bowel function, as well as on blood lipid concentrations and glucose absorption in man. DESIGN: Latin square, randomized, double-blind, diet-controlled. SETTING: Metabolic research unit. SUBJECTS: Twelve apparently healthy men (mean age 23 years), recruited from the Institute's pool of volunteers, no drop-outs. INTERVENTIONS: Four treatment periods of 3 weeks: inulin, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS) and control; analyses of stool weight, intestinal transit, faecal pH, short-chain fatty acids, bile acids, faecal enzymes, blood lipids and glucose absorption. RESULTS: As compared to the control treatment: higher concentration of faecal acetate (inulin and GOS, P < 0.05) and valerate (inulin, P < 0.05), significantly lower concentration of faecal deoxycholic acid (inulin and FOS, P < 0.05 and P< 0.02, respectively) and beta-glucuronidase activity (inulin and GOS, P < 0.05 and P < 0.02 respectively). Other changes of faecal parameters and those of blood lipids and glucose absorption were statistically not significant. CONCLUSIONS: RESULTS indicate that nondigestible oligosaccharides are (partly) fermented in the human colon, but in healthy young men the effects are limited. Also the consumption of 15 g nondigestible oligosaccharides does not seem to alter blood lipid concentrations and glucose absorption in our young healthy adults.

Analysis of fecal bile acids and neutral steroids using gas-liquid chromatography.

In the present pilot study, for investigating the physiological effects of different types of nondigestible oligosaccharides, we have validated the application of methodologies for the analysis of bile acids and neutral steroids in feces of human subjects. The accuracy of the extraction and chromatographic procedures for the analyses of bile acids and neutral steroids was determined by recovery of added compounds to fecal homogenate. The precision of the above procedures was checked by analyzing these compounds in samples (n = 5) of the same fecal homogenate. Recoveries of added bile acids ranged from 86 and 96%, and those of neutral steroids varied from 81 to 97%. The precision expressed as coefficients of variation of bile acids and neutral steroids ranged from 2.3 to 8.3% and from 6.3 to 11.8%, respectively. The intra- and interindividual variabilities expressed as coefficients of variation of bile acids varied from 1 to 58 and from 0 to 74%, respectively. The same variabilities for neutral steroids ranged from 0.5 to 107% and from 1 to 168%, respectively. The methods validated in the present pilot study were adequate for applying to our forthcoming European Union coordinated major study on the physiological effects of different types of nondigestible oligosaccharides and involving large numbers of samples.

Effects of a milk product, fermented by Lactobacillus acidophilus and with fructo-oligosaccharides added, on blood lipids in male volunteers.

OBJECTIVE: To investigate in adult male volunteers the effect of a new fermented milk product, fermented by Lactobacillus acidophilus and with fructo-oligosaccharides added, on blood lipids. DESIGN: Randomized placebo-controlled double-blind two-way cross over trial with two treatment periods of three weeks, separated by a wash-out period of one week. SETTING: the study was performed at the TNO Nutrition and Food Research Institute in Zeist, The Netherlands. SUBECTS: Thirty normal healthy men, aged 33-64y (mean serum total cholesterol level: 5.23 +/- 1.03 (s.d.)), were selected for this study. Normal health was assessed by pre study screening. All subjects were used to an average Dutch food pattern. INTERVENTIONS: During the treatment periods subjects consumed three times daily a 125 ml of either test or reference product as a part of their habitual diet. The test product was a milk, fermented by yogurt starters and Lactobacillus acidophilus, and contained 2.5% fructo-oligosaccharides, 0.5% vegetable oil and 0.5% milk fat. The reference product was a traditional yogurt (milk fermented only by yogurt strains), containing 1% milk fat. Blood samples for serum lipid analysis and blood glucose measurements were taken before the start of the experiment and at the end of both treatment periods. RESULTS: As compared to the reference product, consumption of the test product resulted in significantly lower values for serum total cholesterol (P < 0.001), LDL-cholesterol (P < 0.005), and the LDL/HDL-ratio (P < 0.05) by 4.4, 5.4 and 5.3% respectively. Levels of serum HDL-cholesterol, triglycerides and blood glucose remained essentially unchanged. The beneficial effects of the test product on serum cholesterol were largely related to an increase of this parameter during the consumption of the reference product. CONCLUSIONS: As compared to traditional yogurt, daily consumption of three times 125 ml of test product specifically lowered serum LDL-cholesterol levels in normal healthy male adult subjects with borderline elevated levels of serum total cholesterol within three weeks.

Nondigestible oligosaccharides do not interfere with calcium and nonheme-iron absorption in young, healthy men.

The effect of inulin, fructooligosaccharides, and galactooligosaccharides on true intestinal absorption of iron and calcium was measured in men by using double stable-isotope techniques (oral 57Fe and 44Ca and intravenous 58Fe and 48Ca). The incorporation of iron isotopes into erythrocytes and the urinary excretion of calcium isotopes was measured with an inductively coupled plasma mass spectrometer. Twelve healthy, nonanemic, male subjects aged 20-30 y received four treatments consisting of a constant basal diet supplemented with 15 g/d inulin, fructooligosaccharide, or galactooligosaccharide, or not supplemented (control treatment). These four treatments were given for 21 d each according to a randomized, crossover design. Iron absorption was measured over the last 7 d of treatment (days 15-21) and calcium absorption was measured on day 21 of each treatment period. Mean (+/- SEM) iron absorption was 5.5 +/- 1.6%, 6.1 +/- 1.9%, 5.3 +/- 1.9%, and 5.1 +/- 1.5%, respectively, during treatment with inulin, fructooligosaccharide, galactooligosaccharide, or the control; mean ( SEM) calcium absorption was 25.8 +/- 2.3%, 26.3 +/- 1.9%, 26.3 +/- 2.6%, and 28.1 +/- 4.3%, respectively. None of the differences between treatments was significant. It is concluded that 15 g/d inulin, fructooligosaccharide, or galactooligosaccharide did not have a negative effect on iron and calcium absorption in young healthy men.

A new method to measure iron absorption from the enrichment of 57Fe and 58Fe in young erythroid cells.

Iron absorption can be measured by the incorporation of stable iron isotopes into erythrocytes, 14 days after isotope administration. The disadvantage of this method is the high dose of isotopes needed to obtain a sufficient enrichment. Therefore, in this study cell fractions rich in young erythroid cells were prepared by using a density separation method. From 10 women blood was taken 4, 5, and 7 days after oral and intravenous administration of 57Fe and 58Fe. In these cell fractions and in whole blood taken 14 days after isotope administration, isotope enrichment was measured and absorption calculated. Absorption calculated from the isotope enrichment in the reticulocyte-rich cell fractions (12.2 +/- SEM 3.7%) was not significantly different from absorption based on whole-blood values (13.0 +/- 3.3%). Because a threefold higher isotope enrichment was found in the cell fractions, the required dose of stable isotopes can be reduced to one-third of the dose used in the traditional method without loss of sensitivity.

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.

Dietary intake of food contaminants in The Netherlands (Dutch Nutrition Surveillance System).

To assess the level of exposure to food contaminants (cadmium, lead, PCBs, DDT, hexachlorobenzene, nitrate and malathion) a total-diet study was carried out. A total of 226 food products were analysed individually; the concentration of contaminants in products not selected for analysis was estimated with the help of published data. The results of the analyses and estimations were used as input for the first Dutch National Food Consumption Survey (1987-1988) (n = 5898, age 1-85). Mean intakes of all contaminants analysed did not exceed the acceptable daily intake (ADI) or comparable values in any of the age-sex groups. Comparison of the results with those of previous total diet studies suggests that the intake of all contaminants analysed had declined between 1976-1978 and 1988-1989. In younger age groups an intake of lead and cadmium exceeding the tolerable daily intake (derived from the WHO/FAO provisional tolerable weekly intake) was found in 1.5% of individuals at most. For the older population groups and for the other contaminants in all population groups mean and maximum intakes were substantially below the ADL. However, individual intakes above the ADI for nitrate were found in 3-23% of individuals. For chronic exposure these percentages are likely to be overestimated because of the short time frame for food consumption measurement. In general, the difference between mean intake and tolerable daily intake was smallest for children aged 1-4. Therefore, it is recommended that future research is concentrated on the intake of contaminants in younger age groups.

Bioavailability of calcium of fresh cheeses, enteral food and mineral water. A study with stable calcium isotopes in young adult women.

True fractional Ca absorption from six foods was measured in twelve normal healthy women, aged 20-29 years. The tested foods were commercially available fresh cheese, fresh cheese prepared by new technology and rich in Ca, similar cheese with added Fe, enteral food, mineral water alone and combined with a spaghetti meal. The aim of the study was to investigate: (1) Ca absorption from a new Ca-rich fresh cheese and to compare it with that from the traditional commercial type of fresh cheese; (2) the effect of Fe enrichment of the new cheese on Ca absorption; (3) Ca absorption from the mineral water and the enteral product and to compare it with that from the dairy products; (4) the effect of a meal combined with the mineral water on Ca absorption. All test foods were consumed by all subjects according to a design with two Latin squares. Each treatment of 2 d was followed by a wash-out period of 2 weeks. Ca absorption was measured using a double stable-isotope (44Ca and 48Ca) extrinsic labelling technique. Mean fractional Ca absorption from the new fresh cheese was not significantly different from that from the traditional type (37.7 (SD 10.2)% v. 42.2 (SD 11.6)%). The addition of Fe to the new cheese did not significantly influence Ca absorption. Ca-absorption values from the mineral water (37.0 (SD 9.8)%) and from the enteral product (42.6 (SD 11.4)%) were not significantly different from those from the dairy products (37.7-42.2%, SD 10.2-11.6%). The co-ingestion of a spaghetti meal with the mineral water significantly enhanced Ca absorption from 37 (SD 9.8)% to 46.1 (SD 11.7)%. It is concluded that a new process leading to a fresh cheese with a higher Ca concentration does not alter Ca bioavailability compared with the standard technology and for a constant Ca supply. Thus this new fresh cheese would probably provide more Ca than the standard one. The fractional Ca-absorption values for mineral water and the enteral product indicate that these products can make an interesting contribution to Ca supply for populations with a low Ca intake and patients with specific diseases respectively.

[Supplementary selenium , an antidote against mercury?]. / Seleensuppletie, een antidotum tegen kwik?

The consequences of both a high and a low intake of selenium are described in this article. Mercury released by dental silver amalgam might affect the protective functions of selenium. However, the literature does not sustain the existence of such an effect. In view of the small margin between safe and toxic doses of selenium and the absence of a scientific consensus as to the possible toxic effects of mercury from amalgam (additional to dietary mercury), it does not seem to be warranted to advise suppletion of selenium.

[Selenium and mercury. (Un)healthy antagonism?]. / Seleen en kwik. (On)gezonde wisselwerkingen?

The trace element selenium is involved in the protection against damage caused by free radicals. Selenium prevents carcinogenesis and growth of neoplasms. However, the mechanism is insufficiently known. Furthermore, selenium interacts with mercury, thereby preventing toxic reactions to high doses of mercury. The intake of selenium and the desired minimum and maximum concentrations are described.

The art of lecturing. How to become a scientific entertainer.

It is known to all nutritionists and food scientists that the presentation of papers at (inter)national meetings is not always optimal. In this paper on effective lecturing some very practical advice is presented on how to entertain the audience scientifically. With the prerequisite of a clear scientific message, the basic elements for an optimal presentation are discussed with emphasis on the proper use of audiovisual means, including slides and overhead transparencies. Some additional comments are made about posters, chairpersons of sessions, and audiences.

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.

Body composition, health status and urinary magnesium excretion among elderly people (Dutch Nutrition Surveillance System).

Magnesium (Mg) requirements depend on body weight. Recommended dietary allowances (RDA) are mostly given in absolute amounts and are mostly similar for adults, despite differences in body composition in the adult age range. We therefore studied the interrelations of 24 h urinary Mg excretion with body build and body composition indicators, as well as with factors potentially affecting the metabolism of Mg, among 520 elderly men and women seen in a nationwide survey. Mg intake data were also obtained in the Dutch Food Composition Survey amount 5898 subjects. The results showed lower mean Mg intake among elderly people (especially men) and positive associations of body weight and body height with urinary Mg excretion, but not when expressed per mmol of creatinine excreted. Mg excretion per mmol of creatinine was not associated with body weight, body height, body mass index or body fatness (women), suggesting that the amount of fat mass did not affect Mg excretion. Mg excretion was positively correlated with Mg intake, creatinine clearance, excretion of sodium, potassium and calcium, and coffee consumption, indicating interactions at the kidney level that may increase Mg losses. Elderly people using diuretics and/or anticholinergics and male diabetics had a higher mean Mg excretion per mmol of creatinine. The results show that, besides the Mg intake, several factors affect the urinary Mg excretion among elderly people. These factors were body build and body composition, dietary intake, drug use, kidney function, and diabetes. A quantification of the effects cannot be made yet, and controlled studies on those factors potentially affecting the requirement of Mg are needed.

Motives and perception of healthy volunteers who participate in experiments.

Healthy volunteers who participated in an experiment were asked to complete a questionnaire about their experiences. Special attention was paid to their motives and the informed consent procedure. The motives of healthy volunteers for participating in a study differed according to age. Young volunteers mostly participated because of the financial compensation, while older volunteers mainly participated to get a medical check-up, which was part of the selection procedure, or because of the benefit that other people might obtain from the results of the experiment. In most experiments the volunteers were content with the information given about the experiment, which was provided orally and in a hand-out. The information procedure was crucial for the experiment, because optimum information was of the utmost importance in keeping the volunteers motivated during the experiment. Another conclusion was that the researcher should not be afraid that too much information was given. Adequate information was also important in recruiting new volunteers, because they mostly become interested because of information obtained from their predecessors. A personal approach towards the volunteers during the experiment was appreciated by them and was an important help in keeping the volunteers motivated during the experiment.

The no-effect level of sodium bromide in healthy volunteers.

1. A total of 0, 4 and 9 mg kg-1 body weight sodium bromide was administered orally to 45 healthy female volunteers. 2. The experiment lasted for six menstrual cycles: only during the first three cycles was bromide administered; 3. At the start, at the end of the administration period and at the end of the experiment a physical examination and haematological and routine clinical chemistry tests were performed. Except for nausea in relation to the intake of bromide, no adverse effects were observed. 4. The bromide concentration in plasma rose to 3.22 +/- 0.93 mmol kg-1 in the 4 mg kg-1 group and to 7.99 +/- 1.89 in the 9 mg kg-1 group by the end of the administration period. 5. Before and at the end of the experiment the thyroid hormones (T4, FT4, TBG, T3 and TSH) were analysed. No significant differences were observed between the groups. 6. Before, after three menstrual cycles and at the end of the experiment an EEG with a Visual Evoked Response was recorded. At the 4 and 9 mg kg-1 dose level in the alpha 1-band and the beta-bands significant changes were found (P < 0.1 and P < 0.05, respectively). The Visual Evoked Response showed no significant differences between the three groups. 7. From this experiment and previous experiments a no-effect level in humans for sodium bromide of 4 mg kg-1 body weight is proposed.