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Biomedical subjects

G Schaafsma

Publications and source records attributed to G Schaafsma.

At least 37 records · Page 2Linked to original sources
PubMed1998

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.

Absorption↗
PubMed1997

Calcium excretion, apparent calcium absorption and calcium balance in young and elderly subjects: influence of protein intake.

The present study was conducted to investigate the effect of dietary protein on urinary Ca excretion, apparent Ca absorption and Ca balance in young and elderly subjects. Young adults (n 29) and elderly persons (n 26) consumed diets containing 12% (diet A) and 21% (diet B) of total energy as protein for 3 weeks according to a randomized crossover design. Results showed no differences between the two age groups with respect to the interaction between protein intake and Ca excretion (both in urine and in faeces), apparent Ca absorption and Ca balance. Therefore analyses were done for both age groups separately and also for the whole group. In elderly persons and in the whole group the Ca excretion in faeces (as a percentage of Ca intake) was lower during the higher protein intake (elderly: diet A, 106 (SEM 7)%; diet B, 86 (SEM 7)%; P = 0.018; whole group: diet A, 99 (SEM 4)%; diet B, 84 (SEM 4)%; P = 0.003). In young adults faecal Ca excretion tended to be lower when they consumed diet B (diet A: 94 (SEM 5)%; diet B: 83 (SEM 6)%; P = 0.093). Relative urinary Ca excretion was greater during the higher protein intake in young adults and in the whole group while relative urinary Ca excretion was not different in the elderly (diet A: 15 (SEM 1)%, 14 (SEM 1)%, 15 (SEM 1)%; diet B: 16 (SEM 1)%, 16 (SEM 1)%, 17 (SEM 2)% for the whole group, the young and elderly subjects respectively, P = 0.019; P = 0.016; P = 0.243). The resulting Ca balance was not influenced by the amount of protein in the diet in young adults. Values for the elderly and for the whole group showed that the Ca balance during diet A was significantly more negative compared with Ca balance during diet B, despite the higher urinary Ca excretion during diet B. It can be concluded that increasing the protein intake from 12 to 21% of total energy intake had no negative effect on Ca balance.

Adult↗
PubMed1997

The effect of an increase of protein intake on whole-body protein turnover in elderly women is tracer dependent.

To compare the response of whole-body protein turnover with variations in dietary protein level, whole-body protein turnover was measured by different stable isotope methods in six elderly women (69 +/- 5 y) consuming two levels of protein (10 and 20% of total energy, diets A and B, respectively). Protein turnover was measured during 12 h of overnight fasting with 15N-glycine with urea and ammonia as end products. During the last 4 h of the interval, protein turnover was also estimated by -[1-13C]-leucine infusion. Nitrogen balance [diet A, -0.040 +/- 0.015 g/(kg.d); diet B, 0.002 +/- 0.053 g/(kg.d); mean +/- ] did not differ significantly between the diet periods, although all subjects were in negative nitrogen balance at the end of diet A. Protein breakdown, as measured with 15N-glycine, did not differ from results obtained using -[1-13C]-leucine, whereas protein synthesis was found to be significantly lower using the former isotope. The 15N-glycine method indicated that protein turnover (both synthesis and breakdown) was higher in fasting elderly women when they consumed a 20% rather than a 10% protein diet, whereas the -[1-13C]-leucine method did not show significant differences between the diet periods in the last 4 h of the overnight fasting period. However, the relative increase in net protein breakdown when comparing diet B with diet A, was comparable for both tracers. These data indicate that care is needed with the choice of the tracer used in measuring the components of protein turnover in elderly women with the aim of understanding the physiological basis behind the adequacy of the level of protein intake.

Aged↗
PubMed1997

Reduced bone mass in Dutch adolescents fed a macrobiotic diet in early life.

This study investigated the effect of a macrobiotic (vegan-type) diet, low in calcium and vitamin D, consumed in early life, on bone mineral during adolescence. Bone mineral content (BMC) and bone area were measured in 195 adolescents (103 girls, 92 boys) aged 9-15 years, using dual-energy X-ray absorptiometry. Ninety-three adolescents (43 girls, 50 boys) had followed a macrobiotic diet in childhood, and 102 (60 girls, 42 boys) were control subjects. After adjustment for bone area, weight, height, percent body lean, age, and puberty, BMC was significantly lower in macrobiotic subjects, in boys and girls, respectively, at the whole body, -3.4% and -2.5%, spine, -8.5% and -5.0%, femoral neck, -8.0% and -8.2%, midshaft radius, -6.8% and -5.6%, and also in girls, at the trochanter, -5.8% (p < 0.05). No group differences were observed at the wrist. Group differences were not explained by current calcium adjusted bone mass at age 9-15 years, observations which may hold important implications for fracture risk in later life.

Absorptiometry, Photon↗
PubMed1996

Apparent ileal dry matter and crude protein digestibility of rations fed to pigs and determined with the use of chromic oxide (Cr2O3) and acid-insoluble ash as digestive markers.

Two experiments were conducted to determine apparent ileal DM and crude-protein (CP) digestibilities in rations fed to pigs. An evaluation was made of Cr2O3 and HCl-insoluble ash as digestive markers. In addition, the effects of body weight (BW) on apparent ileal DM and CP (N x 6.25) digestibilities were studied. In Expt 1, thirteen barrows averaging 35 kg BW were fitted with post-valve T-caecum (PVTC) cannulas to determine the apparent ileal DM and CP digestibilities of a wheat gluten-bran ration (B2) and a soyabean-meal ration (E1). Immediately after morning feeding ileal digesta samples were collected on an hourly basis for a total of 12 h. Subsequently. N and marker contents were determined in the samples. The postprandial patterns of N and Cr passage were more similar than those of N and HCl-insoluble ash. Therefore Cr2O3 is more suitable as a marker than HCl-insoluble ash. The apparent ileal CP digestibility coefficient of ration B2 derived using Cr2O3 as a marker was significantly (P < 0.05) higher by 0.018 compared with the value obtained using HCl-insoluble ash. The corresponding values for ration E2 obtained using Cr2O3 and HCl-insoluble ash were both 0.825. In Expt 2, apparent ileal DM and CP digestibilities were determined in eighteen rations using twelve barrows also fitted with PVTC cannulas (BW from 40 to 100 kg). The protein sources for these rations were from different groups of feedstuffs. In four and three of the rations apparent ileal DM and CP digestibilities respectively were significantly different (P < 0.05) when assessed using the two markers. The digestibility coefficients were not systematically higher or lower for either marker. Absolute differences were < 0.049 on average. Significant effects of live weight on apparent ileal CP digestibilities were found.

Animal Feed↗
PubMed1996

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.

Adult↗
PubMed1995

Induction of net mass lipid transfer reactions in plasma by wine consumption with dinner.

Moderate alcohol consumption is associated with a reduced risk of coronary heart disease. Alcohol may exert protection through its effects on the metabolism of plasma lipoproteins. In the present study we investigated the effects of moderate wine consumption with an evening dinner on lipoprotein composition and parameters of reverse cholesterol transport (plasma lipid transfer reactions and cholesterol esterification) in eight healthy middle-aged men. Wine consumption, if compared with mineral water, resulted in increased postprandial plasma levels of triglyceride-(TG)-rich lipoproteins (P < 0.005 or < 0.002 at two different time points) and in increased net mass transfer of cholesterylesters (CE) from high-density lipoprotein (HDL) to apolipoprotein B-containing lipoproteins during in vitro incubation of plasma (P < 0.001). Net mass transfer of TG (in the opposite direction) was also significantly increased by wine (P = 0.014). The concentrations of total plasma cholesterol, HDL-cholesterol and apolipoproteins A-I, A-II and B did not change postprandially and were not affected significantly by wine, but the CE TG-1 in HDL was affected postprandially and decreased by wine consumption. It is concluded that moderate wine consumption with evening dinner induces transfer reactions of CE and TG between HDL and TG-rich lipoproteins. Due to the fact that wine raises plasma TG, it also causes changes in plasma cholesterol metabolism and lipoprotein composition, without major effects on total plasma cholesterol concentration.

Alcohol Drinking↗
PubMed1994

Effect of moderate dose of alcohol with evening meal on fibrinolytic factors.

OBJECTIVES: To evaluate the effects of moderate consumption of alcoholic beverages on the fibrinolytic system and to assess whether these effects could help explain the relation between moderate alcohol consumption and reduced coronary heart disease. DESIGN: Four treatments were allocated in a randomised controlled order on four days over a period of 11 days. SETTING: Metabolic ward of research institute. SUBJECTS: Eight white healthy middle aged men. INTERVENTIONS: Subjects were provided with food for the 11 days. On the four study days mineral water or 40 g of alcohol in the form of beer, wine, or spirits was consumed at dinner early in the evening. MAIN OUTCOME MEASURES: Plasminogen activator inhibitor activity, tissue type plasminogen activator antigen, and tissue type plasminogen activator activity one hour before and one, three, five, nine, and 13 hours after dinner with mineral water or alcoholic beverages. RESULTS: After dinner with alcohol plasminogen activator inhibitor activity rose from 53 (SD 19)% to a maximum of 667 (283%) five hours after dinner (P < 0.001). Tissue type plasminogen activator antigen levels rose from 5.3 (2.2) micrograms/l to a maximum of 10.8 (3.8) micrograms/l nine hours after dinner with alcohol (P < 0.001). Plasminogen activator activity was reduced in the postprandial period (from 1387 (483) IU/l to 323 (288) IU/l five hours after eating; P < 0.001) but was higher than normal early the next morning (1516 (809) IU/l after alcohol, 779 (516) IU/l after water; P = 0.04). CONCLUSION: Moderate alcohol consumption with dinner affects plasminogen activator inhibitor activity, plasminogen activator antigen level, and tissue type plasminogen activator activity temporarily. The effects observed in the early morning are consistent with a decrease in risk of coronary heart disease in moderate drinkers.

Alcohol Drinking↗
PubMed1994

Effects of moderate energy restriction on physical performance and substrate utilization in non-obese men.

Energy restriction (ER) has shown to be an effective 'anti-aging' factor in rodents, resulting in an increased life span and preventing or delaying the occurrence of many age-related diseases in rodents. As a part of a feasibility study on the potential application of ER in humans, we studied the effects of moderate ER on physical performance in 24 apparently healthy, non-obese middle-aged men. After two weeks of weight maintenance the ER group (n = 16) received 80% of their habitual energy intake, while a control group (n = 8) still received their weight-maintaining diet for ten weeks. Physical performance (bicycle ergometer) was estimated by a maximal (until exhaustion) and a submaximal (30 min at 60% of VO2max) exercise test. After the experimental period the subjects in ER group had a significantly shorter cycling time (delta = 1.31 +/- 1.14 vs -0.45 +/- 1.56 min, p = 0.01), and thus had a lower maximal power output (delta = 4.3 +/- 5.9 vs -6.3 +/- 13.6 watt, p < 0.05) and maximal oxygen uptake (delta = 0.03 +/- 0.18 vs -0.18 +/- 0.321/min, p = 0.05) during the maximal exercise test, than the subjects in the control group. None of these changes correlated with weight loss. As in every exercise test, motivation could have played an important role. During the submaximal exercise test no significant changes between the two groups in HR, VO2, RER and FFA, glucose, lactate and catecholamine levels were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Energy restriction, a useful intervention to retard human ageing? Results of a feasibility study.

OBJECTIVE: Energy restriction (ER) retards the ageing process in animal models. It is possible that ER has a similar effect in humans. As a first approach to look after the potential application of ER in man the feasibility of a moderately energy-restricted diet was studied. DESIGN: A controlled intervention study. SETTING: TNO Toxicology and Nutrition Institute. SUBJECTS: 24 middle-aged non-obese men, selected from men responding to advertisements in regional newspapers. INTERVENTIONS: After a run-in period subjects were divided into two groups, a control group (n = 8) and an ER group (n = 16). Groups were matched on age and body mass index. The effects of 10 weeks of moderate ER (80% of habitual energy intake) on body composition, general health (blood pressure, lipid profile, routine clinical chemistry and haematology), physical and mental performance, and feelings of hunger, satiety and state of mind were measured. RESULTS: Subjects in the ER group lost about 7.4 +/- 2.6 kg weight (P < 0.001). This weight loss concerned mainly loss of fat mass. Diastolic and systolic blood pressure decreased significantly within the ER group (P < 0.05 and P < 0.01 respectively). The increase in HDL-cholesterol level was significantly related to weight loss (P < 0.05). CONCLUSIONS: The results show beneficial effects of 10 weeks of moderate ER on blood pressure and lipid profile without adverse effects on physical and mental performance and feelings of hunger, satiety and mood.

Adult↗
PubMed1993

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.

Aged↗
PubMed1993

Alcohol consumption in relation to food intake and smoking habits in the Dutch National Food Consumption Survey.

The interrelationships between alcohol consumption, energy and food intake and smoking habits were studied in 1145 men and 1171 women, aged 22-49 years, in the Dutch National Food Consumption Survey, in which a 48-h dietary record method was used. The aim of the study was to investigate the effects of alcohol consumption on dietary habits and smoking. A strong relationship between alcohol consumption and energy intake was found. The energy derived from alcohol was not compensated for by lower intake of other nutrients. There was no increase in Quetelet's index with increasing alcohol consumption, except for non-smoking men who were heavy drinking on midweek days. Possible explanations for this apparent lack of an overall effect of alcohol calories are discussed. Alcohol consumption was much higher on weekend days than on midweek days. No differences in nutrient intake were found between non-drinkers, moderate drinkers and heavy drinkers on midweek days. On weekend days, however, there was a slightly higher total fat and saturated fat intake in moderately drinking men. For women cholesterol intake was found to be higher in moderate and heavy drinkers. Finally, a strong positive relationship between alcohol consumption and smoking was observed. It is concluded that the observations with respect to energy and nutrient intake and smoking habits are not indicative of a healthier lifestyle in moderate alcohol users between 22 and 49 years of age. Consequently, the more favourable prognosis of moderate drinkers cannot be ascribed to a more healthy lifestyle.

Adult↗
PubMed1992

The scientific basis of recommended dietary allowances for calcium.

Dietary calcium is required for bone development during growth (attainment of peak bone mass), for maintenance of skeletal integrity during adult life, and thus for prevention of osteoporosis. The Recommended Dietary Allowance (RDA) of a nutrient for a particular group is considered to cover the needs of 98% of all individuals of that group, and thus takes into account a margin of safety to allow for interindividual variation in minimum requirements. It appears to be possible, on the basis of the available scientific literature, to calculate the daily amount of calcium that must be absorbed from the diet to compensate for the endogenous calcium losses (through urine, faeces and skin) and the calcium retention in bone. Similarly, it seems to be possible to obtain a reasonable estimate of calcium absorption for the different groups of the population. From these data, and taking into account a margin of safety, figures are obtained for calcium intake that are in reasonably close agreement with the authoritative 1989 RDAs of the USA Food and Nutrition Board, with the exception of the USA allowance for girls aged 19-25 years (probably too high) and older adults (possibly too low). With regard to optimal calcium intake, some important questions still remain unanswered. These bear upon the issue of calcium intake and peak bone mass development, and upon the effects of non-nutritional factors (e.g. genetics and physical activity) and nutritional factors (e.g. sodium, protein, alcohol and caffeine) on calcium requirements. Furthermore, it would appear that bone development and maintenance of bone health may not be the sole criteria for setting RDAs in the near future. These issues are briefly discussed.

Adolescent↗
PubMed1992

Supplementation with selenium-rich bread does not influence platelet aggregation in healthy volunteers.

In order to establish the effect of an increased dietary selenium supply on platelet glutathione peroxidase (EC 1.11.1.9.; GSH-Px) and platelet aggregation, six healthy subjects were supplemented with 200 micrograms Se as Se-rich bread for 6 weeks. Another six subjects received low-Se bread and served as controls. Platelet GSH-Px activity increased significantly in the supplementation group, whereas no effect could be observed on platelet aggregation. The results of this study do not support the hypothesis that an increased dietary Se intake has a favourable influence on platelet aggregation.

Adenosine Diphosphate↗
PubMed1991

Effect of various levels of selenium in wheat and meat on blood Se status indices and on Se balance in Dutch men.

After a 5-week period of low selenium intake, twenty-four Dutch men received 55, 135 or 215 micrograms Se/d as Se-rich meat or bread for a 9-week period. Four unsupplemented subjects served as controls. Plasma Se increased more rapidly than erythrocyte Se levels; the increases were significantly dependent (P less than 0.001) on Se intake level. Glutathione peroxidase (EC 1.11.1.9; GSH-Px) activity in platelets increased rapidly after supplementation and plateaued after 4-9 weeks. At 10 weeks after supplementation ended, plasma Se levels and platelet GSH-Px were still higher than the baseline values whereas erythrocyte Se levels continued to increase. Except for the higher erythrocyte Se levels after supplementation with high-Se meat, there were no differences in bioavailability of Se between meat and wheat products. Daily urinary and faecal Se excretions as well as Se retention increased with an increased Se intake irrespective of the form of the supplement. Regression of Se excretion v. intake indicated that 33 micrograms Se/d is necessary to compensate for urinary and faecal losses.

Adult↗
PubMed1991

Nutrition and blood pressure among elderly men and women (Dutch Nutrition Surveillance System).

Associations between blood pressure and nutrition-related variables (body mass index, dietary intake, and 24-hr excretion of sodium, potassium, magnesium, and calcium in the urine) were investigated in men (n = 138) and women (n = 117) 65-79 years old not using drugs known to affect blood pressure and not on a diet. Among men, body mass index was positively and creatinine clearance was inversely associated with systolic blood pressure, whereas body mass index and urinary sodium:potassium ratio were positively associated with diastolic blood pressure. Among women, both age and urinary calcium:creatinine ratio were positively associated with systolic as well as diastolic blood pressure. Coffee consumption was positively correlated with blood pressure and urinary calcium:creatinine ratio among the women. From the results it appears that, besides "normal" weight, increased potassium intake and urinary excretion may exert a protective effect among elderly men against hypertension when sodium exposure is relatively high. The positive association between urinary calcium:creatinine ratio and blood pressure among the women may be partly due to coffee consumption.

Aged↗
PubMed1991

Do alcoholic beverages have an additional effect on the postprandial gastrin response in humans?

The hormone gastrin plays an important role in the regulation of acid secretion in the stomach which, in turn, stimulates the digestion of food. Previous studies reported that administration of beer and wine but not ethanol and spirits increases gastrin secretion in fasting volunteers. It is not known whether alcoholic beverages combined with a normal meal have an additional effect on the postprandial gastrin response. We therefore measured the gastrin response in eight volunteers who received either alcoholic beverages (40 g alcohol) in the form of beer, red wine or spirits, or mineral water as control in combination with a dinner. Two glasses were drunk before the meal, two glasses during the meal. Plasma gastrin concentrations were twofold increased at one hour after the dinner as compared to predinner values. However, no additional effect of beer, wine or spirits on this postprandial response was seen. The present study does not support the hypothesis that the consumption of beer or wine during a meal has a positive effect on the release of gastrin and therefore most probably does not contribute to an improved digestion of food by stimulation of acid secretion.

Alcohol Drinking↗