Bile acid and cholesterol excretion in human beings given soya-bean- and meat-protein-based diets: a study in ileostomy subjects

1. The effect of partial replacement of meat protein with three different soya-bean-protein products on bile acid and cholesterol excretion was studied in seven ileostomy subjects. Four different tests diets containing 60 g meat, rice and bread protein, or a replacement of 250 g protein/kg total dietary protein by soya-bean protein from soya-bean flour, soya-bean concentrate or soya-bean isolate, were randomly assigned to the subjects in 2-d periods. 2. Ileostomy contents were collected at 2-h intervals during the day and in one portion during the night, and immediately deep-frozen to avoid bacteriological degradation. Bile acids and cholesterol were quantified by gas-liquid chromatography. 3. No difference in daily excretion of bile acids and cholesterol was noted between test diets. Ileostomy sterol concentrations were lower when soya-bean products were fed. 4. Incorporation of moderate amounts of soya-bean products in solid diets does not seem to affect short-term sterol balance in man.     

Meat and soy protein affect calcium homeostasis in healthy women

We showed that increasing dietary protein from omnivorous sources increases intestinal calcium absorption and urinary calcium, whereas a low-protein diet decreases calcium absorption and lowers urinary calcium. To assess the effect of soy protein on this relation, we substituted soy for meat in high- and low-protein diets fed to healthy women. The study consisted of a 2-wk adjustment period followed by a 4-d experimental period in which 20 healthy women consumed, in random order, the following 4 diets: high-protein soy-based, low-protein soy-based, high-protein meat-based, low-protein meat-based. Measures of calcium homeostasis were evaluated at baseline and after 4 d of the experimental period. At 24 h, net acid excretion was higher during the high- compared with the low-protein intervention (P < 0.05), and during the meat compared with the soy intervention (P < 0.05). The high-protein diets increased 24-h urinary calcium (P < 0.001), but urinary calcium did not differ due to the type of protein. Serum concentrations of parathyroid hormone and calcitriol, and urinary nephrogenous cAMP were higher during the low- compared with the high-protein intervention and during the soy compared with the meat protein (P < 0.05). In a subset of subjects, intestinal calcium absorption tended to be lower (P = 0.1) when they consumed the soy diets rather than the meat diets. These data indicate that when soy protein is substituted for meat protein, there is an acute decline in dietary calcium bioavailability.     

Protein digestibility of weaning foods prepared from rice-minced meat and rice-mungbean combination in infants using a short term nitrogen balance method

Three diets based on rice-dehulled mungbean, rice-minced meat and rice-mungbean with hull were tested with infants 11 to 20 months of age using a short term nitrogen balance technique. The results indicate that with isocaloric and isonitrogenous intake, all the subjects given either of the three diets were in positive nitrogen balance. The protein quality, in terms of nitrogen absorption and true digestibility, of rice-meat diet was superior to that of rice-bean diets. Among the rice-bean diets, it was noted that rice-mungbean with hull had a lower digestibility as compared to rice-dehulled mungbean diet. The poor digestibility of rice-mungbean with hull diet is the first limiting factor in its utilization by infants. Dehulling of mungbean before cooking is recommended for preparing weaning food for infant feeding.     

The digestion of protein in young pigs and the utilization of dietary methionine

Forty pigs between 23 and 51 d of age were given ad lib. diets containing wheat and one of five protein concentrates: meat meal A, meat meal B, soya-bean meal, milk and lupins (Lupinus augustifolius). Twenty of these pigs were given indigestible markers from 51 to 56 d of age and were killed at 56 d of age. The diets containing meat meals A and B, soya-bean meal and milk contained 2.3 g total methionine/kg and the diet containing lupins contained 2.1 g/kg. A further forty pigs of the same age were given the same diets supplemented with 1 g synthetic methionine/kg. The weight gains and feed conversion ratios of the pigs given the diets containing 2.1-2.3 g methionine and 3.1-3.3 g methionine/kg were not significantly different. The weight gains of the pigs given lupins (2.1 g methionine/kg) were less than those of the pigs given the diets containing 2.3 g methionine/kg. The apparent digestibility of dry matter (DM) and nitrogen was less for the diets containing the meat meals (0.75 and 0.78 respectively) than for those containing the other protein concentrates (0.80 and 0.84). The retention times in the large intestine of the diets containing soya-bean meal and lupins were 965 and 1083 min which were greater than those of the diets containing the other protein concentrates, mean 732 min. The major site of N digestion and absorption for the diet containing milk was the area of the small intestine 25-50% of total length from the pylorus, while for the other protein concentrates the major site was 50-75% of its total length from the pylorus. The digestion and absorption of N in the large intestine was less (3.4%) for the diet containing milk than for those containing the other protein concentrates (7.5-11.3%). The apparent digestibility of the methionine to the ileum for the five diets ranged from 0.74 to 0.86 while the calculated retention of the apparently-absorbed methionine was 1.00. It was suggested that methionine digestibility could be used as an indicator of availability. The calculated retention of apparently absorbed N in the carcass was 0.71 for the pigs given the diet containing milk and 0.51-0.58 for the pigs given the other diets.     

Diets rich in Maillard reaction products affect protein digestibility in adolescent males aged 11-14 y

BACKGROUND: Adolescents are nutritionally at risk because of their physiologic needs and dietary habits. Maillard reaction products (MRPs) are widely consumed by this population, mainly as a result of their high intake of fast food and snacks. OBJECTIVE: We compared the effects of diets with different MRP contents on dietary protein utilization in adolescent males aged 11-14 y. The brown diet (BD) was rich and the white diet (WD) was poor in MRP content (hydroxymethylfurfural: 3.87 and 0.94 mg/kg; fluorescence intensity: 21.04% and 7.31%, respectively). DESIGN: In a 2-period crossover trial, 18 healthy adolescent males were randomly assigned to 2 groups. The first group consumed the WD for 2 wk, observed a 40-d washout period, and then consumed the BD for 2 wk. The second group received the diets in the opposite order. Subjects collected urine and feces on the last 3 d of each dietary period. Fasting blood samples were collected after both periods. RESULTS: Compared with consumption of the WD, consumption of the BD resulted in 47% higher fecal nitrogen fecal excretion (P = 0.002), 12% lower apparent nitrogen absorption (P = 0.000), and a 6% lower nitrogen digestibility (P = 0.000). The apparent nitrogen retention and the utilization of ingested nitrogen did not differ significantly between the diets, although values after the BD tended to decrease. Serum biochemical variables related to nitrogen metabolism did not differ significantly. CONCLUSIONS: The consumption of a diet rich in MRPs negatively affects protein digestibility. The possible effects of an excessive intake of MRPs during adolescence warrant attention, and long-term effects should be considered.     

Absorption of zinc from soy protein meals in humans

The absorption of zinc from soy protein-containing meals was studied in healthy human subjects by means of extrinsic labelling with 65Zn and whole body counting. Three types of soy protein, a soy flour, a soy concentrate and a soy isolate, were used in two types of meals: one consisting of rice and meat sauce and the other of white or whole-meal bread. Thirty and 100% of the protein of the meat sauce and 50% of the protein of bread was replaced with the soy protein products. Replacement of 30% of the protein in meat sauce had a marginal effect on the percentage absorption of zinc, whereas the absolute amount of zinc absorbed was lower due to the lower zinc content in soy products than in meat. After total replacement of the meat protein, a significantly lower percentage and absolute absorption of zinc was observed. A lower absorption of zinc was observed when soy protein was added to white bread. The absorption of zinc from the whole-meal bread was low and did not change when 50% of the flour protein was replaced by soy protein. We conclude that the effect of soy protein on zinc absorption depends on the degree of replacement, the phytic acid and zinc content of the soy product and the protein content of the meal.     

Effects of iron status and soy protein on iron absorption by rats

The effects of iron nutrition and soy protein on iron absorption by rats was studied. Rats were fed semipurified diets containing either 0, 5, or 20 micrograms of added iron per gram of diet to obtain groups with different iron status. After 3 weeks the rats had mean hemoglobin concentrations of 7.0, 10.7 and 13.2 g/dl, respectively. As the rats became more anemic, percent iron absorption from casein and soy protein diets increased. The relative availability of iron from soy compared with casein-based diets was 70 to 90%. Iron status did not affect the relative iron availability among treatments. The rat trials did not indicate any significant differences between iron absorption from meals containing soy flour (SF), soy protein concentrate (SC) or soy protein isolate (SI) regardless of the iron status of the rat. These studies do not support the hypothesis that the subject's iron status will affect the relative availability of iron from foods. Recent human iron absorption studies suggest that relative iron availability from meals containing soy proteins is lower than expected based on rat studies. Furthermore, differences in iron availability between soy flour and soy isolate observed in human studies are not apparent in these rat studies.     

An acute ileal amino acid digestibility assay is a valid procedure for use in human ileostomates

An acute (24-h) feeding/digesta sampling procedure was evaluated in a preliminary study using growing pigs. The validated acute procedure was then applied using human ileostomates to determine apparent and true ileal amino acid digestibilities of 4 dietary protein sources. The acute method involved feeding ileostomized pigs a single meal containing the test protein as part of a purified diet, with no previous dietary adaptation, followed by an 8-h collection of digesta. Apparent ileal N digestibility did not differ between the acute and conventional (14-d study) procedures. Eight adult human ileostomates each received a single meal of protein-free biscuits and a drink containing sodium caseinate, whey protein concentrate, soy protein isolate, or soy protein concentrate; this meal was followed by a 9-h total digesta collection period. Acid insoluble ash was used as an indigestible marker. True ileal amino acid digestibilities (means +/- SE) ranged from 90.5 +/- 2.74% for cysteine in soy protein concentrate to 105.3 +/- 5.66% for cysteine in sodium caseinate and were markedly higher than their apparent counterparts. True ileal digestibilities for total nitrogen were 101.9 +/- 0.70, 98.3 +/- 0.80, 99.5 +/- 0.80, and 98.5 +/- 1.20% for sodium caseinate, whey protein concentrate, soy protein isolate, and soy protein concentrate, respectively. The 4 protein sources were virtually completely digested in humans by the end of the small intestine.     

Metabolism in rats of selenium from intrinsically and extrinsically labeled isolated soy protein

Absorption, retention and tissue accumulation by rats of 75Se from intrinsically labeled isolated soy protein were compared with utilization of 75Se from the extrinsic sources of [75Se]selenite, [75Se]selenate or [75Se]selenomethionine. Extrinsic sources of selenium were given by gavage or mixed with isolated soy protein. There were no differences in absorption and retention of 75Se from intrinsically labeled soy diet compared to the three extrinsically labeled soy diets. Of the three extrinsic sources tested, 75Se from selenate was better absorbed than from selenite or selenomethionine when incorporated into a soy diet. Absorption of 75Se was significantly lower when given to animals in gavage solution than when mixed with soy diets. After a 14-d test period, retention of 75Se was the same for all four soy diet groups. In gavaged groups, 75Se from selenomethionine was retained to a greater extent than 75Se from selenite. The liver, testes and kidney accumulated more 75Se from the test meal than did the blood and lungs. In the testes more 75Se from selenite and selenate was accumulated than from selenomethionine-labeled diets. Selenium absorption from the soy isolate source was very high (86-96%), indicating that, although soy does not normally contain high levels of selenium, the selenium present is well absorbed from this plant source.     

Nutritional and antinutritional aspects of an Argentinian soy flour assessed on weanling rats

Inactivation of antinutritional factors on an Argentinian deffated soy flour was evaluated in relation to its corresponding original soybeans. Residual urease and trypsin inhibitors activities, protein solubility, available lysine and phytic acid showed acceptable levels. The nutritional value of a diet based on the same soy flour was compared with that of a casein-based diet by allowing them to each one of two groups of weanling IIMBeta rats during 28 days. Non-significant differences were obtained between groups comparing both body weight gain per gram of protein intake as well as the results of histometric studies performed on the small intestine. Thus, this soy flour contained appropriately inactivated antinutritional factors and its protein content and quality were nutritionally suitable. Large intestine hypertrophy was revealed within the soy-fed group suggesting increased microbial proliferation attributable to non-digestible oligosaccharides and fiber-like compounds. These compounds, employed by gut microflora as fermentation substrates, would be also responsible for an increased nitrogen excretion in the soy-fed group in relation to controls. This increment of nitrogen excretion significantly lowered the value of apparent nitrogen digestibility in the soy-fed group in relation to the casein-fed control one. Nevertheless, nitrogen apparent digestibility in the soy-fed group was equal or higher than other values reported from distinct treated soy meal-based diets.     

Novel methodology allows simultaneous measurement of true phosphorus digestibility and the gastrointestinal endogenous phosphorus outputs in studies with pigs

Methodology was developed for measuring the gastrointestinal endogenous phosphorus (P) outputs and true P digestibility values in studies with piglets. Four barrows, average initial body weight 6.8 kg, were fitted with a simple T-cannula at the distal ileum and fed four diets according to a 4 x 4 Latin square design. Four cornstarch-based diets containing four levels of P (1.1, 2.1, 3.2 and 4.3 g/kg diet) on a dry matter (DM) basis were formulated from soybean meal (SBM). Each experimental period comprised 8 d with a 4-d adaptation and 4-d collection of ileal digesta and feces. The apparent ileal and fecal P digestibility values in SBM were affected (P < 0.05) by P levels in the assay diets. The ileal and fecal P digestibility values increased from -24.8 to 37.1% and from 18.8 to 42.5%, respectively, as P contents increased from 1.1 to 4.3 g/kg DM diet. Linear relationships (P < 0.05), expressed as g/kg DM diet intake, between ileal and fecal outputs and dietary inputs of P, suggested that the endogenous P outputs can be determined by linear regression analysis. The endogenous P output was higher (P < 0.05) in ileal digesta than in feces (0.86 +/- 0.09 vs. 0.31 +/- 0.06 g/kg DM diet intake). There was no difference (P > 0.05) between the true ileal (50.7 +/- 7.1%) and fecal (48.5 +/- 5.4%) P digestibility values in SBM. These results suggest that differences in P contents between assay diets are primarily responsible for the large variability in apparent P digestibility values reported within the same ingredient. Apparent digestibility values underestimate the true digestive utilization of P by approximately 25%. True rather than apparent P digestibility values should be determined and used in diet formulation for pigs. In addition, this study shows that the gastrointestinal endogenous P output is important in whole-body P requirement and homeostasis.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phosphlipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phospholipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Urinary calcium and calcium balance in young women affected by high protein diet of soy protein isolate and adding sulfur-containing amino acids and/or potassium

The effects of sulfur-containing amino acids (SAA) and potassium (K) on urinary excretion and retention of calcium (Ca) of 27 young Japanese women were studied. A basal diet low in protein level (50 g per day) was fortified by meat or soy protein isolate (SPI) to a protein level of 100 g per day, and effects of addition of apple to these high protein diets, and addition of SAA and/or potassium (K) to the high SPI diet, especially on urinary Ca excretion, were studied. The addition of meat which increased protein intake to 100 g caused the increase in apparent absorption and urinary excretion of Ca with increased excretion of urinary sulfur (S), phosphate, ammonia, and titratable acids (TA), whereas addition of SPI did not. The addition of apple to high meat diet decreased absorption and urinary excretion of Ca. Urinary Ca, S, K, ammonia, and TA excretion increased by the addition of SAA to high SPI diet in a manner similar to the meat diet. Consequently, SAA-supplemented diet had a significantly negative effect on Ca retention. In SPI+SAA,K diet period, urinary K excretion markedly increased, and increments in urinary Ca, ammonia, and TA excretion were reversed. These changes observed in SPI+SAA, K diet period were similar to those by adding apple to meat diet without any effect on Ca absorption. The results suggest that the hypercalciuria induced by high meat diet is mainly caused by high content of SAA and may be reversed by the ingestion of K-rich foodstuffs, and soy protein does not induce hypercalciuria because of it contains less SAA than animal protein.     

Treatment of dietary casein with formaldehyde reduces its hypercholesterolemic effect in rabbits

Rabbits were fed cholesterol-free, semipurified diets containing 42% (wt/wt) casein or 21% casein plus one of the following nitrogen sources: soy isolate, amino acid mixture simulating casein, amino acid mixture simulating soy isolate, formaldehyde-treated casein or formaldehyde-treated soy isolate. Two additional groups of rabbits were fed the 42% casein diet and the diet containing casein plus soy isolate to which 0.4% (wt/wt) pure formaldehyde was added, this amount being identical to the amount of formaldehyde present in the diets with formaldehyde-treated proteins. Growth was somewhat reduced on the three diets containing 42% casein. The diet containing 42% casein to which no formaldehyde had been added induced severe hypercholesterolemia, the level of serum cholesterol after 8 weeks being about 10 mmol/L. The hypercholesterolemia was markedly reduced by the replacement of half of the casein by soy isolate, formaldehyde-treated soy isolate or formaldehyde-treated casein. No significant reduction of the concentration of serum cholesterol was seen when half of the 42% casein was replaced by an amino acid mixture imitating either casein or soy isolate. Formaldehyde per se did not significantly influence the level of serum cholesterol. We conclude that the differential tertiary structure of intact casein and soy isolate is an important factor in determining the cholesterolemic responses in rabbits to these proteins.     

The enhancement of nonheme iron bioavailability by beef protein in the rat

Beef protein was found to enhance the bioavailability of nonheme iron in the rat. Anemic rats were fed diets containing soy protein concentrate or rice bran as the source of nonheme iron with either lactalbumin or distilled water-washed beef, which was heme free. The criteria used to determine the relative biological value (RBV) of iron was the difference between the products of final hemoglobin x final weight and initial hemoglobin x initial weight during the repletion period. Animals fed diets with only lactalbumin as a source of dietary protein and graded levels of FeSO4 (RBV of FeSO4 = 100%) served as controls. The RBV of the endogenous iron in soy protein and rice bran was found to be 91 and 46%, respectively. Substituting washed beef for lactalbumin increased the RBV of soy protein iron to 96% (results not statistically significant) and of rice bran iron to 75% (results significant, P less than or equal to 0.05). These findings demonstrate the "meat factor" effect in the rat for the first time. Two days after completion of the 11-d hemoglobin regeneration period, the apparent absorption of iron was measured during a 60-h balance period. The apparent absorption of iron by rats fed diets containing beef tended to be higher, compared to animals fed diets containing lactalbumin.     

Nutritional and technological evaluation of an enzymatically methionine-enriched soy protein for infant enteral formulas

Enzymatically modified soy proteins have the amino acid profile and functional properties required for dietary support. The objective of this study was to evaluate the nutritional and technological properties of an enzymatically modified soy protein ultrafiltered fraction with bound methionine (F(1-10)E) to be used as a protein ingredient for infant enteral formulas. F(1-10)E was chemically characterized and biologically evaluated. Thirty-six weaning Wistar rats were fed during 3 weeks with a 4% casein-containing diet. Rats were divided into three groups and recovered for 3 weeks with 18% protein-containing diets based on: (1) F(1-10)E, (2) casein or (3) soy isolate+methionine. Nutritional indicators were weight gain, protein efficiency ratio, plasma proteins, apparent digestibility and protein in the carcass. Additionally, F(1-10)E was added as a protein ingredient of an enteral formula, and its sensory and rheological properties were compared with a hydrolyzed-whey protein commercial formula. F(1-10)E contained 68% protein and 5% sulphur amino acids, with 60% of peptides 0.05) in weight gain (108 g and 118 g, respectively), protein efficiency ratio (2.7), apparent digestibility (93% and 95%), plasma proteins (5.7 mg/100 ml) and carcass protein (61%), and better than soy isolate-based+methionine diet (P<0.05). Viscosity of the commercial formula and our formula was similar during a 24-h period. Sensory acceptability was 8 for our formula and 3.5 for the commercial one, on a scale of 1-10 (P<0.05). Due to its nutritional, sensorial and rheological properties, F(1-10)E could be used as a protein source in infant enteral formulas.     

Effect of diets containing dry beans (Phaseolus vulgaris, L.) on the rat excretion of endogenous nitrogen

Wistar rats of 60.5 +/- 5.0 g fasted for 24 h were injected intraperitoneally with 10 microCi of [14C]glycine. One to two hours after injection the rats were fed a diet containing 10.53 +/- 0.75% protein provided by dry beans or casein, or a protein-free diet and submitted to a 4-d nitrogen balance. Radioactivity in the feces of rats fed casein, cooked beans and raw beans was roughly 2, 5 and 10 times greater, respectively, than in the feces of those fed the protein-free diet. Apparent protein digestibility showed a strong negative linear correlation (r = -0.9805, P less than or equal to 0.01) with radioactivity in the feces. Positive correlation (P less than or equal to 0.01) was demonstrated between radioactivity and either total carbon or total nitrogen in the feces of rats injected with [14C]glycine. Mean value for the radioactivity in the urine of rats fed the different diets did not differ significantly (P less than or equal to 0.05). Endogenous nitrogen excretion of rats on bean diets was estimated by the ratio of total endogenous N to marker N, based on the protein-free diet. The results indicated that rats fed bean-containing diets excreted significantly more endogenous nitrogen than those fed the casein diet, even though the casein diet had stimulated twice as much endogenous excretion than the protein-free diet. As a consequence, apparent digestibility and biological value of bean protein are generally underestimated, although the "real" biological value was not affected by the endogenous nitrogen excretion of the rat.     

Two polyol,low digestible carbohydrates improve the apparent absorption of magnesium but not of calcium in healthy young men

The effects of nondigestible oligosaccharides including polyols on intestinal mineral absorption have been studied extensively in animal experiments, but their impact on mineral absorption in humans remains to be established. We investigated the effects of feeding two fermentable, low digestible carbohydrates, on the apparent absorption and balance of calcium (Ca) and magnesium (Mg) in humans. Nine healthy young men were given a control diet with dextrose or polyols, low digestible, fermentable carbohydrates (LHBC, HPFL) for 32-d periods according to a 3 x 3 Latin-square design. During the 18-d period of adaptation, the products were administered gradually in liquid form, up to a maximum of 100 g/d, which was then consumed for 14 d. Ca and Mg levels were measured in diets and in fecal and urine collections to assess apparent mineral absorption and balance. The relative apparent absorptions of Ca and Mg from the control diet were (means +/- SEM) 33.3 +/- 4.6 and 39.8 +/- 2.7%, respectively. Ingestion of both low digestible carbohydrates significantly increased the relative apparent absorption of Mg by about 25%. LHBC, but not HPFL, ingestion increased urinary Mg excretion. Apparent absorption, urinary excretion and balance of Ca were not altered by the ingestion of either low digestible carbohydrate. Ingestion of the low digestible, fermentable carbohydrates, with balanced diets, improved apparent Mg absorption without significant effects on apparent absorption or retention of Ca in healthy young men. Further human studies are therefore still needed to confirm the effects of these products in other populations.     

Calcium from milk or calcium-fortified foods does not inhibit nonheme-iron absorption from a whole diet consumed over a 4-d period

BACKGROUND: Single-meal studies have indicated that calcium inhibits iron absorption in humans. However, numerous dietary factors influence iron absorption, and the effect of calcium may not be as pronounced when calcium is served as part of a whole diet. OBJECTIVE: We investigated the effect of 3 sources of calcium served with the 3 main meals on nonheme-iron absorption from a 4-d diet. DESIGN: (59)Fe absorption was estimated from whole-body retention measurements in 14 women aged 21-34 y, each of whom consumed four 4-d diets in a randomized crossover design. The diets differed in the source of calcium as follows: a basic diet (BD) with a low content of calcium (224 mg Ca/d), a BD with a glass of milk served at each meal (826 mg Ca/d), a BD with calcium lactate (802 mg Ca/d), and a BD with a milk mineral isolate containing calcium (801 mg Ca/d). The 2 latter calcium sources were added to selected foods of the BD (rye bread, white bread, chocolate cake, and orange juice), and these foods were consumed with the 3 meals. All diets provided 13.2 mg Fe/d. RESULTS: No significant differences in nonheme-iron absorption were found between the BD and the BD supplemented with milk, calcium lactate, or the milk mineral isolate [7.4% (95% CI: 5.3%, 10.5%), 5.2% (3.5%, 7.9%), 6.7% (5.0%, 8.9%), and 5.1% (3.2%, 7.9%), respectively; P = 0.34]. CONCLUSION: Consumption of a glass of milk with the 3 main meals or of an equivalent amount of calcium from fortified foods does not decrease nonheme-iron absorption from a 4-d diet.