Ca Bioavailability Research Articles

Mineral bioavailability and bone mineral contents in pigs given calcium carbonate postprandially

We have further investigated the “meal effect” on mineral bioavailability in pigs by mineral balance studies and measurements of bone ash contents and bending moment. A group of seven pigs (CAA) was given all its dietary Ca as CaCO 3 5 h after the first daily meal for 8 weeks. The control group of seven pigs received CaCO 3 in the meal. Both groups were given normal P within the meals. Ca and P absorption and retention were evaluated by a 10-day balance trial. Several bones were collected at slaughter to determine bone ash, Ca, and P contents and bending moment (three-point bending test). Ingesting Ca after the meal did not affect Ca bioavailability or phosphorus absorption, but did reduce P retention, which in turn decreased the bone scores. Osteopenia, indicated by decreased total mineral contents of bones (and decreased ash:bone volume ratio), was associated with elevated plasma osteocalcin in the CAA group. Thus, CaCO 3 need not be incorporated into a meal for high Ca absorption, provided that Ca is given after a meal, but simultaneous intakes of Ca and P are required for the best mineral retention.

The composition of Indian foods—mineral composition and intakes of Indian vegetarian populations

AbstractThe trace element (Fe, Mn, Zn and Cu) and Ca and P contents of cereals, legume grains, vegetables, milk products and oilseeds commonly consumed by Indian vegetarians were determined. Green leafy vegetables contained the highest amounts of Fe, Mn and Cu (15–171, 90–133 and 4–21 mg kg−1, respectively); buffalo milk, buttermilk and curd contained most zinc (53–63 mg kg−J). Legumes contained the highest levels of P, whilst buffalo milk and curd, and leafy vegetables possessed most Ca. The levels of these elements in prepared foods and diets were entirely consistent with the above findings. In general, the mineral intakes of the populations of children (4–9 years), adolescents (10–19), adults (20–45) and older adults (45–60) examined in this study were lower for Zn and Ca, similar for Fe and Ca, and higher for Mn and P than the recently prescribed Indian Recommended Dietary Allowances (RDAs). It is likely that other constituents of cereals and pulses, such as fibre and phytate, will greatly reduce the bioavailability of trace minerals and Ca in Indian vegetarian diets. In contrast to earlier studies, no significant overall differences were observed between populations from farming and non‐farming backgrounds.

Bioavailability of calcium from bovine-bone-marrow calcium (BBMCa) and calcium carbonate in vitamin D-deficient rats

Bovine-bone-marrow calcium (BBMCa) has been widely used for the enrichment of Ca in foods. However, its biological availability in humans and animals has not yet been fully clarified. We have therefore investigated the bioavailability of Ca from unsterilized BBMCa (UBBMCa), sterilized BBMCa (SBBMCa) (both of which are commercially available), and Ca carbonate as a control compound. Vitamin D-deficient rats were used to examine the Ca bioavailability of the BBMCa, these being unaffected by the vitamin D nutritional status in the animals. Vitamin-D-deficient rats were fed ad libitum a vitamin D-free 1.20% Ca diet prepared by using UBBMCa, SBBMCa, or Ca carbonate as Ca sources for 28 days. Body weight plasma Ca level, and alkaline-phosphatase activity (Alp) of the rats were measured periodically. The femoral-bone-mineral density and biomechanical strength of the rats were also measured after the feeding period. The UBBMCa and SBBMCa groups showed a rapid increase in plasma-Ca level to the normal range and an increase in bone-ash weight, bone-mineral density, and biomechanical strength, the values of which were significantly higher than those in the Ca carbonate group. The bioavailability of Ca from UBBMCa was substantially equal to that from SBBMCa in increasing plasma Ca level, bone-mineral density, and bone biomechanical strength. These findings suggest that the bioavailability of Ca from UBBMCa and SBBMCa is much higher than that of Ca carbonate in the vitamin D-deficient state, and they are available as Ca sources for the enrichment of Ca in food.

Bioavailability of calcium from oyster shell electrolysate and DL-Calcium lactate in vitamin D-replete or vitamin D-deficient rats

Bioavailability of calcium (Ca) from oyster shell electrolysate (Active Absorbable Ca: AACa) and DL-Ca lactate in rats was investigated. Plasma Ca metabolism, bone mineral density and vitamin D-deficient rats were measured and compared each other. Vitamin D-deficient rats were fedad libitum a vitamin D-free diet containing 0.44 % Ca or 1.20 % Ca adjusted with either AACa or DL-Ca lactate with or without oral supplementation of physiological dose (10 IU/rat/day) of vitamin D3 for 28 days. During and after feeding, concentrations of Ca, phosphorus, parathyroid hormone (PTH), 25-hydroxyvitamin D3 (25-OH-D3), 1α, 25-dihydroxyvitamin D3 [1, 25(OH)2D3] and alkaline phosphatase (Alp) activity in plasma were measured. Furthermore, femoral Ca and phosphorus contents, mineral density and mechanical strength were also measured. Despite of the differences of contents and chemical forms of Ca in diets, all the groups showed prompt and complete recoveries in both Ca and vitamin D malnutritions under vitamin D-replete condition and there was no significant difference among all the groups in increases of body weight gains and plasma Ca levels, and in decreases of plasma PTH level and Alp activity. In contrast, the groups fed the same diets under vitamin D-deficient condition showed no significant recoveries in both plasma Ca metabolism and bone mineralization although Ca bioavailability of AACa appeared to be slightly better than that of DL-Ca lactate. These results suggest that bioavailability of Ca from AACa and DL-Ca lactate are substantially equal in increasing plasma Ca levels, bone mineral density and mechanical strength in both vitamin D-replete and vitamin D-deficient rats.

Effect of age, calcium source, and radiolabeling method on whole body 47Ca retention in the rat

In a longitudinal study we determined the effect of animal age as well as Ca source and radiolabeling method on Ca bioavailability by measuring whole body 47Ca retention (WBR) in male Sprague-Dawley rats. The WBR assay was performed without surgery or anesthesia, and the same groups of animals were studied at 8, 16, 20, and 32 wk of age. Rats were administered a 6-mg radiolabeled oral dose of Ca as Ca citrate malate (CCM) or intrinsically or extrinsically labeled CaCO3 or hydroxyapatite (HAP). Fractional Ca retention was measured from the 72-h postdose WBR divided by WBR at time 0. WBR was significantly affected by Ca source with CCM > CaCO3 > HAP at all ages (P < 0.001). The rank order and relative bioavailabilities of these Ca salts in the rat model agreed well with literature values for Ca absorption in adult humans. Although percent WBR decreased significantly with advancing age (P < 0.001), the mean rate of decline (-3.4%/wk) was not affected by Ca source. Extrinsic radiolabeling overestimated (approximately 20%) Ca bioavailability when the rats were young. However, the magnitude of this effect diminished with advancing animal age and was not significant across all ages (repeated measures analysis of variance P = 0.10).

Changes in calcium and phosphorus absorption and retention during long-term magnesium deficiency in rats

The effects of a dietdeficient in magnesium (0.022% Mg) on the bioavailability of dietary Ca and phosphorus were studied in Wistar rats after 1, 5, 6, 7, 8, 9 and 10 weeks. Feeding with a diet deficient in Mg significantly increased Ca absorption and balance from the first week until the end of the experimental period, and increased phosphorus absorbed in weeks 9 and 10. However, phosphorus balance became negative in first week of study, as a result of phosphaturia.

Phytic acid and selected mineral composition of seed from wild species and cultivated varieties of lupin

Seeds of wild lupin species and several cultivars were analyzed for phytate, calcium, zinc, iron, copper and manganese composition. Mineral content showed high variability within varieties, particularly Mn, with 61–327 mg/100 g dry matter for L. albus and 1·5–38 mg/100 g dry matter between other species. The ranges (mg/100 g dry matter) of other minerals were: Ca, 134–350; Fe, 2·4–10·8; Zn, 2·9–17·6; Cu, 0·4–1·4. Phytate varied from 0·4 to 1·2 g/100 g dry matter with cultivars of L. albus and L. cosentinii presenting the lowest values. Very low phytate: Zn and (phytate × Ca) : Zn molar ratios were observed in wild L. digitatus (4·4 and 0·3) and L. pilosis P23030 (5·3 and 0·3), indicating excellent Zn bioavailability. Phytate : Ca molar ratios of all samples indicate similar or better bioavailability of Ca as compared to other legume seeds.

Bioavailability of calcium in sun-cured alfalfa meal and effect of dietary calcium concentration on bone and plasma characteristics during two phases of gestation in gilts.

A study was conducted with gravid gilts to determine the bioavailability of Ca in sun-cured alfalfa meal (AM) and the effect of dietary Ca concentration on bone and blood characteristics during two phases of gestation. Two Ca sources (AM and CaCO3), three dietary concentrations of Ca (50, 75, and 100% of the NRC requirement), and two gestation phases (55 and 105 d) were used in a 2 x 3 x 2 factorial arrangement in a randomized design with five replications (60 gravid gilts). Response criteria were as follows: 1) plasma Ca, P, and alkaline phosphatase (AKP) measured at the onset and at 25-d intervals and 2) metacarpal (MC) and metatarsal (MT) bone breaking strength (kilograms), ash content (percentage), density (grams/cubic centimeter), and ash density (grams of ash/cubic centimeter) at the conclusion of the experiment. Plasma Ca, P, and AKP concentrations were similar between Ca sources. Because the response between Ca sources was similar, the data were pooled among sources. There was a linear decline in plasma P and AKP (P < or = .05) as dietary Ca concentration increased. As gestation progressed from 0 to 100 d, there was a decline (P < .05) in plasma Ca and P. There were no differences in bone breaking strength and ash between Ca sources in either the MC or MT. No differences in bone strength between gestation phases occurred. A gestation phase x dietary Ca concentration interaction (P < .05) was observed for bone ash in both bones.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioavailabilities of calcium, phosphorus and magnesium from whey mineral complex in growing male rats.

The bioavailabilities of Ca, P and Mg from whey mineral complex (WMC) were studied from the viewpoint of the mineral balance and bone properties in growing male rats and compared with bovine bone ash (BBA) and CaCO3. Ca source showed no significant effect on feed intake, body weight gain or feed efficiency (p < 0.05). When the dietary Ca level was 0.3%, the dry weight of the femur in rats fed WMC was significantly higher than that in rats fed BBA. The femur P content of rats fed 0.3% Ca as WMC was significantly higher than that of rats fed BBA or CaCo3. The breaking energy of the femur from rats fed WMC was significantly higher than that from rats fed BBA at a Ca level of 0.2% or 0.3%. There was the same tendency in bone densities as was observed in breaking properties. There was no significant difference in quantitative values for Ca balance among three groups of rats, whereas those rats fed WMC had a significantly higher P retention than other groups. Ca bioavailability from WMC and the effect on the utilization of P and Mg were discussed.

Effect of casein, casein phosphopeptides and calcium intake on ileal 45Ca disappearance and temporal systolic blood pressure in spontaneously hypertensive rats.

Paracellular 45Ca absorption and temporal systolic blood pressure (SBP) measurements were recorded in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats fed on casein (C) and soya-bean-protein isolate (S) diets, containing 20 (H), 5 (H) and 0.5 (L) g Ca/kg. Similar measurements were also taken in SHR rats only fed on C-M and S-M diets supplemented with 30 g caseinophosphopeptides (CPP)/kg. Absorption of 45Ca from the ileal loop was equivalent in both SHR and WKY animals and largely affected by the level of dietary Ca. In addition, animals fed on C diets exhibited significantly (P < 0.05) greater ileal absorption of 45Ca compared with S-fed animals. This result was attributed to the presence of CPP and a greater (P < 0.05) proportion of soluble 45Ca in the contents of the ileum. Animals fed on S diets supplemented with CPP confirmed this finding. The SBP of SHR rats was higher (P < 0.01) than WKY controls after 9-10 weeks of age. The temporal pattern of observed hypertension was independent of dietary influence in the SHR. The severity of hypertension in SHR rats was affected only by dietary Ca deficiency, and not by Ca supplementation or CPP enhancement of Ca bioavailability. These findings suggest that tryptic digestion products of casein in milk can enhance Ca bioavailability by increasing Ca solubility; however, this action had no effect in reducing hypertension in SHR.

Comparative Uptake of Calcium From Milk and a Calcium-Rich Mineral Water in Lactose Intolerant Adults: Implications for Treatment of Osteoporosis

Despite the links between low calcium (Ca) intake and age-related bone loss, hypertension, and colon cancer, the majority of Western populations have average daily Ca intakes substantially below recommended daily allowances. Although dietary products are widely known as a rich and valuable source of Ca in the diet, consumption of diary products is low and has been decreasing because of perceptions of excess calories and fat in the diet, as well as taste aversions. During the last decade, a marked increase in the consumption of bottled waters has occurred. Since some of these waters are characterized by high concentrations of Ca, we have studied Ca bioavailability from a Ca-rich water, using 15 lactose intolerant male individuals as subjects, and compared such bioavailability to that from milk. We report herein that the bioavailability of Ca from the water was generally as good as or better than that from milk, a food product well known for its very high Ca bioavailability. Indeed, in eight of 15 subjects, there was a higher level of Ca absorption from mineral water than from milk; bioavailability was equal in five of 15 subjects; in contrast, in two of 15 subjects, the bioavailability of Ca absorption from milk was greater than that from the mineral water. The potential implications of this observation for the prevention and management of age-related bone loss are important for preventive medicine and indicate a new, important source of dietary Ca for lactose intolerant individuals.

Lactose, Calcium Source and Age Affect Calcium Bioavailability in Rats

Calcium bioavailability was defined as either retention of 45Ca in tibias (Experiment 1) or retention of 47Ca in carcasses (Experiment 2). In Experiment 1, rats (age 21, 40 or 100 d) were fed purified meals extrinsically labeled with 45Ca. The meals contained either 0.5% Ca (control) or 1% Ca [control supplemented with CaCO3, calcium citrate-malate (CCM), milk or cheese] and either no lactose or 20% lactose. Lactose increased Ca bioavailability (P less than 0.05) from the control and milk meals in all age groups. Increases from CCM and CaCO3 were significantly only in the 21-d-old group. Lactose did not affect bioavailability from cheese. In Experiment 2, suckling rats (age 7, 12 or 17 d) were gavaged with 47Ca-labeled milk (fluid skim or lactose-hydrolyzed fluid skim) or an aqueous CaCl2-casein mixture (containing either no sugar, glucose + galactose, or lactose). Bioavailability from milk was higher than from lactose-hydrolyzed milk in all age groups. Lactose and glucose + galactose increased bioavailability over the sugar-free CaCl2-casein mixture in all age groups. Data from these experiments show that lactose enhances Ca bioavailability at several stages of development and the effect is not markedly diminished by high Ca diets. Lactose increases Ca bioavailability from a variety of sources but the magnitude of the effect may vary among sources.

Bioavailability of calcium from four different sources

Bone mineralization and mineral retention were measured to evaluate calcium (Ca) bioavailability from four different sources at two dietary levels (40% or 100% of NRC requirement). The bioavailability of Ca from Ca carbonate, Ca citrate, tricalcium phosphate, and reduced particle size Ca citrate was determined in Sprague Dawley rats. Femur, feces and urine levels of phosphorus and magnesium were also determined. Animals (9/group) were fed semisynthetic diets containing 0.2% or 0.5% Ca from each source for seven weeks. A three-day Ca balance was determined during weeks four and seven. There was no significant effect of Ca source on percent Ca retained or femur Ca concentrations at either level of Ca tested. Animals fed the 0.2% Ca diets retained a larger percent of ingested Ca and had lower bone calcium levels than those fed 0.5% Ca Diets. When Ca intake was low, the source of Ca appears to influence bone strength and stiffness. These results indicate that, in the rat, there is no significant difference in Ca biovailability from the four sources tested.

Effects of Particle Size on the Biological Availability of Calcium and Phosphorus in Defluorinated Phosphate for Chicks ,

A total of 576 d-old, male, broiler chicks were used in two trials 1) to determine the range of Ca and P levels over which the response in bone characteristics is linear and 2) to determine the influence of particle size of defluorinated rock phosphate (DFP) on the bioavailability of Ca and P in DFP. Six treatments were used in Experiment 1 in which varying percentages of added Ca (.00, .06, .12, .24, .36, and .48%) and added P (.00, .05, .10, .20, .30, and .40%) were evaluated in a corn-soybean meal diet containing 23% CP, .47% Ca, and .39% P (.14% available P). Weight gain, feed intake, and tibia breaking strength increased (P<.001) with increasing levels of dietary Ca and P. Treatments in Experiment 2 consisted of: 1) Diet 1, a corn-soybean meal basal diet (23% CP, .50% Ca, .46% P, .21% available P), 2) Diet 1 with .12% added Ca from calcium carbonate (CC) and .07% added P from monosodium phosphate (MSP), 3) Diet 1 with .24% added Ca from CC and .14% added P from MSP, and 4 to 8), Diet 1 with .24% added Ca and .14% added P from five particle sizes of DFP. Feed intake, weight gain, and tibia breaking strength and ash percentage increased linearly (P<.01) and feed.gain ratio decreased quadratically (P<.10) with increasing percentages of added Ca and P in Diets 1 to 3. Feed intake, weight gain, bone breaking strength and bone ash did not differ (P>.10) among the five particle sizes of DFP or for the DFP versus the highest level of added CC and MSP. The availability of Ca and P in the DFP was determined by slope ratio; bone breaking strength and ash were regressed on added Ca and P intake. The bioavailability of Ca and P (combined), relative to that in CC and MSP (both given a value of 100%), in the five particle sizes of DFP was 101, 94, 87, 100, and 90%, respectively (P>.10). These data indicate that particle size, within the range tested, does not affect the bioavailability of Ca and P in DFP for the growing chick.

EFFECT OF MATURITY OF ALFALFA (Medicago sativa) AT HARVEST ON CALCIUM ABSORPTION IN GOATS

Alfalfa hay harvested at vegetative or full bloom stages of maturity was compared to a control diet, in which the calcium (Ca) source was mainly limestone. True Ca absorption was determined using an isotope dilution technique in three goats fed Ca at requirement. Mean Ca intakes of goats fed the control, vegetative or full bloom alfalfa were: 2.40 ± 0.405, 2.31 ± 0.393 and 2.47 ± 0.461 g d−1; bone calcium accretion rates were: 1.27 ± 0.294, 0.90 ± 0.319 and 1.21 ± 0.237 g d−1; total Ca absorption rates (percent of intake) were: 57.1 ± 2.46, 56.7 ± 8.07 and 54.3 ± 3.03, respectively. Although no differences in true Ca absorption among diets were observed in goats fed Ca at requirement, absorption rates exceeded 50% of intake and are higher than previous estimates. Maturity of alfalfa did not significantly affect Ca availability, although there was a trend for availability to diminish with maturity when absorption rates were corrected for Ca absorbed from other dietary ingredients (i.e., 55.8% availability for vegetative, 47.0% for full-bloom alfalfa). Replacing limestone with alfalfa did not alter Ca bioavailability in the total diet. Key words: Goats, calcium true absorption, alfalfa, maturity, limestone.

A Comparison of Intrinsic and Extrinsic Tracer Methods for Estimating Calcium Bioavailability to Rats from Dairy Foods

Dairy products doubly labeled with 45Ca and 47Ca were used to evaluate an extrinsic labeling procedure for calcium bioavailability determination. Nonfat milk, yogurt, and fresh cheese curd were prepared from caprine milk that was intrinsically labeled with 45Ca. The products were then labeled extrinsically with 47Ca and administered to rats by gavage. The 47Ca to 45Ca ratio in bone and teeth averaged about 1.00 with either milk, yogurt, or CaCl2, but the ratio was about 1.04 when dosed with cheese curd. Ca absorption, determined by whole-body counting of 47Ca, was lower (P less than 0.05) in cheese curd (59%) than in either milk (69%), yogurt (72%), or CaCl2 (72%). Expressed as percent of dose, the absorption of 47Ca was highly correlated with bone 47Ca (r = 0.973) and with bone 45Ca (r = 0.946). Correlation between tibia 47Ca and tibia 45Ca was r = 0.923. For the dairy products tested, our results indicated that extrinsic 47Ca was absorbed similarly to intrinsic 45Ca. Moreover, the percent of radioactive dose retained in bone appears to be a valid indicator of relative bioavailability of food Ca.

Effects of phytate reduction, fat extraction, and level of Ca on Ca and Zn bioavailability

The effect of phytate reduction, fat extraction, and addition of Ca in the form of skim or whole milk on Ca and Zn bioavailability from a breakfast containing bran muffins was studied in vitro and in vivo. Ca and Zn solubility were measured after in vitro simulated peptic and pancreatic digestion under pH conditions resembling those in the human GI tract. Absorption of Ca and Zn was measured in rats fed test meals tagged with 45Ca and 65Zn. Radioactivity in the femur and liver relative to levels found in rats injected with the isotopes served as criteria for 45Ca and 65Zn absorption, respectively. In vitro solubility was significantly depressed by the presence of phytate and inversely correlated with the phytate:Zn and the (phytate)(Ca):(Zn) ratios. Ca solubility was enhanced by extraction of fat and markedly increased by reduction in both fat and phytate. None of these effects was seen in vivo. However, 65Zn absorption was significantly decreased by fat extraction and phytate reduction although this treatment increased in vitro Zn solubility. Possible reasons for these discrepancies are discussed.

Mineral utilization of vegetarians: impact of variation in fat intake

One of the benefits associated with consumption of vegetarian diets is that these diets usually have lower contents of total fat and cholesterol and have more favorable polyunsaturated-to-saturated fatty acid ratios. Thus, use of vegetarian diets tends to fit recommendations relative to decreasing risk of cardiovascular disease. However, changes in level and kind of dietary fat may result in alterations in utilization of essential minerals. In studies carried out at the University of Nebraska using healthy human subjects, low-fat diets were found to inhibit the absorption of iron, zinc, manganese, and calcium. Further research indicated that both increase in fatty acid chain length and increase in saturation of fatty acids resulted in a decrease in Ca bioavailability. However, increased dietary cholesterol levels tended to increase Ca bioavailability.

Mineral balance studies in very low birth weight infants fed human milk

Mineral homeostasis often is disrupted in the very low birth weight (VLBW) infant fed either human milk or commercial formula that contains insufficient quantities of available calcium (Ca) and phosphorus (P). Alterations in mineral homeostasis include abnormal patterns of serum (Ca and P concentrations and alkaline phosphatase activity) and urine (Ca and P) biochemical markers, low net Ca and P retentions in comparison with intrauterine estimates of mineral accretion, and decreased bone mineral content. A two-phase study was conducted in our laboratory to test for these alterations in mineral homeostasis. In phase 1, VLBW infants fed a preparation of fortified human milk (either human milk-derived fortifier I or II or cow milk-derived fortifier) or cow milk-based formula specially designed for VLBW infants were evaluated during their hospitalization. In phase 2, after hospitalization, these infants were evaluated during the first 6 months of life when fed either their mother's milk or routine formula exclusively. The bioavailability of Ca and P from the tested preparations varied widely. Although the fortification of human milk resulted in both an improved biochemical pattern and net retention of Ca and P, optimal intrauterine mineral accretion was not achieved in any group tested. Longitudinal assessments of bone mineralization, by single photon absorptiometry, demonstrated that human milk-fed former VLBW infants had reduced bone mineral content. These investigations suggest that former VLBW infants fed human milk exclusively may be at risk for Ca and P deficiencies.

Intestinal absorption of Ca(H2PO4)2 and Ca citrate compared by two methods

The purpose of this study was to compare the absorption of calcium from two soluble Ca salts and determine if the oral Ca load test can be used as a simple measure of relative Ca bioavailability. Eight normal subjects ingested 750 mg Ca as solution of Ca(H2PO4)2 or Ca citrate (two occasions) tagged with 47Ca tracer. Absorption of Ca from the two salts was estimated from both the increase in forearm radioactivity and rise in urinary Ca (oral Ca load test). Both measures indicated that Ca was absorbed at least twice as well from Ca citrate as from Ca(H2PO4)2. However, the increment in urinary Ca 2-4 h after the oral load correlated with fractional absorption when only Ca citrate (r = 0.803, p less than 0.02) was ingested. For group comparisons the oral Ca load test is a rough index of Ca availability but cannot substitute for more direct measures of absorption in an individual.