High Calcium Group Research Articles

Effect of diets with different calcium and phosphorus contents on the skeletal development and blood chemistry of growing great danes

The skeletal development of three groups of great dane dogs, fed a diet composed according to the published nutritional requirements for dogs (controls) or with increased calcium or calcium and...

Effects of dairy food supplements on bone mineral density in teenage girls

Bone mineral density (BMD) is largely genetically determined and this influence is most powerful in the period of rapid skeletal development in childhood and late adolescence but environmental factors such as exercise and dietary calcium intake may influence up to 20%. The aims of the study were to examine healthy late adolescent females for the effects and benefits of a high calcium intake from dairy product foods on bone mineral density, body composition, lipids and biochemistry. The secondary aim is determine whether a high intake of dairy product foods in the diet is acceptable for this age group long term. Ninety-one teenage girls who participated in a two-year randomised controlled study on the effect of dairy food supplementation on dietary patterns, body composition and bone density in post-pubertal teenage girls were approached one year after the cessation of the study to determine the effects of the cessation of dairy supplements on bone mineral density, dietary habits, biochemical markers, body composition and blood lipids. Bone mineral density and bone mineral content were assessed at the hip, spine and total body. Anthropometric data were collected, and exercise, Tanner, dietary assessment, preference and compliance questionnaires were administered. Lipid profiles, hydroxyproline excretion and urinary calcium and sodium excretion measurements were performed. There were no significant differences between the 2 groups for height, weight, lean and fat mass. The supplemented group had significantly higher calcium, phosphorus and protein intake during the supplementation period (p < 0.001). No differences were seen between the groups 12 months after supplementation finished. There were no significant differences in exercise level, preference or acceptability of dairy products or in the lipids and bone markers between baseline the end of supplementation and 1 year follow-up. There was a significant increase in trochanter (4.6%), lumbar spine (1.5%) and femoral neck (4.8%) BMD (p < 0.05) in the high calcium group at the end of supplementation. There was an increase in bone mineral content at the trochanter (p < 0.05) and lumbar spine; however the latter was not statistically significant, in the high calcium group at the end of supplementation. There was no difference in vertebral height or width at any stage of the study, indicating no influence on bone size. In this 3 year study (2 years of supplementation, 1 year follow-up), teenage girls, aged 15-18 years, were able to significantly increase their BMD at the trochanter, femoral neck and lumbar spine when supplemented with dairy product foods to a mean calcium intake of 1160 mg/d. There was also an effect seen on the BMC particularly at the trochanter and to a lesser extent at the lumbar spine. The dietary calcium intake achieved did not adversely affect body weight, fat and lean mass or blood lipid profiles. Twelve months after the supplementation finished the girls had returned to their baseline diet, indicating self-selection of a high dairy product diet may be hard to achieve.

Health status improvement after surgical correction of primary hyperparathyroidism in patients with high and low preoperative calcium levels

Background: We conducted a prospective cohort study to determine whether there are differences in functional health status between patients with low (<10.9 mg/dL) and high (≥10.9 mg/dL) serum calcium levels before surgical correction of primary hyperparathyroidism (HPT) and to compare changes in health status after correction of primary HPT. Methods: The SF-36 Health Survey, which provides demographic and condition-specific information, was used to obtain information on patients with primary HPT seen in a university hospital endocrine surgery clinic over a 4-year period before operation and again 2 months and 6 months after operation. Results: A total of 155 patients were studied; 86 had calcium levels <10.9 mg/dL (normal <10.5 mg/dL) and 69 had serum calcium levels ≥10.9 mg/dL (range 10.9 to 13.4 mg/dL). One hundred four patients completed 6-month reports, 55 with low calcium levels and 49 with high calcium levels. Both high and low calcium groups showed marked and virtually identical impairment of functional health status. Both groups showed marked improvement in health status at 2 months and additional improvement at 6 months, returning to normal or near normal in 6 of 8 SF-36 domains. Conclusions: Patients with primary hyperparathyroidism have significant functional health status impairment independent of the level of serum calcium. Dramatic improvement is seen after surgical correction. Referral for surgical treatment of primary HPT should not be delayed until serum calcium is elevated, as recommended in the 1990 National Institutes of Health consensus statement. (Surgery 1999;125:608-14.)

Health status improvement after surgical correction of primary hyperparathyroidism in patients with high and low preoperative calcium levels

Background: We conducted a prospective cohort study to determine whether there are differences in functional health status between patients with low (<10.9 mg/dL) and high (≥10.9 mg/dL) serum calcium levels before surgical correction of primary hyperparathyroidism (HPT) and to compare changes in health status after correction of primary HPT. Methods: The SF-36 Health Survey, which provides demographic and condition-specific information, was used to obtain information on patients with primary HPT seen in a university hospital endocrine surgery clinic over a 4-year period before operation and again 2 months and 6 months after operation. Results: A total of 155 patients were studied; 86 had calcium levels <10.9 mg/dL (normal <10.5 mg/dL) and 69 had serum calcium levels ≥10.9 mg/dL (range 10.9 to 13.4 mg/dL). One hundred four patients completed 6-month reports, 55 with low calcium levels and 49 with high calcium levels. Both high and low calcium groups showed marked and virtually identical impairment of functional health status. Both groups showed marked improvement in health status at 2 months and additional improvement at 6 months, returning to normal or near normal in 6 of 8 SF-36 domains. Conclusions: Patients with primary hyperparathyroidism have significant functional health status impairment independent of the level of serum calcium. Dramatic improvement is seen after surgical correction. Referral for surgical treatment of primary HPT should not be delayed until serum calcium is elevated, as recommended in the 1990 National Institutes of Health consensus statement. (Surgery 1999;125:608-14.)

Effect of environmental calcium levels on calcium uptake in tilapia larvae Oreochromis mossambicus

Effects of environmental calcium concentrations on the survival, growth, body calcium content and calcium uptake kinetics in developing tilapia (Oreochromis mossambicus) larvae were studied. Fertilized eggs were incubated in high- and low-calcium artificial freshwater (0.88-0.96 mmol l(-1) vs. 0.02-0.03 mmol l(-1) CaCl2 or CaSO4) until 3 days after hatching. Tilapia larvae showed similar hatching rates and wet weights in either high- or low-calcium medium, indicating neither the development nor the growth in tilapia larvae was affected by the environmental calcium levels. The body calcium content in low-calcium groups was about 90-95% that of high-calcium groups, No matter what calcium source was used (CaCl2 or CaSO4), acclimation to low calcium medium caused a stimulation of calcium uptake (measured in 0.2 mmol l(-1) calcium),i.e., 1.2-1.3 fold higher than that of high calcium groups. This enhanced calcium uptake capacity was characterized by a 50% decrease in Km and a 25% increase in Jmax. Effect of different calcium salts on calcium influx was significant only in low calcium level,i.e., calcium influx in low-CaCl2 group higher than that in low-CaSO4 group. These results suggest that tilapia larvae are able to modulate their calcium uptake mechanism to maintain normal body calcium content and growth in environments with different levels of calcium.

Magnesium balance in adolescent females consuming a low- or high-calcium diet

Increasing emphasis is being placed on optimizing calcium intake during growth as a way to enhance peak bone mass. Although some studies in adults have shown that high calcium intake may negatively affect magnesium utilization, few data are available regarding the interaction of calcium and magnesium in healthy children. The purpose of our study was to measure the effect of calcium intake on magnesium balance in 26 adolescent girls (mean age 11.3 y) during a 14-d period. Subjects ate a controlled basal diet containing 667 mg Ca and 176 mg Mg. In addition to the basal diet, subjects were randomly assigned in a double-blind fashion to consume 1000 mg elemental Ca/d as calcium citrate malate or a placebo. Magnesium use did not differ between the low-calcium and high-calcium groups as measured by absorption (50% compared with 55%), urinary excretion (70 compared with 74 mg/d), and fecal excretion (88 compared with 79 mg/d). Accordingly, magnesium balance was not different in subjects consuming 667 or 1667 mg Ca/d and averaged 21 mg Mg/d for the whole study group. Magnesium balance was significantly correlated with magnesium intake (r = 0.511, P = 0.008) and magnesium absorption (r = 0.723, P < 0.001). Prediction intervals from the regression of magnesium balance on intake indicated that the current recommended dietary allowance of magnesium would result in magnesium balance > or = 8.5 mg/d in 95% of the girls. This value appears consistent with long-term accretion rates needed to account for the expansion of the total-body magnesium pool during growth. In summary, our observations support the adequacy of the current recommended dietary allowance for magnesium and indicate that alterations in magnesium utilization should not be anticipated in adolescent females consuming a high-calcium diet.

Role of calcium intake in modulating age-related increases in parathyroid function and bone resorption.

Serum parathyroid hormone (PTH) and bone resorption increase in elderly women and contribute to age-related bone loss. Whether these abnormalities are caused by calcium deficiency resulting from age-related decreases in absorption and renal conservation is unclear. We studied 28 normal elderly women (mean +/- SD, age 69.3 +/- 2.7 yr) who were maintained for 3 yr on usual calcium intake levels (20.4 +/- 7.2 mmol/day [815 +/- 289 mg/day]; n = 15) (known as the usual calcium group) or high calcium intake levels (60.4 +/- 6.5 mmol/day [2414+/260 mg/day]; n = 13) (known as the high calcium group) and a reference group of 12 normal young adult women (age 30.1 +/- 4.4 yr), whose calcium intake was 23.0 +/- 4.8 mmol/day (918 +/- 193 mg/day) (known as the young group). Serum PTH was measured every 2 h, and urinary excretion of deoxypyridinoline (Dpd), a new marker for bone resorption, was measured in 4 h collections. Parathyroid gland secretory capacity was assessed during induced hypocalcemia. The mean 24 h serum PTH was 40% lower (P < 0.001), and the mean 24 h urinary Dpd was 35% lower (P < 0.005) in the high than in the usual calcium group. Mean parathyroid gland secretory capacity also was 47% lower (P < 0.005) in the high calcium group than in the usual calcium group. However, the usual calcium group had a mean 24 h serum PTH level that was 70% higher (P < 0.001) and a mean 24 h urinary Dpd level that was 30% higher (P < 0.005) than the young group, whereas the high calcium group was indistinguishable from the young group. Thus, failure of elderly women to increase their calcium intake to offset age-related increases in calcium requirement contributes substantially to their development of increased parathyroid activity and increased bone resorption, whereas a high calcium intake can reverse both abnormalities.

Dietary calcium reduces blood pressure, parathyroid hormone, and platelet cytosolic calcium responses in spontaneously hypertensive rats.

Dietary calcium effects on blood pressure, parathyroid hormone (PTH), and platelet cytosolic calcium concentrations were investigated. The dietary calcium (low, 0.2%; medium, 0.5%; and high, 2.0% wt/wt) was supplemented in spontaneously hypertensive rats from 6 through 22 weeks of age. Mean systolic blood pressure was decreased by age 12 weeks with calcium supplementation (low, 227 +/- 6 mm Hg; medium, 211 +/- 6 mm Hg; and high, 182 +/- 7 mm Hg; P < .001). By the 10th week of age, the low calcium group had significantly (P < .05) more elevated (44 +/- 2.3 pg/ml) plasma PTH compared with the high calcium-supplemented group (15 +/- 4.5 pg/mL). Regression analysis showed a significant (P < .001) positive correlation (r = 0.3) between systolic blood pressure and PTH. The platelet cytosolic calcium concentration was determined using the fura-2 method. The basal calcium was 134 +/- 5.5 nmol/L for the low calcium group and thrombin increased to 228 +/- 8 nmol/L (P < .0001; +70% change). The normal calcium group had 202 +/- 8 nmol/L; thrombin increased to 239 +/- 10 nmol/L (P < .0026; +19% change). The high calcium group had basal levels 145 +/- 7 nmol/L, with thrombin stimulating to 212 +/- 8 nmol/L (P < .0001; +46% change). Although thrombin increased platelet cytosolic calcium concentration in all groups, normal and high dietary calcium groups had smaller percentage increases (51% and 24% lesser, respectively) compared with the low dietary calcium group.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative Effects of Calcium Deficiency and Supplements on the Intestinal Absorption of Zinc in Rats.

The purpose of this study was to clarify the influence of calcium on zinc status. The animals were divided into four groups consisting of five rats in each group. The control group was fed on basal diet with adequate levels of zinc and calcium while the experimental group was fed diets containing different levels of calcium ad libitum for 15 d. Low calcium did not significantly affect the zinc absorption percentage but there was a decrease in high and very high calcium groups. The retention percentage changes were found parallel to the changes in the absorption percentage curve. When the zinc distribution was expressed as per g of dry tissue, duodenum, brain, and liver zinc content increased in the low calcium group but a decrease in duodenum, ileum, and liver in the high and very high calcium groups was observed. Also the 65Zn amount in some tissues and blood increased substantially in the low calcium group, decreased in the high and very high calcium groups. These results suggest that calcium affects zinc status in rats.

Calcium Carbonate Exacerbates Glomerular Capillary Hypertension and Injury in Rats With Desoxycorticosterone-salt Hypertension

To examine the effects of dietary calcium supplementation on systemic and renal hemodynamics and glomerular injury in experimental hypertension, rats with desoxycorticosterone-salt hypertension were fed either standard chow, containing 1% calcium by weight, or chow supplemented with calcium carbonate to achieve a calcium content of 2% by weight. Ingestion of calcium carbonate failed to reduce systemic blood pressure, but was associated with increased proteinuria and morphologic evidence of glomerular injury. Micropuncture studies revealed that afferent arteriolar resistance was reduced and glomerular capillary pressure further increased in the high calcium group. Thus, calcium carbonate, in moderate amounts, not only failed to ameliorate systemic hypertension but, paradoxically, worsened intrarenal hypertension and injury in rats with mineralocorticoid-induced hypertension.

The Effects of Dietary Calcium on Blood Pressure in Spontaneously Hypertensive Rats May Be Mediated by Parathyroid Hypertensive Factor

A high calcium intake has been shown to attenuate the degree of hypertension in spontaneously hypertensive rats (SHR) and some human hypertensives. Conversely, a low calcium intake has been associated with an increase in blood pressure in both groups. In the present study, the effects of a high (2%), medium (0.6%) and low (0.02%) calcium diet on mean arterial pressure (MAP) and on the expression of a novel circulating hypertensive factor--parathyroid hypertensive factor (PHF)--were examined in SHR. In rats on the low calcium diet, MAP and PHF activity were significantly higher at 8 weeks than in the other two groups. In the high calcium group, MAP was significantly lower than in the other two groups, although it was elevated compared to week 0 values. PHF activity was not detected in the plasma of this high calcium group. Overall, MAP was highly correlated with PHF activity (r = 0.78, P = .0001). These results suggest that the effects of dietary calcium on blood pressure in SHR may be mediated by a novel circulating hypertensive factor, PHF, such that a high calcium diet inhibits, and a low calcium diet stimulates, the expression of this factor.

The effect of dietary sodium on urinary calcium and potassium excretion in normotensive men with different calcium intakes

On the basis of their usual calcium intake, 12 healthy normotensive male students were divided into a low and a high calcium group. Both groups were provided with complete diets containing the same calculated quantities, expressed per MJ, of protein, fat, carbohydrate, sodium, potassium, phosphorus, and calcium. After an initial period of two weeks during which all participants received an additional 100 mmol sodium daily, 6 participants received an additional 22 mmol sodium/day (low sodium), the other 6 participants 178 mmol sodium/day (high sodium). After two weeks the sodium regimes were crossed over for a subsequent two-week period. When the second week of the low sodium period is compared with the second week of the high sodium period, the increase in the calcium/creatinine ratio, expressed on molar basis, was 0.059 for the low and 0.053 for the high calcium group (p less than 0.05). The increase in the molar potassium/creatinine ratio was 0.65 for the low and 0.03 for the high calcium group (p less than 0.025). However, after correcting for the calcium intake the effect in the low calcium group was found to be greater (p less than 0.05). Sodium supplementation was found to have no effect on blood pressure, but mean systolic (p less than 0.10) and diastolic in the high calcium group were lower. This suggests that calcium may well play a role in the regulation of blood pressure.

The influence of calcium intake on plasma calcium and 1,25-dihydroxycholecalciferol concentrations in parturient cows

The effects of a moderately low calcium diet (55 g/day) relative to one providing 120 g Ca/day were studied in 11 dairy cows during the last two weeks before and first week after parturition. The moderately low calcium diet was first fed to all the cows approximately five weeks before calving. The dietary calcium intake of five of these animals was increased to 120 g Ca/day five to 14 days before parturition. Although there were no instances of clinical parturient paresis in any of the cows the fall in plasma calcium concentration around and at parturition was significantly greater in those cows fed the high calcium diet prepartum than in those fed the low calcium diet. The prepartum plasma concentrations of 1,25-dihydroxycholecalciferol tended to be higher in the cows fed the lower calcium diet, although not significantly so. In contrast, these concentrations one day after parturition were higher in the high calcium group. It is concluded that a moderately low calcium diet fed to cows during the last five weeks of pregnancy reduces the likelihood of parturient paresis.

Effect of Dietary Calcium on Blood Pressure of Turkeys

The influence of dietary calcium intake on blood pressure of turkeys was studied in 20 male Broad Breasted White turkeys between 45 and 52 weeks of age. The average systolic (P<.01), diastolic (P<.01), and mean (P<.005) blood pressures were significantly lower in turkeys fed high dietary calcium (1.96%) than the turkeys with normal calcium diet (.98%). Concomitantly, the mean total heart weight (P<.05), left ventricular weight (P<.025), and heterophil to lymphocyte ratio (P<.02) were also significantly lower in the high dietary calcium group. These results indicate that high dietary calcium not only attenuates high blood pressure in turkeys but also reduces the development of left ventricular hypertrophy, which is a consequence of arterial hypertension. In addition, high dietary calcium also reduces the heterophil to lymphocyte ratio, which indicates a reduction of stress.

Effects of Dietary Calcium on Blood and Tissue Lipids, Tissue Phospholipids, Calcium and Magnesium Levels in Rabbits Fed Diets Containing Beef Tallow

Levels of lipids, calcium and magnesium in blood and tissue were examined in rabbits to determine the effects of 20% beef tallow diets containing three levels of calcium, less than 0.02, 0.8 or 1.6%. In plasma, the calcium-deficient (less than 0.02%) diet contributed to elevated cholesterol and phospholipid, but had no effect on triglyceride levels. Plasma calcium decreased in the calcium-deficient group and plasma magnesium decreased in the high-calcium (1.6%) group of rabbits. Lipid levels of some tissues varied with the level of dietary calcium. Cholesterol, total phospholipid, sphingomyelin and phosphatidylethanolamine were generally elevated in livers of calcium-deficient rabbits, but the individual phospholipids were decreased in skeletal muscle. Lungs of the calcium-deficient group also had lower phospholipid levels than the high-calcium group. Liver, kidneys, brain and adipose tissue triglyceride levels were highest in the high-calcium group. The calcium level of skeletal muscle was lower in the calcium-deficient group than in the high-calcium group. Calcium in brain and adipose tissue were highest in the calcium-deficient group. Except for adipose tissue, magnesium levels of the tissues studied were not affected by dietary calcium.

INHIBITION OF GROWTH OF Macrobrachium rosenbergii BY CALCIUM CARBONATE WATER HARDNESS

ABSTRACTSlow growth of adult Macrobrachium rosenbergii in grow‐out ponds having calcium water hardness of 305 to 638 mg/liter calcium carbonate was observed, as was frequent encrustation with Bryozoa sp. and Epistylus sp.Adult M. rosenbergii of ages 5, 13, and 14 months were held in calcium carbonate solutions of from 0.65 to 5.00 mM/liter Ca (65 to 500 mg/liter CaCO3) for up to 90 days. Average daily weight gain was found to be five times greater in the lowest calcium concentration for 5‐month‐old prawns compared with the high calcium group. A seven‐fold difference was found in standard length gains. Lower differences were found for 13 and 14‐month‐old prawns, and a lengthening of the molt cycle in high calcium water was seen.Differences were also seen in post‐molt hemolymph calcium, inorganic phosphorus, and refractive index but not sodium, potassium, chloride, or osmolarity.

Increased cardiac contractility in high calcium perfusion and protein synthesis

Cardiac stress produced by pressure overload results in increased protein synthesis, but it has not been possible to separate the effects of increased contractile action, <i>per se</i>, from those of increased pressure. In a model, where coronary flow may be controlled, right ventricular contractility, measured by d<i>P</i>d<i>t</i> max and Δ<i>P</i> (systolic minus diastolic pressures) was ascertained during perfusion with varied calcium concentrations while the pulmonary artery pressure was kept constant at control levels. In high calcium (4.8 mm CaCl₂) d<i>P</i>/d<i>t</i> max was 165 compared to 51 mmHg. s⁻¹ in controls (1.2 mm CaCl₂) with the Δ<i>P</i> nearly doubled in the high calcium perfusion. Although these parameters of contractility increased in the high calcium perfusion to the same degree as with pressure overload in this model, protein synthesis was the same as in the controls with incorporation of [¹⁴C]lysine 30.9 μmol. g⁻¹ protein N in the high calcium group and 31.1 μmol in the controls. The high calcium group also showed increased protein N and higher ATP levels in the face of unchanged water content or extracellular spaces. The results suggest that neither high calcium perfusion nor increased contractility <i>per se</i> are stimuli for increased cardiac protein synthesis.

The Effect of Calcium Level of Diet on the Metabolism of Calcium, Phosphorus and Magnesium in Pregnant Rats

Metabolism of calcium, phosphorus and magnesium during pregnancy was investigated with 20 primigravida albino rats about 170g body weight of Wister Imamichi strain fed with diets containing Ca 0.534 and 1.077% respectively.The animals were divided into four groups (A, B, C and D), and in the early period of pregnancy, A and B group were fed with low-Ca diet and C and D group were fed high-Ca diet. In the middle period, A and D group fed with low, and B and C group with high, then in the last period A and B fed with high, and C and D with low Ca diet.In the early period, calcium retention increased with the amount of calcium intake, therefore the absorption and the utilization of calcium were better in high calcium groups. In the middle and last period, the absorption rate was decreased and the amount of calcium retention of group C was smaller than that of calcium requirement for growth of fetuses.It seemed that the calcium need to fetuses was removed from the calcium stored in mother rat during the early period of pregnancy.From these results, it is considered that high calcium feeding in the middle or in the last period of pregnancy have no effect on calcium utilization, therefore it is preferable to feed high calcium diet from the beginning of pregnancy.Absorption and utilization of phosphorus in diet are affected by it Ca/P ratio, and the rats of high-Ca group utilized P better than that of the low-Ca groupMetabolism of magnesium resembles to that of phosphorus, and high Ca/Mg ratio in diet seems to have good effect on magnesium utilization.

Effect of a low calcium diet on bone crystallinity and skeletal uptake of Ca45 in rats.

SummaryChemical and X-ray diffraction analyses were performed on femurs of rats receiving a low (0.1%) and high (0.8%) calcium diet with (50 ppm) and without (0 ppm) fluoride supplementaton in the water. In addition, uptake of Ca45 by the ends and shafts of tibia was determined. Bone crystal-linity (i.e., crystal size and/or perfection) was not affected by calcium intake, and the improvement in crystal texture produced by fluoride was the same for the high and low calcium groups. Skeletal uptake of radiocalcium was approximately 20 times higher in calcium deficient animals. Fluoride decreased slightly the uptake of radiocalcium.

Observations on the calcium balance of laying hens

Two groups of Single Comb White Leghorn pullets, 4 months of age, were fed 1·85 and 2·70% calcium in the diet, respectively, for twelve consecutive periods, each consisting of 4 weeks.Records of egg production and egg weight were kept throughout the entire experiment for each hen. Calcium balance and egg-shell quality studies were conducted with 16 pullets for 5 consecutive days out of each 28-day period.A highly significant difference between the lots favouring the high-calcium birds was found in egg production, shell weight, and calcium retention. There were no significant differences between the lots in percentage calcium retention, food consumption, and body weight. The high-calcium group was shown to retain more calcium from the feed and excrete more calcium through eggs. Calcium retention and percentage calcium retention increased upon commencement of egg production to reach a maximum at the second period of production. Both remained fairly constant thereafter.The hens went into negative balance early in production and returned to positive balance during the later part of the first laying year. The return to positive balance could be explained by an increase in calcium retention and a decrease in egg production. There was no reduction in shell weight, or shell weight per unit surface area during the period covered by this trial.