Increase In Dietary Calcium Research Articles

ESTIMATION OF CALCIUM REQUIREMENT OF GROWING YANKASA LAMBS BY FACTORIAL METHOD


 
 
 
 Fifty-two Yankasa lambs of mixed sexes age, 6 to 8 months, were used in this study to determine calcium requirement. Varying levels of dietary calcium viz: 0.28, 0.42, 0.56, 0.70, 0.86, 0.99 and 1.15% were tested in a Completely randomized design. Phosphorus was kept constant at the level in the control ration. The criteria of adequacy employed included clinical observations, growth performance and mineral retention. No clinical abnormality was Observed among the groups throughout the experimental period. Although growth performance improved with increase in dietary calcium level, treatment effects among groups on 030, 0.86, 0.99 and 1.15% dietary levels were not significant (P > 0.05). Apparent dry matter digestibility and calcium retention improved with increase in dietary calcium. Mean calcium requirement for lambs was 305 mg/day/kg body weight. Comparisons with the findings of some temperate workers showed that while the endogenous calcium loss for lambs in this region was lower, their requirement for calcium Was higher than those in the temperate region
 
 
 

Calcium Deficiency Reduces Circulating Levels of FGF23

Fibroblast growth factor (FGF) 23 inhibits calcitriol production, which could exacerbate calcium deficiency or hypocalcemia unless calcium itself modulates FGF23 in this setting. In Wistar rats with normal renal function fed a diet low in both calcium and vitamin D, the resulting hypocalcemia was associated with low FGF23 despite high parathyroid hormone (PTH) and high calcitriol levels. FGF23 correlated positively with calcium and negatively with PTH. Addition of high dietary phosphorus to this diet increased FGF23 except in rats with hypocalcemia despite high PTH levels. In parathyroidectomized rats, an increase in dietary calcium for 10 days increased serum calcium, with an associated increase in FGF23, decrease in calcitriol, and no change in phosphorus. Also in parathyroidectomized rats, FGF23 increased significantly 6 hours after administration of calcium gluconate. Taken together, these results suggest that hypocalcemia reduces the circulating concentrations of FGF23. This decrease in FGF23 could be a response to avoid a subsequent reduction in calcitriol, which could exacerbate hypocalcemia.

Effect of crude protein and phosphorus level on growth performance, bone mineralisation and phosphorus, calcium and nitrogen utilisation in grower-finisher pigs

Two experiments in a 2 × 2 factorial arrangement were conducted to evaluate the effect of crude protein (CP) (130 vs. 200 g/kg) and phosphorus (P) (4.0 vs. 6.0 g total P/kg) level in a phytase supplemented diet (500 FTU [phytase units]/kg) in grower-finisher pigs. Owing to the design of the experiment, as dietary P level increased, there was also an increase in dietary calcium (Ca) level in order to maintain a dietary Ca to P ratio of 1.6:1. In Experiment 1, four diets were fed to 56 pigs (n = 14, initial body weight [BW] 36.7 ± 4.2 kg) to investigate the interaction between CP and P on growth performance, bone mineralisation and digesta pH. Experiment 2 consisted of 16 entire male pigs (n = 4; offered identical diets to that offered in Experiment 1) for the determination of total tract apparent digestibility and nitrogen (N), P and Ca utilisation. There was an interaction between CP and P level on bone ash, bone P and bone Ca concentrations (p < 0.05). Pigs offered low CP–low P diets had a higher bone ash, P and Ca concentrations than pigs offered high CP–low P diets. However, there was no effect of CP level at high P levels on bone ash, P and Ca concentrations. Pigs offered low P diets had a lower ileal pH compared with pigs offered high P diets (p < 0.05). In conclusion, offering pigs a high CP–low P, phytase-supplemented diet resulted in a decrease in bone mineralisation.

High-Protein, Low-Fat Diets Are Effective for Weight Loss and Favorably Alter Biomarkers in Healthy Adults

Although popular and effective for weight loss, low-carbohydrate, high-protein, high-fat (Atkins) diets have been associated with adverse changes in blood and renal biomarkers. High-protein diets low in fat may represent an equally appealing diet plan but promote a more healthful weight loss. Healthy adults (n = 20) were randomly assigned to 1 of 2 low-fat (<30% energy), energy-restricted groups: high-protein (30% energy) or high-carbohydrate (60% energy); 24-h intakes were strictly controlled during the 6-wk trial. One subject from each group did not complete the trial due to out-of-state travel; two subjects in the high-carbohydrate group withdrew from the trial due to extreme hunger. Body composition and metabolic indices were assessed pre- and post-trial. Both diets were equally effective at reducing body weight (-6%, P < 0.05) and fat mass (-9 to -11%, P < 0.05); however, subjects consuming the high-protein diet reported more satisfaction and less hunger in mo 1 of the trial. Both diets significantly lowered total cholesterol (-10 to -12%), insulin (-25%), and uric acid (-22 to -30%) concentrations in blood from fasting subjects. Urinary calcium excretion increased 42% in subjects consuming the high-protein diet, mirroring the 50% increase in dietary calcium with consumption of this diet; thus, apparent calcium balance was not adversely affected. Creatinine clearance was not altered by diet treatments, and nitrogen balance was more positive in subjects consuming the high-protein diet vs. the high-carbohydrate diet (3.9 +/- 1.4 and 0.7 +/- 1.7 g N/d, respectively, P < 0.05). Thus, low-fat, energy-restricted diets of varying protein content (15 or 30% energy) promoted healthful weight loss, but diet satisfaction was greater in those consuming the high-protein diet.

Effects of lead exposure before pregnancy and dietary calcium during pregnancy on fetal development and lead accumulation.

Millions of women of child-bearing age have substantial bone lead stores due to lead exposure as children. Dietary calcium ingested simultaneously with lead exposure can reduce lead absorption and accumulation. However, the effects of dietary calcium on previously accumulated maternal lead stores and transfer to the fetus have not been investigated. We studied the effects of lead exposure of female rats at an early age on fetal development during a subsequent pregnancy. We gave 5-week-old female Sprague-Dawley rats lead as the acetate in their drinking water for 5 weeks; controls received equimolar sodium acetate. This was followed by a 1-month period without lead exposure before mating. We randomly assigned pregnant rats (n = 39) to diets with a deficient (0.1%) or normal (0.5%) calcium content during pregnancy. A total of 345 pups were delivered alive. Lead-exposed dams and their pups had significantly higher blood lead concentrations than controls, but the concentrations were in the range of those found in many pregnant women. Pups born to dams fed the calcium-deficient diet during pregnancy had higher blood and organ lead concentrations than pups born to dams fed the 0. 5% calcium diet. Pups born to lead-exposed dams had significantly (p<0.0001) lower mean birth weights and birth lengths than controls. There were significant inverse univariate associations between dam or pup organ lead concentrations and birth weight or length. The 0.5% calcium diet did not increase in utero growth. Stepwise regression analysis demonstrated that greater litter size and female sex were significantly associated with reduced pup birth weight and length. However, lead exposure that ended well before pregnancy was significantly (p<0.0001) associated with reduced birth weight and length, even after litter size, pup sex, and dam weight gain during pregnancy were included in the regression analysis. The data demonstrate that an increase in dietary calcium during pregnancy can reduce fetal lead accumulation but cannot prevent lead-induced decreases in birth weight and length. The results provide evidence that dietary nutrients can influence the transfer of toxins to the fetus during pregnancy. If these results are applicable to women, an increase in diet calcium during pregnancy could reduce the transfer of lead from prepregnancy maternal exposures to the fetus.

Association between calcium ingested from drinking water and femoral bone density in elderly women: evidence from the EPIDOS cohort.

Although the main source of dietary calcium is dairy products, the calcium contained in mineral water, which is as available as that of milk, could provide a valuable source of calcium. We analyzed the data from the EPIDOS multicenter study to evaluate the relationship between both dietary calcium and that supplied by drinking water and bone density measured at the femoral neck by dual-energy X-ray absorptiometry. The study included 4434 women over 75 years of age who had not received any treatment likely to interfere with calcium metabolism. A significant correlation was found between total calcium intake and bone density at the femoral neck (r = 0.10, p < 0. 001). After adjustment for the main variables influencing bone density, an increase of 100 mg/day in calcium from drinking water was associated to a 0.5% increase in femoral bone density, while a similar increase in dietary calcium from other sources only led to a 0.2% increase; however, this difference was not significant. The consumption of calcium-rich mineral water may be of interest, especially in older women who consume little calcium from dairy products.

Effects of level of calcium or fiber type on digestibility of a tallow-supplemented diet by mice

Female CD1 weanling mice (16 g) were used to study effects of calcium and fiber level on growth and digestibility. Mice were limit fed a basal AIN purified diet with 14% tallow added (4.4 kcal/day) with calcium at either 0.6, 1.0, 1.5, 2.0, or 2.5% of diet dry matter. In addition, 10% (0.22 g/day) total dietary fiber was added to the 0.6% calcium diet from either cellufil, rice bran, wheat bran, or beet pulp. Growth rates, digestibilities, energy retention, and body composition were measured during the 28 day trial. Added calcium linearly (P<0.01) depressed digestibility of dry matter (83 versus 90%), digestibility of energy (87 versus 91%), and calculated Atwater values, while it increased fecal excretion of soap (P<0.01) and fat (P<0.10). For every 1% increase in dietary calcium, metabolizable energy decreased by 2%. Added fiber also increased (P<0.06) fecal fat and soap excretion and depressed dry matter and energy digestibility (P<0.01). Of the 4 tested fibers, mice fed the rice bran diet had the lowest (P<.05) digestibilities of dry matter, energy and fat. By depressing tallow digestibility and increasing fecal fat excretion, caloric value can be altered markedly by adding either calcium or fiber to a diet rich in fat.

Clinical Aspects of Parathyroid Hypertensive Factor

Parathyroid hypertensive factor (PHF) in rats: PHF is an endogenous hypertensive substance which was originally associated with hypertension in spontaneously hypertensive rats (SHR). In this model, PHF was shown to act by increasing intracellular calcium levels in vascular smooth muscle and was linked with a characteristic pattern of abnormalities in overall calcium regulation. The action of PHF was blocked by calcium antagonists, suggesting that the effect of PHF was to increase extracellular calcium uptake. In SHR the parathyroid glands were shown to be the site of PHF secretion. This secretion was inhibited by an increase in dietary calcium. PHF was further shown to be unique to low-renin forms of hypertension, that is, those forms of hypertension characterized by abnormalities in calcium metabolism. PHF in humans: PHF was subsequently found in human low-renin salt-sensitive hypertension. As in SHR, calcium supplementation can lower PHF levels in humans. Similarly, there is circumstantial evidence for the parathyroid origin of PHF in humans. In human hypertensive patients, the presence of PHF has been shown to predict a favorable therapeutic response to calcium channel blockade. Recently, many of the abnormalities in calcium metabolism present in low-renin hypertension have also been described in other disease states. Notable among these diseases is non-insulin dependent diabetes mellitus. A survey of human non-insulin dependent diabetes mellitus has revealed that PHF was present in a disproportionate number of these patients independently of the blood pressure level. The significance of this latter finding needs to be explored, but PHF may prove to have relevance in diseases other than hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Mineral interactions in rats fed AIN-76A diets with excess calcium

The effects of moderate increases in dietary calcium on maternal and foetal mineral interactions were studied in Charles River CD/VAF Plus rats. Female rats were given 0.50, 0.75, 1.00 or 1.25% dietary calcium as calcium carbonate in AIN-76A diets for 6 wk before mating, during mating and for 20 days of gestation. Inductively coupled argon plasma-atomic emission spectrometry was used to determine mineral levels in the tissues of non-pregnant rats after 42 days on the diets, in the tissues of pregnant rats on day 20 of gestation and in the whole body of day-20 foetuses. The femurs of the non-pregnant and pregnant rats had a dose-related linear increase in calcium content. In livers of the non-pregnant rats, dose-related linear increases in the phosphorus, zinc and magnesium content were observed, but there was a dose-related decrease in the iron content. There were dose-related linear decreases in the iron and copper contents of the kidneys from the non-pregnant rats. In pregnant rats dose-related linear decreases were observed in the iron content of the liver and in the zinc, iron and magnesium contents of the kidney. The foetuses from rats given a moderate increase in dietary calcium had dose-related decreases in the whole-body contents of phosphorus, iron, copper and magnesium.

1,25-Dihydroxyvitamin D and not calcium is the major regulator of calbindin-D 9-kDa mRNA levels in vivo.

A possible role of calcium in vivo on intestinal calbindin-D 9-kDa mRNA levels has been studied in rats. In vitamin D-deficient rats, a marked increase in dietary calcium has a small but significant effect on calbindin-D 9-kDa mRNA levels, despite a dramatic increase in serum calcium concentration that clearly resulted from increased intestinal absorption of calcium. On the other hand, vitamin D under all circumstances increased calbindin-D 9-kDa mRNA levels, with the greatest levels found in animals on a low calcium diet where little or no calcium is available for absorption. These results strongly support the idea that 1,25-dihydroxyvitamin D is directly responsible for the induction of calbindin-D 9-kDa.

Effect of Dietary Calcium onIn VitroAortic Tissue Responsiveness to a Hypertensive Factor

It has been proposed that calcium supplementation in the diet is associated with a reduction in blood pressure. In the present study, we investigated vascular tissue sensitivity to a hypertensive factor (HF) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) fed a high calcium diet, a low calcium diet and a food restricted diet. HF, which has been isolated from erythrocytes, increases blood pressure when injected into normotensive rats and stimulates calcium uptake by aortic rings in vitro. Five-week-old rats were divided into the following groups: SHR and WKY fed a regular diet (1% calcium), SHR and WKY fed a high calcium diet (4% calcium), SHR and WKY fed a low calcium diet (0.02% calcium) and SHR and WKY fed a regular diet (1% calcium) in which food intake was restricted to 65% of ad libitum intake. Food intake, body weight, urine phosphate excretion and blood pressure development were followed for 8 weeks. At sacrifice, plasma levels of calcium and phosphate were determined. Tissue responsiveness to HF was calculated by incubating aortic rings from the rats in the different groups with HF and measuring lanthanum-resistant calcium uptake. A 4-fold increase in dietary calcium reduced blood pressure and tissue responsiveness to HF in SHR. Neither parameter was affected by the high calcium diet in WKY. The low calcium diet had no effect on either blood pressure or tissue responsiveness to HF in SHR or WKY. Restriction of food intake induced a reduction in blood pressure and in tissue responsiveness to HF in SHR. It did not affect the same parameters in WKY. The results suggest that the increased tissue responsiveness to HF in the SHR may be associated with high blood pressure.

Dietary calcium and cell membrane abnormality in genetic hypertension.

Adult stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto (WKY) rats were maintained for 10 weeks on one of two diets: 1.0% calcium content and 2.5% calcium content. At the end of this time rats were anesthetized, and blood pressure was determined by means of aortic cannulation; then the rats were exsanguinated. Lymphocytes were isolated for determination of intracellular sodium and potassium concentrations, net sodium influx, net potassium efflux, and intracellular free calcium concentration. Serum ionized calcium was also measured. The increase in calcium content of their diet had no effect on intracellular sodium and potassium concentrations in lymphocytes from WKY rats and SHRSP. In lymphocytes from WKY rats, none of the parameters was affected by the change in dietary calcium intake. In contrast, in lymphocytes from SHRSP the increase in dietary calcium from 1.0 to 2.5% led to significant decreases in net potassium efflux (13.3 +/- 2.3 vs. 19.7 +/- 1.4 mmol/kg dry wt/hr, p less than 0.05, analysis of variance), intracellular free calcium concentration (114.5 +/- 10.2 vs. 166.2 +/- 11.2 nM, p less than 0.001), and systolic blood pressure (125.3 +/- 13.6 vs. 183.3 +/- 16.6 mm Hg, p less than 0.01). Serum ionized calcium increased in SHRSP (2.40 +/- 0.04 vs. 2.16 +/- 0.03, p less than 0.01) but not in WKY rats (2.34 +/- 0.05 vs. 2.31 +/- 0.05) fed the high calcium diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of Laying Hens to Dietary Saturated and Unsaturated Fatty Acids in the Presence of Varying Dietary Calcium Levels

The response of 33-week-old White Leghorn laying hens to dietary palmitic, oleic, or a 50/50 mixture of oleic and palmitic acids at an 8% inclusion level in the presence of 3, 3.6, or 4.2% dietary calcium was investigated over a 7-week period.There was no significant effect of treatments on egg production and egg weight. Although birds on diets supplemented with oleic acid consumed less feed (P<.01) than those on diets supplemented with palmitic acid (102 g vs. 114 g), they gained more weight (P<.01) than birds on diets supplemented with palmitic acid (+105 g vs. −32 g) over the 7-week period. There was no significant effect of the fatty acid treatment on shell quality as estimated by shell deformation. However, increasing the calcium content of the diets reduced feed intake and weight gain (P<.05) and improved eggshell quality (P<.05).The fat content of diets supplemented with oleic acid was better utilized than that from diets with an oleic/palmitic mixture, which, in turn, was better utilized than fat from diets supplemented with palmitic acid (P<.01). Metabolizable energy values of diets followed a trend similar to fat retention and were independent of dietary calcium levels. There were no significant effects of fatty acid supplementation on calcium and magnesium retention, although increasing the calcium content of the diet resulted in a decreased (P<.01) percentage of calcium retention. There were no significant effects of the treatments on shell ash and shell minerals with the notable exception of a decrease (P<.05) in shell magnesium with an increase in dietary calcium. There was no significant effect of the treatments on bone ash or mineral content.

EXPERIMENTAL CARCINOGENESIS IN THE RAT THYROID FOLLICULAR AND C CELLS

It is known that tumours of several endocrine glands can be induced by a combination of a physiological stress and radiation. It was decided to assess the effect of radiation and of changes in dietary calcium on the development of thyroid tumours in the rat. Three hundred rats were given either 0, 5 or 10 micronCi of 131I in their first day of life. Each of these groups was subdivided after weaning, and maintained on a diet that was either high, normal or low in calcium. The animals were killed at intervals up to 27 months of age, and the numbers of thyroid tumours recorded. Follicular tumours were first noted at 9 months of age, and their frequency increased steadily with age. The effect of radiation was highly significant, only one tumour occurred in a non-irradiated animal. There was a small increase in frequency in follicular tumours in the high calcium diet grown as compared to the low calcium diet group. C cell tumours were first noted at 9 months of age, and their incidence again increased with age. Significantly more tumours occurred in the radiated than in the non-irradiated animals. No significant variation occurred in relation to dietary calcium. It is concluded that an increase in dietary calcium, known to be mildly goitrogenic, may also be important in the carcinogenesis of follicular but not C cell tumours, and that radiation, known to be carcinogenic for thyroid follicular cells is also carcinogenic for C cells.

Localization of calcium in the thyroids of rats.

SummaryRat thyroid has a high concentration of calcium which is known to decline with thiourea treatment and increase with inanition or a high calcium-low iodine diet. The histochemical localization of this calcium in normo- and hyper calcemic states was studied. Use of glyoxal bis(2-hydroxyanil) and alizarin red S revealed localization in the follicular cells. Rats rendered hypercalcemic by increase in dietary calcium or by injections of dihydrotachysterol showed virtually identical structural and histochemical appearance of their thyroids as those of control animals.

Effects of Dietary Calcium upon Lipid Metabolism in Mature Male Rats Fed Beef Tallow

In an attempt to elucidate the hypocholesterolemic and hypotriglyceridemic action of dietary calcium, 24 mature male Holtzman strain albino rats were fed a corn-soya ration containing 18% added beef tallow and 2% added cholesterol for 21 days. Dietary calcium was varied at 0.08, 0.2 and 1.2% of diet. Blood lipids decreased with increasing dietary calcium, the major decrease occurring at the 0.2% calcium level. Some tissue lipids decreased; none increased. Fecal lipids did not significantly increase at the 0.2% calcium level, but did at the 1.2% level. Fecal fatty acids became progressively more saturated with increasing calcium intake, but the preferential excretion of saturated fatty acids did not appear to be sufficient to alter significantly the blood fatty acids. Fecal bile acids significantly increased at the 0.2% calcium level, with no additional increase at the 1.2% calcium level. These results suggest that the lowering of blood cholesterol by increase in dietary calcium is mediated in part by increased excretion of bile acids.

STRONTIUM-CALCIUM INTERRELATIONSHIPS IN THE GROWING RAT.

The comparative metabolic behavior of strontium and calcium was studied in growing, female rats exposed either continuously or to single doses of Sr90 and Ca45 while on diets of various total calcium contents. At weaning the discrimination against ingested Sr90 relative to Ca45 was markedly less than that previously observed in mature rats. This discrimination increased and approached the levels observed in mature animals, while growth and Ca45 deposition was still proceeding at a rapid rate. The effect of a fourfold increase in dietary calcium (from 0.5 to 2.0%) over a 200-day feeding period was a twofold reduction in the steady-state level of Sr90 in bone. As previously shown in mature rats, the retention (as opposed to absorption) of a single dose of Sr90 was relatively unaffected by dietary calcium level, while that of Ca45 varied from almost total retention on a 0.1% calcium diet to retention on a 2.0% calcium diet which was similar to that observed for Sr90 on all diets.