Effect Of High Calcium Intake Research Articles

Dietary calcium does not interact with vitamin D3 in terms of determining the response and catabolism of serum 25-hydroxyvitamin D during winter in older adults

Interactions between calcium and vitamin D may have implications for the regulation of serum 25-hydroxyvitamin D [25(OH)D] and its catabolism and, consequently, the vitamin D dietary requirement. We investigated whether different calcium intakes influenced serum 25(OH)D and indexes of vitamin D activation and catabolism during winter and in the context of both adequate and inadequate vitamin D intakes. A 15-wk winter-based, randomized, placebo-controlled, double-blind vitamin D₃ intervention (20 μg/d) study was carried out in free-living men and women aged ≥50 y (n = 125) who were stratified according to calcium intakes [moderate-low (<700 mg/d) or high (>1000 mg/d) intake]. The serum 25(OH)D concentration was the primary outcome, and serum calcium, parathyroid hormone (PTH), 1,25-dihydroxyvitamin D [1,25(OH)₂D], 24,25-dihydroxyvitamin D [24,25(OH)₂D], the ratio of 24,25(OH)₂D to 25(OH)D, vitamin D-binding protein, and free 25(OH)D were exploratory outcomes. A repeated-measures ANOVA showed there was no significant (P = 0.2) time × vitamin D treatment × calcium intake grouping interaction effect on the mean serum 25(OH)D concentration over the 15-wk intervention period. Serum 25(OH)D concentrations increased (P ≤ 0.005) and decreased (P ≤ 0.002) in vitamin D₃ and placebo groups, respectively, and were of similar magnitudes in subjects with calcium intakes <700 mg/d (and even <550 mg/d) compared with >1000 mg/d. The response of serum PTH, 1,25(OH)₂D, 24,25(OH)₂D, the ratio of 24,25(OH)₂D to 25(OH)D, and free 25(OH)D significantly differed in vitamin D₃ and placebo groups but not by calcium intake grouping. We found no evidence of a vitamin D sparing effect of high calcium intake, which has been referred to by some authors as "vitamin D economy." Thus, recent dietary vitamin D requirement estimates will cover the vitamin D needs of even those individuals who have inadequate calcium intakes.

Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality

Calcium intake has been promoted because of its proposed benefit on bone health, particularly among the older population. However, concerns have been raised about the potential adverse effect of high calcium intake on cardiovascular health. To investigate whether intake of dietary and supplemental calcium is associated with mortality from total cardiovascular disease (CVD), heart disease, and cerebrovascular diseases. Prospective study from 1995 through 1996 in California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania and the 2 metropolitan areas of Atlanta, Georgia, and Detroit, Michigan. A total of 388 229 men and women aged 50 to 71 years from the National Institutes of Health-AARP Diet and Health Study. Dietary and supplemental calcium intake was assessed at baseline (1995-1996). Supplemental calcium intake included calcium from multivitamins and individual calcium supplements. Cardiovascular disease deaths were ascertained using the National Death Index. Multivariate Cox proportional hazards regression models adjusted for demographic, lifestyle, and dietary variables were used to estimate relative risks (RRs) and 95% CIs. During a mean of 12 years of follow-up, 7904 and 3874 CVD deaths in men and women, respectively, were identified. Supplements containing calcium were used by 51% of men and 70% of women. In men, supplemental calcium intake was associated with an elevated risk of CVD death (RR>1000 vs 0 mg/d, 1.20; 95% CI, 1.05-1.36), more specifically with heart disease death (RR, 1.19; 95% CI, 1.03-1.37) but not significantly with cerebrovascular disease death (RR, 1.14; 95% CI, 0.81-1.61). In women, supplemental calcium intake was not associated with CVD death (RR, 1.06; 95% CI, 0.96-1.18), heart disease death (1.05; 0.93-1.18), or cerebrovascular disease death (1.08; 0.87-1.33). Dietary calcium intake was unrelated to CVD death in either men or women. Our findings suggest that high intake of supplemental calcium is associated with an excess risk of CVD death in men but not in women. Additional studies are needed to investigate the effect of supplemental calcium use beyond bone health.

The effect of high calcium intake by pregnant Awassi ewes at late gestation on minerals status and performance of ewes and newborn lambs

Calcium (Ca) requirement increase rapidly by pregnant ewes at late gestation as a result of high fetal growth. Furthermore, Ca deficiency results in poor growth and bone development in growing newborn lambs. The aim of this study was to evaluate the effect of calcium supplementation (Calcium carbonate–CC) and vitamin AD 3E injection (75,000 IU/shot) to pregnant Awassi ewes at late gestation (− 45 days prepartum) on their mineral levels and performance of their newborn lambs. Forty pregnant Awassi ewes at late gestation (65 ± 6.1 kg) were selected before parturition (− 45 days; using hormonal sponges for estrus synchronization) and randomly divided to 4 dietary treatments. The treatments were: group 1 Control (1.4% CC); group 2 (2.4% CC); group 3 (1.4% CC + 2 shots vitamin AD3E at − 45 and − 21 days prepartum); group 4 (2.4% CC + 2 shots vitamin AD3E at − 45 and − 21 days prepartum). Blood samples were collected from ewes (− 45, 0 days prepartum: 30 and 60 days postpartum) and lambs (0, 30 and 60 days old). Average milk yield and samples were collected. Body weights of lambs were taken at birth, 30 and 60 days old. Blood serum and milk samples were prepared and analyzed by AAS for Ca, Mg, Co, Mn and Cu concentrations. Calcium concentrations in bloods serum of ewes, 0 and 60 days postpartum, and lambs at weaning (60 days old) from group 4 were significantly ( P < 0.05) higher compared to other groups. No significant effect ( P > 0.05) of treatment on Co, Mg and Cu in blood serum of ewes and lambs except for Cu concentration in ewes. Moreover, a significant increase ( P < 0.01) in milk inorganic% (30 and 60 days samples) in ewes from group 2 when compared with other groups. The average milk yield (AMY) of ewes from group 2 and 4 at late stage of lactation (45–60 days) were significantly higher ( P < 0.05) compared to groups 1 and 3. In addition, Ca% in colostrums samples from ewes in groups 2 and 4 were significantly higher ( P < 0.01). The average daily gain (ADG) and total body gain for lambs up to weaning (60 days old) were significantly higher ( P < 0.05) in groups 1 and 2 compared with the other groups. In conclusion, increasing level of Ca intake in feed of Awassi ewes at late gestation, with or without vitamin AD 3E injections, improve the calcium concentration in colostrums and blood serum of ewes and their lambs without negative effect in their health and performance.

HIGH DAIRY CALCIUM INTAKE IN PUBERTAL GIRLS: RELATION TO BODY WEIGHT GAIN AND BONE MINERAL STATUS

Background: Lack of calcium in­take may exaggerate osteoporosis which is most evident during period of rapid skeletal growth. Objective : To study effect of high calcium intake mainly from dairy prod­ucts in healthy adolescents females on their body weight, bone mineral density (BMD) and bone mineral con­tent (BMC). Subjects and methods : In a com­munity-based, randomized controlled study, 73 females were enrolled whose mean age 11.5 years and sexual maturation aimost at Tanner II. Over a period of 24 months, one group (milk group, n = 44} was supplemented with dairy food prod­ucts to a daily allowance of 1600 mg calcium and the second group (control group, n = 29) was given the usual diets (daily calcium content 800 mg). Body mass index (BMI), body fat and lean, BMD and BMC using dual-energy x-ray absorptiome-try as well as some serological markers of bone-calcium metabolism were measured at start of study then 6 monthly. Results : Milk group showed sta­tistically significant increases in BMD and BMC in the last 3 estimates com­pared to control (P = 0.04, 0.02, 0.03 for BMD and 0.04, 0.01, 0.02 for BMC respectively). However, neither the anthropometric measures nor the ser­ological parameters showed any marked difference in the 2 studied groups whether at start or in any sub­sequent estimate.

The effect of calcium consumption on iron absorption and iron status.

Recent increases in recommended calcium intakes recognize the important role of calcium in skeletal health, but many Americans, especially women, consume far less than recommended amounts. A potential drawback to encouraging increased calcium intake is suggested by the extensive literature showing an adverse effect of high calcium intake on dietary iron absorption, at least in short, highly controlled, experimental studies. However, the applicability of short-term studies involving test meals to long-term iron absorption and iron status is limited given the variety of foods and food combinations in self-selected diets and the ability of individuals to adapt to reduced iron intake. In general, studies of whole diets and studies conducted over several weeks tend to show no effect of increased calcium intake on iron absorption. In addition, experimental studies of calcium and iron status measures such as serum ferritin show no long-term effect of calcium supplementation on iron status. Prevention and treatment of iron deficiency should emphasize adequate consumption of iron-rich foods and, when indicated, the use of iron supplements. Recommended calcium intakes are important for skeletal health and do not appear to increase the risk for iron deficiency in healthy people.

Effects of High Calcium Intake on Fat Digestion and Bile Acid Excretion in Feces of Veal Calves

We tested the hypothesis that apparent digestibility of fat by veal calves is determined by the participation of bile acids in the process of fat absorption and is, therefore, negatively associated with bile acid excretion in feces. Veal calves were fed milk replacers that contained whey protein and either a low (5.2g of calcium/kg of air-dried diet) or high (12.4g of calcium/kg of air-dried diet) concentration of calcium. The high calcium milk replacer contained extra calcium in the form of calcium formate. Final body weight was not significantly influenced by diet after the milk replacers had been fed for 27 wk. Feces were quantitatively collected during wk 23 of the trial. The high calcium milk replacer reduced apparent fat digestibility by 5.6 percentage units and increased bile acid excretion in feces by 90% compared with the low calcium milk replacer. The extra calcium intake decreased apparent absorption of magnesium and phosphorus. We proposed that a high intake of calcium by veal calves would increase the amount of insoluble calcium, magnesium, and phosphate complexes in the intestinal lumen, which, because of the binding of bile acids, would exclude bile acids from the process of fat digestion and inhibit reabsorption of bile acids. As a result, fat digestion is impaired, and bile acid excretion in feces is enhanced. The complex formation in the ileal lumen also explains why high calcium intake reduces magnesium and phosphorus absorption in veal calves.

The effect of high calcium intake on intracellular free [Ca2+] and Na(+)-H+ exchange in DOC-NaCl-hypertensive rats.

The effects of calcium supplementation on blood pressure, intracellular free calcium concentration ([Ca2+]i) and rate of Na(+)-H+ exchange were studied in DOC-NaCl-hypertensive rats. All the animals were uninephrectomized and divided into two main groups: the first group received deoxycorticosterone (DOC) (25 mg/kg, s.c.) once a week and had 0.7% NaCl as drinking fluid while the other received equal volumes of saline and tap water to drink. The animals were further divided according to dietary calcium intake: in the Control and DOC groups the chow contained 1.1% calcium, in the Calcium and DOC+Calcium groups, 2.5%. After 6 and 8 weeks, blood pressure in the DOC group was higher than in the Control group; on the other hand, the development of hypertension was attenuated in the DOC+Calcium compared with the DOC group. The Control and Calcium groups did not differ from each other. Platelets and lymphocytes were used as experimental models to study changes in the regulation of [Ca2+]i, evaluated by fluorescent indicators indo-1 and quin-2. In lymphocytes, basal [Ca2+]i was highest in the DOC group, but similar in DOC+Calcium and Control groups. In platelets, both basal and thrombin-stimulated [Ca2+]i were higher in the DOC and DOC+Calcium groups than in the Control group. In both cell types [Ca2+]i was similar in Control and Calcium groups. In addition, platelets were used to study the ability of the cells to recover from intracellular acidification by first blocking the Na(+)-H+ exchange in a Na(+)-free medium and then restarting the exchange mechanism by increasing the extracellular Na+ concentration at constant speed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of high calcium intake on pressor responsivity in hypertensive rats.

Some proposed mechanisms for the hypotensive effect of high calcium intake involve reduction in vascular responsivity. To assess the effect of dietary calcium on vascular responsivity, spontaneously hypertensive rats (SHR) were placed on normal (N-Ca; 0.4%) or high (H-Ca; 2.8%) casein-based synthetic diet for 4 wk. Intraarterial pressure, pressor response to graded intravenous infusion of norepinephrine (NE) and angiotensin II (ANG II), and in vitro vascular reactivity of tail artery segments to NE and transmural nerve stimulation (TNS) were studied. Urinary electrolyte excretion, plasma renin activity (PRA), aldosterone, NE, and epinephrine (EPI) were also determined. H-Ca SHR had a lower intraarterial systolic and diastolic pressure. However, H-Ca SHR had greater in vivo pressor response to both ANG II and NE. Maximal contractile force developed by tail artery segments in vitro in response to NE and TNS was slightly, but not significantly, higher in H-Ca SHR. In vitro dose-response curves to NE and TNS were not significantly different. Although H-Ca SHR had increased urinary excretion of sodium throughout the study period, PRA and aldosterone levels were similar in both groups. Plasma NE and EPI levels in the two groups were also not different. Despite lowered intra-arterial blood pressure, H-Ca SHR exhibited enhanced pressor response to ANG II and NE in vivo and a similar in vitro vascular reactivity to NE and TNS when compared with N-Ca SHR. Our results do not support a role for alterations in vascular reactivity to NE or ANG II in the hypotensive effect of high calcium intake in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential Response of Muscle and Gastric Histidine Decarboxylase to Compound 48/80 and Dietary Calcium

Previous work from this laboratory had indicated that in vivo, histidine decarboxylase (HDC) activity was stimulated by compound 48/80 in rat leg muscle, and that high dietary calcium had a stimulating effect on gastric HDC activity. In the present investigations the 48/80 effect was also observed in vitro in leg muscle extracts from rats, chicks, and guinea pigs. Compound 48/80 had no effect in vitro on histamine metabolism of gastric tissue homogenates in any of the animal species studied. A dietary effect of high calcium intake was noted in rat gastric tissue but not in rat leg muscle. In vitro addition of 48/80 and/or calcium had no stimulatory effect on bacterial HDC or on muscle carnosinase activity. These findings, in conjunction with a comparison of stomach and leg muscle mast cell populations, confirm an HDC stimulatory role for 48/80 in muscle, in addition to its histamine-releasing function from mast cells.

Effects of high calcium intake on blood pressure and calcium metabolism in young SHR.

Increased dietary calcium intake in the adult spontaneously hypertensive rat (SHR) has been reported to correct low serum ionized calcium concentration ([Ca++]) and to result in a significant amelioration of the prevailing hypertension. In the present study we examined several parameters of calcium metabolism in young (6-week-old) SHR and compared them with those observed in normotensive Wistar-Kyoto (WKY) rats fed equal amounts of a diet containing normal quantities of calcium (0.4%, wt/wt) for 4 weeks. A separate group of SHR was placed on an equal amount of a high calcium (2.8%, wt/wt) but otherwise identical diet. In SHR and WKY eating a normal calcium diet, serum total calcium concentration was not different, but [Ca++] was lower in SHR (1.58 +/- 0.06 vs 1.91 +/- 0.07 mmol/liter, p less than 0.01). Serum immunoreactive parathyroid hormone (PTH) was increased in some, but not all, SHR. No difference was noted between the two groups in the following parameters: calcium intake, serum 1,25 dihydroxycholecalciferol (1,25(OH)2D3), urinary calcium excretion, fractional stool calcium content ([stool calcium/calcium intake] X 100), and in vitro 45Ca uptake by everted gut sacs constructed from segments of duodenum, mid-jejunum, ileum, and proximal colon. A high calcium diet corrected the abnormal serum [Ca++] and PTH but did not alter the progression or severity of the hypertension in SHR. A lower net weight gain was observed in SHR on a high calcium diet when compared to SHR eating normal calcium diet (9.1 +/- 1.8 vs 27.0 +/- 2.0 g).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic balance studies of high calcium intake in osteoporosis

Positive calcium balance of varying degree has been induced by high calcium intake in four patients with frank osteoporosis and in one patient with apparently normal bone. Phosphate retention appeared to be less with calcium gluconate supplementation than with addition of dicalcium phosphate (CaHPO 4). There was often modest increase in urinary calcium but not hypercalciuria during high calcium intake, especially during calcium gluconate administration. Slow intravenous administration of calcium gluconate to one patient resulted in marked hypercalciuria. In the normal patient, who showed moderate storage of calcium during dicalcium phosphate supplementation, the laxative effect of the higher dose of calcium gluconate was associated with increased fecal calcium excretion and negative calcium balance. None of the osteoporotic patients showed definite change clinically or on roentgenograms. In view of the evidence available to date, the most likely mechanism for positive calcium balance during high intake is considered to be inhibition of bone resorption. The effect of high calcium intake upon the clinical, structural and chemical course of osteoporosis is as yet unclear. Until this is defined, no statement can be made about the etiologic role of calcium deficiency or the therapeutic usefulness of high calcium intake in osteoporosis.