High Dietary Ca Research Articles

Daidzein together with high calcium preserve bone mass and biomechanical strength at multiple sites in ovariectomized mice

As the prevalence of osteoporosis is increasing, and the adverse effects of hormone replacement therapy are evident, women are searching for natural alternatives such as soy isoflavones to help prevent postmenopausal osteoporosis. Daidzein is one of the most abundant isoflavones present in soy and it is unique as it can be further metabolized to equol, a compound with greater estrogenic activity than other isoflavones. The objective of this study was to determine the effects of purified daidzein in combination with high calcium (Ca) on preserving femur and lumbar vertebrae (LV1–LV4) bone mineral density (BMD) and biomechanical bone strength at three different sites (femur midpoint, femur neck and LV3) in ovariectomized mice. Sham (SH) mice ( n = 12) received control diet (AIN93G) containing 2 g Ca/kg diet and ovariectomized mice were randomized to 1 of 6 groups ( n = 12/group): OVX (2 g Ca/kg diet), HCa (25 g Ca/kg diet), HD (2 g Ca + 200 mg daidzein/kg diet), HDCa (25 g Ca + 200 mg daidzein/kg diet), LD (2 g Ca + 100 mg daidzein/kg diet) or LDCa (25 g Ca + 100 mg daidzein/kg diet) for 12 weeks. HDCa preserved femur and vertebrae BMD and biomechanical bone strength (at all three sites) compared to the OVX group, however, only femur yield load (at midpoint) was preserved to a level that was greater ( P < 0.05) than HCa alone. Mice fed HD diet had greater ( P < 0.05) femur BMD than OVX group, however, daidzein alone (HD) did not appear to preserve trabecular bone (i.e., vertebrae BMD and vertebra peak load). All mice fed daidzein produced equol and there were no uterotrophic effects of daidzein at either dose. Both daidzein and Ca attenuated the increase in serum IL-1β observed in the OVX group. The results from this study suggest that the combination of daidzein and high Ca favorably affect cortical and trabecular bone as indicated by femur and lumbar vertebrae BMD and biomechanical strength but much of this effect is mediated by the high Ca diet. Further investigation is required to determine optimal dietary levels of daidzein and Ca with the long-term goal of developing a dietary strategy to prevent postmenopausal osteoporosis and related fragility fractures.

Benefit of feeding dietary calcium and nonphytate phosphorus levels above National Research Council recommendations to tom turkeys in the growing-finishing phases

This experiment evaluated the effects of feeding various dietary Ca and nonphytate P (nPP) levels to Large White male turkeys from 3 to 17 wk of age. After consuming a common prestarter diet, poults were fed approximate NRC (1994) levels of dietary Ca and nPP from 3 to 9 wk of age or levels approximately 25% higher. From 9 to 17 wk of age, each starter group was fed approximately 75 (low P), 100 (medium P), or 145% (high P) of the NRC (1994) requirements for Ca and nPP. Diets were fed as crumbles to 6 wk of age and as pellets from 6 to 17 wk of age. There were no effects on BW or feed efficiency to 9 wk of age. Litter P was increased by 21% when high Ca and nPP were fed from 3 to 9 wk. High dietary Ca and nPP fed during the growing-finishing period generally improved bone strength and ash. Tibia strength and ash were higher in the medium P group compared with in the low P group. Wing bone strength was greater in the high P group than in both the birds fed low or medium P. Litter P was increased by 23% when High P was fed in the growing-finishing period compared to the birds fed the Medium P diet during the same period. The results show there is a benefit to bone strength and mineralization when Ca and nPP are fed at levels higher than NRC (1994) recommendations.

Effect of age and dietary calcium on intestinal calbindin D-9k expression in the rat

The capacity of rats and humans to adapt to low dietary Ca by increasing intestinal Ca absorption declines with age. The intestinal calbindin-D-9k protein (calbindin) is thought to play a role in the transcellular transport of Ca across the mammalian intestine. The purpose of these studies was to determine the effect of age and diet on the expression of calbindin at the protein and mRNA levels. Young (2 month) and adult (12 month) male F344 rats were placed on either a high Ca diet (1.2%) or a low Ca diet (0.02%) for four weeks. In the duodenum, the level of intestinal calbindin protein induced by a low Ca diet was 8-fold higher in young rats compared to adult rats. In the ileum, expression of calbindin protein was only about 10% that of the duodenum. In addition, the adult ileum showed the same decreased adaptation to a low Ca diet that was seen in the adult duodenum. In both the duodenum and the ileum, the changes in calbindin protein expression were highly correlated with calbindin mRNA expression and the correlations in each segment were quantitatively similar. In the duodenum, the changes in calbindin protein levels were strongly correlated with both Ca transport and Ca uptake. This quantitative correlation suggests a role for calbindin protein in the age-related decline in Ca absorption. In the ileum, the decreased adaptation to a low Ca diet may also be important given the long transit time through the distal intestine. The changes in both intestinal segments may contribute to the negative Ca balance seen in adult rats fed a low Ca diet.

Digestible energy intake, dry matter digestibility and effect of increased calcium intake on bone parameters of grazing Thoroughbred weanlings in New Zealand

AIMS: To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and the effects of increased calcium (Ca) intakes on apparent mineral absorption and bone characteristics in grazing weanling Thoroughbreds. METHODS: DM intake (DMI) and DEI were determined in 16 weanling Thoroughbreds grazing pasture from their daily faecal DM output, measured over 8 days, divided by the DM indigestible fraction (1–digestible DM) determined in a 6-day digestibility trial. The DM, gross energy content, crude protein, soluble carbohydrate, acid detergent fibre, neutral detergent fibre, lipid, Ca, phosphorus (P), sodium (Na), potassium (K), sulphur (S) and magnesium (Mg) composition of perennial ryegrass/white clover pasture and faeces were determined and their digestibility and/or apparent absorption calculated. Calcium intake and bone growth studies used 17 weanlings, randomly divided into three groups and fed perennial ryegrass/ white clover pasture and 0.5 kg grain, with or without a CaCO3 supplement, for 84 days. The animals in Group 1 (n=6) were on a low Ca diet (3.5 g/kg DM) and were fed pasture only; those in Group 2 (n=5) were on a medium Ca diet (6.3 g/kg DM); and those in Group 3 (n=6) were on a high Ca diet (12.0 g/kg DM). After 44 days the apparent absorption of Ca was determined from the differences between the Ca intakes and faecal Ca outputs. At periods just before and after Ca supplementation the horses were anaesthetised and the left radius, third metacarpus (Mc3) and first phalanx of the left foreleg were scanned using a peripheral quantitative computed tomography scanner to determine cortical mineral content, density, area, periosteal circumference and bone strength. To investigate gastrointestinal tract transit time and DM digestibility, five randomly selected horses were administered Swiss screen bags on several occasions via a nasogastric tube. Each 60 x 10mm bag contained 3.21 (SE 0.37) g of frozen minced grass. Bags were recovered from the freshly passed faeces and frozen until analysis. RESULTS: The DM digestibility of the pasture was 0.62, while the DMI and DEI of weanlings (300 kg, gaining 0.7 kg/day) were 5.5 kg/day and 63 MJ/day, respectively. Increasing Ca intake had no significant effect on DEI, DM digestibility or on the apparent absorption of Ca, P, Na and K, but decreased the apparent absorption of Mg from 0.50 to 0.38. Regardless of Ca intake, the apparent absorption of Ca was 0.56. During the Ca administration trial there were significant increases over time in the bone strength (strain stress index) of the proximal phalanx, Mc3 and radial diaphysis. However, the increase in bone strength was not associated with increase in dietary Ca, as neither the medium- nor high-Ca intake groups differed significantly from the low-Ca controls. The mean transit time for the Swiss screen bags was 25.46 (SE 0.09) h, and transit times were similar whether the horses were grazing or confined in loose boxes, being 26.64 (SE 0.23) h and 24.33 (SE 0.13) h, respectively. The DM digestibility determined using the bags was 0.54, which was significantly lower than the 0.62 determined by direct faeces collection. CONCLUSIONS: Good growth rates were achieved in Thoroughbred weanlings grazing perennial ryegrass/white clover pasture containing 3.5 g Ca/kg DM and a DE of 11.4 MJ/kg DM. Increasing dietary Ca intake 3.5-fold for 3 months had negligible impact on bone growth and development.

Isoflavones with supplemental calcium provide greater protection against the loss of bone mass and strength after ovariectomy compared to isoflavones alone

Although hormone replacement therapy (HRT) and calcium (Ca) supplementation preserve bone mass more when combined, there is a growing concern over the safety of HRT that necessitates thorough investigation of effective, alternative treatments for bone loss. While plant-derived estrogen-like compounds such as isoflavones preserve bone, it is not known whether isoflavones and Ca supplementation attenuate losses in bone mass and strength to a greater extent when combined. This study compared the effects of an isoflavone extract + high Ca to isoflavone extract or high Ca alone on preservation of bone mineral density (BMD) and biomechanical strength in ovariectomized (ovx) rats. Rats were sham-operated (n = 10) or ovx (n = 40). Shams were fed a 0.2% Ca diet. Ovx rats were randomized to a 0.2% Ca diet alone (OVX) or with isoflavone extract (IE; 1.6 g/kg diet) or to a high Ca diet (Ca; 2.5%) alone or a high Ca diet with the isoflavone extract (IE + Ca) for 8 weeks. BMD of femur and lumbar spine were measured by dual-energy X-ray absorptiometry. The biomechanical strength of femurs and individual vertebra was measured by three-point bending and compression testing, respectively. The average food intake was lowest (P < 0.05) among sham and IE groups and greatest (P < 0.05) among the OVX group. Final body weight was lowest (P < 0.05) among shams and highest (P < 0.05) among the OVX group while IE + Ca were lighter (P < 0.05) than all ovx groups. Femur and vertebra BMD was greater (P < 0.05) among IE + Ca and sham rats compared to IE, Ca, or OVX rats. Although there were differences in femur BMD among groups, biomechanical properties at the femur midpoint did not differ among groups, possibly due to the lack of cortical bone loss at this site. Conversely, vertebra biomechanical strength was greater (P < 0.05) among IE + Ca and Ca alone groups compared to IE alone. Uterine weight was higher (P < 0.05) among shams than OVX and IE with no difference among shams, Ca, or IE + Ca rats, suggesting that the isoflavones did not have an uterotrophic effect. In conclusion, isoflavones combined with high Ca are more protective against the loss of femur and vertebra BMD than isoflavones or high Ca diet alone.

Vitamin D 3 metabolism in dogs

Plasma concentrations of the main vitamin D 3 metabolites (i.e., 25(OH)D 3, 1,25(OH) 2D 3, and 24,25(OH) 2D 3) were measured in 14 weeks old large- and small-breed dogs (adult body weight 60 kg vs. 6 kg), raised under the same conditions. Levels of 25(OH)D 3 (approx. 22 μg/l) and 1,25(OH) 2D 3 (approx. 40 ng/l) were similar in both groups, whereas plasma 24,25(OH) 2D 3 concentrations were lower in large-breed dogs (7 μg/l vs. 70 μg/l, large- vs. small-breed dogs, respectively). The lower plasma 24,25(OH) 2D 3 concentrations could be explained by the higher plasma GH and IGF-I concentrations in the large- vs. small-breed dogs, and these hormones are known to suppress 24-hydroxylation. Plasma 24,25(OH) 2D 3 concentrations increased during Ca supplementation in small-breed but not in large-breed dogs (100 μg/l vs. 7 μg/l, respectively). Hypophosphatemia induced by a high dietary Ca content was only seen together with increased plasma 1,25(OH) 2D 3 concentrations in euparathyroid dogs and not in hypoparathyroid dogs. Hyperparathyroidism due to Ca deficiency was accompanied by increased plasma 1,25(OH) 2D 3 concentrations and decreased plasma 24,25(OH) 2D 3 concentrations in both large- and small-breed dogs, together with generalized osteoporosis. Large-breed pups fed on a standard diet supplemented with Ca and P had decreased plasma concentrations of both 25(OH)D 3 and 1,25(OH) 2D 3, which may indicate an increased clearance of these metabolites; the low plasma concentrations of the di-hydroxylated vitamin D metabolites were considered responsible for the disturbance in cartilage maturation (i.e., osteochondrosis) in these dogs. Even lower concentrations of all vitamin D 3 metabolites were seen in young dogs raised on a vitamin D 3-deficient diet, and led to disturbed osteoid and cartilage mineralization (i.e., rickets). These studies indicate that there is a hierarchy of factors regulating vitamin D 3 metabolism in dogs, i.e., GH and IGF-I suppress 24-hydroxylase more than hypercalcemia or hypophosphatemia does; 1,25(OH) 2D 3 and 24,25(OH) 2D 3 are only reciprocally related in hyperparathyroidism; excessive Ca and P intake increases the turnover of vitamin D 3 metabolites; and the synergism between parathyroid hormone and 1,25(OH)D 3 seems to play a role in skeletal mineralization. The low plasma 24,25(OH) 2D 3 concentrations in large-breed dogs raised on standard dog food may play a role in the etiology of disturbances in endochondral ossification during the rapid growth phase.

Effects of calcium and plant sterols on serum lipids in obese Zucker rats on a low-fat diet

Ca may interfere with fat and cholesterol metabolism through formation of insoluble soaps with fatty and bile acids in the intestine. In the present study, we examined the effects of different dietary Ca levels on the serum lipid profile and cholesterol metabolism in obese Zucker rats fed a low-fat diet. We also tested whether dietary Ca interfered with the lipid-lowering effects of a pine oil-derived plant sterol mixture. Increase in dietary Ca intake from 0·2 to 0·8 %, and further to 2·1 % (w/w) dose-dependently decreased serum total cholesterol (r -0·565,P=0·002,n27), LDL-cholesterol (r -0·538,P=0·006,n25), and triacylglycerol (r -0·484,P=0·014,n25) concentrations, and increased HDL-cholesterol (r 0·478,P=0·016,n25) and HDL : LDL cholesterol (r 0·672,P&lt;0·001,n25) in rats fed a 1 % cholesterol diet. Analysis of serum campesterol : cholesterol and sitosterol : cholesterol suggested that Ca dose-dependently increased intestinal cholesterol absorption (r 0·913,P&lt;0·001,n18), whereas serum desmosterol : cholesterol and lathosterol : cholesterol indicated that Ca dose-dependently increased endogenous cholesterol synthesis (r 0·691,P=0·003,n18). Therefore, the decrease of serum LDL-cholesterol appeared to be due to Ca-induced increase in the conversion of cholesterol to bile acids. The increase in Ca intake did not interfere with the beneficial effects of plant sterols on serum total cholesterol, LDL-cholesterol and HDL-cholesterol concentrations. The high-Ca diet with plant sterol supplementation further increased the HDL-cholesterol concentration and HDL : LDL cholesterol. The present findings indicate that the beneficial effects of dietary Ca on the serum lipid profile during a low-fat diet are dose-dependent, and resemble those of bile acid sequestrants. Increased dietary Ca did not impede the lipid-lowering effects of natural plant sterols.

Effects of calcium and plant sterols on serum lipids in obese Zucker rats on a low-fat diet.

Ca may interfere with fat and cholesterol metabolism through formation of insoluble soaps with fatty and bile acids in the intestine. In the present study, we examined the effects of different dietary Ca levels on the serum lipid profile and cholesterol metabolism in obese Zucker rats fed a low-fat diet. We also tested whether dietary Ca interfered with the lipid-lowering effects of a pine oil-derived plant sterol mixture. Increase in dietary Ca intake from 0.2 to 0.8%, and further to 2.1% (w/w) dose-dependently decreased serum total cholesterol (r -0.565, P=0.002, n 27), LDL-cholesterol (r -0.538, P=0.006, n 25), and triacylglycerol (r -0.484, P=0.014, n 25) concentrations, and increased HDL-cholesterol (r -0.478, P=0.016, n 25) and HDL: LDL cholesterol (r 0.672, P<0.001, n 25) in rats fed a 1% cholesterol diet. Analysis of serum campesterol: cholesterol and sitosterol: cholesterol suggested that Ca dose-dependently increased intestinal cholesterol absorption (r 0.913, P<0.001, n 18), whereas serum desmosterol: cholesterol and lathosterol: cholesterol indicated that Ca dose-dependently increased endogenous cholesterol synthesis (r 0.691, P=0.003, n 18). Therefore, the decrease of serum LDL-cholesterol appeared to be due to Ca-induced increase in the conversion of cholesterol to bile acids. The increase in Ca intake did not interfere with the beneficial effects of plant sterols on serum total cholesterol, LDL-cholesterol and HDL-cholesterol concentrations. The high-Ca diet with plant sterol supplementation further increased the HDL-cholesterol concentration and HDL: LDL cholesterol. The present findings indicate that the beneficial effects of dietary Ca on the serum lipid profile during a low-fat diet are dose-dependent, and resemble those of bile acid sequestrants. Increased dietary Ca did not impede the lipid-lowering effects of natural plant sterols.

P21WAF1 and TGF-α mediate parathyroid growth arrest by vitamin D and high calcium

High dietary phosphorus (P) worsens uremia-induced parathyroid (PT) hyperplasia through increases in the growth promoter transforming growth factor-alpha (TGF-alpha). In contrast, P restriction prevents PT hyperplasia by inducing the cell cycle inhibitor p21. Since 1,25(OH)2D3-antiproliferative action in various cell types involve increases in p21, we studied whether induction of p21 by 1,25(OH)2D3 or the vitamin D analog, 19-Nor-1,25(OH)2D2, could counteract the PT hyperplasia induced by high dietary P in early uremia. Normal (N) and uremic (U; 5/6 nephrectomized) female Sprague-Dawley rats were fed high P (HP), low P (LP) or high Ca (HCa) diets and administered intraperitoneally (IP) either vehicle or vitamin D metabolites for seven days, as follows: N-HP; U-HP + vehicle; U-HP + 1,25(OH)2D3 (4 ng/day); U-HP + 19-Nor-1,25(OH)2D2 (30 ng/day); U-LP; U-HCa. Serum PTH and PT gland weight assessed secondary hyperparathyroidism. Immunohistochemical quantitation of two markers of mitotic activity, Ki67 and PCNA measured PT hyperplasia. Immunohistochemical expression of PT p21 and TGF-alpha addressed potential mechanisms regulating PT cell growth. 1,25(OH)2D3 and 19-Nor-1,25(OH)2D2 were effective in suppressing both PTH secretion and PT hyperplasia induced by uremia and high dietary P independent of increases in ionized Ca. Both vitamin D compounds enhanced PT p21 expression and prevented high P-induced increases in PT TGF-alpha content. Induction of PT p21 and reduction of TGF-alpha content also occurred when uremia-induced PT hyperplasia was suppressed by high dietary Ca. In early uremia, vitamin D suppression of high P-induced PT hyperplasia and high dietary Ca arrest of PT growth involve induction of PT p21 and prevention of increases in TGF-alpha.

Calcium requirement estimated by balance study in elderly Japanese people.

The recommended dietary allowance (RDA) for calcium (Ca) of Japanese adults is proposed to be 600 mg/day, which is lower than those of other countries. In this report we estimated the Ca requirement and the RDA for Ca in elderly Japanese utilizing a Ca balance method. Subjects were 10 men aged 65-72 years and 10 women aged 62-77 years. Following a 14 day adaptation period, each participant was subjected to a low Ca diet (Ca 250 mg as a meal) for 6 days. After an interval of 2 weeks or more, another 14 day adaptation period was set and then a high Ca diet (Ca 250 mg as a meal and 600 mg as CaCO3) was served to the subjects for 6 days. Ca balance was calculated at each dose of Ca intake. Ca requirement was estimated by the intersection of the average Ca intake-retention diagram. Daily Ca requirement was 702 mg in the men and 788 mg in the women. The Ca requirement values were multiplied by 1.2 to obtain the RDA for Ca. As a result, RDA for Ca was 842 mg/day for men and 946 mg/day for women. When these values were normalized with the body weight, the RDA for Ca of Japanese and Caucasian women was similar (18.1 and 18.5 mg/kg body weight per day, respectively). Our results suggest the difference in Ca balance between the genders and among populations may be ascribed at least partly to differences in body size. In addition, body weight should be considered when comparing the RDAs among different populations.

Effects of dietary calcium on adipocyte lipid metabolism and body weight regulation in energy-restricted aP2-agouti transgenic mice.

We have demonstrated previously a regulatory role for intracellular Ca2+ ([Ca2+]i) in adipocyte lipogenesis and lipolysis and have recently reported that 1,25-(OH)2-D increases adipocyte [Ca2+]i, which causes increased lipogenesis and decreased lipolysis. We have now tested the hypothesis that suppressing 1,25-(OH)2-D by increasing dietary calcium will suppress adipocyte [Ca2+]i, thereby facilitating weight loss by stimulating lipolysis and inhibiting lipogenesis in calorically (Kcal)-restricted (70% of ad lib) aP2-agouti transgenic (aP2-a) mice. Mice (aP2-a) exhibiting a pattern of obesity gene expression similar to humans were fed a low-Ca (0.4%)/high-fat/high-sucrose diet for six weeks, resulting in a 27% and twofold increase in body weight and total fat pad mass, respectively, with a twofold increase in adipocyte [Ca2+]i pad lib or Kcal-restricted (70% of ad lib) on this diet either unsupplemented (basal) or with 25% or 50% of the protein replaced by non-fat dry milk (medium or high) dairy or supplemented with CaCO3 to 1.2% Ca for six weeks. Adipocyte [Ca2+]i was unaffected by Kcal restriction but was reduced markedly by all three high Ca diets (290 vs. 130 nM, p2+]i and thereby reduce energy storage and increase thermogenesis during Kcal restriction.

Increasing calcium levels in cultured insects

Low calcium (Ca) contents and low calcium:phosphorus (Ca:P) ratios of mealworm larvae and house crickets can result in imbalances of Ca and phosphorus (P) in diets of avian species when these insects form more than a minor proportion of the diet. Appropriate dietary Ca and Ca:P levels are particularly important for normal growth and bone development in chicks, especially of long-legged species such as bustards. Two experiments were carried out to evaluate the efficacy of a selection of practicable dietary options for increasing the Ca levels and Ca:P ratios of cultured mealworm larvae and immature house crickets used for feeding bustards. Dietary treatments contained higher levels of Ca than the insects' standard culture diet components but similar P levels. Dietary treatment significantly increased Ca level and Ca:P ratio of both mealworm larvae and immature house crickets but did not affect P content of either species. Acceptable insect Ca and Ca:P levels were achieved by maintaining insects on commercial high-Ca diet products for as little as 24 hours. Other factors that may have influenced the Ca levels of mealworm larvae and house crickets include physical form and overall nutrient composition of their diets. Zoo Biol 19:1–9, 2000. © 2000 Wiley-Liss, Inc.

Excessive Ca and P Intake during Early Maturation in Dogs Alters Ca and P Balance without Long-Term Effects after Dietary Normalization

Calcium (Ca) and phosphorus (P) balance is important for skeletal development. Although the effects of deficiencies are well known, reports on the effects of excessive Ca and P supply are relatively scarce. Epidemiologic data and a few controlled studies have shown that skeletal abnormalities may develop when Ca intake is excessive, particularly in periods of rapid growth. Changes in Ca and P balance during and/or after a high Ca intake are thought to underlie this phenomenon. In this study, the effects of excessive Ca (3.1 g/kg dry matter) or Ca and P (Ca 3.1 g/kg, P 2.8 g/kg) intake on Ca and P balance in young, rapidly growing dogs during (for the period from 3 to 17 wk of age) and after (for the period from 17 to 27 wk of age) high Ca and P intake were compared with findings in age-matched controls with normal Ca and P intakes (Ca 1.0 g/kg, P 0.8 g/kg). Dogs fed a high Ca diet developed hypercalcemia, and food intake and fractional absorption of Ca and P were significantly lower at 15 wk of age, whereas endogenous fecal and renal Ca excretion were significantly higher than in controls. This resulted in significantly higher Ca retention than in controls only at 9 wk of age, and in disproportionate absorption of Ca and P. In dogs fed a high Ca and P diet, normocalcemia was maintained, fractional absorption of Ca and P were significantly lower at 9 and 15 wk of age, but retention of both was significantly higher at 9 wk than in controls. The endogenous fecal Ca and renal P losses were significantly higher, but renal Ca excretion was not different from that in controls. After normalization of Ca and P intake, Ca and P balance did not differ among groups. In conclusion, excessive Ca and P intake during early maturation alters Ca and P balance, but does not influence Ca and P balance after dietary normalization.

The determinants of iron status in early pregnancy.

In pregnancy, the additional demands for Fe are thought to be met principally through increased maternal dietary Fe absorption and by mobilization of maternal Fe stores. In a general population sample of 576 women we examined the maternal and dietary characteristics which influenced Fe stores (assessed by serum ferritin concentration) in early pregnancy. The effects of these characteristics on two measures of functional Fe status (mean cell volume and haemoglobin concentration) were also considered. Serum ferritin concentrations were lower in multiparous women (P < 0.0001) and in those with a lower BMI (P = 0.01), and rose with increasing alcohol intake (P < 0.0001). Ferritin concentrations fell with increasing Ca intake (P < 0.0001); the proportion of women with serum ferritin values < or = 12 micrograms/l rose from 14% of the women in the lowest quarter of Ca intake to 29% of the women in the highest quarter. Mean cell volume and haemoglobin concentration were not related to Ca intake in early pregnancy. Although Ca added to test-meals reduces Fe absorption, long-term Ca supplementation has not been shown to lower plasma ferritin concentration, suggesting that high habitual Ca intakes would be unlikely to influence Fe status in non-pregnant individuals. Our findings show that in early pregnancy there is an association between high dietary Ca intake and lower Fe stores. This effect of Ca on one aspect of Fe status may result from its influence on Fe bioavailability.

Calcium and phosphorus supplementation decreases growth, but does not induce pyramiding, in young red‐eared sliders, Trachemys scripta elegans

It has been speculated that pyramiding, a condition in which the scutes of the carapace become deformed and elevated, may be caused by an imbalance in dietary calcium (Ca) and/or phosphorus (P). This was tested by feeding 48 red-eared sliders (Trachemys scripta elegans), 12–14 weeks old, one of four diets for 150 days. The control diet was 67% krill and 33% flour (DM), providing 1.38% Ca and 1.03% P. The high Ca (2.24%) and high P (2.56%) diets were created by adding limestone or sodium phosphate, respectively, to the control diet. The fourth diet contained 2.95% Ca and 2.48% P, with a Ca:P ratio similar to the control diet. Turtles were maintained in groups of four in 12 10-gallon aquariums with incandescent heat lamps and full spectrum fluorescent lamps (n = 3 tanks/diet). The incidence of pyramiding, body weight, and carapace length were measured every 50 days. Pyramiding was not induced in any group during this study, with all turtles having shells of normal shape and appearance. At the beginning of the study, the turtles weighed 8.37 ± 1.50 g (mean ± SEM), with a carapace length of 35.08 ± 1.88 mm. Those receiving the control and high Ca/high P diets grew significantly faster in body weight than the turtles receiving the high Ca diet, with the turtles on the high P diet being intermediate (control: 10.83 ± 1.49a; high Ca: 5.82 ± .78b; high P: 7.77 ± 1.94a,b; high Ca/high P: 9.01 ± 1.88a g of gain; P = 0.013). The carapaces of turtles on the high Ca diet also grew significantly slower than those of all other groups (control: 9.87 ± 1.10a; high Ca: 5.18 ± .73b; high P: 8.22 ± 2.17a; high Ca/high P: 8.20 ± 1.07a mm of gain; P = 0.010). These data suggest that oversupplementation of calcium may be detrimental to growth performance in young turtles. Zoo Biol 17:17–24, 1998. © 1998 Wiley-Liss, Inc.

Calcium and phosphorus supplementation decreases growth, but does not induce pyramiding, in young red-eared sliders,Trachemys scripta elegans

It has been speculated that pyramiding, a condition in which the scutes of the carapace become deformed and elevated, may be caused by an imbalance in dietary calcium (Ca) and/or phosphorus (P). This was tested by feeding 48 red-eared sliders (Trachemys scripta elegans), 12–14 weeks old, one of four diets for 150 days. The control diet was 67% krill and 33% flour (DM), providing 1.38% Ca and 1.03% P. The high Ca (2.24%) and high P (2.56%) diets were created by adding limestone or sodium phosphate, respectively, to the control diet. The fourth diet contained 2.95% Ca and 2.48% P, with a Ca:P ratio similar to the control diet. Turtles were maintained in groups of four in 12 10-gallon aquariums with incandescent heat lamps and full spectrum fluorescent lamps (n = 3 tanks/diet). The incidence of pyramiding, body weight, and carapace length were measured every 50 days. Pyramiding was not induced in any group during this study, with all turtles having shells of normal shape and appearance. At the beginning of the study, the turtles weighed 8.37 ± 1.50 g (mean ± SEM), with a carapace length of 35.08 ± 1.88 mm. Those receiving the control and high Ca/high P diets grew significantly faster in body weight than the turtles receiving the high Ca diet, with the turtles on the high P diet being intermediate (control: 10.83 ± 1.49a; high Ca: 5.82 ± .78b; high P: 7.77 ± 1.94a,b; high Ca/high P: 9.01 ± 1.88a g of gain; P = 0.013). The carapaces of turtles on the high Ca diet also grew significantly slower than those of all other groups (control: 9.87 ± 1.10a; high Ca: 5.18 ± .73b; high P: 8.22 ± 2.17a; high Ca/high P: 8.20 ± 1.07a mm of gain; P = 0.010). These data suggest that oversupplementation of calcium may be detrimental to growth performance in young turtles. Zoo Biol 17:17–24, 1998. © 1998 Wiley-Liss, Inc.

Blood pressure responses of mild hypertensive caucasian males to a metabolic diet with moderate sodium and two levels of dietary calcium

This study compared blood pressure (BP) responses of hypertensive males to two moderate (3300mg/d) sodium (Na) metabolic diets differing in calcium (Ca). Ten mild hypertensive Caucasian males were fed a 6-week high Ca diet (1400mg/d Ca) and 5 hypertensive males were fed a low Ca diet (400mg/d Ca). BP was measured twice/week and serum and urine were analyzed for Ca, Na, magnesium (Mg), potassium (K), parathyroid hormone (PTH), 1,25(OH) 2 vitamin D, red cell Mg, and plasma renin activity (PRA). Systolic and diastolic BP decreased (9% and 8%, respectively) in the high Ca group (p<0.04). In the high Ca group, 8 of 10 had systolic BP <140 mmHg and 4 of 10 had diastolic BP <90 mmHg by the study's end. The high Ca group showed a nonsignificant (NS) 13–22% increase in urinary Na and a NS 11–16% increase in urinary Ca. This high Ca, moderate Na diet significantly decreased BP in mild hypertensive males vs. a low Ca, moderate Na diet.

Effect of Bovine Somatotropin Administered to Periparturient Dairy Cows on the Incidence of Metabolic Disease

Thirty-eight dry, pregnant Jersey cows were assigned to diet and bST treatment in a 2 × 2 factorial design. During the dry period, half of the cows were fed a normal TMR (0.4% Ca; 0.3 to 0.4% P), and half of the cows were fed a high Ca TMR (1.5 to 1.6% Ca; 0.4 to 0.7% P). The high Ca diets were designed to induce milk fever and were relatively cationic (194 to 293 meq/kg) compared with the normal diets (–131 to 30 meq/kg). A standard dairy diet was fed to all cows postcalving. Cows received subcutaneous injections of either an oil-based excipient or 500mg of bST in an oil-based excipient every 14 d from 28 d before expected calving until approximately 14 d postcalving. Peripartal bST treatment decreased the incidence of clinical mastitis, did not affect incidence of milk fever, and increased the duration, but not the incidence, of ketosis in mature Jersey cows. Blood data confirmed the clinical responses and indicated that treated cows mobilized more bone Ca than did controls, as was evidenced by increased hydroxyproline concentrations. Treatment with bST did not affect blood concentrations of 1,25-dihydroxyvitamin D, Ca, or Mg. High Ca diets increased the incidence of milk fever and downer cow syndrome compared with normal diets. The effect of bST on mastitis and milk production must be considered as preliminary given the small size of the study. Although bST treatment increased Ca mobilization, the effect was insufficient to prevent milk fever in this model.

Reversal of hypertension and endothelial dysfunction in deoxycorticosterone-NaCl-treated rats by high-Ca2+ diet.

We tested the effect of high-Ca2+ diet on blood pressure and responses of mesenteric arterial rings in vitro in established deoxycorticosterone (DOC)-NaCl hypertension. Ca2+ supplementation (2.5%) of Wistar rats, which was commenced 8 wk after initiation of DOC-NaCl treatment (Ca(2+)-DOC group), reversed the development of hypertension, whereas in animals ingesting a normal diet (1.1% Ca2+; DOC group) blood pressure continued to rise until the end of the 12-wk study. In norepinephrine-precontracted arterial rings, relaxations to acetylcholine (ACh) and sodium nitroprusside were attenuated in the DOC group, but these responses were significantly improved by Ca2+ supplementation. The nitric oxide (NO) synthesis inhibitor NG-nitro-L-arginine methyl ester, in the presence of diclofenac, totally abolished ACh-induced relaxations in the DOC group but only attenuated them in the Ca(2+)-DOC group. The remaining relaxation was further inhibited by apamin, an inhibitor of Ca(2+)-activated K+ channels, and practically abolished after blockade of ATP-dependent K+ channels by glyburide. Interestingly, when endothelium-dependent hyperpolarization was prevented using precontractions induced by KCl, no differences were found in relaxations to ACh between the groups. In conclusion, high-Ca(2+) diet effectively reduced blood pressure in DOC-NaCl hypertension and concomitantly enhanced arterial relaxation. Because the relaxations to ACh in the Ca(2+)-DOC group were augmented in the absence and presence of NO synthesis inhibition but not under conditions of prevented hyperpolarization, these enhanced relaxations could be attributed to promoted endothelium-dependent hyperpolarization in the Ca(2+)-supplemented animals.

Bone histomorphometric changes due to differences in calcium intake under metabolic acidosis in rats.

Effects of differences in calcium (Ca) intake on bone metabolism under metabolic acidosis were examined by bone histomorphometry in rats. Rats were divided into 5 diets; low Ca (0.02%) diet (LCD), moderate low Ca (0.3%) diet (LmCD), standard Ca (0.62%) diet (SCD), moderate high Ca (1%) diet (HmCD) and high Ca (3%) diet (HCD). Each diet rats were subdivided into the acidotic group given a 1.8% ammonium chloride solution as drinking water and control group given deionized water. Blood and double labeled bone were collected 30 days later. Arterial blood pH was significantly lower, and plasma ionized Ca level and urinary Ca excretion were higher in the acidotic groups than those in the control groups in all diets. Breaking force in femur and bone volume in tibial proximal metaphysis were significantly lower in the acidotic groups than those in the control groups in LCD, LmCD and SCD. In the acidotic groups, osteoid thickness was significantly higher in LCD than that in LmCD, HmCD and HCD. Mineral apposition rate in the acidotic groups was significantly higher in LCD and LmCD than that in HmCD and HCD. These results suggest that bone mineral loss and bone fragility under metabolic acidosis may be accelerated by high turnover of bone metabolism due to insufficient dietary Ca intake, but can be prevented by adequate supplementation of Ca.