Effect of dietary calcium and phosphorus levels on the utilization of calcium,phosphorus, magnesium,manganese, and selenium by adult males

The effects of dietary calcium and phosphorus levels on the utilization of phosphorus, calcium, magnesium, manganese, and selenium by nine adult males were examined during a 39-day balance study. The dietary treatments were a moderate calcium-moderate phosphorus diet (MCaMP), a moderate calcium-high phosphorus diet (MCaHP), and a high calcium-high phosphorus diet (HCaHP). The moderate and high levels of phosphorus were 843 and 2443 mg daily, respecitvely; the moderate and high levels of calcium were 780 and 2382 mg daily, respectively. Subjects were unable to maintain positive balance in regard to phosphorus when fed the moderate level of phosphorus (MCaMP) but maintained positive balance in regard to phosphorus when fed the high level of phosphorus (MCaHP, HCaHP). The addition of more calcium to the high phosphorus diets resulted in significantly greater excretion of phosphorus in the feces but significantly less excretion of phosphorus in the urine by subjects. The dietary treatments affected urinary excretion of calcium, magnesium, and selenium significantly, but the effects were small or were compensated for by changes in fecal excretion of the minerals. Thus the dietary treatments had no significant effects on overall retention of calcium, magnesium, manganese, and selenium by these subjects.     

The effects of dietary calcium and phosphorus on the retention and excretion of lead in rats.

1. Rats were given diets containing different amounts of calcium, phosphorus and lead. 2. Pb retention was greatly increased when the diets contained less Ca or P than the minimum estimated requirement of the rat. 3. The release of Pb already incorporated into the skeleton was inhibited by diets low in Ca but was not affected by diets low in P. 4. The retention of Pb given intraperitoneally was not affected by dietary Ca or P. 5. It can be concluded that dietary Ca and P influence the absorption of Pb by the gut and dietary Ca influences the metabolism of Pb in the bone. 6. There were changes in the distribution of Pb among the tissues due to changes of dietary Ca. 7. At low body concentrations, Pb probably affected skeletal growth.     

A comparison of the effects of dietary calcium and phosphorus deficiency on the in vitro and in vivo metabolism of 25-hydroxycholecalciferol in the chick

1. Young chicks fed a diet deficient in calcium showed an eightfold increase in the in vitro renal production of 1,25-dihydroxycholecalciferol (1,25-DHCC) and those fed a diet deficient in phosphorus showed a threefold increase when compared to chicks on a normal diet. 2. The in vivo accumulation of 1,25-DHCC in the gut mucosa was doubled in both low-Ca and low-P groups as was the rate of Ca absorption from the duodenum and the Ca-binding protein activity. The accumulation of 1,25-DHCC in bone increased threefold in the low-Ca group but showed no change in the low-P group. 3. It was concluded that the increased rate of Ca absorption found in dietary P deficiency depends rather upon the capacity of the gut mucosa to accumulate larger amounts of 1,25-DHCC than upon an increased renal production of this metabolite. The mechanism by which this is achieved is unknown, but it unlikely to be a general increase in availability of 1,25-DHCC since no rise occurred in bone 1,25-DHCC levels.     

Influence of dietary calcium and cholecalciferol on composition of plasma lipids in young pigs

Young growing pigs were fed diets containing either 1 or 3 times the daily requirement of calcium and 1, 5 or 25 times the daily requirement of vitamin D (as cholecalciferol) in a completely randomized design with treatments in a 2 X 3 factorial arrangement. Excess dietary calcium increased the phospholipid concentration in the plasma, but not its partitioning among plasma lipoproteins. The level of dietary calcium had no effect on cholesterol, triacylglycerol or protein concentrations in plasma or their partitioning among plasma lipoproteins. Excess dietary calcium decreased body weight gains of pigs. The level of dietary cholecalciferol had no effect on body weight gain or on the concentrations of cholesterol, phospholipid, triacylglycerol or protein in plasma, or on their partitioning among plasma lipoproteins. Increased vitamin D intake resulted in increased plasma 25-hydroxycholecalciferol, whereas high dietary calcium decreased concentrations of 1,25-dihydroxy-vitamin D. Increased dietary calcium also increased plasma calcium concentrations of only plasma phospholipids and decreased growth rate, whereas excess dietary vitamin D had no effect on growth or lipid composition of plasma in growing pigs.     

Influence of dietary phosphorus restriction on calcium and phosphorus metabolism in rats

The effect of dietary phosphorus (P) on calcium (Ca) and phosphorus metabolism was studied in young female rats. P levels in the semipurified diets ranged from 0.1 to 0.4% (w/w). A level of 0.4% P in the diet is recommended for rats. Kidney calcification was observed in rats fed the 0.4%-P diet whereas P restriction prevented this condition. Rats fed the diet containing 0.1% P, showed severe hypercalciuria, hypercalcemia, reduced growth and impaired bone mineralization. These effects did not occur when the diet contained 0.2 or 0.3% of P. This study suggests that in short-term studies P in the diet of female rats can be restricted to 0.2% so as to prevent nephrocalcinosis without affecting their development.     

Tin, copper, iron and calcium metabolism of rats fed various dietary levels of inorganic tin and zinc

Three studies were conducted to determine the effects of various dietary levels of tin (less than 1, approximately 100, approximately 200, approximately 500, approximately 2000 micrograms/g diet) and of zinc (approximately 15, approximately 30, approximately 52 micrograms/g diet) on the metabolism of tin, copper, iron and calcium by growing rats. The accumulation of tin in the kidneys and tibias of animals was proportional to dietary exposure. The concentration of tin in the bones of rats fed greater than 100 micrograms Sn/g diet was 5-fold and 20-fold greater than the levels found in kidney and liver, respectively. Rats fed greater than 500 micrograms Sn/g diet had plasma copper levels that were only 13% of control levels and had depressed copper levels in livers and kidneys. The activity of delta-aminolevulinic acid dehydratase in the erythrocytes of rats fed the highest level of tin was 55% of that found in control animals. The amounts, but not the concentrations, of calcium in the tibias of rats fed greater than 100 micrograms Sn/g diet were less than the levels in the bones of control animals. The moderate variations in dietary zinc levels did not affect significantly the levels of minerals in tissues.     

Effects of dietary calcium, phosphorus and magnesium on intranephronic calculosis in rats

The effects of varying dietary levels of calcium, phosphorus and magnesium on the incidence and severity of intranephronic calculosis were studied. Renal calculi were induced by feeding female rats the AIN-76TM semipurified diet for 4 weeks. During this time period, dietary levels of 350, 450 or 550 mg calcium per 100 g diet did not influence the occurrence of urolithiasis. Increasing dietary magnesium levels from 50 to 350 mg was beneficial in preventing the occurrence of calculi if the diet contained 400 mg or less phosphorus. The protective effects of dietary magnesium were counteracted when dietary phosphorus levels were increased from 400 mg to 550 or 700 mg. If the dietary content of phosphorus and magnesium permitted the formation of renal calculi, the severity of the condition was also influenced by the dietary level of calcium. Some animal groups fed semipurified diets did not have microscopic or radiographic evidence of renal calculi but were found to have significantly elevated renal calcium values. It was suggested that these animals might be in a precalculus-forming state.     

Colon cancer and dietary fat, phosphorus, and calcium in Hawaiian-Japanese men

In a prospective cohort study, 8006 men of Japanese ancestry were examined from 1965 to 1968. A 24-h dietary recall questionnaire was administered to each subject as part of the baseline clinical examination. Dietary data were analyzed for intake of calcium, phosphorus, and total fat in 99 colon cancer cases and in 378 controls chosen from the cancer-free men. This was a nested case-control study design with 14-17 yr of prospective followup for colon cancer incidence. We found no significant association between dietary calcium intake and colon cancer risk. This held true whether phosphorus intake was low (less than 1032 mg/day) or high (greater than or equal to 1032 mg/day), and whether total fat intake was low (less than 61 g/day) or high (greater than or equal to 61 g/day). Adjusted-odds ratios were 0.7-1.4 across eight subgroups of low and high intakes of the three nutrients studied. These data do not support a recent hypothesis that calcium intake might be negatively associated with colon cancer risk, depending on the level of fat and phosphorus intake.     

Effects of dietary aluminum,calcium, and phosphorus on egg and bone of European starlings

Egg and bone of passerine birds nesting in acidified habitats may be affected by high levels of Al or P, or low levels of Ca. Nine treatments of three levels of dietary Al (target levels of 200, 1,000, and 5,000 g/g) and three levels of Ca:P (target levels of NN = 1.3% Ca: 0.9% P; LL = 0.19 Ca:0.45 P; LH = 0.19 Ca: 1.65 P) were fed to 16–17 starling pairs during two breeding seasons. Eggs of starlings fed the LH diet were smaller and weighed less than eggs from the NN and LL treatments. Treatment effects on thickness, strength, and weight of eggshells were not consistent between seasons, probably because of differences in actual dietary levels of Al, Ca, and P or in incubation intervals. In one season, birds fed the highest Al diet had thicker eggshells than those from the other Al treatments (no effect from Ca:P); the following season, eggshells from the NN and LH treatments were thicker and stronger than those from the LL treatment. Eggshells from the NN treatment weighed more than those from the other Ca:P treatments. Starlings on the LH diet had the strongest femurs, but the effect was interactive with different levels of dietary Al. Effects of Ca:P on egg and bone were more evident than Al effects.     

THe effects of the gut microflora and dietary fibre on energy utilization by the chick

1. Groups of adult colostimized chickens were given diets with and without dietary fibre in the form of bagasse or wheat straw. The fibrous materials were analysed for their contents of cellulose, hemicellulose and lignin. The digestible energies (DE) and metabolizable energies (ME) of these diets were measured by a balance method. 2. Groups of germ-free and conventional chicks aged 4 weeks were given diets with and without penicillin or with and without graded levels of wheat straw as a source of fibre and the ME of these diets were determined. 3. The incorporation of the forms of dietary fibre tested reduced the DE and the ME of the diets in adult conventional chickens and the ME in young germ-free and conventional chicks. Both DE and ME were reduced in proportions that suggested that the dietary fibre present was acting largely as an inactive diluent of the dietary energy and was not affecting the absorption of other nutrients. In the young germ-free and conventional chicks, there was a linear relationship between the proportion of wheat straw in one diet and the reduction ME. 4. Dietary penicillin did not alter the ME of the diet in either the germ-free or the conventional environments. 5. The reduction of ME with incorporation of wheat straw was less in conventional than in germ-free chicks. It is suggested that this may be due to the ability of chicks with a gut flora to obtain a small amount of energy from wheat straw.