Apparent Absorption Of Magnesium Research Articles

Effect of consumption of uncooked (RS2) and retrograded (RS3) resistant starch on apparent absorption of magnesium, calcium, and phosphorus in pigs.

The aim of this investigation was to study the effect of uncooked (RS2) and retrograded (RS3) resistant starch on the size and site of the apparent absorption of magnesium, calcium, and phosphorus in swine. In an experiment with a parallel design, three groups of six piglets each consumed for two weeks a diet containing either glucose, RS2 or RS3. The piglets were cannulated at the end of the ileum which allowed estimation of the ileal and colonic mineral absorption. Urine, feces, and ileal digesta were collected for measurement of magnesium, calcium, and phosphorus. Dietary RS2, but not RS3, versus glucose reduced (p < 0.05) the total absorption of magnesium and calcium and the ileal absorption of phosphorus in the pig. Differences between species or in RS and/or mineral intake may explain why RS2 reduced the apparent absorption of magnesium and calcium in pigs in this study and raised it in rats in earlier studies.

Native Corn Starch Versus Either Cellulose or Glucose in the Diet and the Effects on Apparent Magnesium Absorption in Goats

The objective of this study was to determine whether dietary glucose or starch would reduce the inhibitory effect of high K intake on Mg absorption in ruminants. In a 6×6 Latin square design, six goats were fed diets with or without added KHCO3 containing either cellulose, glucose, or native corn starch. The K concentrations of the diets were 7.8 or 34.0g of K/kg of dry matter, and carbohydrates were incorporated so that their concentrations were identical on a glucose equivalent basis (331g of glucose/kg of dry matter). The intake of extra K significantly reduced apparent Mg absorption from 29.8 to 22.1% on average. Glucose, instead of cellulose, in the diet did not affect Mg absorption. Replacement of dietary cellulose by corn starch enhanced the mean efficiency of Mg absorption from 21.8 to 30.9%. Starch versus glucose increased Mg absorption by 5.8 percentage units. No statistically significant interaction was observed between the type of carbohydrate and the amount of K in the diet with regard to Mg absorption. This study showed that the inhibitory effect of dietary KHCO3 on Mg absorption in goats was fully counteracted by the replacement of cellulose with starch in the diet. Possible changes in the pH of ruminal fluid might have mediated the dietary effects on Mg absorption.

Dietary Raw Versus Retrograded Resistant Starch Enhances Apparent but not True Magnesium Absorption in Rats

Dietary raw (RS2) vs. retrograded resistant starch (RS3) raises apparent magnesium absorption in rats. The mechanism proposed is that RS2 enhances magnesium availability for absorption; it does this by increasing ileal solubility of magnesium due to a reduction in pH as a consequence of RS2 fermentation in the gut. The mechanism implies that dietary RS2 vs. RS3 would raise true magnesium absorption and stimulate reabsorption of endogenous magnesium, leading to a lower fecal excretion of endogenous magnesium. Dietary lactulose vs. glucose raises apparent magnesium absorption, and the mechanism proposed is similar to that for the stimulatory effect of RS2 vs. RS3. Thus, we measured in rats fed RS3, RS2, glucose or lactulose true magnesium absorption on the basis of the retention of the orally and intraperitoneally administered radiotracer 28Mg. Feeding rats RS2 instead of RS3 significantly enhanced apparent but not true magnesium absorption, because RS2 lowered fecal excretion of endogenous magnesium. When compared with dietary glucose, lactulose significantly raised both apparent and true magnesium absorption, but did not affect fecal excretion of endogenous magnesium. It is suggested that the proposed mechanism by which RS2 and lactulose would enhance magnesium absorption is disproved by the present data.

Phytate breakdown and apparent absorption of phosphorus, calcium and magnesium in germfree and conventionalized rats

Male germfree and conventionalized rats, 4 weeks old, were fed a phytate-free diet or a diet containing sodium phytate (1.2% in the first experiment and 2.4% in the second experiment) for 3 weeks. Phytate breakdown and apparent absorption of P, Ca and Mg were determined using Cr 2O 3 as a non-absorbable marker and analyzing not only the feces but also the contents of the lower small intestine and cecum. No lower phytate breakdown was observed in GF rats than in conventionalized counterparts. Thus, the presence of gastrointestinal microflora did not increase phytate breakdown, which means that gastrointestinal microflora play no major roll in phytate breakdown in rats. Furthermore, it became apparent by comparing the fecal data with those of the lower small intestine that the large intestine was not a major site of phytate breakdown. Germfree rats showed higher apparent absorption of P, Ca and Mg than their conventionalized counterparts except for Ca in rats fed the diet containing 2.4% sodium phytate. Comparison between rats fed the phytate-free diet and those fed the phytate-containing diets made clear that phytate P was less available than inorganic P and that dietary phytate decreased apparent absorption of Mg but not that of Ca.

Effects of beta 1-->4 linked galactooligosaccharides on use of magnesium and calcification of the kidney and heart in rats fed excess dietary phosphorous and calcium.

Magnesium deficiency was induced in male Wistar rats by adding an excess of phosphorous and calcium to the diet (1.195 g of phosphorous and 1.04 g of calcium/100 g of diet). Feeding of these animals with a diet containing beta 1-->4 linked galactooligosaccharides (4'-GOS) (5 g of 4'-GOS/100 g of diet) increased the apparent magnesium absorption ratios and the concentrations of magnesium in the serum and femur, and reduced accumulation of calcium in the kidney and heart. We speculate that the use of magnesium increased by feeding 4'-GOS to a limited extent prevented the lower magnesium status and the severity of calcification of the kidney and heart caused by excess dietary phosphorous and calcium.

Effect of dietary fructose versus glucose on apparent magnesium absorption in pigs and rats

ZusammenfassungDer Einfluβ des Ersatzes von Glucose durch Fructose auf die scheinbare Absorption von Magnesium bei Schweinen und RattenDer Ersatz von Glucose durch Fructose führte in früheren Untersuchungen zu einem Anstieg der scheinbaren Magnesium‐Absorption bei Ratten. Dieser Effekt war begleitet von einer erhöhten Magnesium‐Löslichkeit im Ileumgehalt. In der vorliegenden Arbeit sollte überprüft werden, ob dieselben Ergebnisse auch für Schweine zutreffen und ob diese Verhältnisse auch für das Colon gültig sind. Dazu erhielten wachsende Schweine, die mit PVTC‐Kannülen versehen waren, Rationen mit Fructose oder Glucose. Danach wurde die scheinbare Absorption von Magnesium im Ileum und Colon gemessen. Die Verabreichung von der Fructose‐Diät führte bei den Schweinen zu einem Anstieg der scheinbaren Absorption von Magnesium im Ileum. Erhielten Ratten die gleichen Diäten wie die Schweine, konnte bei den Fructose‐Diät gleichfalls eine höhere scheinbare Magnesium‐Absorption festgestellt werden. Die Magnesium‐Absorption im Colon wurde bei Schweinen nicht beeinflußt. Die Fructose‐Diäten führte bei den Ratten außerdem zu einer höheren ilealen Magnesium‐Löslichkeit. Dieser Effekt war bei den Schweinen nicht so klar ausgeprägt. Im Durchschnitt wurden beim Schwein zwei Drittel des Magnesiums aus dem Colon und eine Drittel des Magnesiums aus dem Ileum absorbiert.

Calcium and Magnesium Absorption from the Colon and Rectum Are Increased in Rats Fed Fructooligosaccharides

We investigated the effects of fructooligosaccharides on the absorption of calcium, magnesium and water from the colon and rectum of rats fed a control diet or the control diet containing 50 g fructooligosaccharides/kg. Chromium-mordanted cellulose was used as an unabsorbable marker to calculate apparent absorption of calcium and magnesium. There was a positive correlation (r = 0.982, P < 0.001 in rats fed the control diet and r = 0.975, P < 0.001 in rats fed the fructooligosaccharides-containing diet) between the amount of chromium and the dry weight of each fecal pellet in the colon and rectum. Ratios of calcium to chromium and magnesium to chromium in fecal pellets in the colon and rectum were calibrated from the Ca:Cr and Mg:Cr ratios of cecal contents. In rats fed the fructooligosaccharides-containing diet, but not in rats fed the control diet, these ratios were correlated with the fractional length of transit along the colon and rectum, indicating linear disappearance of calcium and magnesium during the colorectal passage. Total apparent absorption of calcium and magnesium, predicted from regression equations with the Ca:Cr and Mg:Cr ratios of cecal contents, agreed well with those calculated from the Ca:Cr and Mg:Cr ratios of feces. The consumption of fructooligosaccharides did not affect net water absorption from the colon and rectum. These results indicated that fructooligosaccharides significantly increased calcium and magnesium absorption and that indigestible and fermentable carbohydrate facilitates colorectal absorption of calcium and magnesium.

Effect of phytic acid and microbial phytase on Cd accumulation, Zn status, and apparent absorption of Ca, P, Mg, Fe, Zn, Cu, and Mn in growing rats.

Three groups of individually housed albino rats (n = 6, initial average weight = 47 g) were fed diets based on egg white and cornstarch (basal diet 8 g Ca, 5.2 g P, 0.76 g Mg, 100 mg Zn, 100 mg Fe, 50 mg Mn, 7 mg Cu, and 5 mg Cd per kilogram diet) over a 4-week period. Group I (controls) was fed the basal diet free of phytic acid (PA) and microbial phytase. In groups II and III cornstarch was replaced by 0.5% PA from NaPA (molar PA/Zn ratio approximately 5). In group III, 2,000 U of microbial phytase from Aspergillus niger per kilogram diet was added. Live weight gain, zinc status (zinc in plasma, femur, liver, and testes; activity of the plasma alkaline phosphatase), and apparent absorption of zinc, iron, copper, and manganese remained unchanged by the different dietary treatments. The apparent phosphorus absorption was highest in the phytase group. PA decreased and microbial phytase improved the apparent absorption of calcium and magnesium. Liver cadmium concentration, total liver and kidney cadmium content, as well as fractional liver and kidney cadmium accumulation in rats fed the diet containing PA were significantly higher than those in the controls. Phytase supplementation lowered liver and kidney cadmium accumulation. Differences in calcium and magnesium bioavailability due to PA and microbial phytase may be one factor in the alteration of tissue cadmium accumulation.

Effects of endoxylanase addition to wheat-based diets on physico-chemical chyme conditions and mineral absorption in broilers

Four wheat cultivars, differing in in vitro viscosity and water-soluble arabinoxylan content, were added to a basal diet on a 50:50 weight basis. These wheat-based diets were fed to male broilers from 3 weeks of age, with and without the addition of 75 mg endoxylanase (70 000 EXU g −1 enzyme) per kg feed. The broilers were killed at 4.5 weeks of age, and the jejunal and ileal contents were sampled. The absorption of sodium, potassium, calcium, phosphorus, and magnesium was calculated, based on the contents of the last 10 cm of these intestinal segments, using Cr 2O 3 as a reference substance. The pH, osmolality and viscosity were measured in the remaining jejunal and ileal contents. Dietary addition of high viscosity wheats (HVW) resulted in higher intraluminal viscosities than on the low viscosity wheat (LVW) diets. The osmolality of the chyme supernatant of the birds fed the HVW diets declined less as the chyme moved from the jejunum into the ileum, compared with the LVW diets. This indicates a less efficient absorption of osmo-active soluble chyme components at higher intraluminal viscosities, as complex formation in the intestinal lumen could not account for this effect. Linear regression analysis revealed a clear negative relationship between the viscosity of the chyme supernatant and the absorption of dry matter and minerals in either one or both of the intestinal segments. Addition of endoxylanase lowered the viscosity of the chyme supernatant to similar levels on all wheat-based diets. Furthermore, it enhanced the apparent absorption of calcium, magnesium, sodium and potassium from the jejunal lumen. However, at the lower ileal level only magnesium absorption was improved by dietary endoxylanase addition.

Dietary Tannins from Cowpeas and Tea Transiently Alter Apparent Calcium Absorption but Not Absorption and Utilization of Protein in Rats

Tannins reportedly alter absorption and utilization of protein and minerals. The present study investigated the effect of tannins extracted from 'Mississippi Silver' cowpeas and black tea when incorporated into nutritionally balanced diets. Condensed tannins were incorporated into the diet of weanling male Sprague-Dawley rats at 0.0, 0.0057, 0.0171 and 0.057 g/100 g diet for 28 d. Ingestion of tannin from cowpeas or tea did not change significantly growth rate, protein efficiency ratio, apparent protein digestibility, nitrogen excretion, relative liver weight, or nitrogen concentration of liver. During d 11-18, apparent calcium absorption was lower in rats fed the medium and high levels of cowpea tannin and in those fed all levels of tea tannin compared with the control group. By wk 4, no differences were observed in apparent calcium absorption among treatment groups. Apparent magnesium absorption was not affected by dietary treatment, nor was femur content of calcium or magnesium. We conclude that at the levels of condensed tannins fed, a short-term reduction of apparent calcium absorption occurred; however, by wk 4 calcium absorption was comparable to that of the control group. The acute change that occurred in apparent calcium absorption did not influence bone calcium content.

Increasing Calcium Intakes Lower Urinary Concentrations of Phosphorus and Magnesium in Adult Ovariectomized Cats

The effect of dietary calcium level on the fecal and urinary excretion of calcium, phosphorus and magnesium was studied in adult cats. Ovariectomized cats were fed purified diets containing 3.2, 4.8, 9.5 or 19.3 mmol calcium/MJ in a 4 x 4 wk crossover study. During the experiment, balance studies were performed and blood samples were taken. The adult ovariectomized cats maintained calcium balance at all four levels of calcium tested. Extra dietary calcium, in the form of CaCO3, caused a slight increase in urinary pH. Urinary concentrations of phosphorus and magnesium dropped, but that of calcium remained unchanged, when the cats were fed diets with increasing calcium levels. The percentages of apparent absorption of phosphorus and magnesium fell when calcium intake was raised. The dietary calcium level did not affect plasma concentrations of calcium, magnesium and phosphorus or plasma activity of alkaline phosphatase.

Effects of dietary concentration and source of fibre on the apparent absorption of minerals by pigs

Four metabolism trials each involving 12 entire male pigs of an approximate initial weight of 45 kg were conducted to determine the effects of the proportion and the source of dietary fibre on the apparent absorption (AA) of calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K). The materials used to provide the dietary fibre were: soya-bean hulls, pea ( Pisum sativum) hulls, maize hulls and oat hulls. Increasing levels of each of the above-mentioned materials that would provide 69, 151, 249 or 367 g of neutral detergent fibre (NDF) were added to a constant daily allowance of a semi-synthetic diet and measurements of the total faecal output over a 10 day period were made. Increasing the proportion of fibre in the diet failed to produce any significant effects on the AA of Ca, P and Mg. Source of fibre also appeared not to be a major factor in influencing the AA of these minerals. The AA of Na and K was significantly reduced ( P < 0.001) by the high NDF content in the diets. The extent of this reduction differed ( P < 0.001) among NDF sources indicating that the chemical composition of fibre in terms of acid detergent libre (ADF), NDF, lignin, cellulose, hemi-cellulose and perhaps pectin content is an important factor relating to its effects on mineral utilization.

Magnesium homeostasis: conservation mechanism in lactating women consuming a controlled-magnesium diet

This study was undertaken to determine whether lactating women consuming a low-magnesium diet compensate for magnesium secreted into breast milk by decreasing urinary magnesium losses. Six lactating (L) women, six nonlactating (NL) women (75 +/- 5 and 61 +/- 5 d postpartum, respectively), and seven never-pregnant (NP) women were studied while consuming a constant magnesium intake of 8.97 +/- 0.01 mmol/d for 20 d. After a 5-d stabilization period on the controlled diet, 24-h urine and fecal samples were collected for the next 15 d. The L women excreted significantly less (P < 0.01) urinary magnesium (2.10 +/- 0.35 mmol/d) than the NP women (3.45 +/- 0.37 mmol/d). No significant differences were detected in mean apparent magnesium absorption among the three groups of women, because of large individual variations of fecal magnesium and small sample size. L women apparently compensated for magnesium losses in breast milk (1.04 +/- 0.06 mmol/d) by reducing urinary magnesium losses (1.38 mmol/d) when consuming 8.97 mmol Mg/d.

High phosphorus intake depresses apparent magnesium absorption in pregnant heifers

ZusammenfassungDer Einfluß einer hohen Phosphoraufnahme auf die scheinbare Magnesiumabsorption bei trächtigen FärsenDer Einfluß der Phosphorversorgungshöhe auf die scheinbare Magnesiumabsorption wurde in einem 31 × 30 Tage dauernden cross‐over‐Versuch an 6 Färsen nach Verfütterung von Rationen mit 5,4 g Magnesium/kg TS und 2,2 oder 6,4 g Phosphor/kg TS untersucht. Die P‐Ergänzung erfolgte über Na2HPO4. Der Na‐Gehalt wurde in den P‐armen Rationen durch NaHCO3 ausgeglichen. Nach der Fütterung der P‐reichen Ration sank die Ausscheidung von Mg über den Harn signifikant von 10,3 auf 8,8 g pro Tag, wobei sich die scheinbare Mg‐Absorption signifikant von 29,9 auf 24,5% erniedrigte. Der höhere P‐Gehalt hatte keinen Einfluß auf die Ca‐Exkretion. Der Mg‐Gehalt in der Ration und die P‐Konzentration bei der P‐reichen Ration lagen höher bzw. die P‐Konzentration bei der P‐armen Ration lag niedriger als in praxisüblichen Rationen. Diese unüblichen Mg‐ und P‐Gehalte der Rationen und der verhältnismäßig geringe Effekt der P‐Aufnahme auf die scheinbare Mg‐Absorption scheinen die Relevanz der Ergebnisse einzuengen. Trotzdem wird das Risiko aufgezeigt, das auftreten kann, wenn hohe P‐Aufnahmen bei gleichzeitiger niedriger Mg‐Aufnahme eine Mangelversorgung an Mg verstärken können.

High Protein Intake Raises Apparent but Not True Magnesium Absorption in Rats

Earlier studies with rats have shown that greater protein intake raises apparent magnesium absorption (ingested magnesium minus fecal magnesium). We addressed the question of whether high protein intake affects true magnesium absorption. Rats were fed either a normal (175 g casein/kg) or a high (525 g casein/kg) protein diet. Extra protein was added at the expense of the glucose component of the diet; the diets were balanced for magnesium, calcium and phosphorus. The high protein diet enhanced apparent magnesium absorption. True magnesium absorption, as measured with the use of oral and intraperitoneal administration of tracer doses of 28Mg, was found to be unaffected by high protein intake. Endogenous magnesium excretion in feces was significantly depressed in rats fed the high protein diet, which was associated with elevated urinary magnesium excretion. High protein intake reduced the amount of magnesium in whole ileal digesta but raised the amount and concentration of magnesium in the liquid phase. We conclude that improvement of apparent magnesium absorption in rats fed high protein diets is due to depressed fecal excretion of endogenous magnesium.

Dietary Native Resistant Starch but Not Retrograded Resistant Starch Raises Magnesium and Calcium Absorption in Rats

The effects on calcium and magnesium absorption of dietary native and retrograded cornstarch were studied in rats. Uncooked high amylose starch granules (35% of total glucose equivalents as enzyme-resistant starch) and cooked and cooled (-20 degrees C) high amylose starch (24% of total glucose equivalents as retrograded resistant starch) were used as test starches, and cooked normal starch (3% of total glucose equivalents as resistant starch) was used as control starch. Native vs. control starch raised the amount of polymerized glucose in ileum, but not in feces. Retrograded starch produced more polymerized glucose than control starch in both ileum and feces. When compared with control starch, ileal pH was significantly lowered by native starch and tended to be raised by retrograded starch. Cecal pH was lowered by the two preparations rich in resistant starch. Apparent absorption of calcium and magnesium was raised by native starch but not by retrograded resistant starch. Calcium concentrations in the liquid phase of the ileum tended to be elevated by native starch but were significantly lowered by retrograded starch relative to control starch. Magnesium and calcium concentrations in liquid cecal contents tended to be raised with native starch; they were unchanged with retrograded starch. It is suggested that native resistant starch raised calcium and magnesium absorption because it tended to enhance the solubility of these minerals in ileal and cecal digesta.

Inhibitory Effect of Soybean Protein vs. Casein on Apparent Absorption of Magnesium in Rats Is Due to Greater Excretion of Endogenous Magnesium

Apparent magnesium absorption is depressed in rats fed diets containing soybean protein or enriched with sodium phytate or phosphate in comparison with casein, whereas it is raised in rats fed lactose. However, the possibility that changes in apparent absorption are caused by changes in fecal excretion of endogenous magnesium cannot be excluded. We studied the effects of casein, soybean protein, sodium phytate, lactose and phosphate on apparent and true absorption of magnesium. True magnesium absorption was measured with the use of oral and intraperitoneal administration of tracer doses of 28Mg. Fecal excretion of endogenous magnesium was calculated from apparent and true absorption. True magnesium absorption was not affected by either substitution of soybean protein for casein or by the addition of sodium phytate to a diet containing casein. Endogenous magnesium excretion in feces was significantly increased by soybean protein and sodium phytate. Thus the observed impairment of apparent magnesium absorption in rats fed soybean protein or sodium phytate is due to enhanced fecal excretion of endogenous magnesium. With the other dietary treatments, enhanced fecal excretion of endogenous magnesium was not associated with a discrepancy in the effects on apparent and true magnesium absorption. Dietary lactose vs. dextrose and supplemental phosphate both stimulated fecal excretion of endogenous magnesium, but lactose raised both true and apparent magnesium absorption, and phosphate depressed both true and apparent magnesium absorption.

Effect of Oat Bran Muffins on Calcium Absorption and Calcium, Phosphorus, Magnesium and Zinc Balance in Men

Metabolic balance studies were conducted in adult human males to investigate the effect of oat bran on the nitrogen, calcium, phosphorus, magnesium and zinc balance, on the intestinal absorption of calcium and on the endogenous fecal calcium, using 47CaCl2 as the tracer. A 40-d control period preceded a 32-d experimental period in which subjects consumed four oat bran muffins daily as part of a constant metabolic diet. No significant changes in the calcium, magnesium or zinc balances were observed, but the nitrogen and phosphorus balances increased. The net or apparent absorption of nitrogen, magnesium and phosphorus expressed per milligram of intake increased significantly in the oat bran period due to the added content of these nutrients in the oat bran muffins. The intake of the oat bran muffins led to a significant increase in urinary phosphorus and significant decreases in urinary calcium and 47Ca excretions. The intestinal absorption of calcium, determined with 47Ca, did not change, whereas the endogenous fecal calcium increased slightly but significantly.

Is vitamin D 3 essential for mineral metabolism in the Damara mole-rat ( Cryptomys damarensis)?

The Damara mole-rat ( Cryptomys damarensis) leads a strictly subterranean existence in an extensive maze of plugged burrows and eats a strictly herbivorous diet. An obvious source of vitamin D 3 (D 3), an important hormone in mineral homeostasis, therefore is lacking in this mammal. The effects of orally ingested D 3 on mineral balance were investigated. In the normal D′ status group of mole-rats, the apparent fractional intestinal absorption of calcium (91.1%), magnesium (91.2%), and inorganic phosphorous (91.2%) was high and increased slightly, (calcium, 94.5%; magnesium, 93.2%; inorganic phosphorous, 92.9%) after D 3 administration. The amount of element absorbed was positively correlated with the amount ingested ( P < 0.001), suggesting that absorption occurs via a nonsaturable process. This might be an adaptation to the sparseness of natural food. The observed positive retention of calcium (94%), magnesium (85%), and inorganic phosphorous (99.9%) is attributed to their evergrowing teeth. These teeth are constantly worn down during digging and it is speculated that they represent a mineral “sink”, assisting in the maintenance of mineral homeostasis. It is also hypothesized that mole-rats have adapted to an environment devoid of D 3 and can attain sufficient calcium for their needs via nonvitamin D 3-dependent processes. Although mole-rats have the “machinery” to use D 3 and D 3 can affect mineral balance, this effect may be disadvantageous if invoked.

Effect of various chloride salts on the utilization of phosphorus, calcium, and magnesium

Only part of the effect of dietary protein on urinary calcium excretion can be ascribed to sulfur amino acids. We hypothesized that chloride, another factor often associated with isolated proteins, and another amino acid, lysine, affect utilization of calcium. The effects of supplemental dietary chloride, inorganic or organic, on calcium, phosphorus, and magnesium utilization were studied in two rat studies. Weanling Sprague-Dawley rats were fed semi-purified diets that contained moderate (1.8 mg Cl/g diet) or supplemental (15.5 mg Cl/g diet) chloride as sodium chloride, potassium chloride, or lysine monohydrochloride with or without calcium carbonate for 56 or 119 days. Rats fed supplemental sodium chloride or potassium chloride had higher urinary phosphorus excretion, more efficient phosphorus absorption, but unchanged tissue phosphorus levels after 7 and 16 weeks of dietary treatment as compared to rats fed moderate chloride. Rats fed supplemental sodium chloride or potassium chloride excreted more calcium in urine at 7 weeks and absorbed calcium less efficiently at 16 weeks. Tissue calcium concentrations were unaffected, but total tibia magnesium and plasma magnesium concentrations were lower in rats fed supplemental sodium chloride or potassium chloride than those fed moderate chloride. Lysine chloride with or without additional calcium elevated urinary calcium excretion even more than sodium chloride and potassium chloride ingestion. Rats fed lysine chloride with supplemental calcium had smaller apparent absorption and urinary losses of phosphorus and magnesium after 16 weeks and lower tibia and plasma magnesium concentrations than rats fed lysine chloride.