Dietary Magnesium Levels Research Articles

Effects of Fluoride on Magnesium Deficiency in the Guinea Pig

Experiments were conducted with young growing guinea pigs to study the magnesium:fluoride relationship at several dietary levels of magnesium and of fluoride. Addition of fluoride (100 or 200 ppm) to a diet suboptimal in magnesium (0.04%) alleviated soft tissue calcinosis. The effect was evident after 6 and 12 weeks of feeding and appeared to be mediated through a sparing of the magnesium requirement. Growth depression, serum magnesium decrease, and bone magnesium loss were moderated by fluoride addition to the low magnesium diet. The magnesium-sparing and anticalcinatory effects of fluoride were less pronounced in animals fed 0.009% magnesium. A higher level of fluoride (300 ppm) was toxic to guinea pigs fed the low magnesium (0.04%) diet, but not to those fed 0.21% magnesium. Magnesium deficiency was associated with an increase in heart potassium content which was retarded by 100 ppm dietary fluoride. In comparison with data reported previously, species differences are apparent in the magnesium:fluoride interrelationship between the guinea pig, dog and rat.

Dietary Phosphorus and Magnesium Deficiency in the Rat

Calcium, phosphorus and magnesium balance was studied in weanling rats, using 3 dietary levels of magnesium (130, 260 and 1,000 ppm) at each of 3 levels of phosphorus (0.3, 0.5 and 1.0%). The effect of changes in dietary phosphorus on magnesium balance varied and was dependent on the dietary magnesium concentration; high intakes of phosphorus lowered the apparent absorption of magnesium when magnesium was ample, but improved absorption when magnesium was limiting. Similarly, high intakes of magnesium reduced the apparent absorption of phosphorus only when ample quantities of phosphate were consumed. Variations in magnesium intake caused a pattern of calcium absorption which closely resembled the pattern obtained for fecal phosphorus, implying a possible effect of magnesium on calcium phosphate solubility in the gut. Accumulation of calcium in the kidneys was aggravated by either an increase in phosphorus or a decrease in magnesium. Microscopic examination of the kidneys after staining with alizarin red S revealed urolithiasis alone when the accumulation of excess calcium was minimal, but both urolithiasis and nephrocalcinosis when considerable calcium was present. This evidence supports the observations of others that intratubular cast deposition is the primary lesion in magnesium deficiency and thus suggests that magnesium might be of value in the prevention or control of spontaneous urolithiasis.

Relationship of Excess Calcium and Phosphorus to Magnesium Requirement and Toxicity in Guinea Pigs

Approximately 300 weanling male guinea pigs were used to determine the order of magnitude of the effect of excess dietary calcium and phosphorus upon the magnesium requirement. Growth rate and hemoglobin level were used as criteria of magnesium adequacy. Blood inorganic phosphorus was inversely correlated with the dietary magnesium level but was not a useful criterion. The nature of the toxicity of excess magnesium was also studied. In the presence of 0.8% phosphorus and 0.9% calcium the average magnesium requirement as measured by growth rate and hemoglobin level was 0.12%. Increasing calcium to 3.2% gave an average requirement of 0.20%. When calcium was 2.5% and phosphorus 1.7% the requirement was 0.40%. It was concluded that excess calcium and phosphorus independently increase the minimal magnesium requirement and that their effects are additive. The addition of 1.2% magnesium to a basal diet containing 0.9% calcium and 0.6% phosphorus had no detrimental effects. When the diet contained 1.7% phosphorus, excess magnesium caused high mortality and an extremely poor rate of growth. The damaging effect was alleviated completely by increasing calcium to 2.5%. Thus, excess magnesium was deleterious only when calcium was limiting.

Interrelations among Magnesium, Vitamin B6, Sulfur and Phosphorus in the Formation of Kidney Stones in the Rat

Dietary levels of magnesium, sulfur and phosphorus have been shown to affect markedly the excretion of a variety of urinary constituents and to influence the deposition of renal calcium oxalate in vitamin B6-deficient rats. Diets high in magnesium or low in sulfur-protected rats against stone formation. The protective effect of high magnesium diets was interfered with when the diets were also low in phosphorus even though there was a decrease in the hyperoxaluria associated with vitamin B6 deficiency. Apatite nephrocalcinosis was observed in rats receiving high phosphorus diets containing vitamin B6 and 0.04% of magnesium. In vitamin B6-deficient rats receiving diets high in phosphorus and containing 0.4% magnesium, renal calculi composed of calcium oxalate and calcium phosphate were formed.

Observations on a Magnesium-fluoride Interrelationship in Chicks

The addition of high levels of both magnesium and fluoride to either practical or semipurified diets complete in all known nutrients produced the following results in young chicks: (1) greater reduction in growth than with either magnesium or fluoride alone; (2) the development of a characteristic leg weakness; (3) decreased calcification of the bone. Increasing the calcium level in the diets from 1.0 to 1.5% reduced but did not prevent the magnesium-fluoride relationship. The growth reduction, leg weakness and reduced bone ash caused by high dietary magnesium and fluoride were obtained only when one-day-old chicks were fed the experimental diets; these results were not observed when chicks at two weeks of age were fed the same diets, nor could the interaction be shown in weanling rats. Plasma alkaline phosphatase activity in chicks was elevated about twofold by added fluoride regardless of the dietary magnesium or calcium levels. The level of alkaline phosphatase in the plasma decreased with age in all groups at approximately the same rate. Dietary magnesium or fluoride levels did not influence the conversion of 3-phosphoglycerate to phosphoenolpyruvate by muscle homogenates. 11 references, 4 tables.

Effect of vitamin B6 and magnesium on renal deposition of calcium oxalate induced by ethylene glycol administration.

SummaryOral administration of ethylene glycol to rats and the resultant renal de-position of calcium oxalate were studied in terms of dietary levels of Vit. B6 and magnesium. Under the conditions of these experiments partial protection against oxalate deposition was achieved with excessive dietary Vit. B6 while complete protection resulted when large amounts of MgO were fed. The in vivo oxidation of ethylene glycol to CO2 was found to be related to amount of Vit. B6 administered. Dietary magnesium levels, however, did not affect oxidation of ethylene glycol and it is suggested that dietary magnesium protects against renal deposition of calcium oxalate by altering the solvent characteristics of urine.

The effect of varying dietary magnesium on the electrocardiogram and blood electrolytes of dogs.

This study is concerned with the effects of varying the dietary levels of magnesium on body weight, blood electrolytes and electrocardiogram in the dog. Animals were fed purified diets containing varying levels of magnesium and potassium salts. A lowered intake of dietary magnesium resulted in a significant decrease in the serum potassium levels with a consequent peaking of the T waves. When the serum magnesium levels decreased to 0.8 mg% or less these electrocardiographic changes usually appeared.

Dietary Magnesium, Calcium, and Vitamin B6 and Experimental Nephropathies in Rats: Calcium Oxalate Calculi, Apatite Nephrocalcinosis

The effects of varying dietary levels of vitamin B6, magnesium and calcium were studied in rats, in terms of the urinary excretion of various metabolites and of the deposition in the urinary tract of calcium oxalate and apatite. Primary renal deposits of oxalate with secondary obstructive sequelae involving the lower urinary tract occurred in vitamin B6-deficient rats, accompanied by increased excretion of oxalic and xanthurenic acids and by a marked decrease in citric acid excretion. The feeding of diets high in magnesium (400 mg per 100 gm) markedly reduced the deposition of oxalate in vitamin B6-deficient rats although they remained hyperoxaluric. The urinary citrate, however, returned to normal levels or above, whereas the excretion of xanthurenic acid was lowered. The efficacy of high concentrations of dietary magnesium in decreasing renal oxalate deposition in vitamin B6 deficiency appeared related to change in the solvent characteristics of the urine. Varying the dietary calcium level from 0.2 to 1.2%, in conjunction with vitamin B6 deficiency, demonstrated a direct correlation between dietary calcium and the extent of oxalate deposition, an effect that became more pronounced when combined with low dietary magnesium. Distinct differences could be observed between two strains of white rats as to relative sensitivity to vitamin B6 deprivation, judged both by weight gain and extent of renal oxalate deposits. Renal deposition of apatite is correlated inversely with the dietary level of magnesium and directly with the level of dietary calcium. At the commonly used magnesium intake of 40 mg per 100 gm, such deposits were seen in minimal amounts in a quarter of the animals. At this magnesium concentration, deficiency of vitamin B6 protected the animals against apatite deposition. The magnesium requirement of weanling white rats, as judged by the occurrence of renal apatite deposits, would appear to be in excess of 40 mg per 100 gm.

Influence of dietary magnesium on cardiac and renal lesions of young rats fed an atherogenic diet.

Young male rats fed an atherogenic diet for 24 to 26 days developed magnesium deficiency. The renal lesions, calcium deposition in tubular lumens in the outer zona intermedia, are morphologically consistent with those seen in animals fed magnesium-free diets. It was necessary to feed 8 to 16 times the normal requirement of magnesium to prevent completely these lesions. The limitations in the pathogenesis of these renal lesions are discussed. The addition of 2 mg. per cent of thyroxine to the diet markedly lowered or abolished deposition of calcium in the kidney; it also lowered atherogenesis to a minimum but did not abolish it. Early lesions of atherosclerosis of the cardiac valves and of the aorta were observed. These were more prominent in animals on a 10 per cent than in those on a 20 per cent protein diet. The atherosclerosis was diminished but not abolished by exceedingly high dietary levels of magnesium in the 10 per cent protein group. Such a decrease was not noted in the 20 per cent protein group. There did not appear to be significant variation in the morphology of the fatty livers in and between the various groups and subgroups as judged by staining with Sudan IV.

Interrelationships between experimental hypercholesteremia, magnesium requirement, and experimental atherosclerosis.

The addition of cholesterol and cholic acid to a diet containing 24 mg. percent of magnesium, an amount normally required for young rats, resulted in magnesium deficiency in rats. This was characterized by hyperexcitability, hyperemia of the ears, calcium deposition in the kidney tubules, low serum magnesium levels, and decreased oxidative phosphorylation of heart mitochondria. All these lesions were prevented by raising the dietary magnesium level four to eight times. Feeding the atherogenic diet produced the deposition of lipide in the aorta and in the heart valves. The extent of this intimal sudanophilia was reduced by large amounts of dietary magnesium although serum cholesterol values did not fall and usually rose. This represents perhaps the first clear cut disassociation between serum cholesterol values and the extent of intimal sudanophilia. Raising the level of dietary protein from 10 to 20 per cent decreased the serum cholesterol levels and the extent of the kidney lesions. Thyroxine administration lowered the serum cholesterol values, abolished the kidney lesions and reduced the intimal sudanophilia. These effects occurred even though the serum magnesium levels remained low.