Effect of protein intake on mineral (calcium, magnesium, and phosphorus) balance in Japanese males

A 26-day balance study was conducted to examine the effect of a high protein diet on calcium, magnesium, and phosphorus utilization in six healthy males (age 20-22 years, body weight 54.0-64.4 kg, body height 165-173 cm). In addition, the effect of physical exercise on calcium, magnesium, and phosphorus balance was also examined. After a 2-day stabilization period, two levels of protein--control (1.0 g/kg of body weight) and high (2.0 g/kg of body weight) protein--diets were given for three 4-day periods at each protein level. During the last 4-day period of each protein level, subjects exercised on a bicycle ergometer for two 1-h periods daily at a load of 1.5 kp., 50 cyc./min. The high protein diet increased urinary calcium and caused a significant negative calcium balance. Magnesium balance tended to be negative in the control diet. There were no significant changes in urinary calcium, magnesium, and phosphorus and also in the calcium, magnesium, and phosphorus balance during physical exercise.     

Effect of glucocorticoids and calcium intake on bone density and bone, liver and plasma minerals in guinea pigs.

The purpose of this study was to see what effect glucocorticoids would have on bone density and mineral distribution in guinea pigs. Adult female guinea pigs were given prednisolone, a synthetic analogue of cortisol, for up to 24 weeks. Bone density and bone, liver and plasma levels of zinc, copper, iron, manganese, chromium, magnesium and calcium were studied in these animals. In one study, the effect of menopause was simulated by using ovariectomy. In another study, dietary calcium was varied to investigate its effect with glucocorticoids. Animals treated with 1 mg prednisolone/kg body weight showed increased femur density compared with controls, but no changes in tissue mineral concentrations. Animals fed 100 mg prednisolone/kg body weight experienced decreased femur density. Differences in effects were not observed between ovariectomized and intact animals. Bone loss was greatest in animals fed the cereal-based closed-formula diet and least in animals fed the low-calcium diet. Changes in mineral content of femurs observed in animals which lost bone mass were increased iron concentration and decreased magnesium concentration. Total liver stores of zinc and magnesium increased. Liver copper increased in concentration per gram as well as in total content. Liver concentration of manganese decreased. Plasma changes in animals fed the high level of drug were decreased iron and calcium, and increased copper. Hemoglobin and hematocrit increased with increasing drug levels. It is suggested that glucocorticoids have marked effects on mineral metabolism which may be related to the bone loss and that these effects may be modified by dietary changes.     

钙及钙镁联合拮抗氟毒性的实验研究

对SD大鼠给予20mgF/kg·day染毒14天,体内氟负荷明显增大,肝、肾明显肿胀,肾脏呈明显的病理变化,血清Ca、Mg、Cu、Zn及Cu/Zn比值发生明显异常改变;补充钙镁能拮抗此一系列毒性反应,在50～150mgF/kg·day范围内,钙呈现一定的剂量效应关系;联合应用钙镁各50mg/kg·day效果更佳。     

Effects of tocopherols and tocotrienols on body composition and bone calcium content in adrenalectomized rats replaced with dexamethasone

Long-term glucocorticoid treatment is associated with severe side effects, such as obesity and osteoporosis. A palm oil-derived vitamin E mixture had been shown previously to be protective against osteoporosis in rats given 120 microg/kg dexamethasone daily for 12 weeks. In this study we determined the effects of two isomers of vitamin E (i.e., palm oil-derived gamma-tocotrienol and the commercially available alpha-tocopherol, 60 mg/kg of body weight/day) on body composition and bone calcium content in adrenalectomized rats replaced with two doses of dexamethasone, 120 microg/kg and 240 microg/kg daily. Treatment period was 8 weeks. gamma-Tocotrienol (60 mg/kg of body weight/day) was found to reduce body fat mass and increase the fourth lumbar vertebra bone calcium content in these rats, while alpha-tocopherol (60 mg/kg of body weight/day) was ineffective. Therefore, in conclusion, palm oil-derived gamma-tocotrienol has the potential to be utilized as a prophylactic agent in prevention of the side effects of long-term glucocorticoid use.     

Calcium requirements during total parenteral nutrition in well-nourished individuals.

Eleven patients, receiving all nutrition intravenously, were given varying doses of calcium (0-20 mg/kg/day) to determine an optimal level for calcium administration during postoperative parenteral nutrition. During each study period, nitrogen, phosphorus, vitamin, and caloric intakes were constant. Negative calcium balance resulted when less than 2 mg Ca++/kg body weight was given daily. During excessive urinary calcium losses, serum calcium concentration remained in the normal range. Increasing calcium intake to approximately 5 mg/kg/day (500 mg/day) yielded an apparent retention of calcium, as did higher doses. Serum calcium did not rise at this time. Urinary calcium excretion was directly proportional to calcium intake. The preliminary data suggest that a minimum dose of 5 mgCa++/kg/day is necessary to attain equilibrium between intake and urinary output. This value is higher than recent suggestions for calcium replacement during intravenous feeding.     

Acute effects of dietary caffeine and aspirin on urinary mineral excretion in pre- and postmenopausal women

Thirty women, ages 35–65, on three separate mornings, drank 180 ml decaffeinated coffee to which 0, 3 or 6 mg/kg body weight caffeine had been added. Caffeine increased three hour total urinary calcium excretion from a baseline value of 10.8 to 15.9 and 17.8 mg, respectively. Sodium and magnesium excretion were also increased after caffeine ingestion. Phosphorus, chloride, potassium, creatinine and urine volume were not different after caffeine consumption. Increased urinary outputs of calcium and sodium were due to the increased urinary concentrations of calcium and sodium after caffeine consumption. Twenty of these women also took 650 mg aspirin 10 hours and 1 hour before consuming a second set of beverages containing 0 and 3 mg/kg body weight caffeine. Aspirin preloading did not affect the three hour total excretion or mineral/creatinine ratio of any of the minerals measured. There were no aspirin-caffeine interactions, indicating that the caffeine effect on mineral excretion may not be mediated by prostaglandin production. Estrogen use or menopausal status had no effect on calcium excretion after caffeine or aspirin.     

Suboptimal intake of magnesium in rats. Effects during growth and gestation

To investigate the interaction of magnesium depletion and source of protein and the effect of this interaction on growth, female weanling Sprague-Dawley rats were fed diets based on 20% casein or 20% soy protein isolate which contained eithe adequate (800 mg/kg) or suboptimal (200 mg/kg) levels of magnesium. The initial suboptimal level of approximately 100 mg/kg magnesium was increased to approximately 200 mg/kg magnesium on day 6 of the study. The nutritional stress of rapid growth resulted in clinical signs of deficiency including audiogenic seizures in the animals fed the casein diet which was low in magnesium. Some clinical manifestations of deficiency persisted through almost all of the 6-week growth period. The lower nutritional quality of soy protein isolate and/or the components of soy which depress mineral bioavailability resulted in a higher rate of alopecia and skin sores in the rats fed the soy low magnesium diet than in those fed the casein low magnesium one. Growth retardation in the magnesium deficient animals occurred during the post-weaning growth phase. Gestational weight gain was also depressed by low magnesium intake to a greater extent than has been previously reported in response to a mild magnesium restriction. Because of recent reports of suboptimal intakes of magnesium by humans, further research of combined effects of subacute magnesium deficiency and utilization of foods containing soy protein is needed.     

牛磺酸锌对染铅大鼠血清微量元素含量的影响

[目的]探讨不同剂量牛磺酸锌(taurine-zinc,TZC)对染铅大鼠血清中铜、锌、钙、镁、铁等微量元素含量的影响。[方法]健康SD大鼠分为对照组、染铅组、TZC小剂量组、中剂量组和大剂量组。除对照组外,各组大鼠给予醋酸铅灌胃(剂量30mg/kg),TZC各组在灌胃铅溶液前1h灌胃TZC(剂量分别为10mg/kg,50mg/kg,100mg/kg)。每天1次,共45d。实验结束后取全血测血铅,取血清测铜、锌、钙、镁、铁含量。[结果]各实验组大鼠血铅含量显著高于对照组,各TZC组血铅显著低于染铅组,差异有统计学意义(P﹤0.05);染铅组血清微量元素含量均低于对照组,其中锌、钙、镁差异有统计学意义(P﹤0.05)。[结论]铅暴露可引起大鼠血清中微量元素含量降低,适量补充TZC可以降低血铅含量,减少体内微量元素流失。     

Effects of various forms of calcium on body weight and bone turnover markers in women participating in a weight loss program

OBJECTIVE: This study examined the effects of calcium intake on body weight, body fat, and markers of bone turnover in pre-menopausal adult women undergoing a 12 week weight loss program of diet and exercise. METHODS: Subjects were prescribed a 12 week diet with a 500 Kcal restriction containing about 750 mg calcium/day, exercised 3 times/week, and were given either placebo capsules, capsules of calcium lactate or calcium phosphate (daily dose about 800 mg calcium), or low fat milk (daily dose about 800 mg calcium). Subjects completed and returned daily diet diaries weekly. RESULTS: Daily calcium intake in mg from diet records + supplement assignment was: 788 +/- 175 (placebo), 1698 +/- 210 (Ca lactate), 1566 +/- 250 (Ca phosphate), 1514 +/- 225 (milk)(no significant differences among the calcium and milk groups). Each group had statistically significant changes in body weight (p < 0.01), but there were no significant differences among groups for the weight loss: 5.8 +/- 0.8 kg (placebo), 4.1 +/- 0.7 kg (Ca lactate), 5.4 +/- 1.3 kg (Ca phosphate), 4.2 +/- 0.8 kg (milk). Body fat was changed significantly in each group (p < 0.01), with milk group showing a little less change than the other groups. Serum bone specific alkaline phophatase activity, a bone synthesis marker, increased similarly in all groups (p < 0.001 within groups, no significance for changes among groups). In contrast, the Ca lactate group, but not other groups, had a drop in urine values for alpha helical peptide, a bone resorption marker (p < 0.05). CONCLUSION: For the conditions of this study, increased calcium intake, by supplement or milk, did not enhance loss of body weight or fat, though calcium lactate supplementation lowered values for a marker of bone degradation.     

Blood methanol concentrations in one-year-old infants administered graded doses of aspartame

Blood methanol concentrations were measured in 24 1-year-old infants administered aspartame, a dipeptide methyl ester sweetener. The doses studied included a dose projected to be the 99th percentile of daily ingestion for adults (34 mg/kg body weight), a very high use dose (50 mg/kg body weight) and a dose considered to be in the abuse range (100 mg/kg body weight). Blood methanol values in infants were compared to values observed previously in adults administered equivalent doses of aspartame. Methanol concentrations were below the level of detection (0.35 mg/dl) in the blood of 10 infants administered aspartame at 34 mg/kg body weight, but were significantly elevated (P less than or equal to 0.05) after ingestion of aspartame at 50 and 100 mg/kg body weight. At the latter doses, mean peak blood methanol concentrations and the area under the blood methanol concentration-time curve increased in proportion to dose. Mean (+/- SEM) peak blood methanol concentration was 0.30 +/- 0.10 mg/100 ml at a 50 mg/kg body weight aspartame dose (n = 6) and 1.02 +/- 0.28 mg/ml at the 100 mg/kg body weight dose (n = 8). Blood methanol values in infants were similar to those observed in normal adults.