Calciuretic effect of cyclic versus continuous total parenteral nutrition

Metabolic bone disease has been reported in patients receiving long-term cyclic administration of total parenteral nutrition (TPN). The exact etiology of this disturbance in mineral homeostasis has not been identified, however many of these patients are markedly hypercalciuric and in negative calcium balance. We have studied the effects of cyclical versus continuous infusion of nutrients on urinary calcium losses in a group of patients beginning a program of long-term home TPN. Cyclic TPN, when administered over either 18 or 12 hours, significantly increased daily urinary calcium excretion compared to continuous 24-h TPN infusion by 19 and 28%, respectively. During cyclic TPN, frank negative calcium balance was observed in 3 of 5 patients studied compared to 2 of 5 patients during continuous TPN. The pattern of urinary calcium loss during cyclic TPN was such that approximately 80% of the daily urinary calcium losses occurred during the 12 hours of TPN infusion. Cyclic administration of TPN increased the urinary calcium losses in all patients suggesting that an intermittent TPN infusion schedule, as typically utilized in home TPN programs, increases the risk of developing negative calcium balance, at least during the early phase of cyclic TPN administration.     

Effects of an oxalate load on urinary oxalate excretion in calcium stone formers.

OBJECTIVE: To investigate the oxalate intake and the effect of an oxalate load on urinary oxalate excretion in calcium stone-forming (CSF) patients. DESIGN: Prospective study. SETTING: University-affiliated outpatient Renal Lithiasis Unit. Patients and controls: Seventy (70) CSF and 41 healthy subjects (HS) collected a 24-hour urine sample and were submitted to a 3-day dietary record to determine mean oxalate (Ox), calcium (Ca) and vitamin C intake. Fifty-eight (58) CSF patients were randomly selected to receive milk (N = 28) or dark (N = 30) chocolate as an oxalate load. INTERVENTION: Administration of either milk (94 mg Ox + 430 mg Ca) or dark chocolate (94 mg Ox + 26 mg Ca) for 3 days. A 24-hour urine sample was obtained before and after the load to determine calcium, oxalate, sodium, potassium, urea, and creatinine. MAIN OUTCOME MEASURE: Oxalate intake and excretion. RESULTS: CSF patients presented mean Ox intake of 98 +/- 137 mg/d, similar to that of HS (108 +/- 139 mg/d). Mean Ox and vitamin C intake was directly correlated with Ox excretion only in CSF. The consumption of dark chocolate induced a significant increase in mean urinary Ox (36 +/- 14 versus 30 +/- 10 mg/24 hr) not observed in the milk chocolate group. Thus, a 2-fold increase in Ox intake in this population of CSF patients produced a significant 20% increase in oxaluria, not observed when Ca was consumed simultaneously. CONCLUSION: The present study suggests that even small increases in Ox intake affect oxalate excretion and the mitigation of urinary oxalate increase by Ca consumption reinforces that Ca and Ox intakes for CSF patients should be in balance. Further studies are necessary to assess whether or not a 20% increase in oxaluria will lead to a higher risk of stone formation.     

Nitrogen balance of healthy Dutch women before and during pregnancy

BACKGROUND: Experimental studies including longitudinal nitrogen balance studies could provide insight into protein metabolism in pregnancy. OBJECTIVE: Our aim was to determine the development of nitrogen balance during pregnancy compared with nitrogen balance before pregnancy in women consuming imposed constant diets. We also tracked changes in muscle mass and lean body mass by measuring urinary 3-methylhistidine (3-MeH) and urinary creatinine. DESIGN: Nitrogen balance was determined over 8 d in 12 healthy Dutch women before pregnancy and at weeks 12, 23, and 34 of gestation. Complete daily diets were supplied during each balance period so that each subject's energy, protein, and macronutrient intakes were similar in amount and composition in all 4 balance periods. RESULTS: Throughout pregnancy there was no significant change in loss of nitrogen in feces and therefore no change in protein digestibility. The amount of nitrogen excreted in urine in late pregnancy (11.0 +/- 1.4 g/d) was significantly (P < 0.01) less than in early pregnancy (12.6 +/- 1.3 g/d). Nitrogen retention increased toward term, even though energy balance became progressively negative. The difference between the first (-0.4 +/- 1.7 g N/d) and third (1.2 +/- 1.6 g N/d) trimester was significant (P < 0.05). No differences were found in either 3-MeH or creatinine excretion between trimesters. CONCLUSIONS: These urinary nitrogen excretion and nitrogen retention data show that when the dietary supply remains constant, nitrogen balance increases toward the end of pregnancy, suggesting a more efficient use of dietary protein later in pregnancy. Urinary 3-MeH and creatinine excretion indicated no change in protein metabolism.     

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.     

Acetate and hypercalciuria during total parenteral nutrition

Hypercalciuria and negative calcium balance are complications of total parenteral nutrition (TPN). Because metabolism of the TPN formula generates an acid load that can induce hypercalciuria, we evaluated the effect of supplementing the formula with acetate. In a randomized crossover study six patients on continuous and six on cyclic TPN received no added acetate or 160 mmol acetate/d replacing 160 mmol chloride/d for 3 d each. Blood and urine measurements were obtained on day 3 of each formula. Acetate, which is metabolized to bicarbonate, increased blood pH and decreased renal acid excretion. Urinary Ca decreased in every patient from 422 +/- 63 to 240 +/- 46 mg/d (10.5 +/- 1.6 to 6.0 +/- 1.4 mmol/d) and from 468 +/- 68 to 285 +/- 54 mg/d (11.7 +/- 1.7 to 7.1 +/- 1.3 mmol/d) during continuous and cyclic TPN, respectively. Filtered Ca load decreased slightly whereas renal tubular Ca reabsorption increased significantly with acetate. Serum parathyroid hormone, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and urinary cyclic AMP were not different.     

Parenteral infusion of long- and medium-chain triglycerides and reticuloendothelial system function in man

Previous study demonstrated that patients who received total parenteral nutrition (TPN) with standard intermittent infusion of long chain triglyceride (LCT) at 0.13 g kg-1hr-1 over 10 hr for each of three days showed a significant decline in 99Tc-sulfur colloid (TSC) clearance rate by the reticuloendothelial system (RES). The present studies evaluated eight patients who received the same total lipid dose of LCT infused continuously as in a three-in-one admixture, and another nine patients receiving the same amount of fat as a medium chain triglyceride (MCT)/LCT (75%/25%) emulsion intermittently over 10 hr at 0.13 g kg-1hr-1 for three consecutive days. Patients were given continuous total parenteral nutrition (TPN) comprised of protein, 1.5 g kg-1day-1, and dextrose, 4.5 g kg-1day-1. RES function was examined by measuring the clearance rates of intravenously injected TSC while receiving TPN containing only protein and dextrose, and again after three days of fat infusion. Mean (+/- SEM) clearance rate constants before and after continuous LCT infusion were 0.38 +/- 0.09 and 0.41 +/- 0.08 min-1, respectively, while those before and after intermittent MCT/LCT infusion were 0.50 +/- 0.18 and 0.73 +/- 0.24 min-1, respectively. In contrast to intermittent LCT infusion, the administration of continuous LCT or an intermittent MCT/LCT mixture does not impair TSC clearance by the RES. These findings suggest that condensing the daily period of LCT infusion at standard dosage may exceed the rate of metabolic utilization, resulting in increased fat removal and diminished TSC uptake by the RES.(ABSTRACT TRUNCATED AT 250 WORDS)     

Negative balance of calcium and magnesium under relatively low sodium intake in humans

The balance of minerals (sodium [Na], potassium [K], calcium [Ca], and magnesium [Mg]) was measured in six female students for 10 d while under a relatively low Na intake (100 mmol/d or 2.2 g/d) with receiving adequate Ca (20 mmol/d or 800 mg/d) and Mg (12 mmol/d or 280 mg/d). Both the plasma renin activity (PRA) and aldosterone level were above the reference ranges throughout the experiment, which implied that the subjects were Na deficient. However, the urine Na excretion was about the same as that ingested, while there was no substantial reduction of sweat Na concentration observed during moderate physical exercise (13.2+/-2.6 mmol/L) (mean+/-SD). On the other hand, the urine Ca and Mg levels were high, but the apparent absorption of Ca and Mg was moderate (21 +/- 5%, 34 +/- 4%, respectively), which resulted in a negative balance of these two elements. It seems that the stored Na in the bone is eluted so as to compensate for the low dietary Na intake, while any excess Ca and Mg also inevitably flows into the blood stream with Na, which inhibited the intestinal absorption of both Ca and Mg and accelerates their excretion in urine.     

Reduction of total parenteral nutrition-induced urinary calcium loss by increasing the phosphorus in the total parenteral nutrition prescription

Hypercalciuria and negative calcium balance are potential complications of total parenteral nutrition (TPN). Dietary phosphorus has been observed to have an hypocalciuretic effect. The present study evaluates the effects of administration of increasing intravenous phosphorus (P) loads on urinary calcium excretion in TPN patients. Urinary calcium exceeded daily calcium intake by 50 mg/d when 700 mg/d P was administered, was equal to intake at 1000 mg/d P, and was 30 mg/d less than calcium intake when 1300 mg/d P was given. These findings suggest that TPN-induced hypercalciuria can be attenuated in the short-term by intravenous phosphate. Reevaluation of the phosphorus requirement in patients receiving long-term TPN should be considered.     

Comparison of the effects of continuous and cyclic nocturnal parenteral nutrition on energy expenditure and protein metabolism

Although cyclic nocturnal total parenteral nutrition is a widely used technique, its metabolic consequences have not been fully investigated. During two successive 7-day periods, 12 patients received randomly either standard continuous (infusion 24 hr/day) or cyclic (infusion between 5 pm and 9 am) total parenteral nutrition (TPN). Calorie and nitrogen intakes were identical during both periods. Energy expenditure was investigated by indirect calorimetry and showed practically no difference between continuous standard (1383 +/- 41 kcal/day-1) and cyclic total parenteral nutrition (1428 +/- 46 kcal/day-1). However, in the cyclic regimen, when compared with continuous infusion, energy expenditure was higher between 5 pm and 9 am and lower between 9 am and 5 pm. At the end of the noninfusion period, the 24-hr profile of the nonprotein respiratory quotient showed a slight decrease in patients receiving the cyclic infusion, in contrast with the stability of the quotient in the standard regimen. However, the nitrogen balance and variations in nutritional status did not differ significantly. In conclusion cyclic TPN is efficient for achieving a positive energy and nitrogen balance and in addition it induces a metabolic profile closer to physiological conditions.     

Reducing parenteral energy and protein intake improves metabolic homeostasis after bone marrow transplantation

The purpose of this prospective study was to compare the metabolic effects of reducing parenteral energy and protein intake in bone-marrow-transplant (BMT) patients from 150% (hi-TPN group) to 100% (lo-TPN group) basal energy expenditure. Cytotoxic therapy was given on days 1-5, BMT on day 6, and TPN beginning on days 6 or 7. The lo-TPN group exhibited higher serum albumin (38 +/- 0.4 vs 32 +/- 0.4 g/L, P less than 0.01) but similar nitrogen balance (-83 +/- 8 vs -86 +/- 8 mg.kg-1.d-1, P greater than 0.05). Serum Na+ remained greater than 134 +/- 1 mmol/L in the lo-TPN group but fell to 127 +/- 1 mmol/L in the hi-TPN group (P less than 0.001) despite similar Na+ intakes and balances. Serum K+ remained less than 4.4 +/- 0.2 mmol/L in the lo-TPN group but rose to 5.1 +/- 0.1 mmol/L in the hi-TPN group (P less than 0.01) despite similar K+ intakes and balances. Delivering TPN at lower-than-normal rates after BMT appears to minimize Na+ and K+ disturbances and improve serum albumin concentrations without having any adverse effect on nitrogen balance.     

Metabolic response of simultaneous versus sequential intravenous administration of amino acids and energy substrates to rats

Three groups of rats were maintained on total intravenous nutrition for ten days. Group SA and SB were infused sequentially (2 X 12 h periods per day), SA received amino acids (AA) during the night and carbohydrates (CHO) + FAT during the day. The SB group received nutrients in the opposite order. A control group received a mixed solution simultaneously for 24 h/day. The sequentially fed groups showed a lower weight gain (2.4 +/- 0.4, 2.6 +/- 0.2 vs 4.9 +/- 0.3 g/day), nitrogen balance (95 +/- 7, 95 +/- 6 vs 139 +/- 7 mg/day) and nitrogen utilization (69 +/- 3, 67 +/- 3 vs 87 +/- 3%) compared with the control group. Administration of energy substrate in the SA and SB was a stronger denominator for O2 consumption and changes in RQ than the periods of physical activity. Control animals did not show any diurnal variations in O2 and RQ. Glucose, FFA and insulin were higher with CHO + FAT administration compared to AA infusion or simultaneous AA/CHO/FAT administration. In conclusion, the results suggest that simultaneous administration of a mixture of AA/CHO/FAT is preferable for whole body nitrogen economy during TPN.     

Nitrate and nitrogen balances in men

Nitrate is a nitrogen-containing compound that is not detected by the traditional Kjeldahl method of nitrogen analysis. Nitrate balance studies were done in order to determine if nitrate production in the human body contributes to the irrationally positive nitrogen balances that have been reported in healthy adults. Seven healthy young men, confined to a metabolic unit, received five diets for 9 days each: a mixed foods diet, a fiber-free egg formula diet, and egg formula with California small white beans, lima beans, and wheat bran added. Nitrate-nitrogen intake with the mixed foods diet was 75 mg/day and nonnitrate nitrogen intake was 19 g/day; crude Kjeldahl nitrogen balance (intake--(urinary + fecal)) was 0.64 +/- 1.23 g/day. Nitrate-nitrogen excretion exceeded intake by 0.10 +/- 0.05 g/day. With the four other diets, nitrate-nitrogen intake was almost nil (about 2 mg/day) and nonnitrate nitrogen intake was 95 mg/kg body weight; crude Kjeldahl nitrogen balances ranged from -0.63 +/- 0.73 to 0.02 +/- 0.45 g N/day. With these four diets, feces contained about 80 mg nitrate-nitrogen/day and urine contained about 8 mg. Saliva obtained before lunch had about 1 ppm nitrate-nitrogen with the formula diets and 5 ppm with the mixed foods diet. Net synthesis of nitrate is quite variable but appears to be of the order of 100 mg nitrate-nitrogen/day. Although the excess nitrate excretion increased total nitrogen excretion by less than 5%, it could account for as much as 10 to 20% of unexplained positive nitrogen balances previously reported in well-controlled studies.     

Calcium absorption is significantly higher in adolescents during pregnancy than in the early postpartum period

BACKGROUND: Early childbearing may limit skeletal consolidation and increase calcium demands in adolescents. OBJECTIVE: The purpose of this study was to characterize calcium absorption in pregnant and lactating adolescents. DESIGN: Fractional calcium absorption was evaluated in 23 adolescents (mean +/- SD age: 16.5 +/- 1.4 y) during the third trimester of pregnancy (34.7 +/- 1.0 wk gestation) and again in 15 of these adolescents 31 +/- 8 d after delivery. Eight adolescents were breastfeeding their infants during the follow-up study. Fractional calcium absorption was determined by using oral ((46)Ca or (44)Ca) and intravenous ((42)Ca) stable calcium isotopes. Total-body and lumbar spine bone mineral density were measured in adolescents during the postpartum period by using dual-energy X-ray absorptiometry. RESULTS: Fractional calcium absorption was significantly greater during pregnancy than at 3-4 wk postpartum [0.526 +/- 0.152 (n = 23) compared with 0.297 +/- 0.108 (n = 15); P < 0.0001]. Lumbar spine z scores measured 19-44 d after delivery (n = 15) were significantly associated with calcium intake during pregnancy (y = -3.53 + 0.107x; R(2) = 0.355, P < 0.02) and were inversely related to fractional calcium absorption during pregnancy (y = 3.489 - 6.66x; R(2) = 0.52, P = 0.002). A total of 33% (5/15) of adolescents had lumbar spine z scores that met the definition of osteopenia (n = 3) or osteoporosis (n = 2) in the early postpartum period. CONCLUSIONS: Calcium absorption in adolescents was significantly higher during the third trimester of pregnancy than in the early postpartum period, and higher calcium intakes during pregnancy appeared to be protective against loss of trabecular bone at the lumbar spine.     

Postoperative parenteral nutrition with high supply of branched-chain amino acids: effects on nitrogen balance and liver protein synthesis

Branched-chain amino acids (BCAA) stimulate muscle and liver protein synthesis in vitro. The significance of this action in catabolic conditions in vivo remains controversial. The effects of a high supply of BCAA in total parenteral nutrition (TPN) on nitrogen balance and liver protein synthesis were studied in a postoperative rat model. After standard operative trauma TPN was commenced with one of two isocaloric programs (I: 20.1% BCAA and II: 50% BCAA) and continued for 48 hr. The relative rate of liver protein synthesis, measured after TPN in vitro by perfusion with 14C-leucine, was similar in both groups (I: 53.4 +/- 17.3 and II: 49.0 +/- 27.3 arbitrary units of synthesis rate, mean +/- SD). The cumulative nitrogen balance was positive with both regimens and was not improved by the high supply of BCAA (I: 2.02 +/- 0.81 and II: 1.87 +/- 0.63 gN/kg/48 hr mean +/- SD). We conclude that after moderate surgical trauma TPN with a high supply of BCAA offers no advantage over conventional TPN.     

Fatty acid composition of adipocyte membrane phospholipids and stored triglycerides in infants receiving total parenteral nutrition

Fatty acid (FA) composition of membrane phospholipids (PL) and stored triglycerides (TG) from adipose tissue was studied in eight infants aged 1 to 4 months receiving total parenteral nutrition (TPN) since birth. During this period, essential fatty acid (EFA) intake consisted exclusively of soybean oil emulsion administered by intravenous route (Intralipid 20%) representing 301 +/- 88 mg/kg/24 hr of linoleic acid and 58 +/- 18 mg/kg/24 hr of alpha-linolenic acid, or 2.3 +/- 0.6% and 0.4 +/- 0.1%, respectively, of total energy intake. The results were compared with those of eight control infants of the same age receiving orally a normal milk diet with an intake of 660 +/- 260 mg/kg/24 hr of linoleic acid and 101 +/- 35 mg/kg/24 hr of alpha-linolenic acid, or 4.5 +/- 0.7% and 0.7 +/- 0.3%, respectively, of total energy intake. Although their EFA intake was significantly lower (p less than 0.01) and administered only parenterally, after 1 to 4 months the infants receiving TPN still had a membrane phospholipid FA pattern of adipose tissue which was not significantly different from that of normal children of the same age. In stored adipocyte TG, the percentage of linoleic acid was significantly lower (p less than 0.01) in infants receiving TPN. This is probably of nutritional importance as at this stage of life the child builds up its stores of EFA. The proportion of the other fatty acids in adipocyte TG was not significantly modified.     

孕期补充钙、铁、锌对胎儿生长发育的影响

目的以孕妇为对象,研究孕中期单纯补钙和补钙同时补铁和/或锌对婴儿生长发育的影响.方法选择初产健康孕妇313名,分别强化维生素D(VD)、钙、铁和锌, 从孕5月至分娩时止.分娩时测量胎盘重量、胎盘和脐带血中微量元素的含量、新生儿的出生体重和身长.结果对照组胎盘重量最大,钙和多种微量元素的含量较低,而钙+铁+锌+VD组相反,并且对照组的胎盘重量(551.1±64.2) g显著大于钙 +铁+锌+VD组(467.1±36.6) g.脐血中血红蛋白含量显著高于母血,碱性磷酸酶活性差异无显著性,脐血血浆中钙、铁、锌含量均高于母血.婴儿的生长发育结果显示,钙+铁+ 锌 +VD组新生儿的出生体重(3.53±0.33) kg和身长值最大,并且出生体重显著大于对照组的(3.28±0.54) kg.结论孕期联合补充钙、铁、锌, 使其达到或接近每日膳食中营养素供给量,这是改善婴儿生长发育的最佳方式.     

Parenteral nutrition for marrow transplant recipients: evaluation of an increased nitrogen dose

The use of total parenteral nutrition in bone marrow transplant (BMT) recipients is well recognized. These patients as a result of treatment with chemotherapy and immunosuppressive agents undergo catabolic stress. The metabolic effect of an increased nitrogen dose during total parenteral nutrition (TPN) was studied in 28 BMT patients. Patients were given TPN formulas providing a nitrogen intake of either 267 +/- 44 mg of N/kg/d or 330 +/- 60 mg of N/kg/d. Total calories, nonprotein and protein, were held constant at 40 kcal/kg/d for all patients. Data was collected for three periods posttransplant beginning at 3 days posttransplant through day 16. Both study TPN formulas improved patient weight and TIBC values over baseline. Nitrogen balance (NB) values were not significantly different at any study period. However, an overall group effect favored the H-N formula (p less than 0.01). BMT patients undergo catabolic stress which was reflected by average values of 24-hour urine urea nitrogen increasing from 8.1 +/- 4 g/d at baseline to 19.8 +/- 7.2 g/d at period 3 (p less than 0.01). The H-N formula did not differentially increase blood urea nitrogen or serum creatinine levels. Metabolic cart measures also showed no increase in metabolic rate, oxygen consumption, carbon dioxide production, or percent contribution of protein to total metabolic expenditure. Providing a caloric intake of 40 kcal/kg/d was excessive, where 30 to 35 kcal/kg/d would meet metabolic demands. Pertinent clinical outcomes including length of stay, relapse rate, and survival were monitored, but no conclusions could be drawn in this study. The H-N formula was more effective in reducing loss of lean body mass without causing detrimental metabolic effects in BMT patients.     

Determination of the optimal number of dairy servings to ensure a low prevalence of inadequate calcium intake in Americans

BACKGROUND: Many Americans are not getting the recommended amounts of calcium in their diet. Since dairy foods provide most of the calcium in the diet, the number of recommended servings of dairy products may need to be revised. OBJECTIVE: 1. To determine the calcium intake of various age groups that met or exceeded the intake of dairy products recommended by the Food Guide Pyramid (FGP). 2. To determine the optimal level of dairy consumption that ensures a low prevalence of inadequate calcium (Ca) intake by Americans. METHODS: Using data from the Continuing Survey of Food Intake by Individuals, 1994-96, 1998, (CSFII) and the National Health and Nutrition Examination Survey, 1999-2000 (NHANES) we determined the calcium intake in individuals who met the recommended daily dairy servings as well as the minimum number of dairy servings required for the mean Ca intake of various age groups to exceed their respective Adequate Intakes (AI). RESULTS: Objective 1: Meeting or exceeding the FGP dairy recommendation led to calcium intakes that met recommended levels. However, very few individuals in all age groups met or exceeded the number of dairy servings recommended by FGP. Objective 2: Results indicated that in children 2-8 yrs, 2 dairy servings/d were required for the mean Ca intake (835 +/- 72 and 822 +/- 68 mg/d, in CSFII and NHANES IV, respectively) to exceed the AI. In children 9-18 yrs, 4 dairy servings/d) were required for the mean Ca intake of the group (1540 +/- 93 and 1518 +/- 86 mg/d) to exceed the AI. Similar data were observed in adults 19+ yrs, e.g., in adults 51+ yrs, 3 dairy servings/d were required for the mean Ca intake of the group (1241 +/- 53 and 1217 +/- 53 mg/d) to exceed the AI. CONCLUSION: Groups that met or exceeded the FGP dairy recommendations were more likely to have a mean calcium intake above the AI but had an average intake of about one serving higher than current recommendations. In individuals 9 yrs and older, 3-4 servings of dairy products are needed to meet or exceed the Ca AI and to ensure a low prevalence of inadequate Ca intake.     

Calcium homeostasis during pregnancy and lactation in Brazilian women with low calcium intakes: a longitudinal study

BACKGROUND: Physiologic adjustments in calcium homeostasis during pregnancy and lactation in women with marginal calcium intakes have not been described. OBJECTIVE: The objective was to examine longitudinal changes in various aspects of calcium homeostasis during pregnancy and lactation in 9 healthy Brazilian women who habitually consumed approximately 500 mg Ca/d. DESIGN: Calcium homeostasis was assessed at 3 time points: 10-12 (early pregnancy, EP) and 34-36 (late pregnancy, LP) wk of pregnancy and 7-8 wk postpartum (early lactation, EL). At each time point, the following variables were measured: dietary calcium intake with a 3-d weighed food record, 24-h urinary calcium excretion (UCa), intestinal calcium absorption (%CaAbs) via administration of stable calcium isotopes with a breakfast meal, serum 1,25-dihydroxyvitamin D, parathyroid hormone (PTH), insulin-like growth factor I (IGF-I), and biochemical markers of bone turnover. RESULTS: Dietary calcium did not change during the study. %CaAbs increased from 69.7 +/- 5.4% ( +/- SEM) during EP to 87.6 +/- 4.5% during LP (P < 0.05) and returned to 65.1 +/- 6.2% during EL. Compared with EP, UCa decreased 22% during LP and 68% during EL (P < 0.05). The net mean change in calcium retention was 212 mg/d during LP and 182 mg/d during EL. Several significant associations were found between the main outcome variables (%CaAbs, UCa, and markers of bone turnover) and serum hormones, especially IGF-I and PTH. CONCLUSIONS: Calcium homeostasis appears to be attained by a more efficient intestinal calcium absorption during pregnancy and by renal calcium conservation during both pregnancy and lactation. IGF-I and PTH seem to play major roles in the adjustment of calcium metabolism during pregnancy and lactation.     

Effects of alternate and simultaneous administrations of calcium and phosphorus on calcium metabolism in children receiving total parenteral nutrition

The effects of alternate and simultaneous administrations of calcium (Ca) and phosphorus (P) on Ca metabolism in children receiving total parenteral nutrition (TPN) were examined. Eight children, aged 2 to 36 months, were studied. The following three solutions were administered: solution 1 contains Ca (533 mg/liter); solution 2 contains P (413 mg/liter); and solution 3 contains Ca (267 mg/liter) and P (207 mg/liter). Solutions 1 and 2 were administered alternately for 24-hr periods. (Results) I. During administration of solution 1, significant hypophosphatemia (4.39 +/- 0.26 mg/dl) and hypercalcemia (9.96 +/- 0.15 mg/dl) were observed and, conversely, during administration of solution 2, significant hypocalcemia (8.36 +/- 0.18 mg/dl) and hyperphosphatemia (6.16 +/- 0.27 mg/dl) were observed. During administration of solution 3, the serum levels of both minerals were maintained within the normal ranges (Ca 9.46 +/- 0.12 mg/dl, P 5.65 +/- 0.21 mg/dl). II. The urinary excretion of cyclic AMP was significantly lower during administration of solution 1 (6.67 +/- 0.45 nmol/mg creatinine (Cr] as compared with solution 3 (7.50 +/- 0.61 nmol/mg of Cr). On the other hand, the excretion was significantly higher during administration of solution 2 (11.55 +/- 1.58 nmol/mg of Cr) as compared with solution 3, indicating the existence of secondary hyperparathyroidism. III. The Ca and P retention rates were significantly higher with solution 3 (Ca 79.0 +/- 5.5%, P 73.2 +/- 7.2% of the intake) than with solutions 1 and 2 alternately (Ca 62.7 +/- 4.5%, P 49.2 +/- 9.3%). (Conclusions) Simultaneous administrations of Ca and P are preferable to their alternate administrations for Ca metabolism in children receiving TPN.