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.     

Influence of multivitamin regimen on urinary oxalate in home parenteral nutrition patients.

BACKGROUND: High urinary oxalate levels have been associated with high ascorbic acid intakes. An alteration in the vitamin regimen for home parenteral nutrition (HPN) patients because of product discontinuation resulted in provision of 500 mg instead of 100 mg ascorbic acid per HPN day. This regimen was associated with high urinary oxalate levels. PURPOSE: To determine if a switch from a multivitamin regimen containing 500 mg to one containing 100 mg of ascorbic acid daily would reduce urinary oxalate levels. METHODS: A 24-hour urine collection for oxalate was analyzed before switching the vitamin regimen back to 100 mg ascorbic acid and repeated 2 months after the change. A paired t test was conducted to compare measurements at baseline and at 2 months. RESULTS: Overall, 18 patients completed both phases of this observational study. The initial urinary oxalate of 517 +/- 63 micromol/day decreased to 425 +/- 47 micromol/day after 2 months (p = .05). However, after applying the exclusion criteria, only 6 patients could be included. The baseline urinary oxalate of 649 +/- 106 micromol/day decreased to 391 +/- 57 micromol/day after 2 months (p = .006). CONCLUSIONS: A change in the parenteral regimen of HPN patients from 500 mg ascorbic acid to 100 mg ascorbic acid is associated with a decrease in urinary oxalate levels. This suggests that a moderate dose of parenteral ascorbic acid (100 mg/day) may limit urinary oxalate appearance in HPN patients.     

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.     

A comparison of renal phosphorus regulation in thermally injured and multiple trauma patients receiving specialized nutrition support

To compare phosphorus intake and renal phosphorus regulation between thermally injured patients and multiple trauma patients, 40 consecutive critically ill patients, 20 with thermal injury and 20 with multiple trauma, who required enteral tube feeding were evaluated. Phosphorus intakes were recorded for 14 days from the initiation of tube feeding which was started 1 to 3 days postinjury. Serum for determination of phosphorus concentrations was collected at days 1, 3, 7, and 14 of the study period. A 24-hour urine collection was obtained during the first and second weeks of nutrition support for urinary phosphorus excretion, fractional excretion of phosphorus, renal threshold phosphate concentration, and phosphorus clearance. Average total daily phosphorus intake during the 14-day study for thermally injured patients and multiple trauma patients was 0.99+/-0.26 mmol/kg/d vs 0.58+/-0.21 mmol/kg/d, respectively, p < .001. Serum phosphorus concentration on the third day of observation was significantly lower in the thermally injured group than those with multiple trauma (1.9+/-0.8 mg/dL vs 3.0+/-0.8 mg/dL, p < or = .01). A trend toward hypophosphatemia in the thermally injured group persisted by the seventh day of feeding (2.7+/-1.2 mg/dL vs 3.3+/-0.6 mg/dL, p < or = .04). Differences in urinary phosphorus excretion was not statistically significant between the thermally injured and multiple trauma groups (271+/-213 mg/d vs 171+/-181 mg/d for week 1, and 320+/-289 mg/d vs 258+/-184 mg/d for week 2, respectively). Urinary phosphorus clearance, fractional excretion of phosphorus, or renal threshold phosphate concentrations were also not significantly different between thermally injured and multiple trauma patients. During nutrition support, serum phosphorus concentrations are lower in thermally injured patients compared with multiple trauma patients despite receiving a significantly greater intake of phosphorus. Renal phosphorus regulation does not significantly contribute to the profound hypophosphatemia observed in thermally injured patients when compared with multiple trauma patients during nutrition support.     

Does dietary recall adequately assess sodium, potassium, and calcium intake in hypertensive patients?

OBJECTIVE: A diet low in sodium, high in potassium, and high in calcium is recommended to lower blood pressure. However, compliance with this diet is poor, probably because of dietary intake underestimation. Therefore, we compared electrolyte intake as estimated from dietary recall with a 24-h urinary excretion. METHODS: Thirty-six patients (26 men and 10 women) with a mean age of 46 +/- 8 y participated in the study. All participants had essential hypertension and were on no drug therapy (n = 20) or non-diuretic monotherapy (n = 16). Patients were instructed to consume a low-sodium (50 mmol/d), high-potassium (supplementation with 30 to 60 mmol/d), and high-calcium (1000 mg/d) diet. Compliance with the diet was assessed at baseline and then 1, 2, and 3 mo after starting the diet. Sodium, potassium, and calcium intakes were carefully estimated from patients' dietary recall and 24-h urinary collection. RESULTS: Estimated sodium intake significantly correlated with 24-h urinary excretion (R = 0.43 P < 0.001). However, estimated sodium intake was lower than urinary sodium excretion by 34% at baseline and by 47% after 3 mo of dieting (P < 0.05). Estimated potassium intake correlated with 24-h urinary excretion. Estimated calcium intake significantly increased from 933 +/- 83 mg/d to 1029 +/- 171 mg/d (P < 0.05). Calcium intake derived from patients' recall far exceeded and only slightly correlated with 24-h urinary excretion (R = 0.23, P < 0.01). CONCLUSIONS: Patients tend to underestimate their sodium intake by 30% to 50%; therefore, urinary sodium excretion is more accurate to assess sodium intake. Thus, 24-h urinary sodium excretion should be used in clinical practice and in clinical trials, especially when dietary non-compliance is suspected.     

Effect of compound Puerarin on the collage IV in streptozotocin-induced diabetic nephropathy rats

OBJECTIVE: To observe the effect of compound Puerarin on collagen IV of streptozotocin-induced diabetic rats. METHODS: Diabetic nephropathy rats were induced by intraperitoneal injection of streptozotocin (STZ). Rats were allocated randomly to control group (10), diabetes model group (10), Vitamin C group (10), Puerarin group (10), vitamin C plus Puerarin group (10). The study period lasted for 12 weeks. During and after the treatment, the general state, blood glucose levels, glycosylated hemoglobin, blood urea nitrogen, serum collagen IV, blood urea nitrogen, serum creatinine, urinary albumin excretion rate of the 24-hour, and clearance rate of creatinine collagen IV protein were determined by immunohistochemistoche analysis as well as type the gene expression of collagen IV alpha 1 mRNA were determined by in situ hybridization analysis in the kidney tissue of different groups. RESULTS: (1) Diabetes mellitus and renal function lesion occurred in the four groups. (2) Vitamin C and Puerarin could improve the general conditions of diabetic Rats, decrease blood urea nitrogen [(8.68 +/- 0.43), (7.98 +/- 0.47) and (5.76 +/- 0.82) micromol/L, serum creatinine [(74.68 +/- 8.20), (75.52 +/- 7.98) and (58.66 +/- 6.65) mmol/L], and urinary albumin excretion rate of the 24-hour [(18.40 +/- 0.37), (17.24 +/- 0.30) and (9.97 +/- 1.27) mg/24 h x 10(-3)]; increase clearance rate of creatinine [(0.59 +/- 0.21), (0.61 +/- 0.14) and (0.69 +/- 0.32) ml/min], the expression of collage IV absorbance [(111.56 +/- 14.61), (110.78 +/- 9.69) and (95.44 +/- 9.97) ] in the diabetic Rats were significantly inhibited at the same time. CONCLUSION: The compound Puerarin might have some functions on preventing ren by inhibiting expression of type IV collagen.     

Calcium and vitamin D3 supplements in calcium and vitamin D3 sufficient early postmenopausal healthy women

OBJECTIVE: To study the calcium homeostasis in healthy, calcium and vitamin D replete early postmenopausal women during oral supplementation with calcium and vitamin D3. DESIGN: A prospective, placebo-controlled, randomised, double-single-blind, 3-week study. SETTING: Outpatient clinic at Copenhagen University Hospital, Denmark. SUBJECTS: In all, 17 started, one was excluded. Totally, 16 healthy women, 45-61 y of age (mean 57.3 y) who were at least 4 y after menopause (mean 6.7 y) completed. INTERVENTIONS: All underwent three consecutive 7-day study periods. Each began with 4 days of normal diet followed by 3 days treatment of either C: one tablet of 1.250 mg calcium carbonate (ie 500 mg Ca2+ per tablet) twice daily (breakfast and dinner), or CD3: as in C but plus 400 IU vitamin D3 b.i.d., or P (only) placebo tablets b.i.d. RESULTS: At baseline plasma 25-hydroxycholecalciferol was normal (66+/-22 nmol/l) and the calcium intake without supplements 850 mg/day. In group C, the 24-h urinary calcium increased by 35% (6.9+/-2.0 mmol), vs the placebo group P (5.1+/-1.6 mmol) (P < 0.05). Addition of 800 IU vitamin D3 daily (CD3) did not increase calcium excretion further (6.6+/-2.1 mmol) but decreased plasma 1,25-(OH)2-vitamin D3 by 21% (P < 0.05). CONCLUSIONS: In this carefully controlled study calcium plus vitamin D3 supplements only had minor influences of uncertain significance on the calcium balance in healthy, calcium and vitamin D sufficient early postmenopausal women.     

术后病人补给不同剂量维生素C的观察

目的：探讨手术后病人血清维生素Ｃ含量的变化并为补给适宜剂量的维生素Ｃ提供依据。方法：选择５４例临床施行中等以上手术病人为观察对象,术前随机分为两组,补给维生素Ｃ５００ｍｇ／ｄ为观察１组,补给维生素Ｃ１０００ｍｇ／ｄ为观察２组。两组均为术后当天开始补给,并于术前及手术后３天、７天取清晨空腹血及留２４ｈ尿测定维生素Ｃ含量。另测９４例正常供血者血清维生素Ｃ含量为正常值。结果：观察１组病人手术后３天血清维     

Vitamin E status of patients receiving long-term parenteral nutrition: is vitamin E supplementation adequate?

Vitamin E status of eight patients receiving total parenteral nutrition (TPN), including 10 IU of all-racemic alpha-tocopheryl acetate daily and Intralipid 20% (500 mL; 12 mg of RRR-alpha- and 92 mg of RRR-gamma-tocopherols) two to three times per week for 69 +/- 45 (mean +/- SD) months was assessed by measuring plasma and adipose tissue tocopherol concentrations. Plasma alpha-tocopherols of TPN patients were similar to controls (17.5 +/- 6.6 mumol/L vs 22.4 +/- 5.1), whereas gamma-tocopherols were significantly reduced (6.0 +/- 3.1 vs 11.2 +/- 3.6, p less than 0.03). The adipose tissue alpha- and gamma-tocopherol/triglycerides (TG) were similar (369 +/- 215 nmol/mmol vs 452 +/- 228, and 125 +/- 102 vs 140 +/- 130, respectively), but cholesterol/TG were increased in the TPN patients (7.8 +/- 2.5 mumol/mmol vs 5.1 +/- 3.5, p less than 0.05), suggesting that adipose tissue was relatively TG-depleted and tocopherol/cholesterol measurements better reflect vitamin E status. The mean alpha-tocopherol/cholesterol ratios were significantly lower in the TPN patients than the controls (55 +/- 36 vs 106 +/- 63, p less than 0.04). Thus, current vitamin E supplementation of TPN patients seems insufficient for maintenance of adequate tissue stores.     

Influence of purine intake on uric acid excretion in infants fed soy infant formulas

OBJECTIVE: These studies tested the hypothesis that increasing intake of purines, delivered as RNA from soy protein-based infant formula, would increase urinary uric acid excretion in infants. METHODS: Study One examined the influence of feeding on serum uric acid in a total of 178 infants from four separate trials with infants fed commercial and experimental soy-based and milk-based infant formulas or human milk. Studies Two and Three compared the effect of a standard purine soy formula (STD Purine; 180 mg purines/L from RNA) and a reduced purine soy formula (Reduced Purine; 65 mg purines/L; 26 mg/L from RNA and 39 mg/L from ribonucleotides) on urinary uric acid excretion in infants. In Study Two, 11 infants ranging in age from 16 to 128 days of age were fed both formulas in a random crossover design. Complete 72-hour urine collections were done at the end of each 11-day feeding period. Urinary uric acid excretion was expressed as mmol/day. In Study Three, 33 infants were enrolled before eight days of age and randomized to one of the formulas one week later. Spot urine samples were collected at 28 and/or 56 days of age and urinary uric acid concentration was expressed as mmol/mmol creatinine. RESULTS: In Study One, each of the feedings resulted in mean serum uric acid levels within normal reference ranges. Soy formula led to higher serum uric acid levels than human milk, and human milk to levels indistinguishable from cow milk-based formulas. In Study Two, infants excreted significantly more uric acid in the urine when fed the STD Purine formula compared to the Reduced Purine formula (0.86+/-.04 vs. 0.57+/-.04 mmol/d) (p = 0.006). In Study Three, infants fed the STD Purine formula had a significantly higher concentration of uric acid in their urine compared to those fed the Reduced Purine formula (2.1+/-0.2 vs. 1.4+/-0.1 mmol uric acid/mmol creatinine) (p = 0.0001). CONCLUSION: These data indicate that healthy infants can digest RNA and subsequently absorb the liberated purine ribonucleotides as determined by urinary uric acid concentration.     

Calcium fractional absorption and metabolism assessed using stable isotopes differ between postpartum and never pregnant women

Determining the fractional absorption (FA) of calcium using the incorporation into urine of stable isotopes given intravenously (IV) and orally has become a routine procedure. We investigated the FA of calcium in two groups of (2-3 mo) postpartum women lactating (LACT) (n = 6) and nonlactating (PPNL) (n = 6), and in never pregnant (NP) women (n = 7). The women consumed a controlled diet containing 30-33 mmol/d calcium (Ca) for 21 d. On d 7 of the controlled diet, the women received 0.05 mmol of 42Ca IV and 0.25 mmol 44Ca orally in milk. Urine samples (24-h) were collected for the next 14 d and morning blood samples were collected from fasting subjects before dosing and at 24 and 48 h after receiving the isotopes. Milk samples from the LACT women were collected from each feeding beginning 24 h before to 72 h after dosing. There were no significant differences in the FA of calcium as measured by stable isotope incorporation into urine (23.8 +/- 2.9%), serum (24.0 +/- 3.4%) or milk (23.6 +/- 3.6%) of LACT women. The fractional calcium absorption measured in urine of the postpartum women (LACT and PPNL, 23.8 +/- 2.9% and 25.0 +/- 3.3%, respectively) did not differ but was greater (P < 0.028) than that of the NP women (17.3 +/- 1.3%). The postpartum LACT and PPNL women had a reduced urinary excretion of calcium (P < 0.01) compared with the NP women. There was a significantly greater incorporation (P < 0.001) by LACT women of the oral isotope dose into milk than into urine. Calcium FA can be determined from incorporation of stable isotopes into breast milk and serum as well as urine.     

Influence of a mineral water rich in calcium, magnesium and bicarbonate on urine composition and the risk of calcium oxalate crystallization

OBJECTIVE: To evaluate the effect of a mineral water rich in magnesium (337 mg/l), calcium (232 mg/l) and bicarbonate (3388 mg/l) on urine composition and the risk of calcium oxalate crystallization. DESIGN: A total of 12 healthy male volunteers participated in the study. During the baseline phase, subjects collected two 24-h urine samples while on their usual diet. Throughout the control and test phases, lasting 5 days each, the subjects received a standardized diet calculated according to the recommendations. During the control phase, subjects consumed 1.4 l/day of a neutral fruit tea, which was replaced by an equal volume of a mineral water during the test phase. On the follow-up phase, subjects continued to drink 1.4 l/day of the mineral water on their usual diet and collected 24-h urine samples weekly. RESULTS: During the intake of mineral water, urinary pH, magnesium and citrate excretion increased significantly on both standardized and normal dietary conditions. The mineral water led to a significant increase in urinary calcium excretion only on the standardized diet, and to a significantly higher urinary volume and decreased supersaturation with calcium oxalate only on the usual diet. CONCLUSIONS: The magnesium and bicarbonate content of the mineral water resulted in favorable changes in urinary pH, magnesium and citrate excretion, inhibitors of calcium oxalate stone formation, counterbalancing increased calcium excretion. Since urinary oxalate excretion did not diminish, further studies are necessary to evaluate whether the ingestion of calcium-rich mineral water with, rather than between, meals may complex oxalate in the gut thus limiting intestinal absorption and urinary excretion of calcium and oxalate.     

Effects of age and intake on vitamin C disposition in females

The pharmacokinetics of vitamin C following a 500 mg oral tablet dose were compared in a group of fourteen healthy young women whose age was 26.0 +/- 2.8 years (mean +/- s.d.), and in a group of fourteen healthy elderly women aged 68.1 +/- 2.6 years. The body composition of each subject was assessed using several anthropometric measurements in order to help explain any observed differences in the pharmacokinetic behavior of vitamin C. The vitamin C doses were characterized with the subjects in two states of vitamin C nutriture: a 'depleted' state which was achieved by 4-5 weeks on a vitamin C-restricted diet of less than 10 mg/d and a 'supplemented' state in which the subjects were given daily doses of 500 mg of vitamin C for 3 weeks. Plasma and urine samples were collected for 72 h following the dose of vitamin C from subjects in a 'depleted' state and for 24 h from subjects in a 'supplemented' state and analysed for their vitamin C content. None of the pharmacokinetic parameters measured differed significantly between the two age groups. In contrast, the vast majority of these parameters were significantly different in depleted and supplemented subjects. The peak times (tmax) were greater in the depleted state in both young and elderly groups whereas the peak concentrations (Cmax) were greater in the supplemented state. The absorption rate constant (Ka) was significantly larger in the supplemented state compared to the depleted state in the young group and the absorption half-life (t 1/2, Ka) was significantly greater in the depleted state in the young group only. The absorption lag time (tlag) did not differ with respect to age or nutritional status. The elimination half-life (t 1/2, Ke) was significantly longer in supplemented subjects. Although the apparent high volume of distribution (Vd) was not significantly different within each age group the Vd was significantly greater in the depleted state when the two age groups were combined. The clearance (CL), and the nonrenal clearance (CLNR) were significantly greater in the depleted state. The renal clearance (CLR) and the amounts of vitamin C excreted in the 0- to 12- and 12- to 24-h intervals were significantly larger in the supplemented state. The urinary excretion data also indicate that, in supplemented subjects, an average of about 40 percent of the administered dose is excreted as unchanged vitamin C in the first 12 h after dosing, with very little being excreted thereafter.     

Nutritional survey of the US Navy SEAL trainees

The nutritional status of 267 male US Navy Sea, Air, and Land (SEAL) trainees was assessed to determine dietary patterns. Diet records, blood samples, 24-h urine collections, and physical characteristics were analyzed. Energy intake was 3886 +/- 73 kcal/d (SEM) with 15.7 +/- 0.2, 42.9 +/- 0.6, and 41.2 +/- 0.5% of the energy derived from protein, carbohydrate (CHO), and fat, respectively. Mean cholesterol intake (1008 +/- 35.7 mg/d [SEM]) exceeded the US Dietary Goal (less than or equal to 300 mg/d) and serum cholesterol concentration was 5.25 +/- 0.41 mmol/L (SEM). Over 38% of the trainees had cholesterol concentrations greater than 5.3 mmol/L, an indicator of high risk for cardiovascular disease. Mean sodium intake was 250 +/- 22 mmol/d. Over 86% of the trainees consumed greater than 144 mmol/d. Urinary Na excretion was high (146.7 +/- 6.7 mmol/d [SEM]) and correlated with Na intake (r = 0.365; p = 0.001). Potassium and selected vitamin intakes approximated the Military Recommended Dietary Allowances. Fat, cholesterol, and Na intakes were high relative to the dietary goals. Whether more dietary CHO would improve performance in endurance training remains to be determined.     

Ascorbate increases human oxaluria and kidney stone risk

Currently, the recommended upper limit for ascorbic acid (AA) intake is 2000 mg/d. However, because AA is endogenously converted to oxalate and appears to increase the absorption of dietary oxalate, supplementation may increase the risk of kidney stones. The effect of AA supplementation on urinary oxalate was studied in a randomized, crossover, controlled design in which subjects consumed a controlled diet in a university metabolic unit. Stoneformers (n = 29; SF) and age- and gender-matched non-stoneformers (n = 19; NSF) consumed 1000 mg AA twice each day with each morning and evening meal for 6 d (treatment A), and no AA for 6 d (treatment N) in random order. After 5 d of adaptation to a low-oxalate diet, participants lived for 24 h in a metabolic unit, during which they were given 136 mg oxalate, including 18 mg 13C2 oxalic acid, 2 h before breakfast; they then consumed a controlled very low-oxalate diet for 24 h. Of the 48 participants, 19 (12 stoneformers, 7 non-stoneformers) were identified as responders, defined by an increase in 24-h total oxalate excretion > 10% after treatment A compared with N. Responders had a greater 24-h Tiselius Risk Index (TRI) with AA supplementation (1.10 +/- 0.66 treatment A vs. 0.76 +/- 0.42 treatment N) because of a 31% increase in the percentage of oxalate absorption (10.5 +/- 3.2% treatment A vs. 8.0 +/- 2.4% treatment N) and a 39% increase in endogenous oxalate synthesis with treatment A than during treatment N (544 +/- 131 A vs. 391 +/- 71 micromol/d N). The 1000 mg AA twice each day increased urinary oxalate and TRI for calcium oxalate kidney stones in 40% of participants, both stoneformers and non-stoneformers.     

Urinary excretion of an intravenous 26Mg dose as an indicator of marginal magnesium deficiency in adults

BACKGROUND: Measurement of magnesium (Mg) status is problematic because tissue Mg deficiency can be present without low serum Mg concentrations. OBJECTIVE: To evaluate a modified version of the Mg retention test using stable isotopes for the assessment of Mg status in general, and the detection of marginal Mg deficiency in particular. DESIGN: A modified version of the Mg retention test using a small dose of (26)Mg was evaluated for assessment of Mg status in 22 healthy subjects. Muscle Mg concentration was used as reference for Mg status. A muscle biopsy was taken from the lateral portion of the quadriceps muscle from each subject. After 2 to 4 weeks, 11 mg of (26)Mg (as MgCl(2) in 14 ml water) were injected i.v. over a period of 10 min and all urine was collected for the following 24 h. Excretion of the isotopic label was expressed as percentage of the administered dose excreted in urine within 24 h. RESULTS: Mean +/- s.d. Mg concentration in muscle was 3.85 +/- 0.17 mmol/100 g fat-free dried solids. Mean +/- s.d. excretion of the injected dose within 24 h was 7.9 +/- 2.1%. No correlation was found between muscle Mg concentration and excretion of the isotopic label (r (2 ) = 0.061, P = 0.27). CONCLUSIONS: In this study, urinary excretion of an intravenous Mg tracer was not influenced by muscle Mg concentration and its usefulness for the detection of marginal Mg deficiency could therefore not be demonstrated. SPONSORSHIP: Swiss Foundation for Nutrition Research and Swiss Federal Institute of Technology, Zurich, Switzerland.     

Nutritional status of land-based U.S. Navy divers

The nutritional status of 16 male, land-based U.S. Navy divers was assessed to collect baseline information for a cold water dive series. Diet records, blood samples, and 24-h urine collections were obtained and analyzed. The divers were deriving 17 +/- 1%, 40 +/- 2%, 32 +/- 2% of their calories from protein, carbohydrate, and fat, respectively. The remaining calories were furnished by alcohol (11 +/- 2%), an amount within the American Heart Association's guidelines. Crude fiber intake was low (3.7 +/- 0.4 g/d) whereas cholesterol (507 +/- 101 mg/d) and sodium intakes (4462 +/- 599 mg/d) were high. Mean intakes of vitamin B6 and folacin were below the Military Recommended Dietary Allowances. Mean blood concentrations and urinary excretion of minerals were normal but urinary sodium excretion was high. Results indicate that the divers' intakes of sodium and cholesterol were high, whereas intakes of complex carbohydrate and crude fiber were low. Whether these dietary patterns are suitable for extended dives, especially in cold water, remains to be determined.     

Amino acid intake and urinary zinc excretion in newborn infants receiving total parenteral nutrition

Zinc deficiency is well described in infants on total parenteral nutrition (TPN). Urinary Zn excretion is the major source of Zn loss in the parenterally fed infant; factors causing increased zincuria will predispose the infant to Zn deficiency and affect the recommended Zn intake dosage. Histidine, threonine, and lysine have been shown to bind Zn increasing its renal ultrafilterability. The effect of the infusion of high and low lysine (206 +/- 34 vs 158 +/- 38 mg.kg-1.d-1; means +/- SD), threonine (147 +/- 24 vs 113 +/- 27), and histidine (124 +/- 34 vs 85 +/- 15) on urinary Zn excretion were determined in 23 newborns on TPN who received similar Zn intakes (6.8 +/- 1.4 mumol.kg-1.d-1). After a 72-h adaptation period each infant had urine collected for two 24-h periods. Despite the significant difference in amino acid intakes, mean urinary Zn excretion was identical (1.58 +/- 0.73 vs 1.56 +/- 0.63 mumol.kg-1.d-1). Hyperzincuria, therefore, does not occur when amino acids are infused at rates appropriate for the safety and nutritional maintenance of neonates.     

Metabolic effects of acarbose in young healthy men

To explore the long-term metabolic effects of acarbose in man, 6 healthy men (25 +/- 2 years; BMI: 21.6 +/- 2.7) were fed a controlled diet in a metabolic ward for 7 consecutive weeks. After an initial 3-week period to ensure a metabolic steady-state, they received 300 mg/d of acarbose (100 mg before each meal) for the remaining 4 weeks. Stool and urine collections were made over 7 d on weeks 3 and 7. Faecal excretion of water, nitrogen, carbohydrate, fat, zinc, magnesium, copper, chromium, iron, calcium and phosphorus and urinary excretion of nitrogen, urea and calcium were measured. In addition, fasting and postprandial blood glucose and insulin levels, as well as fasting triglycerides, total cholesterol, apolipoproteins (Apo) A-I, A-II, and B, zinc and copper, vitamins A, B1, B2, B6, C, and E concentrations were measured before and at the end of the acarbose period. Weight, food consumption, and water balance were not modified by acarbose. Faecal nitrogen excretion increased significantly but the nitrogen balance remained positive. Faecal excretion of carbohydrate, fat, iron and chromium were significantly increased by acarbose. Apos A-I and A-II decreased significantly. Plasma levels of vitamin B6 increased and vitamin A concentrations decreased with acarbose. This study provides new insights into the metabolic effects of acarbose with respect to nitrogen, mineral and vitamin metabolism.     

Blood pressure and excretion of sodium, potassium, calcium and magnesium in 8- and 9-year old boys from 19 European centres

We have measured systolic and diastolic blood pressure and excretions of sodium, potassium, calcium and magnesium in groups of about 50 8- and 9-year-old boys from 19 European centres using standardized methods for the measurement of blood pressure and collection of urine, and by carrying out all analyses in one laboratory. Weight, height, pulse rate and environmental temperature were also studied. Mean systolic blood pressure ranged from 91 to 105 mm Hg and diastolic blood pressure from 51 to 66 mm Hg. Mean 24-h excretion of sodium was between 91 and 146 mmol/d, that of potassium between 29 and 60 mmol/d, that of calcium between 1.5 and 2.6 mmol/d and that of magnesium between 2.7 and 4.2 mmol/d. Mean sodium excretion tended to be lower and potassium excretion tended to be higher in the boys from the north-western parts of Europe. Relations between either systolic or diastolic blood pressure and electrolyte excretions were generally weak or absent. Most remarkable is that only the association between mean diastolic blood pressure and 24-h magnesium excretion (partial regression coefficient (b +/- s.e., -5.04 +/- 2.08 mm Hg/mmol/d) was statistically significant after adjusting for differences in creatinine excretion and environmental temperature. Mean systolic blood pressure was not significantly related with any of the variables measured. The partial regression coefficient (b +/- s.e.) for diastolic blood pressure on weight was 0.186 +/- 0.062 mm Hg/kg, on height 0.165 +/- 0.056 mm Hg/cm, on pulse rate 0.364 +/- 0.100 mm Hg/beats per min and on outside temperature -0.25 +/- 0.07 mm Hg/degrees C.