Urinary 4-pyridoxic acid excretion in 24-hour versus random urine samples as a measurement of vitamin B6 status in humans

Urinary excretion of 4-pyridoxic acid (4PA) in 19 men (n = 5) and women (n = 14) was measured to evaluate the validity of determining the 4PA/creatinine ratio in random urine samples as an alternative to total 24-h 4PA excretion in assessing vitamin B6 nutritional status. The relationships among dietary vitamin B6 intake, 4PA excretion, plasma pyridoxal 5'-phosphate levels, and erythrocyte aspartate aminotransferase activity and in vitro stimulation by added plasma pyridoxal 5'-phosphate were examined. The subjects consumed all meals for 3 days in a metabolic unit, and protein intake was kept constant. Plasma pyridoxal 5'-phosphate concentration was positively correlated with vitamin B6 intake of the previous day (r = 0.61, p less than 0.01). There was a positive correlation (r = 0.59, p less than 0.01) between total 4PA and 4PA/creatinine in the 24-h urine samples. No difference (p greater than 0.05) in 4PA/creatinine between the 24-h samples and either morning or afternoon random samples taken the next day was found. These findings support the use of the 4PA/creatinine ratio in random urine samples as an alternative to 24-h urinary 4PA excretion.     

Ascorbic acid status of smoking and nonsmoking adolescent females

The nutritional status of a group of smoking (N = 11) and nonsmoking (N = 26) adolescent females, ages 14 to 17 years, was evaluated with respect to vitamin C. Dietary intakes of ascorbic acid (AA) were determined from two separate 24-hour food recalls. Plasma AA was determined via the 2,4-dinitrophenylhydrazine method. Significant differences were found between smokers and nonsmokers for vitamin C intake and plasma AA. Smokers had lower dietary intakes (27 +/- 11 mg/day) and plasma AA levels (0.32 +/- 0.19 mg/dl) than did nonsmokers (73 +/- 47 mg/day; 1.46 +/- 0.69 mg/dl). When plasma vitamin C values were adjusted for vitamin C intake, smokers still exhibited a significantly lower plasma AA concentration (0.48 mg/dl vs 1.38 mg/dl for nonsmokers). Cigarette smoking was associated with a significantly decreased AA status in the present group of adolescent females.     

以任意一次尿样还原型维生素C对肌酐比值评定人体维生素C营养水平的方法学研究

<正> 关于评定人体维生素C(以下简称V.C)营养水平,前人已经提出过很多方法。在营养调查中常用的是测定尿V.C排出量。但此法取样手续繁琐,不仅存在许多实际困难,也影响测定结果的准确。鉴于尿肌酐排出量相对恒定,有人曾研究过以尿V.C对肌酐比值做为评定指标,但该法仍须定时收尿或先期测尿肌酐,仍较费事。为解决此问题,本文研究     

某些水溶性维生素营养状况评定的研究

用任意一次尿中某些水溶性维生素排出量与肌酐排出量的比值来作为评定人群的营养状况最为简便,能解决收集24小时尿量不易完整的困难。本文的人体实验结果证明,任意一次尿中肌酐排出量与全日尿中肌酐排出量有显著的相关,即使一日偶尔增加100—300g的酱牛肉,对全日尿中肌酐的排出量影响不大。任意一次尿中硫胺素、核黄素、N’-甲基尼克酰胺的排出量与肌酐排出量的比值,能够反映出绝大多数受试者这些维生素的营养状况,可作为评定人群营养状况的指标。     

Dietary intake and nutritional status of young vegans and omnivores in Sweden

BACKGROUND: Adolescents sometimes become vegetarian for ethical rather than health reasons. This may result in health problems caused by lack of interest in and knowledge of nutrition. OBJECTIVE: We compared the dietary intake and nutritional status of young Swedish vegans and omnivores. DESIGN: The dietary intakes of 30 vegans (15 males and 15 females; mean age: 17.5 +/- 1.0 y) and 30 sex-, age-, and height-matched omnivores were assessed with the use of a diet-history interview and validated by the doubly labeled water method and by measuring nitrogen, sodium, and potassium excretion in urine. Iron status and serum vitamin B-12 and folate concentrations were measured in blood samples. RESULTS: The diet-history method underestimated energy intake by 13% and potassium intake by 7% compared with the doubly labeled water method and 24-h urine excretion, respectively. Reported dietary nitrogen and sodium intakes agreed with the 24-h urinary excretion measure. Vegans had higher intakes of vegetables, legumes, and dietary supplements and lower intakes of cake and cookies and candy and chocolate than did omnivores. Vegans had dietary intakes lower than the average requirements of riboflavin, vitamin B-12, vitamin D, calcium, and selenium. Intakes of calcium and selenium remained low even with the inclusion of dietary supplements. There was no significant difference in the prevalence of low iron status among vegans (20%) and omnivores (23%). Two vegans with low intakes of vitamin B-12 had low serum concentrations. CONCLUSION: The dietary habits of the vegans varied considerably and did not comply with the average requirements for some essential nutrients.     

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.     

Urinary oxalate excretion increases in home parenteral nutrition patients on a higher intravenous ascorbic acid dose

BACKGROUND: Vitamin C can be metabolized to oxalate. Case reports have suggested an association between IV vitamin C and urinary oxalate excretion. Recently, the US Food and Drug Administration required the dose of vitamin C in IV multivitamin preparations to be increased from 100 mg to 200 mg/d. We compared the urinary oxalate excretion level in stable home total parenteral nutrition (TPN) patients receiving both doses of vitamin C. METHODS: Each participant provided a 24-hour urine sample for oxalate determination on the vitamin C dose (100 mg/d), and again after at least 1 month on the increased vitamin C dose (200 mg/d). A 2-day diet diary was completed covering the day before and the day of the urine collection and was analyzed for oxalate and vitamin C content. Comparisons were made using Student paired t test and Wilcoxon signed rank. RESULTS: Thirteen patients (7 males/6 females) aged 63.1 +/- 12.2 years who had no history of nephrolithiasis and had received TPN for 55.9 +/- 78.8 months were enrolled. The most common indication for TPN was short bowel syndrome (38.5%). Eight patients had an intact colon. Urinary oxalate excretion increased on the 200-mg vitamin C dose, from 0.34 +/- 0.13 to 0.44 +/- 0.17 mmol/d (mean increase = 0.10 mmol/d; p = .04; 95% confidence interval 0.004 to 0.19 mmol/d). Oral intake of vitamin C and oxalate did not differ between the 2 collection periods. CONCLUSIONS: In therapeutically used doses, IV vitamin C increases urinary oxalate excretion, potentially predisposing susceptible individuals to nephrolithiasis. This factor should be considered in patients receiving home TPN.     

Estimation of nitrogen excretion based on abbreviated urinary collections in patients on continuous parenteral nutrition

The physiologic response to stress can create a net loss of nitrogen, which is indicative of a catabolic state. Nitrogen balance has been demonstrated to be a useful clinical indicator of a patient's catabolic state and the effectiveness of parenteral nutrition, but requires an estimate of total urinary nitrogen excretion. The standard method for determining total urinary nitrogen excretion is 24-hour urinary urea nitrogen excretion. Unfortunately, the 24-hour urine collection is inconvenient, cumbersome, sometimes inaccurate, and induces a lag in response time to changes in therapy. Although shorter collection times have been proposed, the validity of shorter-timed determinations remains open to question. To evaluate the estimation of 24-hour urine urea excretion from shorter-timed determinations, the urinary urea nitrogen excretion of 4-, 8-, and 12-hour durations was regressed against the 24-hour collection in 56 critically ill adult patients. The 12-hour determination provided satisfactory estimates of the 24-hour nitrogen excretion, but the 4-hour and 8-hour determinations did not. Thus, two times the 12-hour urine urea nitrogen determination can be substituted for the 24-hour determination in calculating nitrogen balance. A 12-hour determination can provide a more rapid turnaround of biochemical analysis, allow more timely nutritional intervention, decrease nursing time, and reduce the frequency of inaccurate or lost specimens.     

The effect of low level radiofrequency electromagnetic radiation on the excretion rates of stress hormones in operators during 24-hour shifts

The aim of the study was to investigate the effect of long term exposure to low level radiofrequency (RF) electromagnetic (EM) radiation on the excretion rates of stress hormones in satellite station operators during 24-hour shifts. Twelve male operators at a satellite station for TV communications and space research were studied during 24-hour shifts. Dosimetric evaluation of the exposure was carried out and showed low level exposure with specific absorption of 0.1127 J.kg-1. A control group of 12 unexposed male operators with similar job task and the same shift system were studied, too. The 11-oxycorticosteroids (11-OCS), adrenaline and noradrenaline were followed by spectrofluorimetric methods on 3-hour intervals during the 24-hour shifts. The data were analyzed by tests for interindividual analysis, Cosinor analysis and analysis of variance (ANOVA). Significant increase in the 24-hour excretion of 11-OCS and disorders in its circadian rhythm, manifested by increase in the mesor, decrease in the amplitude and shift in the acrophase were found in the exposed operators. The changes in the excretion rates of the catecholamines were significant and showed greater variability of both variables. The long term effect of the exposure to low-level RF EM radiation evoked pronounced stress reaction with changes in the circadian rhythm of 11-OCS and increased variability of catecholamines secretion. The possible health hazards associated with observed alteration in the stress system need to be clarified by identification of their significance and prognostic relevance.     

肝硬化合并腹水患者随机尿Na/K比值检测在临床诊疗中的应用及其意义

目的 探讨肝硬化合并腹水患者随机尿Na/K比值的分布及能否正确反映24小时尿钠排量,并确定评价利尿剂反应的随机尿Na/K比值。 方法 以40例肝硬化合并腹水患者为研究对象,每个患者在早8点给利尿剂,采集24小时尿量、用利尿剂后2-4小时和7-9小时随机尿5ml,并检测24小时尿钠排量、随机尿Na/K比值以及分析随机尿Na/K比的ROC曲线。 结果 选择40名尿肌酐排量大于15mEq/Kg的患者进行分析,24小时平均排尿量1722.5±915.3ml(500~3500ml),24小时尿排钠量均值为107.9±91.2(3~366)mmol/L,上午及下午随机尿Na/K比值分别为3.44±3.64、3.97±4.60,对24小时尿排钠量大于78 mmol/L患者进行上午及下午随机尿Na/K比ROC曲线分析,上午随机尿Na/K比值ROC曲线下面积为0.861,下午随机尿Na/K比值ROC曲线下面积为0.929。分析上午及下午随机尿Na/K比值一致性,上午随机尿Na/K比值ROC曲线下面积与下午随机尿Na/K比值ROC曲线下面积之差为0.0682(95%CI=-0.161～0.153,P=0.113),统计学无差异。另外,随机尿Na/K比值在1.25~1.45以上时,可以反映24小时尿排钠量大于78 mmol/L。 结论 随机尿Na/K比值大于1.25时,可以正确反映24小时尿钠排量大于78 mmol/L,随机尿Na/K比值检测是判断利尿剂效果的方便、灵敏而特异的指标。     

Fortified juice drink improved iron and zinc status of schoolchildren

Energy and micronutrient deficiency remain prevalent among Filipino children. Juice drinks are commonly consumed and could be a viable vehicle for fortification to supplement the nutrient gap. This study determined the effects of a newly developed non-carbonated fortified juice drink on the iron, zinc and nutritional status of schoolchildren. One hundred randomly selected anemic children were randomly allocated into two groups in a doubly-masked placebo controlled manner: Group 1 received the fortified juice, Group 2 received the non-fortified juice for 100 days, five days a week under strict supervision. The juice drink was fortified with vitamin A, zinc, iron, vitamin C and lysine. The non-fortified juice was fortified only with vitamin C. All children were dewormed prior to the intervention. Hemoglobin, plasma ferritin and plasma zinc, weight and height were assessed using standard methods before and after intervention. A two-day 24-hour food recall was also collected. The basal prevalence of anemia was significantly reduced in both the fortified group (100% to 13%) and the non-fortified group (100% to 40%) at endline. The mean plasma ferritin levels were similar in both groups at baseline and endline. At endline, mean plasma zinc in the fortified group has significantly increased by 20 μg/dL from a baseline value of 83.9 μg/dL to 103.9 μg/dL, while the non-fortified group remained at similar levels with baseline. Basal weight and height significantly increased among all children at endline. The fortified juice drink was effective in reducing the prevalence of anemia and improved the zinc status of children.     

Urinary excretion of zinc, copper and iron in the streptozotocin-diabetic rat

The influence of the chemically diabetic condition on urinary excretion of zinc, copper and iron was investigated. Male Sprague-Dawley rats were injected with streptozotocin to induce insulin-dependent diabetes (day 0) and 24-hour urinary collections taken 1, 4, 7, 10 and 14 days later. Onset of the diabetic condition was correlated with a rapid and persistent increase in the amounts of the three trace metals excreted daily in the urine. Diabetic rats excreted 3.4-, 5.0- and 4.9-fold more zinc, copper and iron, respectively, than controls in the urine on day 14. Insulin treatment of diabetic rats significantly reduced the quantities of the micronutrients excreted in urine, suggesting that altered hormonal status was the primary cause of increased urinary losses. Enhanced urinary output of the metals was not associated with reduction in the plasma, liver and kidney contents of zinc, copper and iron. Urinary trace metal excretion was correlated with food ingestion and urinary volume with greater amounts lost during the dark period for control and diabetic animals. The influence of endocrine status on urinary excretion of trace metals is discussed.     

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     

妊娠期高血压疾病患者24h尿微量清蛋白水平分析

目的:探讨妊娠期高血压疾病患者24 h尿微量清蛋白水平变化。方法:选择2010年7月～2011年10月正常妊娠者22例(对照组),同期住院妊高征患者61例,其中轻度子痫前期患者27例、重度子痫前期患者34例,采用速率散射比浊法检测24 h尿微量蛋白和24 h尿微量清蛋白。结果:轻度和重度妊高征患者24 h尿微量清蛋白均明显高于正常妊娠孕妇(P<0.001),妊高征重度与轻度相比,24 h尿微量清蛋白增高(P<0.001);重度妊高征患者24 h尿微量清蛋白和24 h微量蛋白阳性率分别为97.10%和100.00%,两项指标无明显差异,轻度组分别为81.50%和55.56%。结论:妊高征患者随病情的加重,24 h尿微量清蛋白及24 h尿微量蛋白水平明显升高,轻度妊娠期高血压疾病患者24 h尿微量清蛋白阳性率高于24 h尿微量蛋白,监测24 h尿微量清蛋白对轻度妊娠高血压的早期诊断和预后具有重要意义。     

Comparative analysis of two regimens of antibiotic prophylaxis in elective colorectal surgery

BACKGROUND: Antibiotic prophylaxis has greatly reduced the rate of postoperative infectious complications since its utilization in the elective colorectal surgery in the last several decades. Although the need of its application is indisputable, the optimal duration of antibiotic prophylaxis is still on debate. AIM: The aim of the present study was to compare two regimens of antibiotic prophylaxis with different duration. MATERIALS AND METHODS: A retrospective clinical study was conducted of 190 patients that underwent elective surgery for colorectal carcinoma in the Clinic between January 1997 and June 2000. The patients were divided into two groups according to the regimen of antibiotic prophylaxis. Group 1 (n = 92) patients received a 24-hour antibiotic prophylaxis and Group 2 (n = 98) had a prolonged antibiotic cover that lasted 5 days. The antibiotic prophylaxis was conducted with a third generation cefalosporin and metronidazole. RESULTS: Of all 190 patients 92 were in Group 1 and 98 in Group 2. Postoperative infectious wound complications were found in 14 (15.2%) patients from Group 1 and in 25 (25.5%) patients from Group 2. The difference did not reach statistical significance (P > 0.05). CONCLUSION: The results of the study show no advantage of the prolonged over short-term antibiotic prophylaxis. Based on the study findings the authors suggest that a 24-hour antibiotic prophylaxis should be recommended for the lower rate of side effects and lower cost.     

Urine Arsenic Concentrations and Species Excretion Patterns in American Indian Communities Over a 10-year Period: The Strong Heart Study

Background

Arsenic exposure in drinking water disproportionately affects small communities in some U.S. regions, including American Indian communities. In U.S. adults with no seafood intake, median total urine arsenic is 3.4 μg/L.

Objective

We evaluated arsenic exposure and excretion patterns using urine samples collected over 10 years in a random sample of American Indians from Arizona, Oklahoma, and North and South Dakota who participated in a cohort study from 1989 to 1999.

Methods

We measured total urine arsenic and arsenic species [inorganic arsenic (arsenite and arsenate), methylarsonate (MA), dimethylarsinate (DMA), and arsenobetaine] concentrations in 60 participants (three urine samples each, for a total of 180 urine samples) using inductively coupled plasma/mass spectrometry (ICPMS) and high-performance liquid chromatography/ICPMS, respectively.

Results

Median (10th, 90th percentiles) urine concentration for the sum of inorganic arsenic, MA, and DMA at baseline was 7.2 (3.1, 16.9) μg/g creatinine; the median was higher in Arizona (12.5 μg/g), intermediate in the Dakotas (9.1 μg/g), and lower in Oklahoma (4.4 μg/g). The mean percentage distribution of arsenic species over the sum of inorganic and methylated species was 10.6% for inorganic arsenic, 18.4% for MA, and 70.9% for DMA. The intraclass correlation coefficient for three repeated arsenic measurements over a 10-year period was 0.80 for the sum of inorganic and methylated species and 0.64, 0.80, and 0.77 for percent inorganic arsenic, percent MA, and percent DMA, respectively.

Conclusions

This study found low to moderate inorganic arsenic exposure and confirmed long-term constancy in arsenic exposure and urine excretion patterns in American Indians from three U.S. regions over a 10-year period. Our findings support the feasibility of analyzing arsenic species in large population-based studies with stored urine samples.     

Metabolism of selenite in men with widely varying selenium status.

OBJECTIVE: This study was undertaken to investigate the metabolism of selenite in men with life-long intakes of deficient, adequate and excess selenium. METHODS: Stable isotopes of selenium were infused for five hours into Chinese men living in deficient, adequate or excessive selenium areas, and 24-hour urine and blood samples were collected daily for the next seven days. Stable isotopic selenium excretion was determined in urine and in whole plasma and plasma fractions. RESULTS: Even though there was a positive correlation of selenium intake with the urinary excretion of this element, this relationship was not linear over the entire range (deficient, adequate, excessive) of selenium intake. When the urine excretion was normalized internally within each group, a sharp increase in the slope of this relationship was found when long-term intake increased to adequate amounts, but the slope reached a plateau when the daily intake exceeded the adequate group. The plasma selenoprotein P fraction was labeled initially, but the incorporation in the glutathione peroxidase fraction subsequently increased by a small amount. A two-month dietary restriction of selenium of the subjects from the excess area did not result in a reduction of urinary excretion of infused selenite. CONCLUSION: A complex relationship exists between long-term intake of selenium and selenium status, and subjects living in the excess area are more saturated with selenium than anticipated. More than two months of depletion are required to affect urinary excretion of selenium.     

Plasma urea-cycle-related amino acids,ammonium levels,and urinary orotic acid excretion in short-bowel patients managed with an oral diet

BACKGROUND AND AIMS: The small intestine contains several enzymes involved in arginine synthesis and converts glutamine to citrulline, the major compound for endogenous arginine synthesis. This study was conducted to assess the plasma status of urea-cycle intermediates and orotic urinary excretion in short-bowel patients. METHODS:Thirteen stable short-bowel syndrome patients (7 men; 60.2+/-15.2 years) were studied. Patients were divided into moderately resected (Group A; n=6) and severely resected (Group B; n=7) according to their remnant bowel length (Group A: 61-150 cm; Group B: < or =60 cm). All subjects were consuming an oral diet plus dietetic supplements. Plasma urea-cycle amino acids, ammonium and urinary orotic acid were determined. RESULTS: Plasma glutamine levels were significantly higher in both patient groups than in the control group (P<0.001). Regarding citrulline, Group B levels were significantly lower vs. controls (P<0.001). Comparisons between patient groups showed higher arginine in Group A (P<0.05) and non-statistically lower citrulline in Group B. Blood ammonium and orotic urinary excretion were normal. CONCLUSIONS: Although plasma citrulline and glutamine alterations were found, patients showed no hyperammonemia or orotic aciduria, which suggests a certain degree of adaptation in arginine and related amino acid metabolism, when an adequate dietary supply of arginine is provided.     

Hypertension and salt intake in an urban population

OBJECTIVE: To evaluate the salt intake and urinary Na+/K+ ratio in a randomized sample from an ethnically mixed urban population. METHODS: A randomized residential sample of 2,268 individuals aged 25-64 in Vit ria, ES, was selected, of whom 1,663 (73.3%) reported to the hospital for standardized tests. Salt, Na+ and K+ intake was estimated from 12-hour urine excretion (7 p.m. to 7 a.m.) and from the monthly salt consumption at home reported in the interview. Clinic arterial pressure was measured twice under standard conditions by two trained investigators, using mercury sphygmomanometry. The Student t and Tukey tests were utilized for statistical analysis. RESULTS: Urinary Na+ excretion was higher in men and individuals of lower socioeconomic level (P<0.000). No difference between ethnic groups was observed. K+ excretion was unrelated to socioeconomic level and ethnicity, but was significantly higher among men (25 18 vs. 22 18 mEq/12h; P=0.002). Positive linear correlation was observed between urinary Na+ excretion and systolic (r=0.15) and diastolic (r=0.19) arterial pressure. Hypertensive individuals showed higher urinary Na+ excretion and Na+/K+ ratio than normotensive individuals. Reported salt intake was around 50% of the intake estimated from 12-hour urine collection (around 45% of 24-hour urinary excretion). CONCLUSIONS: Salt intake is strongly influenced by socioeconomic level and may partially explain the higher prevalence of hypertension in lower socioeconomic classes.     

Day-to-day and within-day variation in urinary iodine excretion.

OBJECTIVE: To examine the day-to-day and within-day variation in urinary iodine excretion and the day-to-day variation in iodine intake. DESIGN: Collection of consecutive 24-h urine samples and casual urine samples over 24h. SETTING: The study population consisted of highly motivated subjects from our Institute. SUBJECTS: Study 1: Ten healthy subjects (seven females and three males) aged 30-46 y. Study 2: Twenty-two healthy subjects (9 males and 13 females) aged 30-55 y. METHODS: Study 1: 24-h urine samples were collected for four consecutive days. Study 2: Each urine voided over 24 h was collected into separate containers. In both studies dietary records were kept. MAIN OUTCOME MEASURES: Twenty-four-hour urinary iodine excretion, 24-h urinary iodine excretion estimated as I/Cr*24 h Cr and as a concentration in casual urine samples. RESULTS: Study 1: Both iodine excreted in 24-h urine and iodine intake varied from day-to-day. Iodine excretion correlated with iodine intake (=-0.46, P=0.01). Iodine intake (mean 89 +/- 6.5 microg/d) was not significantly different from iodine excretion (mean 95 +/- 5.3 microg/d). Study 2: Twenty-four hour iodine excretion estimated as I/Cr*24 h Cr from the morning urine sample was significantly lower than actual 24-h iodine excretion, whereas 24-h iodine excretion estimated as I/Cr*24 h Cr from the first sample after the morning sample and the last sample before the subjects went to bed was not significantly different from actual 24-h iodine excretion. Twenty-four-hour urine excretion estimated as a concentration was lower than actual 24-h iodine excretion in casual urine taken at any time of the day. CONCLUSIONS: For determination of iodine status in an individual, more than one 24-h urine sample must be used. The use of the I/Cr ratio in casual urine samples is a usable measure of iodine status if corrected for the age- and sex-adjusted 24-h creatinine excretion. Further, the study suggests that fasting morning urine samples would underestimate iodine status in this population.