Kinetics of a single administration of 74Se-selenite by oral and intravenous routes in adult humans

The purpose of this study was to explore the fate of a single dose of labeled selenium as determined by its route of administration. Thus, the appearance of a stable isotope of selenium, administered as 74-Se-selenite, was measured in plasma, urine, and feces, with neutron activation analysis, following a 81.7 micrograms dose of 74Se-selenite given either intravenously or orally in two groups (n = 4) of healthy, young adult men, who were otherwise maintained on a diet providing a constant and adequate selenium intake. From these isotopic data, measurable parameters of urine excretion, total body retention and selenite-exchangeable metabolic pool (Se-EMP) were defined to provide a quantitative assessment of selenium metabolism in these subjects. The initial 24-hr urine excretion of the label was higher for the intravenously administered label (18.2 +/- 2.1% of dose) compared to the oral dose (11.7 +/- 2.6% absorbed dose). Thereafter, the excretion of isotope was the same for both groups. For equivalent entry of Se into the body, measured total body retention and Se-EMP were the same for both groups. These initial kinetic data suggest that the overall utilization of selenium from a single administration of selenite is comparable for the two routes of intake and that the host's selenium requirement can probably be met adequately via the intravenous administration of selenite.     

Selenium supplementation affects the retention of stable isotopes of selenium in human subjects consuming diets low in selenium

Twenty-nine women and fifteen men from an area of low Se intake (South Island of New Zealand) consumed 100 micrograms stable 74Se, as selenate given in water after an overnight fast, and blood was collected for 3 weeks. They were then divided into five groups and supplemented with 0, 10, 20, 30 and 40 micrograms Se/d (as selenomethionine) for 5 months. After 5 months, they received a second dose of 74Se identical to the first. Supplementation significantly altered retention of 74Se in the plasma, but not in the erythrocytes or platelets. Subjects receiving the placebo retained the greatest amount, and subjects receiving 30 micrograms supplemental Se/d retained the least 74Se. Supplementation resulted in relatively more isotope being retained in a medium molecular mass protein considered to be albumin, and relatively less in another fraction considered to be selenoprotein P. The lack of many observed changes in retention of stable Se, and the shift in retention among the plasma proteins, suggests that supplemental Se was not being used to replete critical pools of Se, probably because of adaptation to low Se intake.     

Ascorbic acid-selenite interactions in humans studied with an oral dose of 74SeO3(2-)

The interaction between dietary ascorbic acid at extremes of ascorbic acid intake and selenium in young adult male humans was investigated with a stable-isotope approach using 74Se-selenite. Measurements were made of 74Se in plasma, urine, and feces with neutron-activation analysis after oral administration of 74SeO3(2-). Urine excretion and total body retention of isotope and the selenite-exchangeable metabolic pool (Se-EMP) were calculated. Limiting dietary ascorbic acid to about 20 mg/d appeared to reduce the time-related retention of absorbed selenite and the size of Se-EMP. Compared with a diet providing 1 g ascorbic acid/d the low ascorbic acid intake was associated with a lower fractional absorption of the isotope, a reduced retention of the label, and a smaller Se-EMP. These data and those previously obtained in subjects with more usual ascorbic acid intakes point to a possible important role for ascorbic acid in the maintenance of Se homeostasis.     

Effect of chronic selenite supplementation on selenium excretion and organ accumulation in rats

We examined the effect of chronic selenite supplementation on whole body and selected organ selenium (Se) accumulation, urine excretion of total Se and trimethylselenonium ion, and Se balance in adult male rats. Animals were housed in metabolic cages and given either deionized water or water containing 4 micrograms of Se/mL as selenite for 30 d. Absorption of selenite was nearly complete, with only approximately 10% of ingested Se appearing in feces. There was a rapid rise in urinary Se that reached a plateau within a few days and accounted for 54 +/- 2% of the intake. Excretion of trimethylselenonium ion (TMSe) in urine increased rapidly, representing 35-40% of urinary Se in the supplemented animals compared with only 2% for the control group. In one experiment, rats were killed at 30 d and total carcass Se was measured using isotope dilution analysis. Supplemented rats had only a modest increase in whole body Se (94 +/- 4 micrograms Se vs. 66 +/- 3 in controls). Calculation of Se balance in the supplemented rats showed that approximately 35% of ingested Se could not be accounted for by urine plus fecal losses combined with the portion retained in the carcass. The results from this study demonstrate that under the condition of supplementation at 4 micrograms of Se/mL of drinking water, pathways other than urinary and fecal excretion may account for a substantial portion of Se loss.     

Effect of various levels of selenium in wheat and meat on blood Se status indices and on Se balance in Dutch men

After a 5-week period of low selenium intake, twenty-four Dutch men received 55, 135 or 215 micrograms Se/d as Se-rich meat or bread for a 9-week period. Four unsupplemented subjects served as controls. Plasma Se increased more rapidly than erythrocyte Se levels; the increases were significantly dependent (P less than 0.001) on Se intake level. Glutathione peroxidase (EC 1.11.1.9; GSH-Px) activity in platelets increased rapidly after supplementation and plateaued after 4-9 weeks. At 10 weeks after supplementation ended, plasma Se levels and platelet GSH-Px were still higher than the baseline values whereas erythrocyte Se levels continued to increase. Except for the higher erythrocyte Se levels after supplementation with high-Se meat, there were no differences in bioavailability of Se between meat and wheat products. Daily urinary and faecal Se excretions as well as Se retention increased with an increased Se intake irrespective of the form of the supplement. Regression of Se excretion v. intake indicated that 33 micrograms Se/d is necessary to compensate for urinary and faecal losses.     

Selenium supplementation in healthy Belgian adults: response in platelet glutathione peroxidase activity and other blood indices

Selenium status was explored by investigating effects of a 60-d Se supplementation with DL-selenomethionine (100 micrograms Se/d) in a group of 10 adults (plasma Se levels, 0.76-1.33 mumol/L). Plasma, erythrocyte, and urinary Se and activities of glutathione peroxidase (GSH Px) in plasma, erythrocytes, and platelets were measured before intervention and after 5, 15, 30, 45, and 60 d. A placebo was given to six adults. Plasma and urinary Se were the most sensitive indices to Se exposure. Se in plasma increased steadily during the course of the study whereas urinary Se reached a plateau between 30 and 60 d. By contrast erythrocyte Se did only change after 45 d. Enzyme in plasma and erythrocytes did not respond whereas platelet GSH Px did. The plateau of activity that was observed after 15 d for plasma Se in the range 1.40-1.50 mumol/L could mean that the Se status is insufficient for an optimal function of GSH Px and implies that dietary intake in Belgium (less than 50-60 micrograms Se/d) is not adequate.     

Selenium intake and metabolic balance of 10 men from a low selenium area of China

Selenium intake and urinary and fecal Se excretion of 10 healthy men from a low Se area in China were determined for three consecutive days, in summer, fall, and winter of 1983, and the spring of 1984 while self-selected diets were being consumed. Mean daily Se intake was 8.8 micrograms/day with a range of 2.3-35.5 micrograms/day, and was far below the recommended range of safe and adequate Se intake of 50-200 micrograms Se/day (National Academy of Sciences/National Research Council). Mean urinary and fecal Se outputs were 3.7 and 3.4 micrograms Se/day, respectively. Mean Se balance during this time was +1.8 micrograms Se/day. Apparent absorption of Se approximated 57%. The low Se intake in this area is a cause for concern since the residents of Molimo may be at risk for Se deficiency diseases.     

Comparison of the magnitude of the selenite-exchangeable metabolic pool and whole body endogenous selenium in adult rats

The quantitative relationship between the size of the selenite-exchangeable metabolic pool (WSe-EMP) and whole body endogenous selenium (Seend) was investigated in adult male rats. Two experiments based on multiple labeling with stable isotopes were performed. One focused on short-term (7 d, Expt. 1) and the other on long-term (60 d, Expt. 2) relationships. Rats were fed a Torula yeast diet and water supplemented with [76Se]selenite at 0.1 micrograms Se/mL; the in vivo [74Se]selenite tracer was administered orally. Groups of three or four animals were killed at timed intervals and whole carcass or selected organs were analyzed for the stable isotopes 74Se, 77Se and 82Se with hydride generation/inductively coupled plasma mass spectrometry. The value of WSe-EMP was determined from plasma or urine isotope ratios. In Experiment 1, with plasma as the sampling compartment, WSe-EMP at 24 h was 36.5 +/- 1.2% of the baseline value of whole body endogenous selenium (Seend) and 36.3 +/- 1.8% at 7 d. When urine was the sampling compartment, the corresponding values were 3.9 +/- 0.3% and 43.1 +/- 2.8%, respectively. In Experiment 2, WSe-EMP (plasma) was 38.9 +/- 1.3% of Seend at 7 d, increasing to 45.5 +/- 1.6% at 60 d. The corresponding values for urine as the sampling compartment were 45.5 +/- 2.0% (7 d) and 61.5 +/- 1.7% (60 d), respectively.     

Dietary selenium intake and selenium concentrations of plasma, erythrocytes, and breast milk in pregnant and postpartum lactating and nonlactating women

The selenium status of a group of 23 lactating and 13 nonlactating women was assessed from 37-wk gestation through 6-mo postpartum. The mean overall dietary Se intake of both groups of women was 80 +/- 37 micrograms/d. Plasma and erythrocyte Se levels were lower in the lactating than in the nonlactating mothers both before and after parturition. Breast-milk Se concentrations fell from 20 micrograms/L (0.25 mumol/L) at 1-mo postpartum to 15 micrograms/L (0.19 mumol/L) at 3- and 6-mo postpartum. A weak (r = 0.38) but statistically significant (p less than 0.025) relationship was observed between maternal plasma Se level and breast-milk Se concentration. The dietary Se intake of these lactating North American women appears sufficient to maintain satisfactory Se nutriture in their breast-fed infants during the first 6 mo of lactation.     

Selenium status of exclusively breast-fed infants as influenced by maternal organic or inorganic selenium supplementation

A longitudinal dietary Se supplementation study on lactating mothers was performed to determine the possibilities of improving the Se status of exclusively breast-fed infants. A total of 200 mothers randomized into three groups received either no Se supplements, 100 micrograms of selenite, or 100 micrograms of yeast-Se daily. Maternal and infant serum Se concentrations showed a linear correlation during exclusive breast-feeding. Yeast-Se in the dose administered was safe and more effective than selenite in increasing the Se concentrations of maternal serum and milk, and infant serum. The mean estimated daily Se intakes of the infants were 7.7 +/- 2.2, 8.9 +/- 2.2, and 11.5 +/- 4 micrograms, in the control, selenite, and yeast-Se groups respectively. Though the infant Se intakes of the unsupplemented and selenite-supplemented mothers were below the lower limit of the safe and adequate range as set by the US National Research Council, their serum Se concentrations increased steadily over the 6-mo study period. As maternal serum Se also increased by over 50% during the same period the results suggest that a maternal daily intake of 50-75 micrograms is adequate during lactation.     

The retention and distribution by healthy young men of stable isotopes of selenium consumed as selenite, selenate or hydroponically-grown broccoli are dependent on the isotopic form

Twenty-seven healthy young men were randomly assigned to diets that supplied low (32.6 microg/d) or high (226.5 microg/d) levels of selenium for a 105-d study. After consuming the diets for 85 d, subjects were fed a test meal that contained 74Se in the form of selenite or selenate and 82Se incorporated into hydroponically-raised broccoli. Urine, fecal and blood samples were collected daily. Isotope absorption was not different (P > 0.05) for selenate and Se in broccoli; Se absorption from selenite was highly variable and was not included in statistical analyses. Significantly more isotope was absorbed by subjects fed the high Se diet (P = 0. 015). Urinary isotope excretion was greater when selenate was fed than when broccoli was fed (P = 0.0001), and consequently more Se from broccoli (as compared to selenate) was retained (59.2 +/- 2.4 and 36.4 +/- 4.6% for Se in broccoli and selenate, respectively; P = 0.0001). Despite the higher retention, less isotope from broccoli than from selenate was present in the plasma. Plasma proteins separated by gel permeation chromatography showed that most of the isotopes were distributed between two medium molecular weight peaks. Less isotope was found in plasma proteins of subjects fed the high Se diet, but the form of Se had no effect on isotope distribution. These results show that dietary Se intake alters the retention of stable isotopes of Se and that humans retain and distribute Se from broccoli in a different manner than Se from inorganic salts.     

Plasma and urine taurine levels in vegans

Plasma taurine levels and urinary taurine excretion were measured in 12 strict vegetarian (vegan) males who had maintained a vegan diet for 53 +/- 26 mo (SD) and in 14 male nonvegetarian control subjects. Plasma taurine levels differed (45 +/- 7 vs 58 +/- 16 mumol/L, respectively). Urinary taurine excretion was lower (266 +/- 279 vs 903 +/- 580 mumol/d), urinary N pi-methylhistidine was barely detectable, and urinary N tau-methylhistidine was significantly reduced (296 +/- 87 vs 427 +/- 19 mumol/d) in the vegans. Analysis of 3-d dietary diaries kept by the vegans indicated marginal to adequate intake of protein, carbohydrate, vitamin B-6, methionine, and cystine; inadequate intake of zinc; and negligible intake of taurine. Prolonged absence of dietary taurine intake causes decreased plasma taurine and severely restricted urinary taurine output.     

A comparison of methods of assessment of dietary selenium intakes in Otago, New Zealand

The aims of the present study were (1) to compare three methods of assessment of dietary Se intake, i.e. chemical analysis of duplicate diets, diet records and a food-frequency questionnaire (FFQ) designed specifically for Se, and (2) to determine dietary Se intakes of residents of Otago, New Zealand. The FFQ was completed by 110 free-living adults. Diet records (3 d) and duplicate diet collections were carried out by forty-three of these subjects chosen on the basis of low blood Se concentration, and during a period when consumption of the high-Se foods fish, kidney, liver and Brazil nuts was discouraged. Mean Se intakes were similar for duplicate diet analysis (29 (SD 13) micrograms/d) and diet record assessments (28 (SD 15) micrograms/d). Estimates of intakes from the FFQ for the subgroup of forty-three subjects were higher (51 (SD 26) micrograms/d) than those from duplicate diets and diet records. Values from duplicate diet analysis and diet record assessments were strongly correlated (r 0.7, P = 0.0001), but difference plots indicated a lack of agreement between the two methods. Thus, diet record assessment was not adequate for predicting dietary Se intakes of individuals. Significant correlations were found for relationships between Se intake from duplicate diets (microgram/kg body weight per d) and plasma Se, Se intake from diet records (microgram/d and microgram/kg body weight per d) and plasma Se; and Se intake from the FFQ and whole-blood Se. Se intakes from duplicate diets and diet records were similar to those reported previously for New Zealanders, but lower than the recommended intakes in the USA (National Research Council, 1989), Australia (Truswell et al. 1990) and the UK (Department of Health, 1991) and the World Health Organization/Food and Agriculture Organization/International Atomic Energy Agency (1996) normative requirement.     

The effect of income on selenium intake and status in Utah County, Utah

Foodstuffs produced and/or purchased locally were analyzed for Se. The effect of income and gender on Se intake and status of Utah County residents was evaluated by measurement of the following indicators: erythrocyte (RBC) and plasma Se concentration, and activity of Se-glutathione peroxidase (Se-GSH-Px) (EC 1.11.1.9) in RBCs, platelets, and plasma. A Random Digit Dialing procedure was employed to stratify subjects according to gender and annual family income (less than +10,000, +10,000-20,000, greater than +20,000) in a 2 x 3 factorial design, seven subjects per cell. The weekly consumption of 44 foods shown to contribute over 90% of the Se intake of U.S. subjects was recorded for each study participant. The estimated minimum daily intake for this sample was 76.0 +/- 4.5 micrograms Se/day (mean +/- SEM). Available grain products are not produced locally, and their Se content is lower than average values reported by the U.S.D.A. Locally produced meat and dairy products had higher than average Se contents. In spite of lower grain Se and higher meat Se concentrations, subjects in this study derived more Se from grain and dairy products, and less from meat products than did subjects in a nationwide sample. The Se status of Utah County residents is similar to several other populations in the United States. There were no significant differences in Se status or intake due to gender or income. The results suggest that consumption of other foods produced in a "high Se" area can maintain Se intake and status in spite of reduced consumption of meat products generally viewed as more reliable sources of dietary Se.     

The selenite-exchangeable metabolic pool in humans: a new concept for the assessment of selenium status

An in vivo isotope-dilution approach is considered for assessment of selenium status in human subjects. The approach depends upon the dilution of a single dose of the stable isotope 74SeO3(2-) in the selenite-exchangeable metabolic pool. Data from six metabolic protocols, conducted with healthy North American males, are presented in order to analyze characteristics of this pool. Pool size (WSe-EMP) correlated positively with daily selenium intake in subjects consuming diets of known and variable selenium content. When subjects were given a selenium-adequate or -restricted diet for 30 d, WSe-EMP,7d decreased from 4.49 +/- 0.28 to 3.76 +/- 0.22 mg (p less than 0.05). The corresponding 24-h urinary selenium concentration dropped from 0.556 +/- 0.035 to 0.341 +/- 0.058 mumol/d (means +/- 1 SEM). Route of administration (iv vs po) had no apparent effect on WSe-EMP. In subjects of similar selenium status, the WSe-EMP was reproducible within the expected uncertainties of the method. This approach may be suitable for assessment of selenium status for a wide range of chronic intakes.     

On supplementing the selenium intake of New Zealanders. 2. Prolonged metabolic experiments with daily supplements of selenomethionine, selenite and fish

1. The daily intake of selenium by three subjects was supplemented with 100 microgram Se as selenomethionine (Semet-Se) or sodium selenite (selenite-Se)/d for 10-11 weeks, or with 65 microgram Se as in mackerel (Scomber japonicus) (fish-Se)/d for 4 weeks. 2. Urinary and faecal excretion of Se was measured and also Se concentration in whole blood, plasma and erythrocytes. Measurements on blood were made at intervals after supplementation had ceased. 3. Selenite-Se was not as well absorbed (0.46 of the intake) during the first 4 weeks as Semet-Se (0.75 of the intake) and fish Se (0.66 of the intake). 4. Blood Se increased steadily with Semet-Se, from 0.08 to 0.18 microgram Se/ml, but more slowly with selenite-Se, reaching a plateau in 7-8 weeks at 0.11 microgram Se/ml. Plasma Se increased more rapidly with Semet-Se than with selenite-Se, so that initially with Semet-Se plasma Se was greater than erythrocyte Se. 5. Daily urinary excretion increased with all forms of supplement, with initially a greater proportion of absorbed selenite-Se being excreted than Semet-Se or fish-Se. A close relationship was found between plasma Se and 24 h urinary excretion. The findings suggested that there was a rapid initial excretion of presumably unbound Se then a slower excretion of residual unbound, loosely bound or bound Se. 6. Total retentions of 3.5 mg selenite-Se and 4.5 mg Semet-Se were large when compared with an estimate of body content of 6 mg Se, derived in another paper (Stewart, Griffiths, Thomson & Robinson, 1978). Retention of Semet-Se and fish-Se appeared to be reflected in blood Se, whereas for selenite-Se, blood Se reflected retention for only a short period after which Se appeared to be retained without altering the blood Se. This suggested that Semet-Se and selenite-Se were metabolized differently. 7. A double blind-dosing trail with 100 microgram Semet-Se was carried out for 12 weeks on twenty-four patients with muscular complaints in Tapanui, a low-Se-soil area. Blood Se increased in the experimental group (from 0.067 to 0.143 microgrm Se/ml); clinical findings were not conclusive and will be presented elsewhere. 8. Bood Se was measured in New Zealand residents before travelling to Europe or to North America. On return their blood Se was increased, and depending upon the period of time spent outside New Zealand some values reached concentrations found in visitors and new settlers to New Zealand. 9. The results from these studies and the earlier studies of single and multiple dosing have been used to look at the various criteria in use for assessing Se status of subjects. It is suggested that plasma Se be used in preference to 24 h urinary excretion, and in addition to whole blood Se and glutathione peroxidase (EC 1.11.1.9) activity.     

Longitudinal selenium status in healthy British adults: assessment using biochemical and molecular biomarkers

Human selenium (Se) requirements are currently based on biochemical markers of Se status. In rats, tissue glutathione peroxidase-1 (Gpx1) mRNA levels can be used effectively to determine Se requirements; blood Gpx1 mRNA levels decrease in Se-deficient rats, so molecular biology-based markers have potential for human nutrition assessment. To study the efficacy of molecular biology markers for assessing Se status in humans, we conducted a longitudinal study on 39 subjects (age 45 +/- 11) in Reading, UK. Diet diaries (5 day) and blood were obtained from each subject at 2, 8, 17 and 23 weeks, and plasma Se, glutathione peroxidase (Gpx3) enzyme activity, and selenoprotein mRNA levels were determined. There were no significant longitudinal effects on Se biomarkers. Se intake averaged 48 +/- 14 microg/d. Plasma Se concentrations averaged 1.13 +/- 0.16 micromol/l. Plasma Se v. energy-corrected Se intake (ng Se/kJ/d) was significantly correlated, but neither Gpx3 activity v. Se intake (ng Se/kJ/d) nor Gpx3 activity v. plasma Se was significantly correlated. Collectively, this indicates that subjects were on the plateaus of the response curves. Selenoprotein mRNAs were quantitated in total RNA isolated from whole blood, but mRNA levels for Gpx1, selenoprotein H, and selenoprotein W (all highly regulated by Se in rodents), as well selenoprotein P, Gpx3, and phospholipid hydroperoxide glutathione peroxidase were also not significantly correlated with plasma Se. Thus selenoprotein molecular biomarkers, as well as traditional biochemical markers, are unable to further distinguish differences in Se status in these Se replete subjects. The efficacy of molecular biomarkers to detect Se deficiency needs to be tested in Se-deficient populations.     

Short-term dietary selenium restriction in young adults: quantitative studies with the stable isotope 74SeO3(2-)

A 45 d metabolic study was carried out in four young adult male North American residents consuming a controlled diet based on an amino acid mixture. During the initial 10 d, total daily selenium intake was adjusted to 107.7 (SE 0.1) microgram/d, which was reduced to 11.4 (SE 0.1) microgram/d for the remaining 35 d. Two doses of a stable isotope (74SeO3(2-)) were administered orally in the post-absorptive state on days 4 and 39 of the study. Se balance (faecal + urinary excretion) as well as stable isotope excretion studies were carried out for the entire 45 d period; blood plasma and erythrocyte Se concentrations were also monitored. Plasma Se concentrations (microgram/ml) fell progressively from the initial value of 0.132 (SE 0.007) to 0.083 (SE 0.008) at the end of the study. The erythrocyte concentrations of Se did not vary in a consistent manner (average value for the entire study 0.147 (SE 0.002) microgram/ml). Faecal excretion of unenriched Se decreased from 66 (SE 6) microgram/d for days 1-10 to 10.2 (SE 0.8) microgram/d for days 14-40. Mean urinary excretions of the unenriched Se were 43.9 (SE 2.8) microgram/d (days 1-10) and 26.9 (SE 4.6) microgram/d (days 14-40). Total balance (intake-faecal excretion-urinary excretion) for unenriched Se was (microgram/d):-18 (SE 7) days 10-19, -17 (SE 2) days 19-39, -5 (SE 1) days 38-45. Fractional absorption of the ingested label was 0.529 (SE 0.032) and 0.542 (SE 0.038) for the Se-adequate and Se-restricted phases of the study. However, urinary excretion of the absorbed label was reduced from 6.57 (SE 0.73)% for day 1 of the Se-adequate phase to only 3.32 (SE 0.26)% for day 1 of the Se-restricted phase. Similar observations were also made for day 7 of each phase. These findings indicate that immediate contribution of ingested Se to the urinary Se pool is small.     

Zinc levels of hospitalized elderly

Zinc status was evaluated in 99 consecutive elderly patients admitted to a geriatric assessment unit. The assessment of zinc status was based on measurement of plasma, erythrocyte, and urinary zinc levels by atomic absorption spectrophotometry; serum lactic dehydrogenase and alkaline phosphatase by standard laboratory methods; and dietary intake by the food frequency questionnaire method. Mean (+/- standard deviation) plasma zinc concentration was 72 +/- 16 micrograms/100 ml (N = 91). Although 67% of the group had plasma zinc levels in the deficient range, only three patients had values below the normal range for erythrocyte zinc and none fell below the reference range for urinary zinc per 24 hours (N = 15) or the urinary zinc:creatinine ratio. Mean values for the other parameters of zinc status were 1.27 +/- 0.26 micrograms/10(9) RBC for erythrocyte zinc, 285 +/- 217 micrograms/24 hours for urinary zinc, and 588 +/- 309 micrograms/gm for the urinary zinc:creatinine ratio. Serum alkaline phosphatase and lactic dehydrogenase were not specific indicators of zinc status. Forty-six percent had adequate and 54% inadequate dietary intakes (N = 46). Twenty percent were receiving an inadequate intake of meat products, suggesting that the majority (80%) were ingesting an adequate supply of zinc-rich foods. Zinc status appeared to be adequate in this population.     

Urinary orotic acid excretion in sheep: effects of nitrogen, glucose and arginine

The urinary excretion of orotic acid was investigated in four sheep. Nitrogen and energy intake were varied by infusions of urea and glucose. The effect of arginine infusion was also investigated. Nitrogen intake of 10.4 g/d led to a urinary excretion of orotic acid of 357 +/- 61 micrograms/d. Increasing N intake to 21.4 g/d significantly increased urinary orotic acid excretion to 747 +/- 46 micrograms/d. Glucose infusion (300 g/d) significantly decreased orotic acid excretion when N intake was 10.4 g/d, whereas arginine infusion (2.3 g/d) did not alter the excretion of orotic acid under these conditions. When arginine was infused at higher N intake (21.4 g/d), orotic acid excretion decreased from 822 +/- 74 to 624 +/- 46 micrograms/d. It is concluded that increasing N intake is accompanied by an enhanced urinary excretion of orotic acid. This excretion of orotic acid is significantly modified by glucose or arginine.