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Clinical Chemistry 48: 1571-1577, 2002;
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(Clinical Chemistry. 2002;48:1571-1577.)
© 2002 American Association for Clinical Chemistry, Inc.

Riboflavin, Flavin Mononucleotide, and Flavin Adenine Dinucleotide in Human Plasma and Erythrocytes at Baseline and after Low-Dose Riboflavin Supplementation

Steinar Hustad1a, Michelle C. McKinley2, Helene McNulty2, Jørn Schneede1, J.J. Strain2, John M. Scott3 and Per Magne Ueland1

1 LOCUS for Homocysteine and Related Vitamins, University of Bergen, Armauer Hansens Hus, N-5021 Bergen, Norway.

2 Northern Ireland Centre for Diet and Health, University of Ulster, Coleraine, BT52 1SA Northern Ireland.

3 Department of Biochemistry, Trinity College, Dublin 2, Republic of Ireland.

aAuthor for correspondence. Fax 47-55-974605; e-mail steinar.hustad{at}farm.uib.no.


   Abstract
Top
 Abstract
Introduction
 Participants and Methods
 Results
 Discussion
 References
 
Background: Vitamin B2 exists in blood as riboflavin and its cofactors, flavin mononucleotide (FMN) and FAD. The erythrocyte glutathione reductase activation coefficient (EGRAC) has traditionally been used to assess vitamin B2 status in humans. We investigated the relationships of EGRAC and plasma and erythrocyte concentrations of riboflavin, FMN, and FAD in elderly volunteers and their responses to riboflavin administration.

Methods: EGRAC and plasma and erythrocyte concentrations of riboflavin, FMN, and FAD were determined in 124 healthy individuals with a mean age of 69 years. The same measurements were made in a subgroup of 46 individuals with EGRAC >=1.20 who participated in a randomized double-blind 12-week intervention study and received riboflavin (1.6 mg/day; n = 23) or placebo (n = 23).

Results: Median plasma concentrations were 10.5 nmol/L for riboflavin, 6.6 nmol/L for FMN, and 74 nmol/L for FAD. In erythrocytes, there were only trace amounts of riboflavin, whereas median FMN and FAD concentrations were 44 and 469 nmol/L, respectively. Erythrocyte FMN and FAD correlated with each other and with EGRAC and plasma riboflavin (P <0.05). All variables except plasma FAD responded significantly to riboflavin supplementation compared with placebo (P <=0.04). The strongest increases were for riboflavin in plasma (83%) and for FMN in erythrocytes (87%).

Conclusions: Concentrations of all B2 vitamers except plasma FAD are potential indicators of vitamin B2 status, and plasma riboflavin and erythrocyte FMN may be useful for the assessment of vitamin B2 status in population studies.


   Introduction
Top
 Abstract
 Introduction
Participants and Methods
 Results
 Discussion
 References
 
Riboflavin1 is the precursor of flavin mononucleotide (FMN) and FAD (1). These compounds serve as cofactors for several reduction-oxidation enzymes, which play an important part in energy metabolism (1). They are also involved in the metabolism of folate, vitamin B12, vitamin B6, and other vitamins, and this probably explains why plasma riboflavin is a determinant of plasma homocysteine, which is associated with cardiovascular disease, pregnancy complications, and cognitive impairment (2).

Vitamin B2 deficiency is common in many parts of the world, particularly in developing countries (3)(4). Several studies have indicated that vitamin B2 deficiency may be widespread in industrialized countries as well, both in the elderly (5)(6) and in young adults (7).

Vitamin B2 status in humans has usually been assessed by measuring the erythrocyte glutathione reductase activation coefficient (EGRAC), which is the ratio between enzyme activity determined with and without the addition of the cofactor, FAD (8)(9)(10). Apparently, glutathione reductase loses FAD at an early stage in vitamin B2 deficiency, in contrast to key enzymes involved in energy metabolism (11), and this makes EGRAC a useful method for the diagnosis of vitamin B2 deficiency (12)(13). The method is less reliable in populations with a high prevalence of glucose 6-phosphate dehydrogenase deficiency (8) or ß-thalassemia (14), and some other conditions may also influence EGRAC values (8)(15).

The urinary excretion of vitamin B2 (16) and blood vitamin concentrations (13)(17) have also been used as indicators of vitamin B2 status in humans. Relationships between vitamin B2 concentrations in erythrocytes and other indices have been investigated in cross-sectional studies (3)(9)(18)(19)(20), and in general, associations between vitamin B2 and riboflavin intake (18)(19)(20) and between vitamin B2 and EGRAC (3)(9) have been weak or absent. Riboflavin intervention studies have been carried out in humans and animals, and most studies demonstrate a decrease in vitamin B2 in erythrocytes when an organism is depleted (21)(22)(23) and increased concentrations after riboflavin supplementation (3)(8)(9)(21)(24). Similarly, vitamin B2 concentrations in plasma or serum have been investigated in cross-sectional (18)(20) and intervention studies (21)(22)(25)(26), but the results have been less consistent than for erythrocytes. Different study designs make the comparison of results difficult, particularly because only total B2 or FAD was measured in most studies (3)(8)(9)(18)(19)(20)(23)(24). Additionally, different types of anticoagulants have been used for the preparation of plasma, and this may influence sample stability and relative vitamer concentrations (27).

The aim of the present study was to determine whether concentrations of riboflavin, FMN, and FAD in EDTA plasma and erythrocytes reflect vitamin B2 status in humans. We investigated the relationship between these analytes and their correlation with EGRAC in healthy elderly individuals. In a group of individuals with EGRAC >=1.20, indicating suboptimal vitamin B2 status (13), we performed a randomized placebo-controlled, low-dose riboflavin intervention and compared the responses of the separate vitamers.


   Participants and Methods
Top
 Abstract
 Introduction
 Participants and Methods
Results
 Discussion
 References
 
study design
Between January and April 1998, 124 elderly individuals were recruited through senior citizens groups and local folds in Northern Ireland. Their mean age was 69 years, and 69% were women (Table 1 ). Individuals with gastrointestinal, hematologic, vascular, renal, or hepatic disorders or with impaired cognitive function (score <7 on Hodgkinson 10-Point Mental State Questionnaire) were not included, nor were individuals with serum B12 <111 pmol/L or individuals using B-vitamin supplementation. Ethical approval was granted by the Research Ethical Committee of the University of Ulster, and participants gave written, informed consent.


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  		Table 1. Characteristics of the study population.

EGRAC was used to determine vitamin B2 status in the study population, and 52 individuals with suboptimal vitamin B2 status (EGRAC >=1.20) were invited to participate in a 12-week randomized, double-blind, placebo-controlled, low-dose riboflavin intervention. Among these, 46 agreed and received riboflavin (1.6 mg/day; n = 23) or placebo (n = 23), which were taken in the morning. Participants were instructed to maintain their usual diets and to refrain from commencing any form of vitamin supplementation during the intervention.

blood sampling
Blood samples were collected from all participants at the time of screening, and before the start and after completion of the 12-week intervention for those who participated in the intervention study. All samples were collected after an overnight fast, which included the riboflavin and placebo tablets.

Tripotassium EDTA tubes (Vacuette; Greiner Labortechnik GmbH) were used for whole blood, which was placed on ice and centrifuged within 2 h to obtain plasma. The remaining erythrocytes were washed three times with phosphate-buffered saline, the saline and the buffy coat were removed after each centrifugation, and the resulting cells were stored. To obtain serum, blood was collected into Vacuette tubes with clot activator and gel (Greiner) and centrifuged within 2 h. Erythrocytes, EDTA plasma, and serum were stored at -70 °C until analysis.

biochemical analyses
EGRAC (28) was measured by enzyme assay on the Cobas Fara centrifugal analyzer (Roche Diagnostics).

Plasma riboflavin, FMN, and FAD were measured by a modification of the method described by Hustad et al. (27). Briefly, a 40-µL plasma sample was mixed with 400 µL of trichloroacetic acid (100 g/L) containing 15 nmol/L isoriboflavin (internal standard), and 330 µL of the supernatant was neutralized by the addition of 108 µL of K2HPO4 (2 mol/L). The neutralized trichloroacetic acid-treated plasma was subjected to solid-phase extraction by use of C-18 columns as described in the original publication (27), except that the columns were eluted with doubly distilled water instead of phosphate buffer. The eluate was lyophilized overnight (Lyovac GT2; Leybold-Heraeus GmbH), and the analytes were then dissolved in 40 µL of water. The vitamers were separated by capillary electrophoresis on a Beckman P/ACE MDQ (Beckman Coulter Inc.) and detected by laser-induced fluorescence.

Erythrocyte B2 vitamers were analyzed in the same manner, except that samples were homogenized after the addition of trichloroacetic acid by use of a rotating polypropylene pestle.

Serum creatinine was determined by the Jaffe alkaline picrate method for the Hitachi 911 system (F. Hoffmann-La Roche Ltd.).

EGRAC was analyzed in triplicate, whereas riboflavin, FMN, and FAD were analyzed in duplicate. Analytical CVs were 7% for EGRAC and in the range 6–8% for plasma and erythrocyte B2 vitamers. EGRAC and the B2 vitamers were analyzed in separate laboratories, and results were blinded for those who performed the analyses. Quality control for all assays was provided by repeated analysis of stored batches of pooled erythrocytes, plasma, or serum.

statistical methods
Medians with 10th and 90th percentiles and means with SDs were used for descriptive statistics. The biological (intra- and interindividual) CV (CVB) was calculated according to the formula:

where CVT is the total CV and CVA is the analytical CV. Correlation analyses were performed using Spearman coefficients.

The {chi}2 test was used to compare categorical variables, and the Student t-test was used to compare means of continuous numeric variables. Responses to intervention were examined by univariate ANOVA with change (pretreatment - posttreatment values) as the dependent variable and treatment (riboflavin or placebo) as the factor variable. Because data on erythrocyte FMN and FAD were not available for all participants, r2 was calculated to facilitate the comparison of these variables with other vitamin B2 indices.

Tests were two-tailed, and P <0.05 was considered statistically significant. SPSS Ver. 10.0 for Macintosh (SPSS Inc.) was used for all statistical analyses.


   Results
Top
 Abstract
 Introduction
 Participants and Methods
 Results
Discussion
 References
 
population characteristics and blood indices
The study population consisted of 38 men and 86 women with a mean age of 69 years (Table 1Up ). EGRAC and plasma and erythrocyte concentrations of B2 vitamers showed no gender differences (P >0.3). The median (10th–90th percentiles) EGRAC values were 1.18 (1.07–1.29; Table 1Up ). There were only trace amounts of erythrocyte riboflavin (<1 nmol/L), whereas erythrocyte FMN and FAD concentrations were 44 nmol/L (26–80 nmol/L) and 469 nmol/L (351–558 nmol/L), respectively (Table 1Up ). Plasma concentrations were 10.5 nmol/L (5.4–28.4 nmol/L) for riboflavin, 6.6 nmol/L (4.0–11.7 nmol/L) for FMN, and 74 nmol/L (56–97 nmol/L) for FAD (Table 1Up ).

In plasma, the biological (intra- and interindividual) variation of riboflavin concentrations was pronounced, and the CVB was 153%, compared with 55% for FMN and 18% for FAD (data not shown). The variation was similar in plasma and erythrocytes, and the CVB values for erythrocyte FMN and FAD were 45% and 16%, respectively.

bivariate correlations
Erythrocyte concentrations of FMN and FAD correlated significantly (r = 0.57), and both coenzyme forms were negatively associated with EGRAC (r = -0.45 and -0.30, respectively) and positively associated with plasma riboflavin (r = 0.39 and 0.32, respectively; Table 2 ). Plasma concentrations of riboflavin and FMN correlated strongly (r = 0.58), whereas the association between plasma FMN and FAD was less pronounced (r = 0.30; Table 2 ).


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  		Table 2. Spearman correlation coefficients for vitamin B2 indices, age, creatinine, and body mass index.1

The inverse relationship between plasma riboflavin and EGRAC was not significant (Table 2Up ). None of the variables was related to age, creatinine, or body mass index (Table 2Up ).

responses to low-dose riboflavin intervention
Forty-six individuals with EGRAC >=1.20 received either riboflavin (1.6 mg/day; n = 23) or placebo (n = 23) for 12 weeks. Mean dietary intakes of riboflavin (1.6 mg/day) and energy (9.4 MJ/day) were not significantly different between the riboflavin supplementation and the placebo groups (P >=0.2). EGRAC and concentrations of B2 vitamers in plasma and erythrocytes (Table 3 ), as well as sex distribution, creatinine, and body mass index did not differ between the groups (P >=0.3), whereas the mean age was 70 years in the riboflavin group and 67 years in the placebo group (P = 0.04).


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  		Table 3. EGRAC and concentrations of B2 vitamers before and after the intervention.1

EGRAC and all B2 vitamers except plasma FAD responded significantly to riboflavin supplementation compared with placebo (Table 3Up and Fig. 1 ). In plasma, the mean riboflavin increase was 83%, whereas FMN increased by 27% and FAD did not change (data not shown). In erythrocytes, the riboflavin response could not be determined because concentrations were below the limit of quantification (<1 nmol/L), but FMN increased by 87%, whereas FAD increased by only 14% (data not shown) in the riboflavin group.



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  		Figure 1. Changes of EGRAC and B2 vitamer concentrations in individuals receiving placebo or riboflavin.

EGRAC, riboflavin, FMN, and FAD responses (postintervention - preintervention values) are shown in the placebo (left-hand columns in panels) and riboflavin (right-hand columns in panels) groups. Medians are indicated by solid horizontal lines. For erythrocyte FMN and FAD, n = 11 and 13 in the placebo and riboflavin groups, respectively. For the other variables, n = 23 in both groups.

The intervention (placebo or riboflavin) explained 45% of the variance of the EGRAC change (Table 3Up ). Moreover, it accounted for 9–63% of the variance of B2 vitamer responses, except for plasma FAD, which was independent of the intervention (Table 3Up ).

The magnitude of riboflavin, FMN, and FAD responses differed, and relative vitamer concentrations changed in individuals who were supplemented, in both the plasma and erythrocytes. Thus, the riboflavin:FMN ratio increased significantly in plasma, indicating that riboflavin became more abundant relative to FMN, and the FMN:FAD ratio increased in both the plasma and erythrocytes (Table 4 ).


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  		Table 4. Ratios between concentrations of B2 vitamers before and after the intervention.1


   Discussion
Top
 Abstract
 Introduction
 Participants and Methods
 Results
 Discussion
References
 
The objective of the present study was to evaluate plasma and erythrocyte concentrations of riboflavin, FMN, and FAD as indicators of vitamin B2 status. This was done by comparing relationships between potential indicators of vitamin B2 status in 124 healthy elderly individuals and by assessing responses to low-dose riboflavin supplementation or placebo in 46 individuals with EGRAC >=1.20, indicating suboptimal vitamin B2 status. We found that EGRAC and plasma riboflavin correlated with FMN and FAD in erythrocytes (Table 2Up ). Riboflavin supplementation significantly reduced the EGRAC compared with placebo, and all B2 vitamers except plasma FAD increased (Table 3Up and Fig. 1Up ).

study design and limitations
The intervention study was randomized and placebo-controlled, and baseline measurements were repeated to partly correct for regression toward the mean. Because EGRAC was used both to select for the intervention and as a response variable, the design is not ideal for comparing responses of EGRAC to responses of other vitamin B2 indices.

The intervention riboflavin dose of 1.6 mg/day was comparable to United Kingdom Reference Nutrient Intakes (29). By selecting a low dosage and withholding riboflavin on the days of blood sampling, we avoided interference from a transient increase in plasma riboflavin after vitamin intake. This increase may be substantial for high-dose riboflavin (30), but it is probably less important in connection with ordinary meals (21)(30).

Erythrocytes from the intervention period, sufficient to measure FMN and FAD in addition to EGRAC, were available for only 24 participants. These individuals did not differ from the rest of the individuals who took part in the intervention study with respect to sex distribution, age, dietary riboflavin, energy intake, EGRAC, and B2 vitamer concentrations (P >=0.1).

concentrations of B2 vitamers in plasma and erythrocytes
Plasma and erythrocyte concentrations of riboflavin, FMN, and FAD (Table 1Up ) were in the same range as reported in several other studies (17)(31). The biological variability of riboflavin was pronounced compared with FMN and FAD (Table 2Up ). This is in agreement with previous reports (2)(27)(30) and may reflect that concentrations of flavin coenzymes, particularly FAD, are regulated within a relatively narrow range, as opposed to riboflavin.

In plasma, FMN was strongly associated with its precursor, riboflavin, whereas FAD correlated less strongly with its precursor, FMN (Table 2Up ). The strength of these relationships was the same as reported in other studies (2)(27). Associations between concentrations of proximate metabolites within the same compartment and between EGRAC and concentrations of erythrocyte FAD (Table 2Up ) are expected because of metabolic interdependence. Furthermore, covariations may also reflect that EGRAC and concentrations of riboflavin, FMN, and FAD are determined by vitamin B2 status.

vitamin B2 homeostasis
Concentrations of individual B2 vitamers in the blood have been examined in vitamin B2 deficiency (22)(25). In men maintained on restricted riboflavin intake for several months, the sum of plasma riboflavin and plasma FMN was lower than in the control group, whereas plasma FAD was not significantly different (22). In Cebus monkeys who were severely vitamin B2-deficient, both FAD and riboflavin decreased in serum, but riboflavin decreased before FAD during the development of deficiency (25). These vitamers have been investigated after riboflavin repletion as well, and in vitamin B2-deficient rats, whose growth was improved by successive addition of dietary riboflavin, serum riboflavin increased relatively more than FAD (21).

Individual B2 vitamers have also been investigated in tissues, and hepatic concentrations of riboflavin and FMN were lower than FAD in vitamin B2-deficient rats, compared with controls (12)(32)(33). Moreover, FMN decreased more than FAD in rat liver during the development of vitamin B2 deficiency, and FMN concentrations were subsequently restored more slowly on realimentation (34).

The differential responsiveness of riboflavin, FMN, and FAD during vitamin B2 depletion and repletion probably reflects mechanisms involved in vitamin B2 homeostasis (11)(33)(35). Such mechanisms may ensure adequate tissue concentrations of coenzymes, particularly of FAD (11)(33)(35). Preservation of FAD concentrations within a narrow range, at the expense of other B2 vitamers, might explain why riboflavin and FMN are the most responsive vitamers in individuals with suboptimal vitamin B2 status who receive low-dose riboflavin supplementation (Table 4Up ).

riboflavin, fmn, and fad as indicators of vitamin B2 status
Riboflavin was the most responsive plasma index in individuals who were supplemented (Table 4Up ), but the variability of the response was high, and the intervention explained only 22% of the variance (Table 3Up ), which probably reflects that factors other than vitamin B2 status determine plasma concentrations of riboflavin. Consequently, this index is probably useful for population studies, but it may be less suitable for the assessment of vitamin B2 status in individuals.

Patients with hypothyroidism are prone to develop nonalimentary vitamin B2 deficiency, which is associated with impaired activity of riboflavin kinase (36)(37). This enzyme converts riboflavin to FMN and is therefore important for flavin coenzyme synthesis (36)(37). Thus, riboflavin may not be useful for the assessment of vitamin B2 deficiency in hypothyroidism. Moreover, vitamin B2 metabolism may be influenced by respiratory infections, catabolic states, and certain other conditions (15)(38)(39), which may be associated with increased mobilization of the vitamin from the liver and other tissues into the blood (15)(39).

The increase in plasma FMN was just significant in the riboflavin-supplemented group compared with the placebo group (Table 3Up and Fig. 1Up ), but in erythrocytes, FMN increased 87%, and all individuals who were supplemented responded (Fig. 1Up ). Moreover, the intervention accounted for more than one-half of the variance of the response (Table 3Up ), suggesting that erythrocyte FMN may be more useful than plasma riboflavin for the determination of vitamin B2 status for a particular individual.

Plasma FAD does not appear to reflect changes of vitamin B2 status because concentrations did not increase on supplementation (Table 3Up and Fig. 1Up ). Erythrocyte FAD responded significantly, however, although not as strongly as erythrocyte FMN (Table 4Up ). Moreover, erythrocyte FAD concentrations correlated significantly with several other vitamin B2 indices, including plasma riboflavin, and this supports the idea that concentrations of erythrocyte FAD are determined by vitamin B2 status.

In conclusion, concentrations of all B2 vitamers except plasma FAD are potential indicators of vitamin B2 status, and plasma riboflavin and erythrocyte FMN may be useful for the assessment of vitamin B2 status in population studies. Riboflavin and FMN responded more strongly than FAD in individuals with suboptimal vitamin B2 status who were riboflavin supplemented. This probably reflects homeostatic mechanisms maintaining adequate concentrations of flavin coenzymes, particularly FAD, under conditions of variable vitamin B2 intake.


   Acknowledgments
 
We thank Anne-Kirstin Thoresen for expert technical assistance.


   Footnotes
 
1 Riboflavin is used specifically to name the precursor of FMN and FAD, whereas the term vitamin B2 is used in the generic sense to denote riboflavin, FMN, and FAD.


   References
Top
 Abstract
 Introduction
 Participants and Methods
 Results
 Discussion
 References
 

  1. Rivlin RS, Pinto JT. Riboflavin (vitamin B2). Rucker RB Suttie JW McCormick DB Machlin LJ eds. Handbook of vitamins 2001:255-273 Marcel Dekker New York. .
  2. Hustad S, Ueland PM, Vollset SE, Zhang Y, Bjørke-Monsen AL, Schneede J. Riboflavin as a determinant of plasma total homocysteine: effect modification by the methylenetetrahydrofolate reductase C677T polymorphism. Clin Chem 2000;46:1065-1071.[Abstract/Free Full Text]
  3. Bamji MS, Sarma KV, Radhaiah G. Relationship between biochemical and clinical indices of B-vitamin deficiency. A study in rural school boys. Br J Nutr 1979;41:431-441.[ISI][Medline] [Order article via Infotrieve]
  4. Boisvert WA, Castaneda C, Mendoza I, Langeloh G, Solomons NW, Gershoff SN, et al. Prevalence of riboflavin deficiency among Guatemalan elderly people and its relationship to milk intake. Am J Clin Nutr 1993;58:85-90.[Abstract/Free Full Text]
  5. Bailey AL, Maisey S, Southon S, Wright AJ, Finglas PM, Fulcher RA. Relationships between micronutrient intake and biochemical indicators of nutrient adequacy in a ‘free-living’ elderly UK population. Br J Nutr 1997;77:225-242.[ISI][Medline] [Order article via Infotrieve]
  6. Madigan SM, Tracey F, McNulty H, Eaton-Evans J, Coulter J, McCartney H, et al. Riboflavin and vitamin B-6 intakes and status and biochemical response to riboflavin supplementation in free-living elderly people. Am J Clin Nutr 1998;68:389-395.[Abstract]
  7. Benton D, Haller J, Fordy J. The vitamin status of young British adults. Int J Vitam Nutr Res 1997;67:34-40.[ISI][Medline] [Order article via Infotrieve]
  8. Beutler E. Effect of flavin compounds on glutathione reductase activity: in vivo and in vitro studies. J Clin Invest 1969;48:1957-1966.
  9. Bamji MS. Glutathione reductase activity in red blood cells and riboflavin nutritional status in humans. Clin Chim Acta 1969;26:263-269.[ISI][Medline] [Order article via Infotrieve]
  10. Glatzle D, Körner WF, Christeller S, Wiss O. Method for the detection of a biochemical riboflavin deficiency. Stimulation of NADPH2-dependent glutathione reductase from human erythrocytes by FAD in vitro. Investigations on the vitamin B2 status in healthy people and geriatric patients. Int Z Vitaminforsch 1970;40:166-183.[ISI][Medline] [Order article via Infotrieve]
  11. Ross NS, Hansen TP. Riboflavin deficiency is associated with selective preservation of critical flavoenzyme-dependent metabolic pathways [Review]. Biofactors 1992;3:185-190.[ISI][Medline] [Order article via Infotrieve]
  12. Prentice AM, Bates CJ. A biochemical evaluation of the erythrocyte glutathione reductase (EC1.6.4.2) test for riboflavin status. 2. Dose-response relationships in chronic marginal deficiency. Br J Nutr 1981;45:53-65.[ISI][Medline] [Order article via Infotrieve]
  13. Bates C. Riboflavin [Review]. Int J Vitam Nutr Res 1993;63:274-277.[ISI][Medline] [Order article via Infotrieve]
  14. Anderson BB, Perry GM, Clements JE, Studds C, Fashola R, Salsini G, et al. Genetic and other influences on red-cell flavin enzymes, pyridoxine phosphate oxidase and glutathione reductase in families with ß-thalassaemia. Eur J Haematol 1989;42:354-360.[ISI][Medline] [Order article via Infotrieve]
  15. Bamji MS, Bhaskaram P, Jacob CM. Urinary riboflavin excretion and erythrocyte glutathione reductase activity in preschool children suffering from upper respiratory infections and measles. Ann Nutr Metab 1987;31:191-196.[ISI][Medline] [Order article via Infotrieve]
  16. Horwitt MK. Interpretations of requirements for thiamin, riboflavin, niacin-tryptophan, and vitamin E plus comments on balance studies and vitamin B-6. Am J Clin Nutr 1986;44:973-985.[Abstract/Free Full Text]
  17. Schrijver J, Speek AJ, van den Berg H. Riboflavin. Section III. Flavin adenine dinucleotide in whole blood by HPLC. Fidanza F eds. Nutritional status assessment. A manual for population studies 1991:251-256 Chapman & Hall London. .
  18. Bartlett MN. Red blood cell niacin and plasma riboflavin levels in a group of normal children. J Nutr 1955;57:157-168.
  19. Beal VA, Van Buskirk JJ. Riboflavin in red blood cells in relation to dietary intake in children. Am J Clin Nutr 1960;8:841-845.[Abstract/Free Full Text]
  20. Du Plessis JP, De Lange DJ. Biochemical evaluation of the nutritional status of urban primary school children: riboflavin status. S Afr Med J 1965;39:1176-1180.
  21. Burch HB, Bessey OA, Lowry OH. Fluorometric measurements of riboflavin and its natural derivatives in small quantities of blood serum and cells. J Biol Chem 1948;175:457-470.[Free Full Text]
  22. Bessey OA, Horwitt MK, Love RH. Dietary deprivation of riboflavin and blood riboflavin levels in man. J Nutr 1956;58:367-383.
  23. Bamji MS, Sharada D. Hepatic glutathione reductase and riboflavin concentrations in experimental deficiency of thiamin and riboflavin in rats. J Nutr 1972;102:443-447.
  24. Bates CJ, Prentice AM, Paul AA, Sutcliffe BA, Watkinson M, Whitehead RG. Riboflavin status in Gambian pregnant and lactating women and its implications for Recommended Dietary Allowances. Am J Clin Nutr 1981;34:928-935.[Abstract/Free Full Text]
  25. Mann GV, Watson PC, McNally A, Goddard J. Primate nutrition. II. Riboflavin nutrition in the Cebus monkey and its diagnosis. J Nutr 1952;47:225-241.
  26. Suvarnakich K, Mann GV, Stare FJ. Riboflavin in human serum. J Nutr 1952;47:105-118.
  27. Hustad S, Ueland PM, Schneede J. Quantification of riboflavin, flavin mononucleotide, and flavin adenine dinucleotide in human plasma by capillary electrophoresis and laser-induced fluorescence detection. Clin Chem 1999;45:862-868.[Abstract/Free Full Text]
  28. Powers HJ, Bates CJ, Prentice AM, Lamb WH, Jepson M, Bowman H. The relative effectiveness of iron and iron with riboflavin in correcting a microcytic anaemia in men and children in rural Gambia. Hum Nutr Clin Nutr 1983;37:413-425.[ISI][Medline] [Order article via Infotrieve]
  29. Report of the panel on dietary reference values of the Committee on Medical Aspects of Food Policy. Report on health and social subjects 41, dietary reference values for food, energy and nutrients for the United Kingdom. Department of Health 1995 Her Majesty’s Stationery Office London. .
  30. Zempleni J, Galloway JR, McCormick DB. Pharmacokinetics of orally and intravenously administered riboflavin in healthy humans. Am J Clin Nutr 1996;63:54-66.[Abstract/Free Full Text]
  31. Nielsen P. Flavins. De Leenheer AP Lambert WE Nelis HJ eds. Modern chromatographic analysis of vitamins 1992:355-398 Marcel Dekker New York. .
  32. Bessey OA, Lowry OH, Love RH. The fluorometric measurement of the nucleotides of riboflavin and their concentration in tissues. J Biol Chem 1949;180:755-769.[Free Full Text]
  33. Fass S, Rivlin RS. Regulation of riboflavin-metabolizing enzymes in riboflavin deficiency. Am J Physiol 1969;217:988-991.[Free Full Text]
  34. Burch HB, Lowry OH, Padilla AM, Combs AM. Effects of riboflavin deficiency and realimentation on flavin enzymes in tissues. J Biol Chem 1956;223:29-45.[Free Full Text]
  35. Lee SS, McCormick DB. Effect of riboflavin status on hepatic activities of flavin-metabolizing enzymes in rats. J Nutr 1983;113:2274-2279.
  36. Rivlin RS, Langdon RG. Effects of thyroxine upon biosynthesis of flavin mononucleotide and flavin adenine dinucleotide. Endocrinology 1969;84:584-588.[ISI][Medline] [Order article via Infotrieve]
  37. Lee SS, McCormick DB. Thyroid hormone regulation of flavocoenzyme biosynthesis. Arch Biochem Biophys 1985;237:197-201.[ISI][Medline] [Order article via Infotrieve]
  38. Consolazio CF, Johnson HL, Krzywicki J, Daws TA, Barnhart RA. Thiamin, riboflavin, and pyridoxine excretion during acute starvation and calorie restriction. Am J Clin Nutr 1971;24:1060-1067.[Abstract]
  39. Brijlal S, Lakshmi AV. Tissue distribution and turnover of [H-3]riboflavin during respiratory infection in mice. Metabolism 1999;48:1608-1611.[ISI][Medline] [Order article via Infotrieve]



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