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At least 19 recordsLinked to original sources
PubMed1996

Kinetics and thermodynamics of the binding of riboflavin, riboflavin 5'-phosphate and riboflavin 3',5'-bisphosphate by apoflavodoxins.

The reactions of excess apoflavodoxin from Desulfovibrio vulgaris, Anabaena variabilis and Azotobacter vinelandii with riboflavin 5'-phosphate (FMN), riboflavin 3',5'-bisphosphate and riboflavin are pseudo-first-order. The rates increase with decreasing pH in the range pH 5-8, and, in general, they increase with increasing ionic strength to approach a maximum at an ionic strength greater than 0.4 M. The rate of FMN binding in phosphate at high pH increases to a maximum at an ionic strength of about 0.1 M, and then decreases as the phosphate concentration is increased further. The dissociation constants for the complexes with FMN and riboflavin decrease with an increase of ionic strength. Inorganic phosphate stabilizes the complex with riboflavin. The effects of phosphate on riboflavin binding suggest that phosphate interacts with the apoprotein at the site normally occupied by the phosphate of FMN. Redox potentials determined for the oxidized/semiquinone and semiquinone/hydroquinone couples of the riboflavin and FMN complexes were used with K delta values for the complexes with the oxidized flavins to calculate values for K delta for the semiquinone and hydroquinone complexes. The hydroquinone complexes are all less stable than the complexes with the two other redox forms of the flavin. Destabilization of the hydroquinone is less marked in the complexes with riboflavin, supporting a proposal that the terminal phosphate group of FMN plays a role in decreasing the redox potential of the semiquinone/hydroquinone couple.

Anabaena↗
PubMed1991

Amplified colorimetric assay of alkaline phosphatase using riboflavin 4'-phosphate: a simple method for measuring riboflavin and riboflavin 5'-phosphate.

Alkaline phosphatase hydrolyzes riboflavin 4'-phosphate to produce riboflavin. This is converted to riboflavin 5'-phosphate, using riboflavin kinase, which reconstitutes apoglycolate oxidase to give hologlycolate oxidase. This enzyme catalyzes the oxidation of glycolate with simultaneous production of hydrogen peroxide which is detected via the formation of a colored product through the action of peroxidase. The system allows the detection of 4 amol after a 2-h incubation.

Alcohol Oxidoreductases↗
PubMed2000

Structural and functional analysis of the riboflavin synthesis genes encoding GTP cyclohydrolase II (ribA), DHBP synthase (ribBA), riboflavin synthase (ribC), and riboflavin deaminase/reductase (ribD) from Helicobacter pylori strain P1.

The functions of the riboflavin synthesis gene homologues ribA, ribBA, ribC, and ribD from Helicobacter pylori strain P1 were confirmed by complementation of defined Escherichia coli mutant strains. The H. pylori ribBA gene, which is similar to bifunctional ribBA genes of Gram-positive bacteria, fully complemented the ribB mutation and partially restored growth in a ribC mutant. However, ribBA did not complement the ribA mutation in E. coli, thus explaining the presence of the additional separate copy of the ribA gene in the H. pylori chromosome. In E. coli exclusively ribA conferred hemolytic activity and gave rise to production of molecules with fluorescence characteristics similar to flavins, as observed earlier. The E. coli hemolysin ClyA was not involved in causing the hemolytic phenotype. No riboflavin synthesis genes on plasmids conferred iron uptake functions to a siderophore-deficient mutant of E. coli. Marker exchange mutagenesis of the genes in H. pylori was not successful indicating that riboflavin synthesis is essential for basic metabolic functions of the gastric pathogen.

Aminohydrolases↗
PubMed2000

Plasma and urine riboflavin during riboflavin-free nutrition in very-low-birth-weight infants.

BACKGROUND: Very-low-birth-weight (VLBW; birth weight <1500 g) infants receive enteral and parenteral nutriture that provides greater daily riboflavin (vitamin B2) than does term infant nutriture, and elevated plasma riboflavin develops in these infants after birth. The purpose of this study was to measure plasma and urine riboflavin concentrations in VLBW infants during riboflavin-free nutrition. Our hypothesis was that elevated plasma riboflavin develops in VLBW infants because of high daily intake and immature renal riboflavin elimination. METHODS: Eighteen clinically healthy VLBW infants received parenteral nutrition and preterm infant formula during the first postnatal month. On postnatal days 10 and 28, the infants received specially prepared riboflavin-free enteral and parenteral nutrition for the 24-hour study period. Serial collections of plasma were made at time 0 and at 12 and 24 hours. Urine was collected continuously for the 24-hour period in 4-hour aliquots. Samples were analyzed for riboflavin concentration. RESULTS: During the 24-hour riboflavin-free study period on postnatal day 10, plasma riboflavin decreased 56% from 185 +/- 37 ng/mL (mean +/- SEM), and urine riboflavin decreased 75% from 3112 +/- 960 mg/mL. Similarly, on postnatal day 28, plasma riboflavin decreased 79% from 184 +/- 32 ng/mL, and urine riboflavin concentration decreased 91% from 5092 +/- 743 ng/mL during the 24-hour riboflavin-free study period. Riboflavin half-life (t(1/2)) was 18.5 hours on postnatal day 10 and decreased 48% by postnatal day 28. Riboflavin elimination was 145.1 +/- 20.6 mg/kg per day on postnatal day 10 and increased 40% by postnatal day 28. CONCLUSION: The VLBW infants who received parenteral nutrition and preterm infant formula had elevated plasma riboflavin on postnatal days 10 and 28. Plasma riboflavin t(1,2) was shorter and renal riboflavin elimination was greater on postnatal day 28 than on postnatal day 10. Plasma riboflavin was normal after 24 hours of riboflavin-free nutrition. The pattern of plasma and urine riboflavin in VLBW infants suggests a lower daily intake would maintain plasma riboflavin close to normal.

Aging↗
PubMed1997

[Effect of various riboflavin supplementations during lactation on riboflavin levels in milk, liver and carcass in lactating rats].

The present study investigated the effect of various dietary riboflavin supplementations (0 to 4000 mg/kg) during lactation on riboflavin concentrations of liver, carcass (bled body without intestine and liver), and milk in the rat. The experiment was conducted until the 14th day of lactation; milk samples were drawn on the 7th and 13th day of lactation. Riboflavin concentrations of milk raised continuously with increasing riboflavin supplementation; in the range between 0 and 10 mg/kg riboflavin supplementation, there was a linear relationship, and in the range between 12 and 4000 mg/kg there was a logarithmic relationship between riboflavin supplementation and riboflavin concentration in the milk. Maximum riboflavin concentration of milk obtained by supplementation with 4000 mg/kg was twelve-fold higher than without riboflavin supplementation. For riboflavin supplementation up to 12 mg/kg, riboflavin concentrations in milk on the 7th day of lactation and that on the 13th day of lactation were not different. In contrast, in rats fed diets with higher riboflavin supplementation, riboflavin concentrations were higher by 25% in average in milk on the 13th day of lactation than in milk on the 7th day of lactation. Contrary to the milk, riboflavin concentrations in liver and carcass exhibited a saturation, which was achieved at a supplementation of 6 mg/kg (liver) and 10 mg/kg (carcass), respectively. Maximum riboflavin concentrations obtained at a supplementation of 4000 mg/ kg were 1.9- and 2.3-fold higher for liver and carcass, respectively, than concentrations obtained without riboflavin supplementation. The dose-response relationship using riboflavin concentrations of liver and carcass as response factors indicates a riboflavin requirement of 8 to 9 mg/kg for lactating rats fed a semisynthetic diet with 17.4 MJ ME/kg dry matter and 20.8% protein in dry matter.

Animals↗
PubMed1984

A 13C-NMR study on the interaction of riboflavin with egg white riboflavin binding protein.

The interaction between riboflavin and riboflavin binding protein (RBP) was studied by 13C-NMR spectroscopy. The 13C-NMR spectra of riboflavin selectively enriched at the 2-, 4-, 4a-, and 10a-positions and of (3-[13C]methyl)riboflavin were measured both in the free and RBP-bound forms. The 13C signals of 13C-enriched riboflavin or 3-methylriboflavin bound to RBP are broader than those of the free form, reflecting the restriction of flavin mobility. The 2-, 4-, and 10a-13C signals of riboflavin show no pH-dependent shift in the neutral to acidic pH region either in the bound or free form but the 4a-13C signal of bound riboflavin shifts to lower field in the acidic pH region while that of the free form remains unshifted. The 2-, 4-, 4a-, and 10a-13C signals of free riboflavin exhibited pH-dependent change in the alkaline pH region with a pK value of about 10, in association with the N(3)-H deprotonation. The pH titration profile of the 2-, 4-, and 4a-13C signals of bound riboflavin indicates that the pK of N(3)-H is shifted substantially to the alkaline side when riboflavin is bound to RBP. The 3-methyl-13C signal of 3-methylriboflavin shows no pH-dependent shift whether the compound is free or bound to RBP. The binding of riboflavin and 3-methylriboflavin was also studied spectrofluorometrically. The analysis of the pH dependence of the association constant revealed that one ionizable group in RBP with pK of about 5 and N(3)-H of riboflavin play important roles in the binding. We conclude that RBP preferentially binds the neutral, i.e., N(3)-protonated, form of riboflavin and that the neutral form in turn is stabilized by the hydrophobic environment of RBP surrounding the N(3) region of the bound riboflavin molecule.

Carbon Isotopes↗
PubMed2002

Effect of riboflavin supplementation on plasma homocysteine in elderly people with low riboflavin status.

OBJECTIVE: To investigate the effect of riboflavin supplementation on plasma homocysteine (tHcy) concentrations in healthy elderly people with sub-optimal riboflavin status. DESIGN: A double-blind, randomized, placebo-controlled riboflavin supplementation trial. SETTING: Community based study in Northern Ireland. SUBJECTS: From a screening sample of 101 healthy elderly people, 52 had sub-optimal riboflavin status (erythrocyte glutathione reductase activation coefficient, EGRAC>or=1.20) and were invited to participate in the study. INTERVENTION: The intervention had two parts. Part 1 was a 12 week randomized double blind, placebo-controlled intervention with riboflavin (1.6 mg/day). Following completion of part 1, the placebo group went on to part 2 of the study which involved supplementation with folic acid (400 micro g/day) for 6 weeks followed by folic acid and riboflavin (1.6 mg/day) for a further 12 weeks, with a 16 week washout period post-supplementation. The purpose of part 2 was: (a) to address the possibility that homocysteine-lowering in response to riboflavin may be obscured by a much greater effect of folate, and that, once folate status was optimized, a dependence of homocysteine on riboflavin might emerge; and (b) to demonstrate that these subjects had homocysteine concentrations which could be lowered by nutritional intervention. RESULTS: Although riboflavin supplementation significantly improved riboflavin status in both parts 1 and 2 of the study (P<0.001 for each), tHcy concentrations were unaffected (P=0.719). In contrast, folic acid supplementation (study part 2) resulted in a homocysteine lowering of 19.6% (P=0.001). CONCLUSION: Despite the metabolic dependency of tHcy on riboflavin, it did not prove to be an effective homocysteine-lowering agent, even in the face of sub-optimal riboflavin status.

Aged↗
PubMed1986

Riboflavin-binding protein. Concentration and fractional saturation in chicken eggs as a function of dietary riboflavin.

The concentration of riboflavin and riboflavin-binding protein were determined in the plasma, egg yolk and albumen from hens fed a riboflavin-deficient diet (1.2 mg/kg) supplemented with 0, 1, 2, 3, 10 and 40 mg of riboflavin/kg. We observed that the deposition of riboflavin in egg yolk and albumen is dependent on dietary riboflavin and reaches half-maximal values at about 2 mg of supplemental riboflavin/kg. The maximal amount of riboflavin deposited in the yolk is limited stoichiometrically by the amount of riboflavin-binding protein, whereas the maximum amount of riboflavin deposited in albumen is limited by other factors before saturation occurs. The amount of riboflavin-binding protein in yolk and albumen is independent of dietary riboflavin. If there is a specific oocyte receptor for riboflavin-binding protein, it cannot distinguish between the apo and holo forms of the protein. Riboflavin-binding protein is about six times more concentrated in yolk than in plasma.

Animals↗
PubMed1982

Growth and riboflavin status of rats fed different levels of protein and riboflavin.

The relationship between riboflavin and protein utilization was studied in 5-week-old male Sprague-Dawley rats, by using a factorial design with three levels of riboflavin (8, 16 and 24 microgram per rat per day) and protein (1.0, 1.6 and 2.2 g casein per rat per day) in a 9-week experiment. With the lowest level of casein, protein intake was growth limiting, and the level of riboflavin intake had no effect on either weight gain or liver nitrogen retention. With the two higher levels of casein, both weight gain and liver nitrogen retention increased with riboflavin intake, but 24 micrograms riboflavin per day was inadequate for maximal utilization of nitrogen from 2.2 g casein. Neither protein nor riboflavin intake affected the concentration of liver nitrogen per gram of fresh tissue. Increasing the protein intake from 1.0 to 1.6 g increased riboflavin retention in the liver, but additional protein had no further effect. Liver and muscle (gastrocnemius) riboflavin concentrations, as micrograms per gram wet tissue, increased with riboflavin intake. At the two higher intakes of riboflavin, tissue riboflavin levels decreased and the erythrocyte glutathione reductase activity coefficients (EGR-AC) increased with protein intake. These findings are consistent with the view that the effect of protein on riboflavin requirement is related to the rate of growth and not to protein intake, per se.

Aging↗
PubMed1990

Growing Escherichia coli mutants deficient in riboflavin biosynthesis with non-limiting riboflavin results in sensitization to inactivation by broad-spectrum near-ultraviolet light (320-400 nm).

Two mutants of Escherichia coli unable to synthesize riboflavin were grown with limiting (2 micrograms ml-1) and non-limiting (10 micrograms ml-1) concentrations of riboflavin. These riboflavin auxotrophs when grown to exponential phase with non-limiting riboflavin are more sensitive to broad spectrum near-ultraviolet light (NUV, 320-400 nm) inactivation than when they are grown with limiting riboflavin. Exponential phase cells of the riboflavin auxotrophs grown with limiting riboflavin are sensitized when irradiated in saline supplemented with riboflavin. This suggests that extracellular riboflavin is important as a NUV sensitizer when intracellular levels of riboflavin are reduced. The concentration of riboflavin in crude extracts from exponentially growing cells correlates well with the sensitivity of these mutants to NUV inactivation. The level of riboflavin supplementation has little effect on the NUV sensitivity of the parental strain.

Escherichia coli↗
PubMed1992

Effect of riboflavin-binding protein deficiency on riboflavin metabolism in the laying hen.

Normal chicken eggs contain substantial amounts of riboflavin, all of which is bound to a specific, high-affinity, riboflavin-binding protein (RfBP). Two hens, genetically unable to produce RfBP and thus unable to deposit sufficient riboflavin in their eggs, were compared to two normal hens with respect to the biological half-life of [14C]riboflavin, the tissue distribution of 14C-labeled flavins, and the relative contributions of tissue and dietary riboflavin to flavins deposited in the egg. The biological half-life of [14C]riboflavin was slightly but insignificantly less in the RfBP-deficient hens (11.5 +/- 1.7 days vs 15.1 +/- 3.3 days). The 14C-labeled flavin content of a variety of tissues 3 weeks after the intraperitoneal injection of 5 microCi of riboflavin was also very similar among the four hens. In contrast, the 14C-labeled flavin content of egg yolk, egg albumen, and blood plasma from RfBP-deficient birds was less than 10% of normal. For all hens, the specific radioactivity of flavins in yolk and albumen was similar to that in liver but less than that in heart. We conclude that riboflavin deposited in egg had equilibrated with the large hepatic flavin pool and was not derived preferentially from unlabeled dietary riboflavin. Other than the inability to deposit riboflavin in their eggs, hens of the mutant strain have normal riboflavin metabolism.

Administration, Oral↗
PubMed1985

Relationship between changes in properties and contents of riboflavin derivatives of NADPH-cytochrome P-450 reductase in the liver microsomes of riboflavin-deficient rats.

Weanling male rats were fed a riboflavin-deficient diet for 5-8 weeks, and the decrease in NADPH-cytochrome P-450 reductase (FpT) activity in the liver microsomes was compared with the contents of riboflavin derivatives. The decrease of FpT activity for the reduction of cytochrome c was greater than that for the reduction of ferricyanide. The FpT's of riboflavin-deficient and control rats were indistinguishable in the Ouchterlony immunodiffusion test against anti-FpT, and were shown to have the same molecular weight of 78,000 by SDS-polyacrylamide slab gel electrophoresis. However, the purified FpT of the riboflavin-deficient rats contained 14.2, 4.9, and 1.9 nmol of FAD, FMN, and riboflavin per mg of protein, respectively, while that of the control rats contained 10.6 and 9.5 nmol of FAD and FMN per mg of protein, respectively. After riboflavin injection into the riboflavin-deficient rats, NADPH-cytochrome c reductase activity and FMN content of the FpT were restored to the control levels in 36 h, NADPH-ferricyanide reductase activity recovered in 18 h, and riboflavin content diminished in 18 h. On incubation of the purified FpT of the riboflavin-deficient rats with FMN, NADPH-cytochrome c reductase activity and FMN content were restored to those of control rats. These results indicated that a part of FMN in the FpT of the riboflavin-deficient rats was replaced with FAD and riboflavin.

Animals↗
PubMed1980

Vibrational modes of flavin bound to riboflavin binding protein from egg white. Resonance Raman spectra of lumiflavin and 8-substituted riboflavin.

The resonance Raman (RR) spectra of 8-halogenated-riboflavin, 8-demethyl-riboflavin(8-H-RF), 8-amino-riboflavin(8-NH2-RF), 8-methoxy-riboflavin(8-OCH3-RF), lumiflavin, and 3-methyl-lumiflavin were observed. The Raman lines with the highest frequency are at 1624, 1620, and 1615 cm-1 for 8-chloro-riboflavin, 8-bromo-riboflavin, and 8-iodo-riboflavin, respectively. This systematic shift confirms that the 1631 cm-1 line of riboflavin is derived from the benzene part of isoalloxazine. Substitution at the 8-position by an amino or methoxy group, which has a large influence on the electronic structure of isoalloxazine, changes the RR spectrum markedly in comparison with that of 8-halogenated riboflavin. The 1583 cm-1 line of riboflavin, which involves the vibrational displacement of N(5) and C(4a) atoms of isoalloxazine, is shifted to the low frequency side by substitution at the 8-position with an amino or methoxy group. The corresponding line of 8-H-RF, on the contrary, shifts to the high frequency side. The RR spectrum of lumiflavin is very different from that of riboflavin in the range from 1200 to 1300 cm-1. Although the pi-electronic structure is little affected by the substitution at the 10-position, the Raman spectrum of lumiflavin in this region is very sensitive.

Binding Sites↗
PubMed2002

Riboflavin, flavin mononucleotide, and flavin adenine dinucleotide in human plasma and erythrocytes at baseline and after low-dose riboflavin supplementation.

BACKGROUND: Vitamin B(2) 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 B(2) 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 > or =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 < or =0.04). The strongest increases were for riboflavin in plasma (83%) and for FMN in erythrocytes (87%). CONCLUSIONS: Concentrations of all B(2) vitamers except plasma FAD are potential indicators of vitamin B(2) status, and plasma riboflavin and erythrocyte FMN may be useful for the assessment of vitamin B(2) status in population studies.

Aged↗
PubMed1984

Effect of riboflavin supplementation on riboflavin nutriture of a secondary school population in Nigeria.

Riboflavin status was assessed in 42 secondary school students before and after supplementing the food intake with 5 mg riboflavin daily for 7 days. Energy, protein, and riboflavin intakes were determined on foods actually consumed by each student. Riboflavin nutriture was based on urinary riboflavin excretion and erythrocyte glutathione reductase activity coefficient. The energy and riboflavin intakes of the students were 68 to 82% and 80 to 88%, respectively, of the recommended allowance. The basal urinary riboflavin excretion was 0.335 mg/g creatinine and increased significantly to 3.51 mg/g creatinine after supplementation. The basal erythrocyte glutathione reductase activity coefficient values indicated an overall prevalence of 38% biochemical ariboflavinosis (erythrocyte glutathione reductase activity coefficient greater than 1.30) and dropped significantly (p less than 0.001) from 1.26 to 1.08. The results confirm that urinary riboflavin is of limited value in the assessment of riboflavin status while erythrocyte glutathione reductase activity coefficient more precisely assesses metabolic availability of riboflavin and more accurately detects biochemical ariboflavinosis.

Adolescent↗
PubMed1977

[Analgos of riboflavin, lumiflavin and alloxazine derivatives. II. Effect of roseoflavin on 6,7-dimethyl-8-ribityllumazine and riboflavin synthetase synthesis and growth of Bacillus subtilis].

The replacement of 8-CH3 group in the riboflavin molecule results in the formation of specific antimetabolites. They are rozeoflavin, 7-desmethylrozeoflavin, 8-amino (nor) riboflavin, 8-ribitylamino (nor) riboflavin. Effect of rozeoflavin and other riboflavin analogues on the growth and regulatory characteristics of Bacillus subtilis strains with different genetic state of riboflavin operon is studied. Roseoflavin at a concentration of 0.05 mkg/ml inhibits DRL synthesis in rib-b110 strain. An analogue inhibits the growth of auxotrophic and prototrophic strains at concentrations of 0.5 mkg/ml and 50 mkg/ml respectively. Riboflavin (1 mkg/ml) recovers the growth of bacteria. The curve of rozeoflavin regulation of DRL and riboflavin synthetase synthesis is shifted in 100 times in the direction of lesser concentrations as compared with riboflavin and 8 amino (nor) riboflavin. 180 mutants resistant to 100 mkg/ml of rozeoflavin were selected. 150 mutants over-synthetize riboflavin.

Bacillus subtilis↗
PubMed2002

Role of riboflavin in beer flavor instability: determination of levels of riboflavin and its origin in beer by fluorometric apoprotein titration.

A method for the quantitative determination of riboflavin levels in beer was developed. The method is based on the quenching of riboflavin fluorescence, which occurs when riboflavin binds to the aporiboflavin-binding protein from egg white. The method does not require any pretreatment of the beer before analysis, other than dilution, and proved to be simple, reliable, and sensitive. The lowest concentration that could be detected was approximately 10 nM riboflavin. The possible interference of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) with the determination of the riboflavin content of beer was excluded, because beer contains only a very small amount of FAD (0.03 microM) and no FMN. The riboflavin levels of the types and brands of beer investigated were in the range of 0.5-1.0 microM. The origin of the riboflavin in beer proved to be the malt. Hop and yeast hardly contributed to the riboflavin content of beer. Besides its use in the determination of riboflavin levels, the aporiboflavin-binding protein also provides a way to remove riboflavin from beer, which reduces the light sensitivity and the related lightstruck off-flavor formation in beer.

Beer↗
PubMed1984

Relation of riboflavin nutriture in healthy elderly to intake of calcium and vitamin supplements: evidence against riboflavin supplementation.

The status of riboflavin nutriture was evaluated in 24 healthy elderly female residents of a private, nonprofit facility for the care of ambulatory elderly. Riboflavin intake by history was greater than or equal to the recommended dietary allowances (RDA) for this nutrient in all but three subjects, and the average intake in the group as a whole was 50% greater than the RDA. Confirmatory of the findings by history, the status of riboflavin nutriture was excellent in nearly all subjects as evaluated by urinary riboflavin excretion and erythrocyte glutathione reductase activity coefficient. By contrast, calcium intake was greater than or equal to the RDA in ony four of the 24 subjects. The adequacy of calcium intake was found to depend upon a sufficiently high percentage of the total dietary intake of riboflavin being derived from milk and dairy products. It was observed that individual calcium intakes were less than 80% of the RDA unless 40% or more of the total intake of riboflavin was derived from milk and dairy products rather than from other food sources. In those subjects taking daily supplementation with a single multivitamin tablet containing low levels of riboflavin, the total intake of riboflavin and its urinary excretion were increased similarly, suggesting that even small amounts of riboflavin are not retained by elderly subjects consuming a diet adequate in riboflavin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗