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

Abstract

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.

Dietary Reference Values for riboflavin

“…However, the results of Hustad et al (2002) are in contrast with an observational study (Vasilaki et al, 2010) that reported, in 119 healthy subjects, a positive correlation between plasma FMN and FAD, and between plasma free riboflavin and plasma FAD or FMN (r = 0.5, 0.49 and 0.55, respectively; p < 0.001).…”

“…Erythrocyte FMN (but not FAD) was positively correlated with erythrocyte free riboflavin (p < 0.001). However, contrary to Hustad et al (2002), erythrocyte FAD was weakly but significantly correlated with plasma FAD (r = 0.21, p < 0.05).…”

“…Free riboflavin, FMN and FAD are transported in plasma bound to albumin and to immunoglobulins (Ig) (IgA, IgG and IgM), as shown in healthy subjects (Innis et al, 1985) and in patients (Innis et al, 1986). Hustad et al (2002) (Section 2.4.3.1) reported FAD as the major form in plasma in healthy individuals compared to free riboflavin or FMN (median concentrations were 74, 10.5 and 6.6 nmol/L, respectively).…”

Literature search and review related to specific preparatory work in the establishment of Dietary Reference Values for Riboflavin

“…In Table 2, key reasons for categorizing studies in moderate or high risk of bias are described. No controlled diet during intervention period (Madigan, Tracey et al 1998;McKinley, McNulty et al 2002;Tavares, Moreira et al 2009) No controlled diet during intervention period (Hustad, McKinley et al 2002;McNulty, Dowey et al 2006) biomarkers could not be measured for all study subjects for unknown reasons (Hustad, McKinley et al 2002) Clear presentation of study results are missing, main results presented in figures with percentage of change (McNulty, Dowey et al 2006) Prospective cohort Risk of bias in exposure assessment; high correlation between micronutrients in the diet (Hankinson, Stampfer et al 1992;Badart-Smook, van Houwelingen et al 1997;Brzozowska, Kaluza et al 2008;de Vogel, Dindore et al 2008;Kabat, Miller et al 2008;Maruti, Ulrich et al 2009;Uccella, Mariani et al 2011;Bassett, Hodge et al 2012;Bassett, Severi et al 2012;Zschabitz, Cheng et al 2013) Risk of bias in exposure assessment; high correlation between micronutrients in the diet (Fortes, Forastiere et al 2000;Dallosso, McGrother et al 2004) Small population size (Fortes, Forastiere et al 2000) Information on exposure and outcome assessment is limited (Liu, Hazra et al 2013) No appropriate reporting of/adjustment for confounding (Dallosso, McGrother et al 2004) Dietary intake and status were measured during pregnancy and not in lactation phase (Shaw 1993;Ortega, Quintas et al 1999) Case-cohort Risk of bias in exposure assessment; high correlation between micronutrients in the diet (de Vogel, Dindore et al 2008) Nested casecontrol Risk of bias in exposure assessment; high correlation between micronutrients in the diet (Jacques, Chylack et al 2001;…”

“…Hustad et al studied riboflavin status after riboflavin supplementation in 46 elderly men and women (mean age about 69 years) selected for a suboptimal riboflavin status (EGRAC ≥ 1.20) from a larger population of 124 subjects (Hustad, McKinley et al 2002). This randomised controlled trial was of high risk of bias.…”