Riboflavin and vitamin B-6 play vital roles in many biological processes, including one-carbon metabolism. However, the metabolic and health effects of vitamin B-6 and riboflavin deficiency in populations around the world are less well-studied than they are for folate and vitamin B-12. 

There is little evidence that riboflavin deficiency is more widespread than generally thought, especially in high-income countries, since the status of this vitamin is rarely assessed at a population level. 

This study aimed to investigate vitamin B-6 and riboflavin status, their metabolic interactions, and their relationship to the methylenetetrahydrofolate reductase (MTHFR) genotype in adults. 

Further analysis of vitamin -B6 and riboflavin biomarkers was conducted among participants, with information about their dietary intake as a secondary outcome.

A total of three cohorts were used in this study: the National Adult Nutrition Survey (NANS) of Ireland, the Trinity-Ulster Department of Agriculture (TUDA) cohort study, and the Genovit case-control study. 

Researchers conducted face-to-face interviews with all study cohorts using standardized protocols to obtain health and lifestyle information. In addition to collecting medical and demographic details, medications, and vitamin supplement usage, a comprehensive health and lifestyle questionnaire was also administered.

The researchers measured weight, height, waist, and hips; The researchers measured muscle mass with the Tanita BC-420 (Tanita Ltd), and blood pressure was measured using a validated clinical automated blood pressure recording device.

In this study, 5612 adults aged 18-102 were surveyed based on the Irish National Adult Nutrition Survey (NANS), Trinity-Ulster Department of Agriculture (TUDA), and Genovit cohorts (volunteer samples). 

As riboflavin’s functional indicator, plasma PLP (pyridoxal 5′-phosphate), and erythrocyte glutathione reductase activation coefficient (EGRac) were measured.

Results of the Study

Researchers observed 52.1 nmol/L of PLP concentrations in the participants with the variant MTHFR 677TT genotype combined with reduced riboflavin utilization compared with 76.8 nmol/L in the non-TT genotype participants with sufficient riboflavin utilization. 

  1. There were significant differences between younger and older adults in all variables except RBC folate. 
  2. Plasma PLP and serum total vitamin B-12 levels in younger adults were significantly higher than those in older adults, as well as plasma homocysteine levels. 
  3. Riboflavin status was better in older adults (lower EGRac values). 
  4. A deficiency of vitamin B-6 was found in 6% of young adults and 14% of older adults, respectively, whereas riboflavin deficiency was prevalent in both young (39%) and senior (29%) adults.

There was an association between PLP (pyridoxal 5′-phosphate) and vitamin B-6 consumption, supplement use, and fortified foods in participants with dietary data.

According to these results, PLP (pyridoxal 5′-phosphate) may be metabolically dependent on flavin mononucleotide (FMN) to maintain vitamin B-6 status, especially in individuals with the MTHFR 677TT genotype. 

Randomized trials are necessary to investigate riboflavin’s effects within the dietary range.

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