VITAMIN B2 AND ITS STATUS IN VEGETARIANS AND VEGANS

Abstract

The main goal of this review was to briefly highlight the key points of today’s knowledge about the role and metabolism of vitamin B2 as well as to compare its status in vegans, vegetarians, and omnivores according to present data. Biologically active forms of water-soluble vitamin B2 (riboflavin) are represented by flavin mononucleotide (FMN) and flavin adenine diphosphate (FAD), which are coenzymes in the reactions of the electron transport chain and the pyruvate dehydrogenase complex. Riboflavin is also involved in the metabolism of fatty acids, the synthesis of cholesterol and steroid hormones. Riboflavin also participates in the folate cycle. Vitamin B2 is crucial for the metabolism of other vitamins. FMN is necessary for the for-mation of the active form of vitamin B6, while FAD is necessary for the synthesis of niacin. Severe clinical insufficiency of vitamin B2 is not common. Besides insufficient riboflavin consumption, hypothyroidism can also be a cause of vitamin B2 deficiency as thyroxine regulates the conversion of ribo-flavin to its active forms  FMN and FAD. Lack of riboflavin can cause tissue damage; especially of the epithelial, reproductive, and nervous system. The variety of its manifestations is related to the fact that riboflavin deficiency also disrupts the metabolism of vitamins B6, or PP. Similarly, riboflavin deficiency can also disrupt the folate cycle, increasing the level of homocysteine which damages vascular intima and leads to endothelial dysfunction and atherosclerosis as a result. Rapid urinary excretion of riboflavin makes it safe even if taken in a high dose, changing the urine colour into bright-yellow. This safety of riboflavin makes it unharmful to be used as an oral tracer for monitoring compliance in clinical research. Ultra-high doses of ribo-flavin (more than 400 mg/day) can cause diarrhoea or polyuria. The content of vitamin B2 in animal-derived products is higher than in plant-based ones. This also determines its lower intake in vegans and vegetarians compared to omnivores. While there is a shred of evidence that plant-based diets in-crease the production of bioavailable riboflavin by the gut microbiota, this does not appear to be sufficient to completely compensate for the vegetari-ans’/vegans’ reduced dietary intake of vitamin B2, as most of the researches point the fact that vegans and vegetarians are more prone to lack vita-min B2 than omnivores. At the same time, it should be noted that there exists no universally adopted optimal method for assessing the status of vit-amin B2 in the body. Further research and standardization of methods may ease to assess the prevalence and risks of riboflavin deficiency in various dietary groups