Living organisms extract most of their energy from oxidation-reduction (redox) reactions, which involve the transfer of electrons. Vitamin B2 (riboflavin) is the precursor of 'flavocoenzymes' that participate in redox reactions by various metabolic pathways (3) , support the metabolization of drugs and toxins (4) and are essential for the metabolism of carbohydrates, fats and proteins.
The flavoenzyme-dependent 'glutathione redox cycle' plays an important antioxidant role , protecting the body against reactive oxygen species that can have harmful effects. Riboflavin deficiency has been associated with increased oxidative stress (4) . Another oxidation reaction dependent on flavoenzymes generates uric acid, one of the most effective water-soluble oxidants present in the blood (5) .
Flavoproteins are involved in the metabolism of other vitamins of the vitamin B complex such as vitamins B3 , B6 and B9 (6, 7, 8) .
Although the mechanism is unclear, animal research suggests that vitamin B2 (riboflavin) deficiency may impede iron absorption , increase intestinal iron loss, or prevent the use of iron for hemoglobin synthesis. In humans, improving the nutritional status of riboflavin has been shown to increase the level of circulating hemoglobin (9) .
The European Food Safety Authority (EFSA) , which provides scientific advice to policy makers, has confirmed that clear health benefits have been demonstrated from dietary vitamin B2 intake, as it contributes to the following:
