Vitamin B2

Riboflavin, also known as vitamin B2, is a water-soluble B vitamin that plays a fundamental role in human metabolism. It is an essential component of two major coenzymes: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which participate in over 100 different enzymatic reactions throughout the body.

The primary function of riboflavin is in energy metabolism. FMN and FAD serve as electron carriers in the electron transport chain, the final pathway of cellular respiration that generates ATP. These coenzymes are also essential for the metabolism of carbohydrates, fats, and proteins, helping convert food into usable energy. Without adequate riboflavin, cells cannot efficiently produce the energy needed for their functions.

Beyond energy production, riboflavin plays crucial roles in cellular growth and development. It is required for the proper functioning of many cellular processes, including DNA repair, synthesis of other vitamins (such as conversion of vitamin B6 to its active form), and maintenance of healthy red blood cells. Riboflavin also helps maintain healthy mucous membranes in the digestive tract and supports normal immune function.

Riboflavin has been extensively studied for its potential role in migraine prevention. Clinical trials have shown that high-dose riboflavin supplementation (typically 400 mg/day) can reduce the frequency and duration of migraine attacks in some individuals. The mechanism is thought to involve improved mitochondrial function in brain cells.

As a water-soluble vitamin, riboflavin is not stored in significant amounts in the body and must be consumed regularly through diet. Excess riboflavin is excreted in urine, often causing a characteristic bright yellow color. Deficiency, known as ariboflavinosis, is uncommon in developed countries but can occur with poor diet, alcoholism, or certain medical conditions.

Riboflavin's primary mechanism of action involves its conversion to two active coenzymes: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes function as electron carriers in numerous oxidation-reduction reactions throughout the body.

In energy metabolism, FAD and FMN are essential components of the electron transport chain located in the inner mitochondrial membrane. They accept electrons from NADH and FADH2 and transfer them through a series of protein complexes ultimately to oxygen, generating ATP through oxidative phosphorylation. This process provides the majority of cellular energy in aerobic organisms.

Riboflavin coenzymes also participate directly in the metabolism of macronutrients. FAD is required for the beta-oxidation of fatty acids, the citric acid cycle (as a component of succinate dehydrogenase), and the catabolism of several amino acids. FMN is a cofactor for the enzyme that converts vitamin B6 (pyridoxine) to its active form (pyridoxal phosphate), linking riboflavin status to vitamin B6 function.

The mechanism behind riboflavin's effect on migraines is thought to involve mitochondrial function. Brain cells have high energy demands and abundant mitochondria. Riboflavin supplementation may enhance mitochondrial energy metabolism, potentially reducing susceptibility to migraine attacks. Some research suggests that individuals with migraines may have subtle mitochondrial dysfunction that responds to riboflavin supplementation.

Riboflavin also has antioxidant properties through its role in the glutathione redox cycle. FAD is required for the enzyme glutathione reductase, which maintains glutathione in its reduced (active) form. Glutathione is a major intracellular antioxidant that protects cells from oxidative damage.

As a water-soluble vitamin, riboflavin is absorbed in the upper gastrointestinal tract through active transport at low concentrations and passive diffusion at higher concentrations. It circulates in the bloodstream bound to albumin and other proteins. The body has limited storage capacity for riboflavin, with small amounts found in the liver, heart, and kidneys. Excess riboflavin is rapidly excreted unchanged in urine.

Riboflavin is found in a variety of foods, with particularly high concentrations in organ meats, dairy products, and fortified grains. It is stable during cooking but can be destroyed by exposure to light, which is why milk is often sold in opaque containers.

Riboflavin deficiency, known as ariboflavinosis, typically occurs alongside other B vitamin deficiencies. It affects the skin, mucous membranes, and eyes. Deficiency is uncommon in developed countries due to food fortification but can occur with poor diet, alcoholism, or malabsorption conditions.

Riboflavin requirements are based on the amount needed to maintain normal functional levels of the vitamin in the body. Needs increase during periods of growth, pregnancy, and lactation. Athletes and very active individuals may have slightly higher requirements.

Riboflavin supplements are available as riboflavin itself or as riboflavin 5'-phosphate (also called flavin mononucleotide or FMN). Both forms are well-absorbed. Riboflavin is the most common form in supplements.