Riboflavin (B2)

What is vitamin B2?

Vitamin B2, or riboflavin, is an essential vitamin that helps us metabolize nutrients, produce energy, and fight off disease. Riboflavin exists in different forms, including in its free form and its phosphorylated form (bound to a phosphate group). The two major forms of phosphorylated riboflavin are flavin mononucleotide (FMN) and flavin dinucleotide (FAD). These are considered the active forms of riboflavin.¹

As a water-soluble vitamin, riboflavin is not stored in the body in large amounts. Since we cannot produce riboflavin, we must get this vitamin through foods or supplements.

Why we need it

Riboflavin serves as a coenzyme, or a substance required by an enzyme for a chemical reaction to take place. Specifically, riboflavin supports enzymes involved in the electron transport chain, a process through which our cells produce energy.¹

Additionally, riboflavin helps the body absorb and utilize other essential nutrients. Vitamin B6, for example, requires FMN to be converted into its active form.² Riboflavin also helps us absorb iron, a mineral that allows oxygen to be transported throughout the body.³

Riboflavin also has antioxidant effects, as it helps protect the body from oxidative stress (a phenomenon in which reactive substances can cause damage to the body’s cells and tissues). Riboflavin acts as a coenzyme for antioxidant enzymes like glutathione reductase, which neutralize reactive oxygen species, thus reducing oxidative stress.² Through its antioxidant activity, riboflavin helps protect against cataracts, migraines, and diseases like diabetes and cancer.³

Where it’s found

Riboflavin is found in a wide variety of foods, including dairy, meat, grains, and some vegetables. Riboflavin may be naturally present in these foods or added in after processing. Specific examples of riboflavin-rich foods include:

Milk
Cheese
Organ meats
Enriched or fortified breads and cereals
Eggs
Nuts
Mushrooms
Dark leafy greens

Riboflavin can also be taken as a supplement. In foods and supplements, riboflavin may be present in its free or phosphorylated form.

Daily requirements

The Recommended Dietary Allowance (RDA) for riboflavin (i.e. the amount that is likely to meet the needs of most healthy people) is 1.3 milligrams (mg) per day for male adults (over the age of 19), and 1.1 mg per day for female adults.⁴ For women who are pregnant or breastfeeding, the RDA increases to 1.4 mg per day and 1.6 mg per day, respectively.⁴

Riboflavin deficiency

Riboflavin deficiency, also known as ariboflavinosis, can affect systems throughout the entire body. Symptoms of riboflavin deficiency include mouth sores, dry skin, sore throat, hair loss, migraines, and inflammation of the skin.³ Riboflavin deficiency may also increase the risk of other nutrient deficiencies, such as iron or vitamin B6 deficiency.^{2, 5}

Riboflavin deficiency is rare in developed countries, as most people get enough riboflavin through their diet.³ Certain people, however, may be at higher risk for riboflavin deficiency. For example, riboflavin deficiency is more common among people who consume excessive amounts of alcohol, as well as elders, infants, vegetarians, and pregnant or breastfeeding women.⁵

Can you get too much riboflavin?

Riboflavin is safe and does not appear to cause any negative side effects, even when consumed in large doses. This is partly because riboflavin can be easily excreted from the body, so it is not likely to build up in the blood.¹ That said, there is currently no Tolerable Upper Limit (i.e., a maximum amount of a nutrient that is considered safe) established for riboflavin.⁴

Fun facts

Riboflavin can be destroyed when exposed to light. For this reason, milk nowadays is typically packaged in opaque containers instead of clear glass bottles (to conserve its riboflavin content).¹

Riboflavin is naturally bright yellow colored (hence its name, as flavin originates from flavus, which means “yellow” in Latin). Because of this, consuming large amounts of riboflavin can cause the urine to turn noticeably yellow in color.⁶