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                                      Vitamin B2

Riboflavin (vitamin B2)

Vitamin B2, also known as riboflavin, is arguably the only vitamin that gives you a visual cue as to its passage through your body. When there is a lot of vitamin B2 in the diet (or in a supplement), your urine turns bright yellow to show you it is there. In fact, the —flavin in riboflavin comes from flavus, the Latin word for yellow.

Vitamin B2, like the other B vitamins, is involved in energy metabolism. It has also recently been found to affect the metabolism of iron in important ways

Riboflavin, also known as vitamin B2, helps:

keep skin, eyes and the nervous system healthy

the body release energy from food


Riboflavin was discovered in 1920, isolated in 1933, and first made in 1935.[4] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system

How does it work?:

Riboflavin functions as a coenzyme, meaning that it is required for enzymes (proteins) to perform normal physiological actions. Specifically, the active forms of riboflavin flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) function as cofactors for a variety of flavoproteine enzyme reactions:

Flavoproteins of electron transport chain, including FMN in Complex I and FAD in Complex II

FAD is required for the production of pyridoxic acid from pyridoxal (vitamin B6) by pyridoxine 5'-phosphate oxidase

The primary coenzyme form of vitamin B6 (pyridoxal phosphate) is FMN dependent

Oxidation of pyruvate, α-ketoglutarate, and branched-chain amino acids requires FAD in the shared E3 portion of their respective dehydrogenase complexes

Fatty acyl CoA dehydrogenase requires FAD in fatty acid oxidation

FAD is required to convert retinol (vitamin A) to retinoic acid via cytosolic retinal dehydrogenase

Synthesis of an active form of folate (5-methyltetrahydrofolate) from 5,10-methylenetetrahydrofolate by Methylenetetrahydrofolate reductase is FADH2 dependent

FAD is required to convert tryptophan to niacin (vitamin B3)

Reduction of the oxidized form of glutathione (GSSG) to its reduced form (GSH) by Glutathione reductase is FAD dependent

For the molecular mechanism of action see main articles Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)

Good sources of riboflavin include:



fortified breakfast cereals


UV light can destroy riboflavin, so ideally these foods should be kept out of direct sunlight.

How much riboflavin do I need?

The amount of riboflavin adults (19-64 years) need is about:

1.3mg a day for men

1.1mg a day for women

You should be able to get all the riboflavin you need from your daily diet.

Riboflavin can't be stored in the body, so you need it in your diet every day.


Riboflavin is LIKELY SAFE for most people when taken by mouth. In some people, riboflavin can cause the urine to turn a yellow-orange color. When taken in high doses, riboflavin might cause diarrhea, an increase in urine, and other side effects.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Riboflavin is LIKELY SAFE for pregnant or breast-feeding women when taken in the amounts recommended. The recommended amounts are 1.4 mg per day for pregnant women and 1.6 mg per day in breast-feeding women. Riboflavin is POSSIBLY SAFE when taken by mouth in larger doses, short-term. Some research shows that riboflavin is safe when taken at a dose of 15 mg once every 2 weeks for 10 weeks.

Hepatitis, Cirrhosis, Billary obstruction: Riboflavin absorption is decreased in people with these conditions.

Drying medications (Anticholinergic drugs) interacts with RIBOFLAVIN

Some drying medications can affect the stomach and intestines. Taking these drying medications with riboflavin (vitamin B2) can increase the amount of riboflavin that is absorbed in the body. But it's not known if this interaction is important.

Medications for depression (Tricyclic antidepressants) interacts with RIBOFLAVIN

Some medications for depression can decrease the amount of riboflavin in the body. This interaction is not a big concern because it only occurs with very large amounts of some medications for depression.

Phenobarbital (Luminal) interacts with RIBOFLAVIN

Riboflavin is broken down by the body. Phenobarbital might increase how quickly riboflavin is broken down in the body. It is not clear if this interaction is significant.

Probenecid (Benemid) interacts with RIBOFLAVIN

Probenecid (Benemid) can increase how much riboflavin is in the body. This might cause there to be too much riboflavin in the body. But it's not known if this interaction is a big concern.