Vitamin B2 (Riboflavin)

Recommended Daily Intake

The Recommended Dietary Allowance (RDA) for vitamin B2 for adult men is 1.3 mg/day, for women 1.1 mg/day, 1.4 mg/day during pregnancy and 1.6 mg/day during breastfeeding ^[1].

Vitamin B2 Deficiency (Ariboflavinosis): Who is at risk?

• Chronic alcoholics and people who starve or suffer from anorexia nervosa
• Individuals with celiac or Crohn’s disease, HIV/AIDS, liver disease, cancer ^[3], individuals with chronic kidney failure on low-protein diet ^[13],
• In poor regions of Africa and Asia: children with gastrointestinal infections ^[17]
• Individuals with hypothyroidism ^[6] or adrenal insufficiency, which make vitamin B2 less effective
• Premature infants with neonatal jaundice on phototherapy ^[5]

Vitamin B2 deficiency is a risk factor for cataracts, migraine, peripheral neuropathy, night blindness, iron-deficiency anemia, heart disease, high blood pressure, preeclampsia (high blood pressure and edema in pregnancy), birth defects (cleft lip and palate, growth retardation), esophageal and cervical cancer ^[1,5].

Vitamin B2 deficiency is usually accompanied with deficiencies of other B-complex vitamins ^[5].

Diagnosis and Treatment

Vitamin B2 deficiency is diagnosed by a blood test ^[5]. Treatment is with vitamin B2 supplements.

Vitamin B2 (Riboflavin) Supplements

By mouth (available over-the-counter)

Oral vitamin B2 in the form of tablets, capsules, softgels, lozenges, powder or liquid containing riboflavin or riboflavin-5-phosphate (monophosphate) are available without prescription. Vitamin B2 is also usually included in vitamin B-complex, prenatal and multivitamin supplements.

Tablets or capsules may contain 10, 15, 20 100, 200, 250, 300 or 400 mg of vitamin B2.

Injections

In the UK, ampules for intravenous infusion containing vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B9 (folate) and vitamin C are available.

There is insufficient evidence about vitamin B2 supplements effectiveness in prevention or treatment of HIV/AIDS-related lactic acidosis, cervical cancer, acne, hair loss, muscle cramps, canker sores, memory loss, Alzheimer’s disease, burns, alcoholism, liver disease or sickle cell anemia; increasing energy levels or athletic performance, boosting the immune system, promoting weight loss, slowing aging or improving skin (rosacea) or nail health ^[3,8].

Recommended Riboflavin Dosage in Adults

• For riboflavin deficiency, tablets 5-30 mg/day
• For preventing migraine headache, tablets 400 mg/day
• For preventing cataracts 2.6 mg/day, optionally in combination with vitamin B3 (niacin) 40 mg/day. NOTE: Vitamin in doses higher than 10 mg/day may worsen cataracts ^[5].
• Reference: ^[3]

Vitamin B2 Supplements Safety: Side Effects, Toxicity

No toxic effects of vitamin B2 supplements were identified so far ^[3]. High doses (400 mg/day) may trigger diarrhea and excessive urination (polyuria) in some people ^[3]. Vitamin B2 supplements can give urine and stool fluorescent bright yellow or orange color (flavinuria), which causes no harm ^[1,12]. No Tolerable Upper Level for riboflavin has been set, because overdose has not been observed ^[1]. Any vitamin B2 taken in excess is excreted with urine ^[16].

Overconsumption of vitamin B2 from foods is practically impossible; even by eating a lot of fortified foods you will not likely get too much vitamin B2.

Safety During Pregnancy and Breastfeeding

Vitamin B2 by mouth in doses within Recommended Daily Allowance (1.4 mg/day) is pregnancy category A, which means no harmful effects for the babies were observed during human trials, and doses above 1.4 mg/day are pregnancy category C, which means, insufficient human trials were made to prove its safety at these doses ^[7,14].

Vitamin B2 is safe to use during breastfeeding ^[14].

Vitamin B2 Interactions With Drugs and Nutrients

The following drugs may reduce vitamin B2 activity: quinine, chlorpromazine, tricyclic antidepressants, adriamycin, phenobarbitol ^[1].

In individuals with vitamin B2 deficiency and anemia, vitamin B2 supplements increase bioavailability of iron ^[3].

Vitamin B2 is required for proper action of vitamins B3 (niacin), B6 (pyridoxine), B9 (folic acid), B12, iron and zinc ^[1].

Vitamin B2 Absorption and Body Stores

• Vitamin B2 is water-soluble so it can not be stored in the body fat and can be therefore depleted from the body in several weeks.
• Vitamin B2 is absorbed in the upper small intestine (jejunum); absorption is much better when taken with foods ^[16].

Frequently Asked Questions

1. What are other names for vitamin B2?

The other name for vitamin B2–riboflavin–originates from ribose, which is a component of vitamin B2 molecule, and the Latin word for yellow–flavus–because vitamin B2 as a compound is yellow ^[1].

2. What is riboflavin mechanism of action and function?

Riboflavin acts as an activating substance (cofactor, coenzyme) for enzymes involved in tissue respiration and thus production of energy from carbohydrates, proteins and fats ^[1]. It is also involved in the metabolism of vitamin B3 (niacin), B6 (pyridoxine), B9 (folate) and iron ^[1].

3. What are health benefits of high vitamin B2 doses (400 mg/day)?

Riboflavin in a dose 400 mg/day may help reduce migraine headache frequency in adults ^[3]. However, in one 2004 study, a combination of riboflavin 400 mg, magnesium 300 mg and feverfew herb extract 100 mg was not more effective than 25 mg of riboflavin alone ^[15].

4. Is vitamin B2 an antioxidant?

On the level of the chemical reactions, vitamin B2 acts as an antioxidant, but no health benefits of vitamin B2 supplements related to its antioxidant activity have been proven so far in humans ^[1].