Vitamin B2 (Riboflavin)

What is riboflavin and what does it do in the body?

Riboflavin (vitamin B2) is the core component of two main coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). These coenzymes play a role in energy production, cell function, growth and development, and in fat, drug, and steroid metabolism. According to NIH, conversion of tryptophan to niacin requires FAD, whereas conversion of B6 to its coenzyme form depends on FMN; riboflavin also helps keep blood homocysteine normal. ^[1] EFSA notes that FAD is also required for the enzyme methylenetetrahydrofolate reductase (MTHFR) in the folate cycle. ^[2]

More than 90% of the riboflavin in foods is in the form of FAD or FMN. According to NIH, the body absorbs very little riboflavin beyond 27 mg in a single dose and stores only a small amount in the liver, heart, and kidneys; the excess is either not absorbed or is excreted in urine. About 95% of FAD and FMN in foods is bioavailable, up to about 27 mg per meal or dose. Large-intestine bacteria also produce free riboflavin. Riboflavin is light-sensitive; for this reason, prolonged light therapy for neonatal jaundice or skin diseases can lead to deficiency. ^[1]

How much riboflavin is needed per day?

The U.S. Food and Nutrition Board, on which NIH relies, sets the RDA for adults over 19 years at 1.3 mg for men and 1.1 mg for women; it is 1.4 mg in pregnancy and 1.6 mg in breastfeeding. ^[1] EFSA (2017), using the inflection point of the urinary riboflavin excretion curve as a biomarker, set the adult average requirement (AR) at 1.3 mg/day and the population reference intake (PRI) at 1.6 mg/day; the PRI was derived with a 10% coefficient of variation that accounts for variability in requirement, physical activity, and the MTHFR 677TT genotype. The PRI is 1.9 and 2.0 mg/day in pregnancy and breastfeeding, respectively. ^[2] In Türkiye, a 2008 book published on the HSGM website gives the riboflavin requirement as 0.6 mg per 1,000 calories. ^[8]

These three values come from different institutions, and their criteria are not the same: NIH uses the RDA, EFSA uses the PRI, and the Türkiye source gives a requirement tied to energy intake. According to NIH, based on NHANES 2003–2006, fewer than 6% of the U.S. population consume less riboflavin than the EAR from food and supplements. ^[1]

Which foods contain riboflavin?

Foods rich in riboflavin are eggs, organ meats (kidney and liver), lean meat, and milk. Most riboflavin in foods is in the FAD form; in eggs and milk, the predominant form is free riboflavin. In the U.S. and many countries, grains and grain products are fortified with riboflavin. ^[1]

The table is based on NIH’s U.S. servings and the U.S. Daily Value (DV) of 1.3 mg for adults; 20% and above counts as a “high source,” so eggs are not a high source. The amount lost into boiling water is about twice that with steaming or microwave methods. ^[1] In Türkiye, the book on the HSGM website lists liver, meat, milk and milk products, eggs, cheese, fish, green leafy vegetables, and grains as sources, and includes warnings against leaving foods in light and against discarding cooking water and yogurt whey. ^[8]

Who gets riboflavin deficiency?

According to NIH, deficiency (ariboflavinosis) is extremely rare in the U.S. Symptoms are skin disorders, redness and swelling of the mouth and throat mucosa, cracks at the corners of the mouth (angular stomatitis), cracked lips (cheilosis), hair loss, sore throat, and redness and itching of the eyes; in severe and prolonged deficiency, anemia and cataract can develop. Because people with deficiency usually have other nutrient deficiencies as well, some of the symptoms may be caused by those. Early changes reverse easily, but supplements rarely reverse later structural changes such as cataract. ^[1]

The groups at risk are the following: ^[1]

• Vegetarian athletes: Exercise strains the pathways that use riboflavin; the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine state that this group is at risk of deficiency. ^[1]
• Pregnant and breastfeeding women who rarely eat meat and dairy products: Deficiency in pregnancy can increase the risk of preeclampsia. ^[1]
• Vegans and people with low dairy intake. ^[1]
• People with riboflavin transporter deficiency: In a rare neurological disease caused by mutations in the SLC52A3 or SLC52A2 genes, high-dose riboflavin can be lifesaving, especially if started shortly after symptoms appear. ^[1]

Status assessment: According to NIH, riboflavin status is not routinely measured in healthy people. An erythrocyte glutathione reductase activation coefficient (EGRAC) of 1.2 or below is generally interpreted as adequate, 1.2–1.4 as marginally deficient, and above 1.4 as deficient; however, the appropriate cutoff values are uncertain, and the test cannot be used in people with glucose-6-phosphate dehydrogenase deficiency. A 24-hour urinary excretion of at least 120 µg/day in adults indicates adequacy, and below 40 µg/day indicates deficiency. ^[1] EFSA, on the other hand, states that EGRAC is a useful biomarker and that 1.3 or below indicates adequate status in all population groups; however, it does not consider EGRAC data alone sufficient for deriving a reference value. The cutoff is 1.2 for NIH and 1.3 for EFSA. ^[2]

Does riboflavin help migraine?

Mitochondrial dysfunction is thought to play a role in some types of migraine, and because riboflavin is required for mitochondrial function, it has been investigated. ^[1]

Adults: In the 1998 randomized study by Schoenen et al., 55 patients with migraine were given 400 mg of riboflavin or placebo daily for 3 months. In the intention-to-treat analysis, attack frequency (p=0.005) and the number of headache days (p=0.012) decreased; the proportion of “responders” with at least 50% improvement in headache days was 15% in the placebo group and 59% in the riboflavin group (p=0.002; number needed to treat 2.3). Three mild adverse events were seen: two in the riboflavin group (diarrhea, polyuria). ^[3] The 2022 meta-analysis by Chen et al., combining eight RCTs and one controlled clinical trial (673 people in total), reported that B2 supplementation significantly reduced migraine days (p=0.005; I²=89%), duration (p=0.003), frequency (p=0.001; I²=65%), and pain score (p=0.015; I²=84%); the high heterogeneity between studies limits the certainty of the result. ^[5]

Guidelines: The 2012 guideline update by AAN and AHS assigned 15 of 49 class I/II articles to complementary treatments and rated riboflavin and magnesium “probably effective” (level B). ^[6] The AAN/AHS 2012 guideline was retired on 16 September 2015 because of butterbur safety concerns; AAN no longer supports its recommendations. This does not establish that riboflavin or magnesium is ineffective or harmful; the historical guideline should not be presented as current guidance. NIH reports that AAN and AHS concluded that riboflavin is probably effective for migraine prevention and recommended that it be offered for this purpose; it adds that the Canadian Headache Society also recommends a dose, but notes that the supporting evidence is of low quality and that side effects (such as a change in urine color) are minimal. ^[1] These guideline levels reflect limited-quality evidence, not certainty; the decision on use and dose belongs to a physician.

Children: In the double-blind RCT by MacLennan et al., 48 children were given 200 mg of riboflavin or placebo daily; a reduction of at least 50% in pain attacks occurred in 12/27 children on riboflavin and 14/21 on placebo (p=0.125), and there was no difference in primary or secondary outcomes; a high placebo response was notable. ^[4] NIH cites two small randomized studies in which 50–200 mg/day of riboflavin did not reduce the number or severity of migraines compared with placebo; in contrast, in a retrospective study of 41 children in Italy, attack frequency decreased (no control group). ^[1]

What is the relationship between the MTHFR 677TT genotype and blood pressure?

FAD is a cofactor of the MTHFR enzyme, and in the MTHFR 677C→T polymorphism the TT genotype is sensitive to riboflavin status; EFSA took this genotype into account when deriving the PRI. ^[2] Wilson et al. identified 157 people with the MTHFR 677TT genotype among 1,427 treated hypertensive patients (without overt cardiovascular disease); 91 took part in the study and received 1.6 mg of riboflavin or placebo daily for 16 weeks. A treatment effect of 5.6±2.6 mmHg on systolic blood pressure was found (p=0.033); the diastolic effect was not significant (p=0.291). The result applies only to people with this genotype who are on drug treatment and rests on a single randomized trial. ^[7]

The 2025 Cochrane review assessed four randomized trials involving 374 participants; three had a high overall risk of bias. The effect on systolic and diastolic blood pressure was very uncertain. This synthesis means that the positive finding from the single genotype-specific trial above should not be interpreted as an established blood-pressure-lowering effect. ^[10]

Riboflavin in pregnancy and breastfeeding

According to NIH, in pregnant and breastfeeding women who rarely eat meat or dairy products, deficiency can lead to adverse outcomes for both mother and infant, and deficiency in pregnancy can increase the risk of preeclampsia. The limited evidence on the benefit of riboflavin supplementation in pregnancy is mixed in both developed and developing countries. Intake in pregnancy is positively associated with the infant’s birth weight and length; infants of mothers consuming less than 1.2 mg per day are at higher risk of deficiency and some birth defects (such as heart outflow tract defects), but there is no association between maternal intake and the risk of cleft lip and palate. ^[1] These are association data and do not show that supplementation changes the outcome.

Does riboflavin prevent cancer?

According to NIH, the data are limited and mixed. In the Melbourne Collaborative Cohort Study (41,514 people, mean 15 years), a significant inverse association between dietary riboflavin and lung cancer risk across quintiles was found only in current smokers. In EPIC (385,747 people, up to 12 years) there was no association with colorectal cancer; in the Canadian National Breast Screening Study (89,835 women) there was no association with lung cancer; in the Women’s Health Initiative observational study (88,045 postmenopausal women), total riboflavin intake was associated with a lower risk of colorectal cancer. ^[1] These studies are observational; additional riboflavin has not been shown to change cancer risk.

Riboflavin safety and interactions

According to NIH, riboflavin from foods, even at many times the RDA, does not cause observable toxicity; its solubility and absorption capacity are limited. Because no adverse effects were reported at 400 mg per day for at least 3 months, the Food and Nutrition Board did not set an upper limit (UL); however, the board, noting that limited data do not mean high intake is without effect, calls for caution with excessive amounts. NIH states that riboflavin has no known clinically significant drug interaction. ^[1] Riboflavin is a yellow, naturally fluorescent vitamin; NIH notes that a change in urine color is mentioned as an example of a side effect in the Canadian Headache Society guideline. ^[1]

What is the status of riboflavin in Türkiye?

As a supplement, riboflavin falls under the Turkish Food Codex Communiqué on Dietary Supplements (2013/49) of the Ministry of Agriculture and Forestry. According to the current text with amendments incorporated, the Communiqué requires that only the vitamins and minerals listed in Annex-1 be used in the forms specified in Annex-2 and that daily maximum limits comply with Annex-3, does not permit statements on labels and in advertising claiming to prevent, treat, or cure disease, and prohibits the production and marketing of dietary supplements for infants and young children under 2 years (before the November 21, 2015 amendment, this limit was 4 years); products aimed at the 2–4 age group are evaluated separately by the Ministry. ^[9] Presenting a supplement as a treatment for a condition such as migraine cannot appear on labels and in advertising within this framework.

Evidence table: claim, population, and limits

This guide does not recommend personal doses; high-dose riboflavin for migraine, pregnancy, and regular medication use are evaluated with a physician.

Correction: 19 October 2026

The 2025 Cochrane synthesis was added to the blood-pressure assessment. Retirement of the 2012 migraine guideline is now explained in the text, summary card, table and FAQ.