Benefits
Energy metabolism
Riboflavin forms FMN and FAD, coenzymes the body needs to turn carbohydrates, fats and proteins into usable energy. This is a requirement, not a boost: correcting a real shortfall restores normal function, but there is limited evidence that extra riboflavin raises energy levels in someone whose intake is already adequate.
High-dose use studied in adults (400 mg per day)
In a 3-month placebo-controlled trial in 55 adults with migraine, 400 mg a day reduced attack frequency and headache days; 59% had at least 50% fewer headache days versus 15% on placebo. A review of 11 trials found consistent results in 5 adult trials but mixed results in children, and a trial in 42 children using 50 mg a day found no reduction in attacks.
Blood pressure in people with the MTHFR 677TT gene variant
Riboflavin is the cofactor for the enzyme MTHFR. In a 16-week trial in 91 adults with treated high blood pressure and the MTHFR 677TT genotype, 1.6 mg a day lowered systolic pressure by about 5.6 mmHg more than placebo, while diastolic pressure did not change significantly. These results apply to this gene variant only.
Antioxidant enzyme support
FAD is needed by glutathione reductase, the enzyme that keeps the antioxidant glutathione in its active form. This is established biochemistry; no study cited here tested whether riboflavin supplements reduce oxidative damage in people who are not deficient.
Skin, lips and mouth
Signs of riboflavin deficiency include skin disorders, cracks at the corners of the mouth, swollen cracked lips, sore throat and hair loss. Getting enough riboflavin prevents these deficiency signs; nothing cited here shows that extra riboflavin improves skin in someone who already gets enough.
Iron handling and red blood cells
A review of riboflavin and health found reasonably good evidence that poor riboflavin status interferes with iron handling and contributes to anemia when iron intake is low. This comes from deficiency research, not from trials of supplements in people with adequate intake.
Mechanism of action
Coenzyme role
Riboflavin is converted into FMN and FAD, which carry electrons in redox reactions throughout metabolism.
Energy metabolism
FMN and FAD are needed by flavoproteins that break down carbohydrates, fats and proteins, including enzymes of the mitochondrial energy pathways that produce ATP.
Enzyme cofactor
FAD is a cofactor for glutathione reductase, which maintains reduced glutathione for antioxidant defense, and for MTHFR, an enzyme in folate and homocysteine metabolism.
Other B vitamins
Flavin coenzymes are needed to metabolize other B vitamins, notably vitamin B6 and folate, and to convert the amino acid tryptophan into niacin.
Clinical trials
Randomized, placebo-controlled trial of riboflavin 400 mg a day versus placebo for 3 months, analyzed by intention to treat. (Schoenen et al. 1998, Neurology)
55 adults with migraine.
Riboflavin reduced attack frequency (P=0.005) and headache days (P=0.012) more than placebo. 59% of the riboflavin group had at least 50% fewer headache days versus 15% on placebo (P=0.002). Three minor adverse events occurred: diarrhea and frequent urination in two people on riboflavin, and abdominal cramps in one on placebo. A single small 3-month trial at a dose far above nutritional needs.
Randomized, double-blind, placebo-controlled crossover trial: 16 weeks of riboflavin 50 mg a day and 16 weeks of placebo, with a 4-week washout. (Bruijn et al. 2010, Cephalalgia)
42 children aged 6 to 13 with migraine, 14 of whom also had tension-type headache.
The reduction in migraine attack frequency did not differ between riboflavin and placebo (P=0.44), and the authors concluded there is no evidence that 50 mg prevents migraine attacks in children. Headaches with a tension-type pattern fell more with riboflavin (P=0.04).
Randomized, placebo-controlled trial of riboflavin 1.6 mg a day for 16 weeks in adults with treated hypertension selected for the MTHFR 677TT genotype. (Wilson et al. 2013, Hypertension)
91 adults with high blood pressure and the MTHFR 677TT genotype, identified from 1,427 patients; most were taking several blood pressure medications.
Riboflavin status improved (P<0.001) and systolic blood pressure fell by 5.6 mmHg more than placebo (P=0.033); the change in diastolic pressure was not significant. The result applies to people with this gene variant, alongside their usual medical care.
Follow-up of an earlier 16-week riboflavin trial; participants with the TT genotype received riboflavin 1.6 mg a day or placebo for 16 weeks, with treatment groups reversed from the first trial. (Wilson et al. 2012, Am J Clin Nutr)
83 adults with cardiovascular disease from the original trial, of whom 31 had the MTHFR 677TT genotype.
Across both intervention periods, riboflavin lowered systolic blood pressure by 9.2 mmHg (P=0.001) and diastolic by 6.0 mmHg (P=0.003) in the TT group. A small genotype-selected group studied by one research team.