One group of researchers treated 49 migraine patients with large amounts of vitamin B2 (400 mg per day). Both the frequency and severity of migraines decreased by more than two-thirds.¹ In a follow-up three-month, double-blind trial, the same researchers reported that 59% of patients assigned to receive vitamin B2 had at least a 50% reduction in the number of headache days, whereas only 15% of those assigned to receive a placebo experienced that degree of improvement.² The effects of vitamin B2 were most pronounced during the final month of the trial.³ In a preliminary study, a much smaller amount of vitamin B2 (25 mg per day for three months) reduced the frequency of migraines by about one-third in chronic migraine sufferers.⁴

All of the studies that found riboflavin to be effective for preventing migraine were conducted in adults. In a double-blind trial, supplementation with 200 mg per day of riboflavin did not decrease the frequency or severity of migraines in children whose average age was 11 years.⁵

Deficiencies of iron, vitamin B12, and folic acid are the most common nutritional causes of anemia.⁶ Although rare, severe deficiencies of several other vitamins and minerals, including vitamin A,^7,8vitamin B2,⁹vitamin B6,^10,11vitamin C,¹² and copper,^13,14 can also cause anemia by various mechanisms. Rare genetic disorders can cause anemias that may improve with large amounts of supplements such as vitamin B1.^15,16

Vitamin B2 (riboflavin) supplementation (1.6 mg per day) has been shown to lower homocysteine levels by 22 to 40% in a subset of the population that has a certain genetic variant of an enzyme involved in folic acid metabolism (the 677Cà T polymorphism for the methylenetetrahydrofolate reductase gene).¹⁷ Approximately 15 to 20% of the population carries this gene and could benefic from taking riboflavin. Since genetic testing is expensive and not readily available, it would seem reasonable for all people trying to lower their homocysteine levels to include riboflavin in their regimen of B vitamin supplementation.

Women who are deficient in vitamin B2 (riboflavin) are more likely to develop preeclampsia than women with normal vitamin B2 levels.¹⁸ These results were observed in a developing country, where vitamin B2 deficiencies are more common than in the United States. Nevertheless, insufficient vitamin B2 may contribute to the abnormalities underlying the disease process.

People with low blood levels of antioxidants and those who eat few antioxidant-rich fruits and vegetables have been reported to be at high risk for cataracts.^19,20

Vitamin B2 and vitamin B3 are needed to protect glutathione, an important antioxidant in the eye. Vitamin B2 deficiency has been linked to cataracts.^21,22 Older people taking 3 mg of vitamin B2 and 40 mg of vitamin B3 per day were partly protected against cataracts in one trial.²³ However, the intake of vitamin B2 in China is relatively low, and it is not clear whether supplementation would help prevent cataracts in populations where vitamin B2 intake is higher.