Vitamin B2 (riboflavin) is an essential vitamin that participates in many biological reactions. Supplementation is effective for riboflavin deficiency. In addition, research suggests it may help prevent migraine attacks, cataracts, and bone loss, improve depression, and kill blood-borne pathogens. Read below to learn more about B2, its main health benefits, and recommended doses.
What Is Vitamin B2?
Vitamin B2, also known as riboflavin, is a vitamin that plays an integral role in the body. It is activated to produce the cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are necessary for many biological reactions such as those required for breaking down fats, proteins, and carbohydrates [1, 2].
Vitamin B2 is essential to maintain the integrity of mucous membranes, skin, eyes, liver, and nervous system. This vitamin is also involved in the metabolism of other vitamins such as B3, B6, B9, and B12 .
The main dietary sources of this vitamin include :
- Organ meats
- Dairy products
- Collard greens
- Fortified cereals
Vitamin B2 is also available in supplements for people concerned with their dietary B2 intake or who take it to reduce migraines, prevent cataracts, or maintain healthy skin, hair, and nails, among others.
- Essential vitamin
- Effective at improving vitamin B2 deficiency and high blood homocysteine levels
- May reduce the risk of cataracts
- May reduce migraine attacks
- May kill blood-borne pathogens
- May reduce depression
- May prevent bone loss
- May improve cognitive function
- Insufficient evidence for some benefits
- Most people don’t need supplementation
- Repeated supplementation with high doses can be toxic to the liver and retinas
- Has been reported to cause anaphylaxis
Vitamin B2 Deficiency and High Blood Homocysteine
Methylenetetrahydrofolate reductase (MTHFR) is a key regulator of homocysteine (and folate) metabolism. Mutations in the gene that encodes this enzyme cause high blood homocysteine levels (hyperhomocysteinemia), which greatly increases the risk of heart disease by damaging the blood vessels and promoting their hardening and clogging [3, 4].
Because riboflavin is required as a cofactor for MTHFR function, deficiency in this vitamin greatly increases blood homocysteine levels. Supplementation with riboflavin is frequently used to lower blood homocysteine levels in people with a deficiency in this vitamin or with the underactive MTHFR variant (677TT), thus reducing the risk of heart disease [5, 6, 7].
1) Eye Health
Increased dietary consumption of riboflavin has been associated with a significant decrease in age-related cataracts and lens opacity in several studies [8, 9, 10].
Corneal ectasia is the progressive thinning of the cornea, often as an adverse effect of laser eye surgery. The combination of riboflavin with UVA radiation (corneal cross-linking) triggers a reaction that strengthens the cornea by producing thicker collagen fibers. Multiple studies with follow-up periods of up to 6 years have shown disease stabilization and improvement with this procedure [11, 12, 13, 14, 15, 16, 17, 18, 19, 20].
Corneal cross-linking was also beneficial to patients with eye inflammation [21, 22].
Taken together, the evidence suggests that riboflavin helps prevent cataracts and its use combined with UVA radiation helps stop the progression of corneal ectasia and improve eye inflammation. You may discuss with your doctor if any of these strategies may be beneficial in your case.
Although the exact mechanism remains unclear, some scientists believe that mitochondrial defects in people with migraines disturb energy metabolism in the brain. This possibly increases the excitability of brain cells and renders them hyperresponsive to migraine triggers .
Riboflavin has been suggested to reverse these mitochondrial defects. Three studies on over 100 adults showed that riboflavin supplementation helped prevent migraine attacks. Its combination with ubiquinone and magnesium was similarly effective in another trial on130 people [24, 25, 26, 27].
However, 2 studies on 60 children found riboflavin ineffective [28, 29].
Based on the available evidence, 2 meta-analyses concluded that supplementation with vitamin B2 is a safe, inexpensive, and effective way to prevent migraine attacks in adults, but not in children [30, 31].
The evidence suggests that riboflavin helps prevent migraines in adults but not in children. You may use riboflavin supplements as an add-on to your treatment regime if your doctor recommends it.
3) Killing Blood-Borne Pathogens
Riboflavin activated by UV radiation damages the DNA and RNA of viruses, bacteria, and parasites and reduces their growth and survival. This technology can be applied to donated blood to prevent the transmission of infections with blood transfusions .
Treatment of whole blood with this technology reduced the infectivity of several:
- Bacteria (such as E. coli, Staphylococcus aureus, S. pyogenes, and Klebsiella pneumoniae) [33, 34]
- Viruses (such as hepatitis B, ebola, herpes simplex, and polio) [35, 36, 33]
- Parasites (such as Babesia microti, Leishmania donovani, Plasmodium falciparum, and Trypanosoma cruzi) [37, 38, 39, 40]
In a clinical trial on over 200 people receiving blood transfusions, this technology reduced the incidence of transfusion-transmitted malaria .
In another trial on 70 children with severe conditions that required frequent transfusions, this technology didn’t increase the frequency of adverse reactions and excessive immune response .
Importantly, the technology didn’t reduce the survival and viability of red blood cells and platelets [43, 44, 45, 46, 47].
All in all, this technology seems effective at killing blood-borne pathogens while preserving the viability and function of blood cells.
In a study on 98 female nurses, marginal riboflavin deficiency was associated with depression .
In another study on over 6,500 adolescents, vitamin B2 intake was associated with a reduced incidence of depression, but only in girls .
In a clinical trial on 14 elderly, depressed people, supplementation with B vitamins (B1, B2, and B6) as an add-on to tricyclic antidepressant treatment improved depressive symptoms and cognitive function .
In another trial on 29 young healthy adults, supplementation with 10x the recommended daily dose of 9 vitamins for 1 year improved mood. The improvement was especially associated with increased blood levels of riboflavin and vitamin B6 .
In a study on 865 pregnant women, the consumption of riboflavin during the third quartile was associated with a reduced incidence of postpartum depression .
Taken together, the evidence suggests that riboflavin helps prevent depression, especially in women. You may discuss with your doctor if supplementing with riboflavin may be helpful in your case. Importantly, never use it as a replacement for proven therapies prescribed by your doctor.
5) Bone Health
In a study of people with hyperhomocysteinemia (MTHFR C677T “AA” genotype), those who had the lowest intake of riboflavin had a 1.8-2.6X increased incidence of fractures. Similarly, another study on over 1,200 women found that those with this genotype and low bone mineral density could increase it by eating more vitamin B2 [53, 54].
In another study on over 5,300 elderly people, high dietary vitamin B2 was associated with increased bone mineral density in the neck .
Feeding pregnant rats with B2-deficient diets induced abnormal fetal development and skeletal malformations in a very old study .
Vitamin B2 also induced the development of immature bone-forming cells (osteoblasts) in test tubes .
Although a bit limited, the evidence suggests that riboflavin supplementation may help prevent bone loss in risk populations. If this is your case, you may discuss this complementary approach with your doctor.
1) Cognitive Function
Dietary vitamin B2 intake was associated with improved cognitive test scores in a study on 554 primary school children in rural Kenya .
In another study on 137 elderly people, high vitamin B2 intake was associated with improved abstract performance .
Although the results are promising, the evidence is insufficient to support the use of riboflavin to enhance cognitive function. Further clinical research is required.
Riboflavin consumption (in addition to vitamin B6) was associated with a reduced incidence of colorectal cancer in a study on over 88,000 postmenopausal women .
Another study on over 6,500 people found that high vitamin B6 was associated with reduced incidence of proximal colon cancer but increased rectal cancer in women .
A meta-analysis of 10 studies and over 12,000 women found that vitamin B2 intake was only weakly associated with a reduced risk of breast cancer .
A study on over 41,000 people found that high vitamin B2 intake was only weakly associated with reduced incidence of lung cancer in smokers, but not in non-smokers or former smokers. However, another study on almost 386,000 found no association, even in smokers. Similarly, vitamin B2 levels were not associated with lung cancer in a study on almost 90,000 women [63, 64, 65].
In a study on almost 15,000 men, there was no association between vitamin B2 intake and prostate cancer incidence or death rate .
In a study of 21 esophageal cancer cases from two Iranian regions with low and high cancer risk, the daily vitamin B2 intake of all the cases was below the average .
All in all, the evidence is mixed and mainly suggests that vitamin B2 intake has little or no effect on cancer development. More research is needed to draw firm conclusions.
Vitamin B2 (along with other B vitamins) helped reduce the length, pain intensity, and frequency of nocturnal leg cramps in a clinical trial on 28 elderly people .
A single, small clinical trial cannot be considered sufficient evidence that riboflavin reduces cramps. Larger, more robust clinical trials are needed to validate this preliminary result.
Animal and Cell Research (Lack of Evidence)
No clinical evidence supports the use of riboflavin for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies should not be interpreted as supportive of any health benefit.
Riboflavin significantly reduced the expression of HMGB1 (high-mobility group protein B1), which is one of the factors responsible for inflammation in systemic inflammatory response syndrome (sepsis), in mice .
In different animal experimental models, riboflavin supplementation reduced inflammation and pain .
In mice, vitamin B2 supplementation increased iron and zinc uptake, rate of conception, weight gain during pregnancy, weight of the pups, and percentage of hemoglobin .
Riboflavin protected mice from liver damage caused by a toxic chemical (carbon tetrachloride) and restored blood supply (ischemia-reperfusion injury) [72, 73].
In mice with multiple sclerosis, supplementary riboflavin helped suppress the neurological disability symptoms of this condition .
However, riboflavin supplementation failed to improve the disability status of multiple sclerosis in a clinical trial on 29 people .
The FDA has established the following recommended dietary allowances (RDA) of vitamin B2 :
- Infants of 0-6 months: 0.3 mg
- Infants of 7-12 months: 0.4 mg
- Children of 1-3 years: 0.5 mg
- Children of 4-8 years: 0.6 mg
- Children of 9-13 years: 0.9 mg
- Males of 14 years or older: 1.3 mg
- Girls of 14-18 years: 1 mg
- Women over 18 years: 1.1 mg
- Pregnant women: 1.4 mg
- Breastfeeding women: 1.6 mg
Vitamin B2 Deficiency
Vitamin B2 deficiency is extremely rare in healthy, non-malnourished people. Large studies found it affected 0% of children aged 2-8 years old, 5% of girls aged 14-18, and 2% of adults .
Vitamin B2 is more common in people with digestive and absorptive disorders, who have undergone bowel resection, are malnourished, or affected by rare genetic syndromes (such as Brown-Vialetto-Van Laere and Fazio-Londe) .
Other causes of deficiency include hormone disorders (aldosterone and thyroid hormone insufficiency), therapy with some drugs (such as tricyclic antidepressants and tetracyclic antibiotics), and alcohol abuse .
Classical signs of vitamin B2 deficiency include [2, 1, 78, 79, 80]:
- Cracks on the lips and at the corners of the mouth
- Inflammation of the mouth lining
- Mouth ulcers
- Red lips
- Sore throat
- Dry skin
- Eczema on the scrotum
- Fluid in the mucous membranes
- Hypersensitive, watery, and itchy eyes
However, because vitamin B2 deficiency is almost invariably associated with low levels of other vitamins, many of these signs are actually caused by other deficiencies .
If you experience several of these symptoms, consult your doctor to establish the underlying cause and develop an appropriate plan to improve your health.
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.
Call your doctor for medical advice about side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.
Riboflavin is likely safe when taken with food or at normal supplement doses. In some people, it can cause the urine to turn yellow-orange in color. When taken in high amounts it may cause diarrhea and increased urine .
Taking high doses (over 100 mg) repeatedly can cause the buildup of a toxic byproduct that is formed when riboflavin reacts with light (tryptophan-riboflavin). This compound causes oxidative damage and is especially toxic to the liver and the retina .
A 15-year-old boy developed a severe allergic reaction (anaphylaxis) from a dietary supplement with riboflavin .