Vitamin B2 is a water-soluble vitamin, so it dissolves in water. All vitamins are either water soluble or fat soluble. Water-soluble vitamins are carried through the bloodstream, and whatever is not needed passes out of the body in urine.
People need to consume vitamin B2 every day, because the body can only store small amounts, and supplies go down rapidly.
Riboflavin occurs naturally in some foods, added to others, and it can be taken as supplements. Most of it is absorbed in the small intestine.
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Why is vitamin B2 important?
Cruciferous vegetables are a source of vitamin B2, but steam them rather than boiling them.
Vitamin B2 helps break down proteins, fats, and carbohydrates. It plays a vital role in maintaining the body's energy supply.
Riboflavin helps convert carbohydrates into adenosine triphosphate (ATP). The human body produces ATP from food, and ATP produces energy as the body requires it. The compound ATP is vital for storing energy in muscles.
Along with vitamin A, vitamin B is essential for:
- Maintaining the mucous membranes in the digestive system
- Maintaining a healthy liver
- Converting tryptophan into niacin, an amino acid
- Keeping the eyes, nerves, muscles and skin healthy
- Absorbing and activating iron, folic acid, and vitamins B1, B3 and B6
- Hormone production by the adrenal glands
- Preventing the development of cataracts
- Fetal development, especially in areas where vitamin deficiency is common
Sources of vitamin B2
Vitamin B2 comes from food.
Sources of B2 include:
Meat, fish, and dairy products provide vitamin B2.
- Fish, meat, and poultry, such as turkey, chicken, beef, kidneys, and liver
- Dairy products
- Fortified cereals
- Lima beans, navy beans, and peas
- Sweet potatoes
- Cruciferous vegetables, such as broccoli, Brussels sprouts, spinach, dandelion greens, and watercress
- Whole-grain breads, enriched breads, and wheat bran
- Yeast extract
Vitamin B2 is water soluble, so cooking foods can cause it to be lost. About twice as much B2 is lost through boiling as it is through steaming or microwaving.
How much vitamin B2 do we need?
According to Oregon State University, the recommended daily allowance (RDA) of vitamin B2 in for men aged 19 years and over is 1.3 milligrams per day, and for women, it is 1.1 milligram per day. During pregnancy, women should have 1.4 milligrams per day, and when breastfeeding, 1.6 milligrams per day.
Vitamin B2 deficiency
Vitamin B2 deficiency is a significant risk when diet is poor, because the human body excretes the vitamin continuously, so it is not stored. A person who has a B2 deficiency normally lacks other vitamins too.
There are two types of riboflavin deficiency:
- Primary riboflavin deficiency happens when the person's diet is poor in vitamin B2
- Secondary riboflavin deficiency happens for another reason, maybe because the intestines cannot absorb the vitamin properly, or the body cannot use it, or because it is being excreted too rapidly
Riboflavin deficiency is also known as ariboflavinosis.
Signs and symptoms of deficiency include:
A lack of vitamin B2 can lead to mouth ulcers and other complaints.
- Angular cheilitis, or cracks at the corners of the mouth
- Cracked lips
- Dry skin
- Inflammation of the lining of the mouth
- Inflammation of the tongue
- Mouth ulcers
- Red lips
- Sore throat
- Scrotal dermatitis
- Fluid in mucous membranes
- Iron-deficiency anemia
- Eyes may be sensitive to bright light, and they may be itchy, watery, or bloodshot
People who drink excessive amounts of alcohol are at greater risk of vitamin B deficiency.
Safety concerns and risks
Normally, vitamin B2 is considered safe. An overdose is unlikely, as the body can absorb up to around 27 milligrams of riboflavin, and it expels any additional amounts in the urine.
However, it is important to talk to a physician before taking any supplements, especially as these can interfere with other medications.
Supplements can interact with other medications, and B2 supplements may impact the effectiveness of some drugs, such as anticholinergic medications and tetracycline.
Sometimes a doctor may recommend supplementation, for example, if a patient is using a drug that can interfere with the absorption of riboflavin.
Drugs that may interfere with riboflavin levels in the body include:
- Tricyclic antidepressants, such as imipramine, or Tofranil
- Some antipsychotic drugs, such as chlorpromazine, or Thorazine
- Methotrexate, used for cancer and autoimmune diseases, such as rheumatoid arthritis
- Phenytoin, or Dilantin, used to control seizures
- Probenecid, for gout
- Thiazide diuretics, or water pills
Doxorubicin, a drug used in cancer therapy, may deplete levels of riboflavin, and riboflavin may affect how doxorubicin works.
The University of Maryland Medical Center (UMM) note that very high amounts of vitamin B2 may lead to itching, numbness, burning or prickling, yellow or orange urine and sensitivity to light. To prevent an imbalance of B vitamins, they suggest using a B-complex vitamin if supplementation is needed.