Vitamin B2 (Riboflavin)
What is it?
Also known as vitamin B2, riboflavin was the second B complex vitamin to be discovered. In pure form it is a yellow-orange, water soluble compound.
What it does in the body
What it does in the body
Metabolism
Riboflavin is part of two coenzymes known as flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) which are essential for tissue respiration and the generation of energy from the metabolism of carbohydrates, amino acids and fats. Riboflavin is vital for normal reproduction, growth, repair and development of body tissues including the skin, hair, nails, connective tissue and immune system. Riboflavin is mainly converted into FAD and FMN in the small intestine, liver, heart and kidney.
Brain and nerve function
Nerve development and the metabolism of brain neurotransmitters require riboflavin.
Blood cells
Blood cells require riboflavin for their development and for iron metabolism.
Hormones and glands
Riboflavin is involved in adrenal gland function and in the production and regulation of certain hormones.
Absorption and metabolism
Riboflavin is easily absorbed from food. A small amount is stored in the liver and kidneys, but amounts above about 25 mg are excreted in the urine so a regular dietary intake of is it necessary. Excess riboflavin excreted in the urine causes it to become bright yellow in color, which many people notice when they take B vitamin supplements.
Deficiencies
Severe riboflavin deficiency is rare and often occurs with other B vitamin deficiencies. Symptoms include red, swollen, cracked lips, mouth and tongue; aversion to bright light; loss of appetite; weakness; fatigue; depression; anemia; loss of vision; burning and itching of the eyes; and dermatitis. Decreased sensitivity to touch, temperature, vibration and position may occur in the hands and feet. Riboflavin deficiency may be associated with an increase in throat and esophageal cancers. Cancer, cardiac disease and diabetes may lead to or exacerbate riboflavin deficiency.
People who are lactose intolerant and who cannot drink milk (which is a good source of riboflavin) may be at risk of deficiency. Those with malabsorption disorders, diarrhea and irritable bowel syndrome may also be at risk. Mild riboflavin deficiency may be quite common in elderly people whose diets are low in red meat and dairy products. Systemic infections, even without gastrointestinal tract involvement, may increase riboflavin requirements.
Cataract
Riboflavin deficiency may be associated with the development of cataracts. Researchers involved in the New York State Lens Opacities Case-Control Study assessed the risk factors for various types of cataract among 1380 participants aged 40 to 79 years. They found an increased risk with low levels of several nutrient including riboflavin.1 Riboflavin is necessary for the activity of an enzyme which exerts protective effects on the eye.
Rheumatoid arthritis
In a 1996 study UK researchers assessed the links between riboflavin status and rheumatoid arthritis in patients and in those without the disease. The results showed that biochemical riboflavin deficiency was more frequent in patients with active disease. Riboflavin is necessary for the action of an enzyme which has anti-inflammatory activity and deficiency could reduce the activity and beneficial effect of that enzyme.2
Sources
The richest sources of riboflavin include organ meats such as liver, kidney and heart. Milk, yeast, cheese, oily fish, eggs and dark green leafy vegetables are also rich sources. Flour and cereals are enriched with riboflavin.
Riboflavin is stable when heated but will leach into cooking water. It is easily destroyed by light, and foods stored in clear containers will lose their riboflavin content in a short period of time. Alkalis, such as baking soda, also destroy riboflavin.
| Food | Amount | Riboflavin (mg) |
|---|---|---|
| Lambs liver, fried | 100g | 4.03 |
| Almonds, blanched | ½ cup | 0.98 |
| Scallops, fried | 6 pieces | 0.85 |
| Pink salmon, canned | 1 can | 0.84 |
| Malted milk powder | 4-5 tsp | 0.75 |
| All Bran | ½ cup | 0.42 |
| Spinach, cooked | 1 cup | 0.42 |
| Milk, whole and skim | 1 cup | 0.40 |
| Mackerel, cooked | 1 fillet | 0.36 |
| Veal, cooked | 100g | 0.35 |
| Wheatgerm | ½ cup | 0.29 |
| Lamb, cooked | 100g | 0.27 |
| Pork sausages, grilled | 100g | 0.25 |
| Eggs, boiled | 1 medium | 0.25 |
| Milk chocolate | 100g | 0.24 |
| Fruit yoghurt | 1 tub | 0.23 |
| Feta cheese | 1 cup | 0.23 |
| Oats | 1 cup | 0.21 |
| Beef steak, grilled | 100g | 0.21 |
| Green peas | 1 cup | 0.19 |
| Soy milk | 1 cup | 0.17 |
| Pork, cooked | 100g | 0.11 |
| Cheddar cheese | 1 slice | 0.11 |
| Brazil nuts | ¼ cup | 0.17 |
Recommended dietary allowances (RDA)
The RDAs for riboflavin in the USA were revised in 1998.
| Men | Women | Pregnancy | Lactation | |
|---|---|---|---|---|
| USA | 1.3 mg | 1.1 mg | 1.4 mg | 1.6 mg |
| UK | 1.0 mg | 0.8 mg | 1.0 mg | 0.9 mg |
| Australia | 1.7 mg | 1.2 mg | 1.5 mg | 1.7 mg |
The Australian recommended daily intake is based on a requirement of 0.15 mg for every 1000 kJ of food taken in. Women pregnant with or breastfeeding more than one baby have higher riboflavin requirements.
Supplements
Supplements may be of benefit for those at risk of deficiency, particularly for elderly people, alcoholics or those with absorption difficulties. Stress and heavy exercise may increase riboflavin needs.
Toxic effects of excess intake
High doses of riboflavin are not well absorbed so the risk of toxicity is very low. Possible reactions to excess intakes include itching, numbness, sensations of burning or pricking, and sensitivity to sunlight.
Therapeutic uses of supplements
Riboflavin supplements are used to treat or prevent riboflavin deficiency.
Anemia
Riboflavin supplements may be of benefit in the treatment of sickle cell anemia and may also enhance the effectiveness of iron supplements when these are used to treat anemia.
Migraine
High doses of riboflavin may be effective in the treatment of migraine. In a 1998 study done in Belgium, researchers tested the effects of either 400 mg of riboflavin or a placebo on 55 patients with migraine in a randomized trial lasting three months. The results showed reductions in attack frequency and headache days. Fifty nine per cent of patients in the riboflavin group improved compared to 15 per cent in the placebo group. No serious side effects occurred. The researchers felt that because of its effectiveness, excellent tolerability, and low cost, riboflavin is a valuable option for migraine prevention.3
Carpal tunnel syndrome
Riboflavin may help to relieve the symptoms of carpal tunnel syndrome, a neurological disorder of the wrists and hands which causes pain and stiffness.Riboflavin is usually combined with vitamin B6 to treat this disorder and treatment with both vitamins may be more effective than treatment with B6 alone.4,5 This is possibly due to the fact that riboflavin is involved in the conversion of vitamin B6 to its active form.
Other uses
Skin problems such as acne, dermatitis, eczema and ulcers; eye problems such as cataracts; and muscle cramps, may be improved by treatment with riboflavin supplements. Like the other B vitamins, riboflavin can be used to treat stress.
Interactions
With other nutrients
Riboflavin is necessary for the activation of vitamin B6 and is also necessary for the conversion of tryptophan to niacin.
With drugs
Sulfa drugs, anti-malarial drugs, estrogen, cathartic agents and alcohol may interfere with riboflavin metabolism. High doses of riboflavin can reduce the effectiveness of the anticancer drug methotrexate. Some antibiotics and phenothiazine drugs may increase riboflavin excretion.
Riboflavin must be activated in the liver. This activation may be inhibited by major tranquilizers, and some antidepressants. Long-term use of barbiturates may adversely affect riboflavin status.
Cautions
High doses of riboflavin can produce urine discoloration which can affect urine analysis results.