Vitamin B2 (Riboflavin) is a water-soluble member of the B complex group of nutrients. It has been recognised as the yellow pigment in milk since 1879. The same yellow pigment was later identified in yeast and became known as the Yellow Enzyme. It was soon realised that the enzyme was essential for growth in man and vitamin B2 was then discovered. Riboflavin’s yellow colour is a natural characteristic. Following supplementation with the vitamin, the urine turns bright yellow. This is completely harmless and is a result of the body ridding itself of excess.
Richest food sources of riboflavin are:
- milk and dairy produce: yoghurt, eggs, cheese
- yeast extract (Bovril, marmite)
- brewer’s yeast
- liver and meat
- vegetables and beans (in lower quantities).
Unlike other members of the B complex family, riboflavin (B2) is plentiful in dairy foods but is relatively lacking in cereals and grains. For this reason, cereals of the type sold under proprietary brand names are sometimes fortified with the vitamin. Tea and beer both contain riboflavin but are not recommended as sources because of the detrimental effects of tannin and alcohol on the nutrient.
Vitamin B2 is quickly and easily absorbed through the soft intestinal wall. It is then carried in the blood to the tissues responsible for transforming it into a co-enzyme.
It is a water-soluble substance, which needs replenishing daily from dietary sources. Small amounts are found in the liver and kidneys but like other B vitamins, it is not stored there. Any excess is excreted from the body within hours of ingestion. The body knows how much it needs and rids itself efficiently of any surplus making it impossible to overdose on this vitamin.
Riboflavin is extremely susceptible to damage from light. When milk is left on the doorstep or even exposed to bright light on supermarket shelves, the riboflavin is converted to a substance called lumiflavin. Lumiflavin is quite inactive as a vitamin as it retains no trace of the original nutrient. It is, however, a highly destructive substance, particularly in relation to vitamin C.
When the riboflavin/lumiflavin conversion takes place in foods containing vitamin C ascorbic acid content is reduced by half.
Riboflavin retains its stability in the presence of heat and is thus undamaged by most cooking methods. As with other B vitamins it is its water solubility which can lead to losses of the nutrient: it leaches out into the washing, soaking, or cooking water to some extent. A small amount can be reclaimed by using the cooking water for gravy or sauces, but the amount to be gained from this method is minimal and difficult to assess.
Most food processing, canning, frying or boiling will bring about losses of riboflavin to some extent and long-term storage also has a destructive effect.
The contraceptive pill or oestrogen containing hormone replacement therapy are the more common drugs that appear to threaten the vitamin B2 status and can result in low levels in the body.
In young animals riboflavin deficiency results in impaired growth and in adults the reproduction system can be affected.
Since riboflavin is required for the production of red blood cells, low dietary intake can result in anaemia.
Deficiency can also cause skin conditions such as dermatitis or an unhealthy flaking scalp, which can give rise to hair loss.
The more serious symptoms of deficiency relate to the moist mucous covered areas, i.e. the eyes and mouth. Insufficient riboflavin can lead to conjunctivitis, sore bloodshot eyes and cataracts.
Mouth ulcers, a sore cracked mouth and inflammation of the tongue and lips can also occur. The eyes can be further affected by symptoms such as burning, gritty sensations, ulcers on the eyelids or sensitivity to light. Eyes may tire easily and feel strained and weak.
Changes to the skin may include red scaling around the nose, mouth, forehead and ears. The scalp can also be affected in this way. Its surface becomes dry and flaky and this can lead to hair loss or hair that is lank and greasy in appearance and texture.Riboflavin deficiency can also be caused by long-term poor dietary habits such as continual dieting, faddish eating, exclusion diets (including diets for stomach ulcers), junk food or irregular meals.