Vitamin B2

Riboflavin, used across energy metabolism and in recycling other vitamins, including B6 and folate. It is the one that turns urine bright yellow, which is harmless.

Central to energy production in every cell, and needed to activate vitamins B6 and folate.

• Milk and yoghurt
• Eggs
• Liver
• Almonds
• Mushrooms
• Fortified cereals

Destroyed by light — which is why milk is no longer sold in clear glass.

1.3 mg (men) · 1.1 mg (women) for most adults. The upper limit, past which harm becomes likely, is None established.

Reference intakes are population figures. Pregnancy, illness, age and medication all move an individual’s needs, which is one of several reasons this page is information rather than advice.

A sustained shortage has a name here: Ariboflavinosis. That is worth pausing on — nutrients whose deficiency earned a name are the ones where the consequences were severe enough, historically, to be described as a disease.

Most at risk: People avoiding dairy, heavy drinkers, and during pregnancy.

Low dairy and meat intake, alcohol dependence, and malabsorption. Rarely isolated — it usually accompanies other B vitamin shortfalls.

Cracks at the corners of the mouth, a sore magenta tongue, sore throat and sensitivity to light.

Every sign here has other, often likelier, explanations. A list of symptoms is a reason to look into something, never a diagnosis.

Erythrocyte glutathione reductase activity is the research measure; it is seldom used clinically. Diagnosis is usually on diet and appearance.

Dairy, eggs, lean meat, mushrooms, almonds and fortified cereals. Riboflavin is destroyed by light, which is why milk is not sold in clear glass.

Not toxic in ordinary amounts and readily excreted. Higher doses have been studied for migraine prevention, which is a conversation to have with a doctor rather than a reason to self-prescribe.

No known toxicity. Turns urine bright yellow, which is harmless and often mistaken for a problem.