Uses in the body: promotes normal growth and development, helps release energy from food, maintains health of mucus membranes. Is also needed for healthy skin, eyes and nervous system; plays a role in fertility.

Signs of deficiency: dry skin, cracked lips, red and flaky skin especially round nose and eyes, sore mouth and tongue, eye irritation and light sensitivity, poor concentration and memory, burning sensation in feet.

Therapeutic uses: pregnant and breastfeeding women, those on the contraceptive pill or oestrogen replacement therapy, young people during growth spurts, the elderly, athletes, people on high-protein diets or those suffering from stress or alcohol or drug abuse. People with mouth ulcers and gastric ulcers may also benefit.

Dietary sources: beef or lamb's liver, wild rice, wholewheat pasta, soya milk, wholegrain cereals, brewer's yeast, yeast extract, pulses, seeds, milk and other dairy produce. Can be destroyed if foods left in strong sunlight.

Dosage:
Recommended daily allowance: 1.6mg
Typical therapeutic daily dosage: 50mg to 100mg
Daily intake shouldn't exceed: 200mg

Cautions: shouldn't be taken at the same time as antibiotics (erythromycin and tetracycline) or methotrexate (an anti-cancer drug) as it interferes with their absorption. Not suitable for people with kidney disease or children under 12. May cause urine to turn bright yellow (to overcome this, increase daily fluid intake). Diuretics can increase the need for B2.

Best taken: with breakfast. A yeast-free form is best for those sensitive to yeast infections.