Necessary for more than 60 enzymes in the body. Multiplication of cells, so important during pregnancy, and for immune system, mucous membranes, skin, and red blood cells. Manufacture of amino acid neurotransmitters (serotonin, dopamine, melatonin).

Deficiency Signs and Symptoms
Depression, convulsions (especially in children), anaemia, impaired nerve function, cracking of the lips and tongue, seborrhoea or eczema.
Antagonists: hydrazine dyes (FD&C yellow), oral contraceptives, alcohol, excessive protein intake.

Naturopathic Dosage Range
50 – 100 mg

Main Uses
PMS – reduces symptoms of breast tenderness, depression, bloating and irritability.
Carpal tunnel syndrome – commonly a deficiency.
Depression – shown to be low in depressed states, essential for neurotransmitter manufacture.
Morning sickness – reduces nausea and vomiting.
Autism – as supplement, not cure, helps brain chemistry, better if used with magnesium.
Atherosclerosis – deficiency shows increased homocysteine levels, inhibits platelet aggrigation.
Diabetes – to prevent complications.
Immune enhancement – low in AIDS even though consuming enough in diet, correlated to decreased immune function. 

Some toxicity in large doses for long periods. More than 2000 mg can result in nerve toxicity.
Safest at 50 mg per day.