Vitamin B9, or folic acid, is an oxidised form of folate, from the Latin word meaning leaf, and folates can be found especially in dark green leafy vegetables, as well as in other food sources including meat, poultry, dairy products, seafood, legumes, nuts, fruits and fruit juices, whole grains, and some beers.
Vitamin B9 is an essential vitamin, which cannot be endogenously synthesised, but which is necessary for making and repairing DNA. B9 is also involved in several other biological reactions including the synthesis of neurotransmitters. It is particularly important in periods of pre- and post-natal human development, when it aids the rapid growth and division of cells.
Folate is necessary to make both red and white blood cells, and deficiency may cause a type of anaemia, with attendant weakness, fatigue and loss of concentration, as well as other cognitive disorders including depression and forgetfulness. It may also produce ulcers, headaches, irritability and palpitations.
Folate deficiency in pregnancy is implicated in neural tube defects occurring in the first month, which is why it is required by women from conception onward, and many countries have made it mandatory to fortify cereal products with folic acid for this reason.