Folic acid is a yellowish-orange crystalline powder that is odourless and tasteless. It is soluble in water, particularly hot water. It is a member of the B complex group of vitamins and is needed by the body daily to maintain health. Folic acid has to be converted to an active form, folinic acid, before it can be used by the body, and vitamin C (ascorbic acid) is required to assist in that conversion.
Folic acid was originally known as vitamin M because it was thought to be an anti-anaemic factor for monkeys. It has also been called vitamin Bc, pteroylglutamic acid (PGA), the lactobacillus casei factor and the anti-anaemia vitamin. Folacin is the American collective term for all references to the vitamin including the growth factor for ‘Streptococcus lactis’, which is found in spinach and is named folic acid.
The existence and significance of folic acid was first noted by Dr. Lucy Wills in 1931. Dr. Wills had observed that pregnant women were prone to a particular type of anaemia that did not respond to the usual treatment of liver extract, which was known to help in cases of pernicious anaemia.
In 1941, an American biochemist found that spinach cured a particular dietary anaemia in chicks and four years later, Dr. Tom Spies isolated the compound and called it folic acid because it came from leafy green foliage. This substance was also found to cure the anaemia described fifteen years earlier by Dr. Lucy Wills, called megaloblastic anaemia.
Folic acid is measured in micrograms (mcg or µg).
Folic acid was isolated in 1945 in spinach by Dr. Tom Spies and, for most people, leafy green vegetables are still the best general sources of the nutrient.
The richest food source is dried brewer’s yeast and yeast extract. Other good sources are lamb’s and pig’s liver, oysters, soya flour (full fat), wheatgerm and wheat bran. Dairy produce like milk and eggs, citrus fruit and most meats contain some folic acid, but not enough to be regarded as main sources.
There are many types of folic acid in the food we eat, not all of which are available to the body. Synthetic folic acid used in supplements is, however, easily absorbed and utilised.
What does it do in the body?
Folic acid is essential for the metabolism of nucleic acids.
There are two nucleic acid types:
- Ribonucleic acid (RNA)
- Deoxyribonucleic acid (DNA)
RNA and DNA are essential to protein synthesis. This process is important to all the tissues in the body, the blood in particular and also to the formation of healthy cells. RNA and DNA are also involved in passing on genetic information from parents to offspring. This is known as the genetic code, which is a pattern passed on from one generation to another.
No direct studies have been carried out on the absorption of folic acid. It appears that about three quarters of that ingested is absorbed from the small intestine. Folic acid is stored to some extent in the liver. Small amounts are excreted through the faeces and urine and some is lost in the shedding of dead surface skin cells.
Cooking in large quantities of water or at very high temperatures destroys folic acid content, so the least possible amount of water should be used to boil or braise vegetables and cooking time should be kept to a minimum.
Vitamin C appears to be able to protect the stability of folic acid, so it is fortunate that the two nutrients often occur in the same green vegetables. When food is re-heated, vitamin C is destroyed and folic acid is oxidised. Folic acid is also sensitive to oxygen and sunlight. Foods containing the compound should be eaten soon after purchase, or kept in a dark place until used.
Folic acid deficiency falls into four separate categories:
- As a dietary defect, where food eaten contains little or no folic acid, megaloblastic anaemia can occur. It is unusual to see this in prosperous countries, except during pregnancy when the developing foetus requires as much folic acid as the mother and her requirements are increased. The elderly have a higher requirement for folic acid and are at risk if their diet is inadequate and regularly contains pre-cooked food.
- Deficiency from malabsorption as in the case of coeliac disease, or other disorders of the small intestine, where folic acid is usually absorbed. This would need to be diagnosed by a medical practitioner who would be aware of the risk of deficiency in conditions such as these. Alcohol prevents the absorption of folic acid from food and inhibits its action in the liver.
- Excessive demand for folic acid occurs when there is unusually active cell proliferation as in leukaemia and some other cancers. Again, this group would need to be medically diagnosed and treated.
- Interference with folic acid metabolism by many drugs, oral contraceptives, drinking excessive amounts of alcohol and nicotine addiction.
Deficiency symptoms are those of anaemia and can include:
- mental confusion.
Folic acid is more stable as a nutrient and is used more efficiently as a vitamin when its natural companion ascorbic acid is present. It is inextricably linked with vitamin B12 in its role in red blood cell production.