|
Folic Acid
DESCRIPTION
Folic acid was originally found in yeast, where it was recognised
to be an "anti-Anaemia" factor. Folic acid is a
member of the B complex and has the chemical name pteroyl
glutamic acid.
STABILITY
Folic acid is unstable to
heat, air, water and alkali, and careful cooking methods must
be employed to ensure adequate amounts of this Vitamin A re
retained.
FUNCTIONS
Folic acid is needed for
many physiological reactions. More specifically, folic acid
is needed for the synthesis of DNA and therefore for cell
division. It is also involved in the production of the non-essential
Amino Acids methionine and glycine.
DEFICIENCY
Folic acid deficiency causes
a megaloblastic Anaemia (see Vitamin B12 ). This is often also
associated with a diminished number of white blood cells (leucopenia).
Rapidly generating tissues
are affected by folic acid deficiency and so the intestinal
mucosa may also suffer. In babies and young children, growth
may be affected.
Those who are most at risk
from folic acid deficiency are as follows:
The elderly (who tend to
have poorer diets or impaired absorption)
Those with intestinal malabsorption syndromes (particularly
steatorrhoea, where the stools contain undigested fat)
Pregnant women (the developing foetus make considerable demands
on the maternal folic acid stores)
Alcoholics
REQUIREMENTS
Upper safe level for daily
supplementation = 400µg
Recommended Daily Allowance
= 200µg
SUPPLEMENTAL USES
Birth Defects:
Supplements of folic acid (400 µg per day) are highly
advisable prior to conception as well as in the first twelve
weeks of Pregnancy, as low folic acid intake is strongly associated
with the birth defect spina bifida (1).
Anaemia:
Folic acid supplements must be used under medical supervision
for the treatment of diagnosed megaloblastic Anaemia, as folic
acid can mask a Vitamin B12 deficiency (2) (see under vitamin
B12 section). Normally, folic acid is only prescribed after
Vitamin B12 has already failed to bring a response.
Alcoholics:
Alcoholics may benefit from a supplement of folic acid as
they tend to have depleted levels of this vitamin (3).
Coronary Heart Disease:
Recent research shows that folic acid supplements may offer
protection against heart problems in later life by maintaining
low blood homocysteine levels (4).
SAFETY
The overall risk from folic
acid mega-dosing is deemed very slight.
INTERACTIONS AND CONTRA-INDICATIONS
Vitamin B12 :
As previously mentioned, folic acid supplements taken by people
with developing Vitamin B12 deficiency may obscure a correct
diagnosis and delay the appropriate treatment.
Zinc:
Very high folic acid intakes may also result in disturbed
Zinc absorption.
Methotrexate:
Certain drugs used in the treatment of cancer (e.g. methotrexate)
are specifically designed to inhibit folic acid. People being
given these drugs should therefore only take folic acid containing
supplements under strict medical supervision.
Anticonvulsant Drugs:
Folic acid should not be taken with anti-convulsant drugs
unless directed by a medical doctor.
FOOD SOURCES
Food (µg/100g)
Brewer’s yeast 2400
Wheatgerm 310
Wheat bran 260
Nuts 110
Pig’s liver 110
Leafy green vegetables 90
Bread, wholemeal 39
Eggs 30
Bread, white 27
Fish, fatty 26
Bananas 22
Potatoes 14
REFERENCES
1. Butterworth CE Jr and
Bendich A. Folic acid and the prevention of birth defects.
Annu Rev Nutr, 16:73-97, 1996.
2. Matthews JH. Cobalamin and folate deficiency in the elderly.
Baillieres Clin Haematol, 8;3:679-697, 1995.
3. Cravo ML et al. Hyperhomocysteinemia in chronic Alcoholism:
correlation with folate, Vitamin B12 and Vitamin B6 status.
Am J Clin Nutr, 63;2:220-224, 1996.
4. Lowering blood homocysteine with folic acid based supplements:
meta-analysis of randomised trials, 316:894-8, 1998.
|
