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Report on Folic Acid and the Prevention of Disease
The British Nutrition Foundation welcomes the Committee on Medical Aspect of Food and Nutrition Policy (COMA) Report on Folic Acid and Prevention of Disease, which was published on 13th January 2000.
The report endorses current advice that folic acid supplementation of the diets of women of child bearing age can reduce the risk of neural tube defects (NTD) in their offspring. The mechanism for this remains unclear.
Current advice is that all women of child bearing age should take a 400m g daily supplement in addition to usual dietary intake (around 200m g per day in women of child bearing age). Natural folates are less bioavailable than the synthetic form, folic acid, hence the emphasis on folic acid. Natural folate would also be expected to have an impact on risk; but achieving a sufficiently high intake by diet would be more difficult. Nevertheless, the value of a diet rich in folate-containing foods e.g. fruit and vegetables is considered important.
Current advice for women who have already had an NTD baby is 5mg folic acid per day.
The report concludes that universal fortification of flour with folic acid at 240m g per 100g in food products as consumed, would reduce the risk of a NTD affected pregnancy by 41% without resulting in unacceptably high intakes in any other group of the population. There is concern still that, in older people, high folic acid intakes can potentially mask vitamin B12 deficiency, which can result in pernicious anaemia and irreversible neurological damage. The metabolism of folate and B12 are inter-related.
It is acknowledged that a number of genetic polymorphisms exist that may effectively influence requirements for folate e.g. making its use less efficient in the body. Such a genetic factor may be linked with an increased risk of NTD. Also, at least one of these polymorphisms has been speculated to be linked with associations between folate intake/metabolism and the level of homocysteine in the blood. As many as 10% of the population may be homozygous for this gene mutation and approximately 50% are considered to be carriers of one rather than two mutated genes.
In the past few years there has been increasing interest in the ability of folic acid supplementation to reduce blood levels of homocysteine, which is considered to be a predictor of cardiovascular disease risk. However, it is yet to be established (though studies are underway) that such a reduction leads on to a reduction in heart attacks. Consequently COMA does not advocate supplementation for those at risk of heart disease, although the need for further data is recognised.
Work is also underway to establish whether there are associations between folate/folic acid intake and risk of neurological disease and colon cancer. Specific recommendations are not made by COMA, as the existing data are very preliminary.
© British Nutrition Foundation 2000