Folic acid fortification could be safely doubled, says study

By Stephen Daniells

- Last updated on GMT

Related tags: Folic acid

With the impending introduction of folic acid fortification in
Ireland and the UK, a new study reports that double the US level of
folic acid can safely be used in flour.

Researchers from Trinity College Dublin, led by Mary Rose Sweeney, commissioned a local bakery to bake three batches of bread with different folic acid levels (50, 100, or 200 micrograms) and found that consumption of two servings of the 50 and 100 microgram breads resulted in metabolised folic acid. Writing in the open access journal BMC Public Health, the researchers report that consumption of two servings of the 200 microgram bread, or a 400 microgram supplement lead to measurable levels of un-metabolised folic acid in test subjects blood. "This is good news in that it is possible to have optimum protection from a neural tube defect affected birth without having exposure to un-metabolised folic acid,"​ said co-author Professor John Scott. Deficiency of folic acid, a B vitamin that occurs naturally in foods such as grains, lentils, chick peas and green leafy vegetables, in the very early stages of pregnancy can lead to neutral tube defect, such as spina bifida, in the infant. Mandatory fortification of grain products with folic acid in North America since 1998 has led to a significant reduction in NTD incidence. Although the UK and Ireland have been seriously looking into it, no European country has introduced parallel measures so far. The UK's FSA launched its final consultation in December, and Ireland's National Committee on Folic Acid Fortification made a positive recommendation last July on fortification of most white, brown and wholemeal breads sold in the country. The new study recruited 20 subjects (10 women, 10 men, age range 20-40) and, after an instructed them to consume a daily 400 microgram supplement of folic acid (Clanfolic) for 14 weeks, in order to reach the "serum folate plateau". Subjects were then instructed to consume two slices of bread (200 micrograms per slice) for seven days. One slice was to be consumed at 09:00 and the second at 13:00. A seven-day washout period followed this first intervention, before subjects were instructed to consume two slices of bread (100 micrograms per slice) for seven days. Another seven-day washout period followed and subjects were finally instructed to consume two slices of bread (50 micrograms per slice) for seven days. Sweeney and co-workers report that consumption of the 50 and 100 microgram bread slices with a 4-hour interval in between slices was fully metabolised each time. However a 400 microgram supplement or 200 microgram consumed once in a single slice of bread lead to metabolised folic acid in test subjects blood. "Whether these [excess] levels would accumulate indefinitely or plateau at some point with prolonged repeated exposure in a population exposed to these levels under a fortification programme is unknown and ongoing surveillance is indicated,"​ wrote Sweeney. The researchers noted, that despite no un-metabolised folic acid being detected in the serum after consumption of the 100 microgram bread (the level supplied to the average American in the US fortification programme), it should be noted that many Americans are thought to consume between 215-240 micrograms due to overage (the practice of adding a little extra to meet the mandate). "Based on the cumulative evidence to date it seems that the threshold dose above which un-metabolised folic acid appears in serum lies around 200 micrograms,"​ said the researchers. "These are important considerations for policy makers planning an intervention,"​ they concluded. In the case against folic acid fortification, fears have been raised that high levels may mask detection of vitamin B12 deficiency, especially in the elderly. If this deficiency is not identified it can eventually lead to dementia. According to the UK FSA's Scientific Advisory Committee on Nutrition, folic acid intakes of one mg/day would not be expected to mask vitamin B12 deficiency, and most adverse effects in relation to vitamin B12 deficiency have been reported at doses at or above 5mg/day. Source: BMC Public Health ​In press "Folic acid fortification and public health: Report on threshold doses above which unmetabolised folic acid appear in serum" ​Authors: M.R. Sweeney, J. McPartlin, J. Scott

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