The report, prepared by professor A David Smith of the Department of Pharmacology at the University of Oxford and professor Helga Refsum of the Department of Nutrition at the University of Oslo said that here is increasing evidence that high intake of folic acid may cause harm.
“On public health grounds, taking into account the precautionary principle, it is difficult to justify exposing the whole population of 4.4 million to folic acid,” the report, which was also backed by the New Zealand Baking Industry Research Trust and the New Zealand Food and Grocery Council (NZFGC), said.
This report comes in the background of the country’s Ministry for Primary Industries calling for submissions on its new consultation paper to decide between the existing policy of voluntary folic acid fortification or move to make it mandatory to do so.
Problem of neural tube defects exaggerated
Backers of folic acid fortification have highlighted how folate combats neural tube defects, but the authors said that the current prevalence of neural tube defects (NTDs) in New Zealand is not precisely known and so there is no baseline from which estimates of the effects of folic acid fortification can be made.
“All that can be said is that the prevalence had been falling for several years until 2003 and, if this decline has continued, the prevalence may by now have reached about 7 per 10,000 births per year. This is likely to be a floor level, where folic acid may have no further effect,” the said.
According to the report, the lack of baseline data is a serious problem because it is government policy to monitor closely the effects of fortification, but in the current situation such monitoring will not be possible.
The report also said that it is difficult to estimate the impact folic acid fortification have on the prevalence of NTDs in New Zealand because there is no reliable data on the current prevalence of NTD pregnancies.
“The general folate status of New Zealand women of child-bearing age is very good. It is the same as, or better than, that of women in the US after the introduction of mandatory fortification,” Smith and Refsum said.
“Based on the best evidence available, we suggest that fortification may prevent no more than 6 NTD pregnancies per year, but quite possibly none,” they said.
Very few other benefits
The report also suggested that there are rather few population studies on other possible beneficial effects of folic acid fortification.
“The data on other congenital defects is inconsistent and this may in part be due to changes in diagnostic practice over time. Some defects appeared to be more common after fortification, while others may have decreased,” they said.
The report admitted though that there were significant and important decreases in stroke mortality, and also in stroke incidence, following fortification in USA and Canada.
The report also debunked using results derived from randomized clinical trials to back folate fortification, saying the doses of folic acid used in such trials are much in excess of the amounts that are obtained from food after fortification.
More harm than good
The report came out strongly against the harm folic acid fortification can cause, stating that in the elderly, the most concerning effect is the increased risk of anemia and cognitive deficit in those with high folate and low vitamin B12 status.
“The ability of folic acid to interfere with the action of the widely-used antifolate drugs has not been thoroughly studied,” the authors said, adding that evidence that folic acid supplements lead to a higher death rate of children treated with anti-malarial drugs in countries with endemic malaria is of great concern.
The report added that women who are exposed to folic acid fortification have a higher risk of twin pregnancy if they use artificial reproductive technology, but there is no convincing evidence that normal pregnancy is affected.
Folate and cancer share a complex relationship
The authors also highlighted the complex relationship between folate and cancer stating that folate has a dual role in cancer, depending on the stage.
For normal tissues folate is protective against factors that tend to make the cells neoplastic. For pre-neoplastic cells and cancer cells, however, folate can be harmful because it stimulates cell multiplication, the report said.
“Whether or not fortification with folic acid will reduce, or increase, the risk of cancer depends upon the timing of the exposure in an individual, the sensitivity of particular cancers to folate, the prevalence of particular subgroups at greater risk, and the baseline level of folate in the population,” they said.