“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,” said the report that was backed by the New Zealand Baking Industry Research Trust and the New Zealand Food and Grocery Council (NZFGC).
The cancer question
Smith and Refsum's report said folate fortification could be harmful for preneoplastic cells and cancer cells because it stimulates cell multiplication.
“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 wrote.
However in a nationally televised interview, Dr Andrew Marshall of the Paediatric Society of New Zealand, debunked the report and noted the US had seen reduced cases of cancer since mandatory fortification.
“There's a different meta-analysis using a similar population of 35,000 which is much stronger. It shows no relationship with cancer, no increased risks, no statistical risk, so he is selective in the studies that he chooses and he's chosen a weaker study, which showed a borderline,” Dr Marshall said.
In response, Smith said all the evidence suggests that folic acid may only accelerate growth of an existing cancer or preclinical cancer, not cause cancer itself.
“Experimental studies suggest that good folate status before cancer has developed, may protect against later cancer development. Thus, some people may benefit, while others may suffer. We discuss this issue in detail in our report,” he said.
Neural tube defects?
Marshall also pointed out the benefits of folate in terms of reducing neural tube defects (NTDs) in newborns and infants. Using US data it is estimated 24 NTDs could be reduced in New Zealand each year.
Smith had indicated in the report that backers of folic acid fortification have exaggerated, highlighting that the current prevalence of neural tube defects 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.
He added in response to Marshall’s comments that the folate status in New Zealand women is excellent, and indeed better than in US, which has mandatory folic acid fortification.
The report comes as the country’s Ministry for Primary Industries has been calling for submissions to decide between the existing policy of voluntary folic acid fortification or to go to mandatory fortification.
Food industry: Marshall comments are insulting
Katherine Rich, chief executive for the New Zealand Food and Grocery Council (NZFGC), told FoodNavigator-Asia that the food industry body would be making its submission to the Ministry for Primary Industries by the deadline of July 16.
Public and perhaps governmental mood has changed little since 2009, she observed, when mandatory folic acid fortification was first mooted.
On the television interview Marshall suggested the NZFGC was colluding with Smith and Refsum for more favourable results, suggestions Rich took offence at.
“The implication from a local New Zealand doctor that somehow a small industry association in New Zealand can sway the professional opinion of world class Oxford academics of significant standing is insulting,” she said.
“Calling Professor Smith a folate hater on national television was a low point in the fortification discussion. Both Professor Smith and Refsum are in favour of folic acid, but used in the right way. They have raised some concerns and New Zealand regulators should be giving considerable thought,” she added.
A report last month 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 there is increasing evidence that high intake of folic acid may cause harm.
