Health & Science
Food for thought
by Marilyn Head
The number of birth defects and strokes would fall if it was mandatory to fortify New Zealand food with folic acid, say health experts.
The science is unambiguous and has been since 1991,” declares Joanne Dixon, geneticist at Wellington’s Central Regional Genetics Service. She is talking about two seminal trials that emphatically and rigorously established that folic- acid supplementation could reduce the incidence of neural tube defects (NTDs) like spina bifida and anencephaly by up to 70 percent.
“I was training in Canada when the studies were being done,” says Dixon, “and I came back to New Zealand brimming with enthusiasm about saturating the environment with folate and thinking, ‘Good, this is one abnormality we won’t have to deal to again.’ And here we are 14 years later and nothing has been done!
“People are devastated when they’re given the diagnosis. What they face is a child who will have a profound physical, and possibly mental, disability for the rest of its life. Of course they love that baby – but they often ask me, ‘How did this happen? What could I have done to prevent this?’ And they are even more devastated when they learn that they could have reduced their risk of having a child with an NTD by taking folic acid.”
The neural tube – basically the spinal column that houses the nervous system – closes within 15 to 28 days of conception, before many women are even aware that they are pregnant. Folate is needed for enzymes that synthesise DNA at this critical stage of development.
“We all carry genes that enable us to process folate,” explains Dixon, “but about 11 percent of Europeans carry a variant gene that doesn’t process it as efficiently. Although the mechanism is not well understood, it doesn’t matter if the mother is deficient or the foetus is genetically unable to utilise folate effectively, the solution is clear – swamp the foetus with synthetic folate by giving the mother at least 800 micrograms of folic acid daily during preconception and very early pregnancy.”
And therein lies the difficulty. At least half of all pregnancies are unplanned, so by the time a pregnancy is confirmed it’s already too late to supplement. And although most New Zealanders get sufficient folate through their normal diet, dietician Carol Gibbs warns that it’s almost impossible to raise the levels high enough to prevent NTDs through food alone – a therapeutic dose is needed.
“Fortifying foods with folic acid,” says Gibbs, “is the only way of reaching all the child-bearing population, regardless of socio-economic status, knowledge or motivation.”
Fifty countries, including the US and Canada, have mandatory fortification. New Zealand and Australia, which share the same food standards, have opted for a voluntary approach, while allowing folate to be added to some foods. But food-industry uptake has been disappointingly low and largely limited to breakfast cereals. “Of course we would prefer voluntary fortification,” says Gibbs, “but if it’s not effective, what’s the point?”
Dixon goes further: “Voluntary stuff doesn’t work, because the pregnancies are unplanned, women don’t like to take pills regularly, they take them at the wrong time, and even if we tell a whole bunch of women this year that they have to take folic acid, next year we get a whole new bunch.”
The evidence is that, even with supplementation and some fortified foods, folate levels are still far too low to reduce NTDs. “Apart from anything else,” says Gibbs, “the target group of women is not really big on breakfast cereals – it’s a matter of finding the right vehicle.”
The options seem to be fortifying either bread or flour. The latter is favoured, because it’s technically easier to fortify at source and has the potential to deliver folate through a variety of foods, including pastas, biscuits and breads. But both the millers’ and bakers’ national associations have been reluctant to take that step, partly because of high initial costs, but also because additives would prevent them from marketing the products as “All Natural”.
Which leaves mandatory fortification. Consideration of this option was one of the recommendations of a comprehensive report published by the Ministry of Health in 2003 and strongly supported by Annette King, Minister for both Health and Food Safety. Other public health initiatives, such as iodising salt to prevent goitre or fluoridating water to prevent dental caries, have been introduced in the past in order to provide health benefits to the majority of the population. Folate fortification, however, would significantly benefit only a few families – about 80 to 100 each year – who face the prospect of having a child with an NTD, and who sometimes choose to terminate the pregnancy. Should the vast majority be responsible for the very few?
“Yes!” says Dixon, emphatically. “We must buy into the public good.”
And folate may deliver more “good” than we think. When the US introduced mandatory fortification in 1992, not only did the incidence of NTDs fall by 20 percent but also 20,000 fewer people had strokes. There’s cautious optimism that increased folate may mitigate some forms of cancer and dementia as well as heart disease.
For leading US epidemiologist Godfrey Oakley, the message is clear. “Every day there is no fortification,” he says, “children get birth defects unnecessarily and adults die from strokes unnecessarily. Mandatory folic acid fortification is simple, safe, inexpensive – there can be no rationale for delaying its introduction.”
New Frontiers
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