Q+A: Greg Boyed interviews David Smith
 
Oxford Pharmacologist claims an increased risk of cancer if New Zealand was to make it mandatory to put folic acid in bread.
 
“I would say that several hundred additional cases of cancer may occur in the population [per year].”
 
“So we estimate that 10% of New Zealanders will be at increased risk of cancer if folic acid is added to flour.”
 
Mandatory fortification would see “a reduction of five neural tube defect cases in pregnancies per year”, but “harmful effects” means that’s not worth it.
 
“Quite recent evidence now is that there is significant potential for harm.”
 
“You’re affecting the health of the whole population if you add something to food. It’s got to be a very serious decision to be taken.”
 
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Q+A
 
GREG BOYED INTERVIEWS DAVID SMITH
 
 
GREG BOYED
We spoke to Professor Smith in Sweden via Skype, so you’ll have to excuse the quality at times. I began by asking him why we wouldn’t put folic acid in bread.
 
DAVID SMITH - Folic Acid Researcher
You’ve got to ask the question, ‘Why do it?’, and the reason why you need to ask that question is that the idea was to reduce the number of neural tube defect pregnancies in New Zealand.  But there are two problems there. One is that we don’t actually know what the number is precisely, because the authorities haven’t been measuring neural tube defects properly since 2003. Then we have to ask the question, ‘What will the reduction be in the number of neural tube defects if we have folic acid added to flour by law?’ Our estimate is - and that’s Professor Helga Refsum and I who have done the study of this - is that there will be a reduction of five NTD cases in pregnancies per year.
 
GREG             Surely, David, though, even if it’s one - you’re saying up to five - that’s worth it, is it not?
 
DAVID            Well, it would be worth it if there were no harmful effects. But you have to consider folic acid is a synthetic chemical. It doesn’t occur in nature in significant amounts. What occurs in nature is a different form of folate, and so this is a synthetic chemical we’re adding to the food. And we’ve got to ask the question, ‘Does it cause any harm?’
 
GREG             Is there or is there not a risk of cancer as a result of putting folic acid into bread?
 
DAVID            I believe that there is. But, of course, in science it’s very hard to be definite and say it’s proven. Folate is required to protect cells against cancer. But once there are cancerous cells or pre-cancerous cells in the body, giving folate actually stimulates their growth. What’s been found in these studies is that not everyone is susceptible to folic acid in relation to cancer; it’s sub groups of the population. So we estimate that 10% of New Zealanders will be at increased risk of cancer if folic acid is added to flour.
 
GREG             As far as scientific evidence goes at this point, those in favour of adding folic acid say it’s a natural, normally occurring vitamin. The Prime Minister’s own science advisor, Dr Peter Gluckman, as well as science advisors in the UK, say there’s no reason to delay this. What’s your response to that?
 
DAVID            I think the advisors are basing their advice on earlier evidence. Quite recent evidence now is that there is significant potential for harm. And you’ll notice that no European country has added folic acid to flour by law. It’s voluntary. So what I think needs to happen in New Zealand is another period of wait and see how the voluntary fortification is working.
 
GREG             David, critics say claims of links to cancer are inconclusive, borderline and dispelled by further research. You yourself have said this could reduce the number of people born with spina bifida by up to five a year, yet your numbers on its carcinogenic properties are a bit woolly, let’s be fair.
 
DAVID            No, they’re not woolly. Scientific standards of meta-analysis on 38,000 people is not woolly. It’s a strong indication that there’s some risk there.
 
GREG             So how much risk?
 
DAVID            Well, it’s difficult to quantify precisely, and I don’t want to give a figure that will be quoted against me. But I would say that several hundred additional cases of cancer may occur in the population.
 
GREG             Every year?
 
DAVID            Yes. This is a public health action. You’re affecting the health of the whole population if you add something to food. It’s got to be a very serious decision to be taken. You can’t just do it lightly, and you have to balance the benefit. Of course there may be some benefit in neural tube defects - relatively small, in my view. But the potential for harm is much greater.

ENDS

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