In this morning's Herald is an article on the inclusion of folic acid (aka folate) in bread. This has hit the news recently because (among other things) bakers are concerned about the cost of adding this supplement to bread. (One figure that's been bandied about is that someone would have to eat 11 slices of bread to get their recommended daily dose, but this surely a 'straw man' argument: while the NZ diet tends to be low in folate it's not at zero - any amount of bread would supplement that low intake.)
There are a number of issues associated with this story, one being a perceived toxicity associated with folate & another being one of the ethics of mass medicalisation of a population.
But the one I want to touch on to begin with is related to this paragraph: On TV One's Q&A programme, Ms Wilkinson faced criticism from Green MP Sue Kedgley, then presenter Paul Holmes, followed by all three members of the analysis panel. I'd assumed that this 'analysis panel' would include some input from someone who could give expert opinion on the science behind the folate-in-bread proposal. But from reading on, the panel members comprised a political scientist, a local-body politician, & a union representative. I suppose that's to be expected in a program with an emphasis on political questions, but it's still disappointing as it would have been useful to have that science input included.
So, why are we adding folate/folic acid to bread anyway? The quick answer is, because we're required to under an agreement with Australia. The underlying rationale is that a lack of folate in early pregnancy (typically before a woman may even be aware that she's pregnant) is implicated in neural tube defects such as spina bifida. (Other environmental influences include insulin-dependent diabetes, & some types of medication.) In some estimates up to 90% of the population is folate-deficient to some degree, with a number of underlying reasons for this. Hence the former Health minister's comment that the change would see four to 14 fewer neural tube defect-affected pregnancies a year - women would not get the recommended 400 microgram daily intake from bread alone, but any consumption would add to their existing intake.
Neural tube defects (NTDs) occur when the hollow neural tube - which gives rise to both brain and nerve cord - doesn't form properly, and include disorders such as spina bifida. It's estimated that between 50 & 70% of NTDs could be prevented by increasing the amount of folate in a woman's diet, especially during the period from 1 month prior to conception through to 3 months into the pregnancy. Obviously it's not really possible to predict the date of conception, so ideally a woman would be ensuring her diet had the recommended level of folate from the time she began trying to conceive. Of course, things are complicated by the involvement of those other environmental factors, plus there may also be a genetic tendency to NTDs in some families. (Because of this one review recommends that - in developing countries anyway - iron-folate tablets could be provided to parents who already have a child with an NTD, rather than trying to ensure that all women take a supplement prior to & early in pregnancy.) A 2001 Cochrane review of the use of folate to prevent NTDs states that periconceptional folate supplementation has a strong protective effect against neural tube defects, and makes the further recommendation that information about folate should be made more widely available throughout the health and education systems. And the authors conclude that the benefits and risks of fortifying basic food stuffs, such as flour, with added folate remain unresolved.
So that's the crunch point really, isn't it? Just what are the benefits & risks, and the costs involved?
If the estimate of 4 - 14 fewer NTD-affected pregnancies each year is accurate, then that probably involves a reasonably substantial decrease of social and economic costs - the immediate & ongoing cost of supporting affected individuals and their families can be quite high. (For an individual with severe spina bifida, one estimate suggests a lifetime cost of around $500,000 dollars.) In many countries adding folate to flour is seen as the most cost-effective way of reducing NTDs. But is this sufficient reason for treating entire populations ('mass medicalisation'? After all, at most only half the population is ever likely to become pregnant, & in New Zealand 'only' about 1 in 1000 pregnancies involves an NTD.
It does seem that folate may have wider benefits - low levels of folic acid in the diet may possibly be linked with a decline in the self-repair capacity of DNA (in relation to this they've also been linked to intestinal cancers in mice - but bear in mind my previous comments with regard from generalising from mice to men!). There's also a suggestion that folate deficiency could be implicated in cardiovascular disease. In other words, it's quite possible that supplementation of folate through measures like flour fortification would have benefits over and above those flowing from a reduction in NTDs.
What about the risks, then? Apparently high doses of folate (higher than the maximum recommended daily allowance) can mask the effects of vitamin B12 deficiency - in such cases the harmful effects of this particular deficiency would thus go untreated. And while one person quoted in the original press story was concerned that folate supplementation could be linked with an increased risk of cancer, I couldn't find anything supporting this in an (admittedly quick) search of the literature. But in any case, I would have thought that if anythng, low folate levels would be more likely to be implicated in cancer risk.
In other words, this is another complex story - and one where the inclusion of a science-based viewpoint would have added some useful depth to the original article.