If any government decides to mass-medicate every bread-buying New Zealander with a certain additive, it has to be very sure that the costs to the community don't outweigh any health benefits, and that there are no long-term ill-effects on the population.

Minister for Food Safety Kate Wilkinson faces an interesting test as she decides whether to review or delay a controversial new food standard, which will force all bakers to add folic acid to every single loaf of bread.

The question is, will this centre-right politician - who campaigned vigorously on ridding New Zealand of the "nanny state" - endorse such a major intervention?

Come September, when the food standard comes into force, New Zealanders will have no choice but to consume folic acid in their bread. Only organic bread will be exempt from the requirement to medicate - but at 1 per cent of the market and priced out of the reach of poorer families, it would be surprising if any decision-maker held this out as genuine choice.

Political ideology and the centre-right principle of freedom of choice aside, however, the big issue is the growing concern that too much folic acid might create long-term health problems for bread-loving Kiwis.

Folic acid has been seen as a miracle vitamin since the 1980s, when increasing pregnant women's folic acid intake was linked to reductions in birth defects.

No one, and in particular bakers, disputes the beneficial effects on pregnant women. Pregnant women can benefit hugely from taking supplements and eating a healthy diet.

Where some part company is when regulators turn from targeted health programmes for small numbers of women at risk, to a programme of effective mass medication - dosing every man, woman, and child.

And while the benefits to pregnant women are well known, it's the unknowns for everyone else - some 4.3 million New Zealand citizens - which drives current industry opposition and international discussion as some researchers are starting to ask whether too much folic acid could have negative effects, in particular fuelling certain cancers in certain parts of the population.

Bread-makers have made huge efforts to bring these concerns to the attention of the Government. They have gone to great lengths to offer a voluntary system which introduces greater fortification but preserves choice for New Zealanders, particularly those with children.

Should the minister decide to embrace the food standard, it will not be enough to argue that controversy was "inherited" from the former Labour government.

Since the former government decided to support the food standard, much has happened which has meant other countries respected by New Zealand are having second thoughts about mandatory fortification.

Both Britain and Ireland have put plans to fortify all bread on hold while they evaluate new studies questioning a link between too much folic acid and certain cancers in pockets of the population.

A report released by the Irish Department of Health in March which recommended a delay in fortification plans in light of concerning new research noted: "New studies are under way and results will be available in 2009 that should clarify if there is an increased risk that links dietary folic acid with cancer. The decision to introduce mandatory fortification of bread in Ireland should be put on hold until definitive data are available on the safety of this initiative."

Practical problems have also arisen since New Zealand committed to the food standard two years ago. Bread companies have conducted clinical dosage trials and concluded that dosing the bread accurately every time within the tolerance levels will be impossible.

Official reports written by the New Zealand Food Safety Authority (NZFSA) have been made publicly available. Parts of the reports make disturbing reading to any sandwich-making Kiwi parent.

While it's been estimated that a pregnant woman will have to eat 11 slices of bread a day to receive the amount of folic acid required, the NZFSA reports confirm in black and white that some New Zealand children will, as a result of mandatory fortification, eat more than their recommended daily intake of folate/folic acid.

In rather alarming advice, the minister at the time was told by NZFSA: "There are unknown risks that may not become apparent for one or two generations. Children will be exposed to much higher levels of folic acid than in previous generations. It may not be until this generation of children have their own children that adverse effects become apparent."

This kind of comment does not instil confidence and starts to read like a medical experiment on a grand scale.

In another report, NZFSA puts a figure on the number of New Zealand children they are concerned about.

"We continue to have concerns that 13.8 per cent of males aged 5 to 8 years and 8.2 per cent of New Zealand females are going to exceed the upper level intake for folic acid ..."

These are the "concerns" that will need to be explained in the event the Government endorses the food standard. It may not be a task the minister will relish.

Officials estimate that this New Zealand folic acid experiment could prevent between one and five neural tube defects, but what of the potential costs to other parts of the New Zealand population which have not been factored in?

While recent studies are not conclusive, academics are starting to ask questions about whether there are links between too much folic acid and rates of prostate and colon cancer.

Like Britain and Ireland, the only commonsense position for New Zealand is to delay implementation until more information is gathered.

So why would any Government want to attach itself to this folic acid tar baby?

It's potentially a very unpopular move.

New Zealanders simply don't like the idea of governments tampering with their bread. The New Zealand Food Safety Authority's own research concluded "84 per cent of consumers interviewed, even after providing information on the reasons for fortification, did not support mandatory fortification".

Could the real reason be out of concern for our relationship with Australia if New Zealand pulls out of this transtasman food standard?

New Zealand takes its relationship with Australia extremely seriously, but revoking a single food standard on the grounds of public health concerns is hardly going to undo a friendship forged on the battlefields on Gallipoli.

Hopefully this is not the case. New Zealanders, after all, look to the Hon Kate Wilkinson to be a strong Minister for Food Safety, rather than a de facto Minister for Foreign Affairs.

New Zealand, like other nations, should put this folic acid experiment on hold until the potential risks of this grand health experiment are better understood.

* Katherine Rich is chief executive of the New Zealand Food and Grocery Council.