A nutritionist believes more women will now receive an important vitamin supplement as it is added to the country's bread supply.

From today, non-organic wheat flour used in bread-making in New Zealand will be fortified with folic acid, which helps to prevent neural tube defects such as spina bifida in unborn babies.

Announcing the move to fortify some bread-making flours with the acid in 2021, then-Minister for Food Safety Ayesha Verrall said the B vitamin was "safe and essential for health; particularly for development of babies early in pregnancy".

"Folate is naturally present in food; folic acid fortification restores what is lost during processing such as flour milling," she says.

Waikato University researcher Dr Sara Mustafa says it's a major step forward in preventing a devastating disease.

"Folic acid is the supplementation form of folate, and that is much better absorbed than folate.

"If it's fortified in bread, it can reach more people from different kinds of socio-economic backgrounds as well."

She says other countries have already added folic acid into their bread-making processes.

"I think it's very important, we're actually a bit behind compared to the rest of the world, there's 80 other countries that have already done it including the US, Australia; it's very significant."

Mustafa says adding vitamin supplements to food is common practice overseas.

But Baking New Zealand president says he wants to see the research behind adding the supplement to the bread supply.

Bernie Sugrue says he thinkst the amount of bread a woman would need to eat for it to make a difference is unviable.

"If, you know, a lady is pregnant and needs to have that folic acid in their diet there are other supplements they could be taking.

"And also, the amount of bread they'd have to have, I believe, to do any benefit for them is quite a lot of bread."

Sugrue says it's up to the flour mills to supply fortified flour to bakers.

-Finn Blackwell/RNZ.