Well! It seems from a news story that the British government is about to introduce folate fortification of foodstuffs.
The story starts in the 1970s when Smithells, studying neural tube defect, found that mothers of children with NTD had low folate levels. Wald then ran a classic trial which showed convincingly that folate supplements reduced the risk of a second affected pregnancy in a woman who had already given birth to an affected child. It's known that the neural tube forms and closes very early in gestation, and certainly before the mother will realise that she is pregnant - hence any folate supplementation has to be done pre-pregnancy. That pretty much rules out supplements as a population strategy to reduce NTD, except perhaps n the USA where taking all sorts of vitamins and supplements is remarkably common. Hence the idea of putting folate into an ordinary foodstuff - flour. There is a precedent from the success of putting iodine into salt to eliminate goitre and endemic cretinism
But folate in flour has its opponents. Some people object to anything they dub mass medication; and the folate will of course do no good to any male, or to any female too young or too old for pregnancy. Not only won't do any good, but it may just possible do harm: giving folate to someone who has a deficiency of vitamin B12 (e.g. old people with very poor diets) can precipitate sub acute combined degeneration of the spinal cord. Furthermore, NTD seems to be on the way out anyway - the incidence of NTD has been dropping since the 1970s, presumably due to overall improvements in the availability of salad and green vegetables. (Note that to study NTD incidence accurately you need to add abortions to the birth prevalence - birth prevalence of NTD is particularly high in Northern Ireland because abortion remains illegal there.)
However, as blogged here 10 years ago (this is an ongoing saga) many jurisdictions already fortify flour with folate, and the result seems to be the good without the harm.
Of course whether a government consumed by Brexit is capable of doing anything about anything remains to be seen.