Going further into this (and I think it relates to the "older man" questions as well).
50 years ago we did not need to supplement with folate to cut the risk of our children having autism. Very, very few children had autism (although some had undiagnosed Aspergers). Oh, maybe folate did cut your risk - from 1/10 000 to 1/ 14000 or some such thing - but the bottom line was the chances of your child having autism were slim. Clearly, folate is not a smoking gun or the catalyst for this change in our society.
Assuming the study is correct (and it might be) why is folate now important in decreasing the chance of autism? I see 2 possibilities:
1. Folate was always associated with decreasing the chance of autism. It simply used to be that very few people got autism, ergo, not much attention was paid to it.
2. Smoothing in us has changed whereby we now need more folate than we used. What has changed is unknown.
I don't really think that Norwegian diets of yesteryear had more folate in them that they do now. I could be wrong, but folate has been tied to spina bifida for years, so I suspect its use is fairly high. Moreover, while our diet of yesterday may have contained more whole, clean foods - I don't think it necessary had more fruit and veg. They just did not have those things in winter.
The older man thing is similar. It could be that younger fathers are associated with less autism (let's say a 20% less (made-up figure)). If the autism rate is 1/10 000 in the general public and 1/8000 with older fathers, the chances of your child getting autism was pretty low, no matter the fathers age. If the risk is 1/50 it is a whole other ballgame. Likewise, perhaps something in us has changed that means older father are more likely to have autistic offspring?
In any event, I do know if I were planning to become pregnant, I would look seriously into the role of folate and autism prevention. Smoking gun/catalyst for change/correlation but not causation…whatever… a 40% reduction in the chance of autism is nothing to sneeze at!
Edited by kathymuggle - 7/8/13 at 7:24pm