Ok, so spinach doesn't really cause autism...

But... it's more than likely that E. coli (which is commonly found in spinach) and other gram negative bacteria exposure in utero, is a cause for autism. Here's an explanation in normal people terms, along with some suggestions as to the next steps for research. 

- All of the sources and legitimate scientific explanations / jargon are included too. Yes, neuropharmacologists and neurophysiologists, this is useful for you too.