[wemwemwem]

In terms of the crackpot theory I'd suspect more people ate longer stored food in 1980 than today. In terms of changes that could explain a rise in a very infrequent thing I'd suspect a lot more people eat a measurable amount of transcontinental "fresh" which probably has a lot more nutritional loss than frozen for example.

[UncleMeat]

An awful lot of "I'd suspect."

I'll let the professional researchers work to tease it out.