How does actual celery or spinach treat you? Just curious because it's all over naturally in root vegetables like carrots and many leafy greens.
Doesn't surprise me someone would have problems with it though, different folks have problems with all manners of food (eg. dairy, eggs, etc) but that doesn't mean necessary they are bad for the population at large.
I hardly ever eat plain celery (but it's mostly water anyway) and I haven't noticed an issue with spinach (though again, I don't eat more than half a bowl full), so I have a feeling it's in the concentration.
I don't think it's an issue for everyone, but I know it is for some. Took me quite a while to figure it out, so I'm always hoping it might give someone an "Aha!" moment.