It's the oxalic acid.

I've noticed that too!

Spinach has oxalic acid. That may cause the weird sensation after eating it.

I do wash it. I do, though, eat an entire Fresh Express bag (when it cooks down it is next to nothing) so I wonder if that is it, or that cooking it releases something that makes my teeth feel weird.

I get the same thing. Even if it's washed very well. I have a very good salad spinner, and am careful about washing greens, yet spinach is the only one that does that to me.

Maybe it wasn't rinsed well? Spinach does grow in sand...

Why do my teeth feel so gross after I eat cooked spinach? Like there is an odd film on them out something...gritty. anyone else? Is spinach bad for teeth enamel?