Google absolutely does that: https://myaccount.google.com/purchases

They scan your email and extract what you purchased, when, for how much, and when it was delivered. It appears to be as close to universal as they can get it — they’ve extracted info from some pretty niche retailers emails on my account.

There’s no publicly viewable equivalent for scanned health info but, internally, who knows. It wouldn’t be at all surprising if some of that data went into a training set for ad targeting, at the very least.

Wow, that's eerie. And I thought I had everything disabled.

Can this be disabled?

Yes. You can disable it by switching to Fastmail or a similar email provider.

(Sorry.)

And never send email to gmail accounts, and make sure nobody ever sends you mail from gmail accounts, I presume? That’s quite unworkable.

Of course you’re right; perfect privacy is impossible.

But at least we can pick the low hanging fruit and not give our own info to Google voluntarily.