Is it "healthy" or "healthful?" Or just nauseous?

R.L.G., whoever that is, at The Economist's Johnson blog, gives us a healthy, or maybe healthful, dose:

I just remembered how irritating I find the distinction a strange minority of English-speaking natives insist on: that "healthy" can only mean "in a state of health", and that "healthful" must be used to describe green vegetables, exercise and other things that make a person healthy.

Both norma loquendi and slightly more rarefied usage tests back me up: "healthy food" is about 20 times as common as "healthful food" on Google. And Google's N-Gram Viewer shows that while "healthful food" (the red line) was about as common as "healthy food" (the blue line) in books until 1980 or so, "healthy food" has been the overwhelming usage since.

I think the insistence on "healthful" is an over-eager application of the principle that one word can't mean both "causing X" and "experiencing X". Many sticklers don't like "nauseous" for the state of feeling nausea. But plenty of words do such double-duty, like "suspicious" and "doubtful", without raising ire. Both a criminal and a detective can be suspicious (in very different ways), and both a piece of evidence and a sceptical judge can be doubtful.

But "nauseated", at least, is fighting a decent rear-guard battle. "Healthful food" is particularly obnoxious to me because it flies in the face of overwhelming native English practice.

I hate flies in my face.