Healthy vs. Healthful

An associate of mine once retorted concerning a grammatical point, "English is a young language." Yes, it may be young and changing; but to me carelessness should not be one of the results. Rarely now do we find the word "healthful." It's healthy food, healthy lifestyle, etc. No! To be healthy, something must be alive. Now the lobster in the tank at the store may be healthy at that time; but when I'm about to eat it, I trust it will not be alive and, hence, not healthy. How healthful it will be I'll leave to the nutritionists. Further, "eat healthy" is wrong on two counts: see the above discussion plus the fact that an adverb is needed. Hence, we should say, "eat healthfully."