The Question:

Why do we say some foods are healthy? They're healthful. If they were healthy, wouldn't they still be alive?

The Answer:

There are those who make a distinction between healthful, meaning "conducive to health; wholesome or salutary:

a healthful diet

" and healthy, meaning "possessing or enjoying good health or a sound and vigorous mentality:

a healthy body; a healthy mind

." Most people use "healthy" for both meanings. Merriam-Webster's Dictionary of English Usage notes that this distinction was invented in 1881 (several centuries after both words first appeared), and that "if you observe the distinction between healthful and healthy you are absolutely correct, and in the minority." On the other hand, "If you ignore the distinction you are absolutely correct, and in the majority."

"Healthful" sounds dry to my ear, but you can take your choice.

—The Fact Monster