At the end of November, Shuna of eggbeater posted a handful of her food writing pet peeves. Among them, she distinguished "healthful" from "healthy." "Food is not healthy," she wrote, "people are."
Poised to type "healthy" one morning in early January, I remembered the peeve but not the details. Are people full of health, and thus healthful, or are bran muffins? I reached for the reference closest to my keyboard, Fowler's Modern English Usage, a guide to British English. The book has an entry for healthy/healthful, but only so the author can ask why Americans care so much about the difference—"The currency of the disliked use in America is not clear to me."—and point out that "healthful" is considered old-fashioned by major British dictionaries.
Expecting an explanation about the two words, Fowler's head-scratching tone surprised me, and I fished other reference books from my shelves. My main dictionary gives "healthy" as the second definition for "healthful," though the first definition is "beneficial to health of body or mind," the sense that Shuna intended. (A similar meaning occupies the third slot for "healthy.") Among The Chicago Manual of Style, Strunk & White, and The Associated Press Stylebook, none mention the topic. Maybe this isn't an issue after all?
The American Heritage Dictionary finally provided a surprising usage note for "healthful" and "healthy." Authorities pronounced them distinct only in the late 1880s, while "'healthy' has been used to mean 'healthful' since the 16th century." The usage panel, whom I imagine as masked nobles meeting in a secret room, seems amused by the claims of the "healthful" camp.
"Healthy food" isn't wrong; neither is "healthful food." Use the one you prefer and ignore naysayers. As with most style choices, be consistent so that you don't confuse your readers. Personally, I agree with Fowler that "healthful" sounds awkward. Besides, who wants to remember another usage rule when the default word choice is fine?
Note: Thanks to Shuna for letting me use her post as a springboard for discussion.