But 1 ounce of almonds -- dry-roasted, with no salt -- contains 170 calories and 15 grams of fat. Kostas said one-quarter cup a day may be fine, or even less.

"But not a whole cup," she said. "Many people overdo nuts.

"Overall, most of these foods are, in fact, healthy. But keeping them on the "good for you" list requires a bit of restraint, measuring and reading of ingredient lists, where, unlike the health section, there's no stretching the truth.