Iceberg lettuce gets a bad rap for having few nutrients. In part that's because it has more water by weight than any other food (96 percent). But other types of lettuce — like Romaine and butter lettuce — are virtually just as hydrating, plus they offer way more vitamin A (80 percent of the daily value in just 1 cup). To help you absorb fat-soluble vitamin A, dress your salads with an olive oil-based dressing.