His original "Graham bread" was made with the intent of supressing carnal urges, which he believed were the source of many maladies (He also warned that ketchup and mustard caused insanity).
Graham crackers have long since ceased to be considered a health food, but they have remained popular as a snack food. Today, graham crackers are made with much greater amounts of sugar and other sweeteners than used in the original recipe. Cinnamon is also commonly added to graham cracker mix to enhance the flavor.
Graham crackers are essential ingredients for various popular snack foods, including moon pies and s'mores.
See also: Digestive biscuit