Sweetness is one of the five basic tastes and is universally regarded as a pleasurable experience, except perhaps in excess. Foods rich in simple carbohydrates such as sugar are those most commonly associated with sweetness, although there are other natural and artificial compounds that are sweet at much lower concentrations, allowing their use as non-caloric sugar substitutes. Examples of foods that may be used as non-sugar sweet substitutes include saccharin, aspartame, acesulfame potassium, sucralose, xylitol, erythritol, and stevia. Other compounds, such as miraculin, may alter perception of sweetness itself.