Extrinsic acid erosion is when the source of acid originates from outside of the body. Acidic food and drink lowers the pH level of the mouth resulting in demineralisation of the teeth. A variety of drinks contribute to dental erosion due to their low pH level. Examples include fruit juices, such as apple and orange juices, sports drinks, wine and beer. Carbonated drinks, such as colas and lemonades, are also very acidic and hence have significant erosive potential. Foods such as fresh fruits, ketchup and pickled food in vinegar have been implicated in causing acid erosion. Frequency rather than total intake of acidic juices is seen as the greater factor in dental erosion; infants using feeding bottles containing fruit juices (especially when used as a comforter) are therefore at greater risk of acid erosion.