Xylitol is a popular sugar substitute in sweets and it is already known to cause less damage to teeth than sugar. It has also been suggested that the addition of xylitol to products may help to prevent tooth decay by stopping the growth of decay-producing bacteria. However, according to new evidence published in the Cochrane Library there is little high quality evidence that it is beneficial in the fight against tooth decay, which affects up to 90% of children and most adults worldwide.