Diet is one of the most important aetiological factors in dental caries. This chapter describes the relationship between sugar consumption and dental caries through history. Cariogenicity of food items and diet, as well as factors that influence the cariogenicity, is reviewed. The interplay of diet with other preventive measures also receives attention. Prevention through diet with natural sugar alcohol, xylitol and beneficial bacteria (probiotics) is discussed. Finally, diet counselling for caries prevention for specific age groups is summarised, and dietary suggestions with health benefits are reported.