does it cause tooth decay?
Yes, in 2003 WHO report stated that "Sugars are undoubtedly the most important dietary factor in the development of dental caries".
Sugar
2003 WHO report stated that "Sugars are undoubtedly the most important dietary factor in the development of dental caries". 
where does the sugar in fruit come from Fructose where did it get its name from? Sanskrit ("śarkarā"), meaning "ground or candied sugar", came Persian "shakar".
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Sugar [SEP] Tooth decay
The 2003 WHO report stated that "Sugars are undoubtedly the most important dietary factor in the development of dental caries". A review of human studies showed that the incidence of caries is lower when sugar intake is less than 10% of total energy consumed.