WHO guidelines:

The WHO recently published a set of guidelines in 2015 for the maximum sugar intake in adults and children. By conducting a meta-analysis of several randomised controlled trials they identified an association between consumption of free sugars and increased body weight as well as consumption of free sugars and dental caries.  
Based on the evidence reviewed, they were able to generate guidelines on sugar consumption:
• They strongly recommend a reduced intake of free sugars throughout the life course.
• They strongly recommend reducing the intake of free sugars to less than 10% of total energy intake.
• They also recommend, although this is only a conditional recommendation, that the intake of free sugars be further reduced to below 5%.

The evidence has shown that body weight and dental caries are reduced when sugar intake is limited to a maximum of 10% of the daily energy intake.

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