Fifty-five studies were included (three intervention studies, eight prospective cohort designs, 21 population studies and 23 cross-sectional studies). GRADE quality assessment was based on the cohort studies only.
The authors reported that overall, 42 out of 50 studies in children and five out of five studies in adults showed at least one positive association between sugars and dental caries.
Effect of reducing or increasing sugars (GRADE evidence: moderate): Seven cohort studies consistently reported higher dental caries with higher sugar intake. A meta-analysis of all study designs favoured lower sugar intake in terms of the DMFT score (SMD 0.82, 95% CI 0.67 to 0.97; three studies; Ι²=84%) and for caries prevalence (RR 7.15, 95% CI 2.82 to 8.14; two studies; Ι²=71%).
Effect of restricting free sugars intake to less than 10% energy (GRADE evidence: moderate): Results from five cohort studies showed consistently more caries with higher sugar intake (more than 10% energy) compared with lower intake (less than 10% energy).
Effect of restricting free sugars intake to less than 5% energy (GRADE evidence: very low): The analysis (based on three population surveys) showed lower caries progression when per capita sugars intake was less than 10 kg per year (approximately 5% energy).
Further results were reported in the review.