Intake of free sugars is associated with a risk of non-communicable diseases including dental caries, and authoritative organisations recommend limiting intake to <5% energy intake (E) or lower (1, 2). National surveys of schoolchildren in India indicate the prevalence of obesity is rising >10%/year(3) and that 52.5% of young adolescents are affected with dental caries(4), yet, there is a dearth of data on dietary intake of sugars by this population. The objective of this research was to assess the intake of total and free sugars, and the contribution of food sources to free sugars intake, in a random sample of 11–13-year-old schoolchildren in Delhi, India. The study was approved by The University of Adelaide Human Research Ethics Committee and the Independent Ethics Committee of the Centre for Chronic Disease Control, New Delhi. The target sample size of 360 was based on a ± 5% margin of error in estimated sugars intake. A statistician external to the research team generated a random sample of 150 schools stratified by district (n = 11). Schools were recruited in turn from the list until 10 schools had consented. Teachers shared study information with parents who were invited to complete an online consent form. Child assent was obtained before data collection. Participants recorded all food and drink consumed over three consecutive days, including one weekend day, in a food diary. The information recorded was entered into an online dietary assessment tool, Intake24 (Southeast Asia version), during an interview with each participant during which portion size was ascertained with reference to the database of over 2400 food photographs of more than 100 foods. The Intake24 database converted food and drink reported into the intake of total and free sugars through integrated food compositional tables. Of 514 pupils providing consent, 393 participants (76.5%) (169 girls, 224 boys) completed the study. In girls, the median (IQR) daily intakes of total and free sugars were 95.0 (70.1-120.2) g/day and 43.0 (28.1-68.5) g/day respectively. The corresponding values in boys were significantly higher at 104.0 (80.2-138.7) g/day and 53.1 (34.1-76.5) g/day (p = 0.004). No between-gender difference was observed in the median percent contribution of sugars to E: total and free sugars contributed 14.9% (IQR 11.4-18.1%) and 7.1% (IQR 4.8-10.1%) respectively. The percent contribution of the main sources of sugars to free sugars intake were: (i) Sugars Preserves and Syrups (31.2% (IQR. 9.6-51.7%)); (ii) Cakes and Biscuits (13.7% (IQR 0-26.4%)); (iii) Desserts (5.4% (0-17.5%)) and (iv) Sugar-Sweetened Beverages and Juices (2.1% (IQR 0-15.7%)). In conclusion, in this sample of 11-13-year-old schoolchildren from Delhi, free sugars intake was above the WHO <5% E threshold. Forms of sugars that are added to foods by the consumer made the largest contribution to intake.

Currently, there is considerable emphasis on the relationship between dietary sugar consumption and various health outcomes, with some countries and regions implementing national sugar reduction campaigns. This has resulted in significant efforts to quantify dietary sugar intakes, to agree on terms to describe dietary sugars and to establish associated recommendations. However, this information is infrequently collated on a global basis and in a regularised manner. The present review provides context regarding sugar definitions and recommendations. It provides a global review of the available data regarding dietary sugar intake, considering forms such as total, free and added sugars. A comprehensive breakdown of intakes is provided by age group, country and sugar form. This analysis shows that free sugar intakes as a percentage of total energy (%E) are the highest for children and adolescents (12–14%E) and the lowest for older adults (8%E). This trend across lifecycle stages has also been observed for added sugars. The available data also suggest that, while some reductions in sugar intake are observed in a few individual studies, overall intakes of free/added sugars remain above recommendations. However, any wider conclusions are hampered by a lack of detailed high-quality data on sugar intake, especially in developing countries. Furthermore, there is a need for harmonisation of terms describing sugars (ideally driven by public health objectives) and for collaborative efforts to ensure that the most up-to-date food composition data are used to underpin recommendations and any estimates of intake or modelling scenarios.

Diet and nutrition impact on many oral diseases, in particular dental caries. Consumption of fluoridated water coupled with a reduction in non-milk extrinsic sugar intake is an effective means of caries prevention. However, studies on the fluoride concentration of bottled waters suggest increased consumption of these waters, in preference to fluoridated tap water, would lead to a marked decrease in caries protection. Concerns have been raised about the bioavailability of fluoride from artificially-fluoridated water compared with naturally-fluoridated water. This issue has been addressed in a human experimental study that has indicated that any differences in fluoride bioavailability are small compared with the naturally-occurring variability in fluoride absorption. Research has unequivocally shown sugars to be the main aetiological factor for dental caries, and information on intakes guides health promotion. Repeat dietary surveys of English children over three decades indicate that levels of sugars intake have remained stable, while sources of sugars have changed considerably, with the contribution from soft drinks more than doubling since 1980. Dental caries eventually leads to tooth loss, which in turn impairs chewing ability causing avoidance of hard and fibrous foods including fruits, vegetables and whole grains. A very low intake (<12 g/d) of NSP and fruit and vegetables has been found in edentulous subjects. Provision of prostheses alone fails to improve diet. However, initial studies indicate that customised dietary advice at the time of denture provision results in increased consumption of fruits and vegetables, and positive movement through the stages of change. Feasible means of integrating dietary counselling into the dental setting warrants further investigation.

Oral health is related to diet in many ways, for example, nutritional influences on craniofacial development, oral cancer and oral infectious diseases. Dental diseases impact considerably on self-esteem and quality of life and are expensive to treat. The objective of this paper is to review the evidence for an association between nutrition, diet and dental diseases and to present dietary recommendations for their prevention. Nutrition affects the teeth during development and malnutrition may exacerbate periodontal and oral infectious diseases. However, the most significant effect of nutrition on teeth is the local action of diet in the mouth on the development of dental caries and enamel erosion. Dental erosion is increasing and is associated with dietary acids, a major source of which is soft drinks.

Despite improved trends in levels of dental caries in developed countries, dental caries remains prevalent and is increasing in some developing countries undergoing nutrition transition. There is convincing evidence, collectively from human intervention studies, epidemiological studies, animal studies and experimental studies, for an association between the amount and frequency of free sugars intake and dental caries. Although other fermentable carbohydrates may not be totally blameless, epidemiological studies show that consumption of starchy staple foods and fresh fruit are associated with low levels of dental caries. Fluoride reduces caries risk but has not eliminated dental caries and many countries do not have adequate exposure to fluoride.

It is important that countries with a low intake of free sugars do not increase intake, as the available evidence shows that when free sugars consumption is <15–20kg/yr (~6–10% energy intake), dental caries is low. For countries with high consumption levels it is recommended that national health authorities and decision-makers formulate country-specific and community-specific goals for reducing the amount of free sugars aiming towards the recommended maximum of no more than 10% of energy intake. In addition, the frequency of consumption of foods containing free sugars should be limited to a maximum of 4 times per day. It is the responsibility of national authorities to ensure implementation of feasible fluoride programmes for their country.

Although theoretically all glycoprotein sugars can be derived from glucose, it may be hypothesized that specific dietary sugars could be preferential substrates for glycoprotein synthesis. To test this hypothesis, groups of rats received either continuously (continuous-labelling experiment) or for a single nutritional period (pulse-labelling experiment) a 13C-rich diet containing either maize starch or artificially labelled [13C]glucose. Some groups of rats were also provided during a single nutritional period with low amounts (20–200 mg/animal) of low-13C dietary sugars (mannose, galactose, fucose or fructose). If specific dietary sugars were preferentially incorporated into glycoproteins instead nf glucose-derived labelled sugars, a decrease would be expected in the intestinal or serum glycoprotein-sugar 13C enrichment monitored by gas chromatography-isotope-ratio mass spectrometry (GC-IRMS). Contrary to this hypothesis the results showed no significant decrease with any of the specific dietary sugars. Furthermore, with dietary low-13C mannose or galactose, a significant increase in 13C enrichment of glycoprotein-sugars was observed compared with some other nutritional groups. Moreover, in the pulse-labelling experiment, dietary mannose and galactose induced similar patterns of 13C enrichment in intestinal and serum glycoprotein-sugars. Therefore, although specific dietary sugars do not appear to be preferential substrates for glycosylation under conditions and doses relevant to current concepts of nutrition, regulatory roles of some specific dietary sugars in relation to glycoprotein-sugar metabolism might be hypothesized. These findings could lead to similar studies using stable-isotope methodology in man which could have practical consequences, especially in parenteral nutrition where glucose is the only sugar provided to the metabolism.