Effects on dental caries
Evidence from observational studies, conducted in a number of different countries, has confirmed that high SSB intake increases the risk of developing dental caries, particularly in children [50-61]. Similar findings are reported in adults, however, the number of studies is limited [62-66]. It is widely accepted that acids in SSB and NNS play a major role in the development of dental erosion. Evidence from observational studies in children suggests that consumption of SSB is associated with an increased risk of dental erosion [67-70]. A recent cross-sectional study in Brazil showed that school children consuming one or more SSB a day had a 70% higher risk of dental erosion than those with lower or no intakes (four times per week or less) . An additional study, following approximately 1150 English children from the age of 12 to 14 years, showed that high consumption of carbonated SSB was a strong predictor of the amount of dental erosion observed at the age of 14. The risk of erosion was increased by approximately 50% for each additional SSB intake per day . Diabetes also has a detrimental effect on oral health and is linked to the development of gingivitis and periodontal disease [72, 73]. While it is well established that diabetes is a risk factor for periodontitis (via an elevated inflammatory response to periodontal microflora), authorities have suggested that inflammatory periodontal disease may increase insulin resistance in a way similar to obesity, thereby impairing glycaemic control [72, 74]. Thus, increasing evidence suggests that high SSB intake is a risk factor for dental caries and erosion, and suggests that intake should be limited, and at least partially replaced by healthier alternatives. Physicians and oral health providers should be aware of the potential negative impact on heath and of the possible bidirectional relationship of SSB, periodontal disease and diabetes.
Effects on cognitive performance and mood
Severe dehydration (i.e. over 13, 24 and 37 h of fluid restriction) is known to exert detrimental effects on cognition performance in adults. Ability to concentrate and alertness were noticeably reduced . In adult men, mild dehydration without hyperthermia has been shown to degrade specific aspects of cognitive performance and to promote adverse changes in vigilance and working memory . In adult women, one recent publication demonstrated that mild dehydration decreased alertness but increased sleepiness, fatigue and confusion ; whereas a second publication demonstrated that mild dehydration degraded mood, increased the perception of task difficulty, lowered concentration and increased headache symptoms . Children, with their higher surface area-to-mass ratio, reduced body cooling pathways and sensitivity of thirst detection mechanisms, are considered to be at higher risk for dehydration than adults. In infants, dehydration is associated with confusion and irritability . Results need to be confirmed by future research and studies of alterations of cognitive performance require deeper attention. In a study conducted in UK, free access to drinking water in class was associated with improved total fluid intake . In view of such results, it is clear that primary schools should promote water drinking in class.
Drinking safe and sufficient water as a means of healthy hydration should be emphasized as a cornerstone in preventing and managing overweight and obesity in the context of serious chronic disease.
Water, a vital nutrient, has numerous critical roles in the body as the main constituent of cells, tissues and organs . However, water is often forgotten in dietary recommendations although the physiological basis of hydration is well known [82, 83]. Water, quantitatively important and most essential nutrient, has no generally promoted dietary reference intake values. It has no calories and contains no sugars.
Although early studies suggested the benefits of large fluid intake in patients (particularly those with chronic kidney diseases), there has been a rising furor about the exhortation ‘to drink at least eight glasses of water per day’. Some authors have questioned this claim and mentioned that, there is no clear evidence of benefit from drinking increased amounts of water [84, 85]. However, there is no evidence to show that drinking such a level of fluid might be bad for health. Some other have also decried this practice [86, 87] while they have not provided striking arguments to demonstrate that there no clear evidence of a lack of benefit. There is recent evidence that increased fluid intake may be beneficial in preserving kidney function [88, 89].
It is important to establish if replacement of caloric beverages with non-caloric beverages (water or diet beverages) could have public health significance. It may be a simple strategy for promoting weight reduction on the long term. Recent studies have shown that increasing water intake and reducing carbonated SSB consumption is effective at preventing excessive weight gain in schoolchildren [90-93]. A randomized, controlled cluster trial in German schoolchildren found a significant 31% reduction in risk of overweight after a 12-month programme of promoting increased water consumption alone (e.g. by providing water fountains, refillable water bottles and structured classroom lessons on the hydration needs of the body), compared with control groups . A UK study of similar design focused on reducing carbonated drink consumption, which also included the promotion of drinking more water. Compared with the control group, there were significant reductions in carbonated drink consumption and in the proportion of overweight and obese children in the intervention groups after 12 months . Similarly, a Brazilian interventional study reported that decreasing SSB and fruit juice intake reduced BMI among overweight children (−0.4 kg m−2 in those participating in a healthy lifestyle educational programme vs. −0.2 kg m−2 in the control group [P = 0.11]); this difference was statistically significant among girls (P = 0.009) . Researchers found in middle-aged and older adults that the addition of two glasses of water consumed before meals resulted in a greater loss of weight when compared with a group who did not drink water. When combined with a hypocaloric diet, consuming 500 mL water prior to each main meal lead to greater weight loss than a hypocaloric diet alone in middle-aged and older adults . A recent study performed in obese and overweight adults shifted from SSB to water is in favour of benefits from water intake for weight control. An average weight loss of 2% to 2.5% was observed .
While such studies have reported positive results, further action is required at the public health and health care provider levels, to elicit change among the general population. In anticipation of the potential benefits of healthy-hydration advice, countries such as Mexico, the United States and Indonesia, have proposed public-health models [96-99] and initiated healthy-hydration guidance.