Water intake: validity of population assessment and recommendations

Water intake: validity of population assessment and recommendations Joan Gandy 0 0 School of Life and Medical Services, University of Hertfordshire , Hatfield AL10 9AB , UK Good hydration is vital for good health and well-being. Until recently, there was little interest in collecting data on water and drink and beverage intake. However, there is increasing evidence that a low water intake or mild dehydration may be linked with the risk of chronic diseases. Accurate estimates of intake in populations are essential to explore these relationships. This will enable the identification of specific populations at the risk of low water intake and allow exposure assessment of potential contaminates and specific nutrients present in drinks and beverages. In addition, data from these population studies are used as the basis of national and international recommendations on water intake and to set and evaluate national health policies. For example, EFSA based their recommendations on data from population studies from 13 European countries. The range of intakes varied from 720 to 2621 mL/day; this diversity cannot be explained by environmental differences alone. However, this variability may, at least partially, be explained by the inconsistency in methodologies used as none of surveys used a dietary assessment tool validated for total water intake or beverage and drink intake. It is reasonable to suggest that this may result in incomplete data collection and it raises questions on the validity of the recommendations. The relationship between water consumption and health warrants further investigation, and robust methodologies are essential to ensure that these data are accurate and useful for setting public health priorities and policies. Water intake; Dietary assessment methodologies; Hydration; Fluid intake; Recommendations - There is increasing evidence of the links between water intake and physical disease and cognitive performance [1– 3]. The prevalence of dehydration in adults has been estimated to be 16–28 % depending on age [4] with the elderly being at increased risk of dehydration and associated morbidities [5, 6]. However, to establish health and disease risk relationships in all age groups with intake and to make reliable recommendations on water intake, it is essential to have accurate estimates of intake in populations. Current methodologies need to be improved to ensure accurate data before such relationships can be fully explored. This will inform both recommendations and public health programs. Recommendations on total water intake The sources of water are fluids, or beverages, (including drinking water and water in fluids, e.g., tea, wine, soft drinks) and water in food. There is often confusion about the use of the term “beverages” or “fluids” to represent water intake apart from water in food; for the purposes of this review, the term drinks and beverages will be used. All foods contain water although the amount of water in a food will vary between individual foods and diets. The European Food Safety Authority (EFSA) estimated that 20–30 % of total daily water intake in Europe comes from food [7]. However, the overall percentage of water in foods will vary between countries and seasons and depend on food types Table 1 Dietary reference intakes (adequate intakes) for total water set by the European Food Safety Authority (EFSA) and the Institute of Medicine (IOM) Adequate intake (L/day) a 80 % of total water intake; b through milk and dietary patterns. For example, in Ireland, it is estimated to be 33 % [8] and in 40 % in four cities in China [9] where more liquid foods, e.g., soups, broths are consumed. Both EFSA [7] and the Institute of Medicine (IOM) [10] in the USA have published gender- and age-specific recommendations on water intake as shown in Table 1. However, they took slightly different approaches in determining their recommendations. The IOM concluded that it was not possible to give an estimated average requirement due to extreme variability in water requirements that cannot be explained by different metabolism, variability in environmental conditions and activity. Moreover, the scientific evidence available at that time was insufficient to establish an intake level of total water intake that would reduce the risk of chronic diseases. Therefore, IOM set adequate intakes (AI) based on median intakes observed in national surveys, which form the basis of recommended daily allowances [10]. In contrast, EFSA [7] based their AIs on “a combination of observed intakes in population groups with desirable osmolarity values of urine and desirable water volumes per energy unit consumed.” They also recommended that the AIs only apply in moderate environmental temperatures and at moderate physical activity levels (PAL 1.6). The population intake data used by IOM are a single data set using the same methodology within one, albeit climatically diverse. However, EFSA used population surveys fro (...truncated)