Relevance of Assessment Methods for Fluid Intake.

Reliable data at population level are essential to firmly establish links between fluid intake, hydration and health, investigate dose-response relationships and develop meaningful public health strategies or reference intake values. However, limited research exists regarding the most appropriate methodology for assessing beverage or total fluid intake (TFI). To date, methodologies have been developed to assess food and nutrient intake without due consideration of water or fluid intake behavior. A recent crossover study showed that a 24-hour food recall significantly underestimated mean TFI by 382 ml (95% CI 299-465) compared with a fluid specific 7-day record. The authors postulated that this average difference was mainly the result of missed drinking acts between meals a 24-hour recall was used. Using a 7-day record administered in paper form or on-line has also been shown to lead to a significantly different mean TFI of 129 ml. Therefore, the choice of methodology might result in measurement errors that limit between-survey or between-country comparisons. Such errors may contribute to variations in estimates of TFI that cannot be explained by differences in climate, physical activity or cultural habits. A recent survey confirmed the variation in methodologies used in European national dietary surveys. Since these surveys form the basis for setting adequate intakes for total water intake, measurement error between surveys should be limited, highlighting the need for the development of a consistent methodology that is validated for water and TFI estimation.