Urinary hydration biomarkers and water sources in free-living elderly

Accurate estimates of water intake and hydration status in populations are essential to identify populations at risk of dehydration and define strategies to improve standards of water intake.

To evaluate the hydration status and the contribution of food and beverages to the total water intake in a sample of free-living physically active Portuguese elderly.

A sample of 74 individuals (28 men), aged 60 to 83 years, were included in this study. A 24 h urine sample was collected; 24 h urine volume and osmolality were quantifi ed in order to estimate the free water reserve (FWR) used to assess the hydration status. A 24 h food recall corresponding to the day of urine collection was obtained. Food and beverages were grouped according to their nutritional composition, namely water content. The contribution of those groups to total water intake and its association with the hydration status were estimated. Urinary markers and food groups' contribution to total water intake were compared between sexes and according to the median FWR, using the t-test and Mann Whitney test.

Less than 10% of the participants were classifi ed as hypohydrated/at hypohydration risk. Water from food was nearly half of the total water intake (47% in females and 48% in males, p = 0.757). "Water" (22%) and "foods with reduced water content" (19%) were the groups that contributed the most to the total water intake in women and men, respectively. In men, the contribution of "alcoholic beverages" was signifi cantly higher than that of women (10.5% vs 1.7%, p < 0.001).

Even though most of the study participants were classified as euhydrated, the contribution of water-rich and nutritionally dense food, and non-alcoholic beverages, particularly in men, should be promoted.