Proper hydration helps regulate important body functions including temperature regulation, joint lubrication, nutrient and waste transportation, kidney performance, and overall chemical reactions. In addition to water and other fluids, people can meet hydration needs through the foods they eat. Fruits and vegetables, for example, can contribute greatly.
Daily Water Requirements
The amount of water needed is not straightforward. The water contribution from foods varies as well as recommendations based on factors such as age, weight, physical activity, caloric intake, and environmental conditions.
Gender Variation
According to the National Academies of Sciences, Engineering, and Medicine, the Adequate Intake (AI) for total water, including sources from foods and beverages is approximately 3.7 liters (125 ounces or 15.5 cups) per day for men and 2.7 liters (91 ounces or 11.5 cups) per day for women.
Age and Weight Differences
Mallett et al. determined that for every kg of body weight, an individual adult needs 30 to 35 mL of water. This translates to approximately 8.6 to 10 cups per day for a 150-pound person. Children between 2 and 8 years would need 77.1 mL/kg, which for a 50-pound child would be approximately 7.5 cups per day. And 9 to 18-year olds need 40.4 mL/kg, which means a 59-pound child or adolescent would need to consume approximately 10 cups per day.
Caloric Intake
Manz and Wentz put forth that Calorie intake should also be considered, recommending between 1.21 to 1.31 mL/Calorie for American adults. This translates to approximately 10 to 11 cups for a 2000 Calorie diet.
Water from Food Sources
Most fruits and vegetables are composed primarily of water. For instance, lettuce and cucumber respectively contain approximately 95% and 96% water. Zucchini is about 94% water and watermelon and strawberries are about 92% and 91% water. Not only do these foods contribute substantially to hydration, they provide essential vitamins, minerals, fiber, anti-oxidants, and other phytonutrients.
Health Impacts of Hydration
Proper hydration supports numerous physiological processes, including cognitive function, physical performance, and kidney health. Dehydration as mild as 1-2% of body weight can impair attention, memory, and mood. Small deficits in hydration can also reduce endurance, increase fatigue, and affect thermoregulation, which is essential for maintaining physical performance.
Moreover, sufficient water intake is crucial for kidney health, helping to prevent kidney stones and urinary tract infections. Chronic kidney disease (CKD) affects approximately 15% of adults in the United States. Adequate hydration helps flush out waste products and reduces the concentration of substances in urine that can lead to kidney stone formation and help reduce CKD risk.
Summary, Conclusion, and Application
Proper hydration is crucial for optimizing health and performance and mitigating risks of chronic illness such as CKD. Recommended intakes can vary by age, weight, gender, and even caloric intake. Including water-rich foods like soups, smoothies, and fresh produce can help significantly.
Although complex calculations can be used, thirst and urine color can be equally if not more effective guides. For example, a pale-yellow urine typically indicates adequate hydration. Carrying a water bottle and drinking when thirsty and/or when urine color turns a stronger yellow can also help.
If you are unsure about water intake, making an appointment with a medical provider, including a registered dietitian can help ensure you are meeting your hydration needs.
About the Author
Patrick Traynor, PHD, MPH, RD, CPT is a registered dietitian with an insurance-based practice, MNT Scientific, LLC in South Lake Tahoe, CA, Minden, NV, & Ashland, OR. In office or video appointments can be requested online at MNTScientific.com or by calling (530)429-7363. Inquiries can be directed to info@mntscientific.com