Patient Education Healthy Living: Hydration
Water & hydrationWater is essential for human life and accounts for up to 75% of one’s body weight, depending on one’s age. Water has a role in most bodily functions such as the regulation of body temperature, lubrication ofng the lungs and skin, controlling blood pressure, and transporting nutrients, oxygen and waste around the body.1
DehydrationWhile humans can survive for several weeks without food; a lack of water will result in death after only three to five days; and even less in hot or dry environments.2. Dehydration is refers to the loss of water and salts that are essential for normal body function and healthy living. Mild dehydration is the loss of no more than 5% of the body’s fluid. A loss of 5-10% is considered moderate dehydration, while a 10-15% loss becomes severe dehydration, a life-threatening condition. However, even a fluid loss of 1-2% can have an adverse effect on physical and mental performance.1 Symptoms of dehydration include lethargy, headaches, dizziness, confusion, and thirst. The urine also changes colour from a pale, straw yellow to dark yellow or even brown. A reduction in body weight can also be observed when dehydration is moderate or severe.
RecommendationsUnder average conditions, The World Health Organization (WHO) recommends a daily intake of 2.5l of fluid for women and 2.9l for men, and intakes of 4.5 to 5.5l under specific conditions such as during exercise, in hot climates or during pregnancy and lactation. All non-alcoholic fluids contribute towards healthy nutrition and fluid requirements; however, some beverages are better choices than others. Scientists on a beverage guidance panel system (see Fig 1) developed a guidance system which ranked all beverages on a scale of one to six based on calorie/nutritional composition and related health benefits/risks. Water was given the highest rating whilst unsweetened tea, coffee and herbal infusions were all given a rating of two. In addition, a similar guide was produced by The British Nutrition Foundation that ranked water first amongst suitable beverages for topping up fluid levels, closely followed by unsweetened tea, coffee and herbal infusions.4
Tea and hydrationFor the general population, the rehydrating properties of tea are as good as those of water. Tea is 99% water and is the second most consumed drink in the world. Brewed tea contains approximately half of the caffeine content as brewed coffee. 5, 6 Contrary to popular belief, tea is not dehydrating. Only when more than 250mg of caffeine is consumed in one sitting, can these dehydrating effects begin to occur - which is the equivalent of approximately 6 cups of tea or 3 cups of freshly brewed coffee. 5, 6, 7 Unfortunately, there has been limited research done on tea consumption in South Africa.
Figure 1. US Beverage Guidance System (adapted from Popkin et al)
- Jequier E & Constant F (2010). Water as an essential nutrient: the physiological basis of hydration. European Journal of Clincal Nutrition 64, 115-123
- Benelam B & Wyness L (2010) Hydration and health: a review. Nutrition Bulletin 35, 3–25.
- Popkin BM et al (2006) A new proposed guidance system for beverage consumption in the United States. American Journal of Clinical Nutrition 83, 529–42.
- British Nutrition Foundation (2010) Healthy hydration guide. www.nutrition.org.uk/nutritioninthenews/hydration/healthyhydration-guide
- USDA National Nutrient Database for Standard Reference,Release 26. Basic Report 14355, Tea, black, brewed, prepared with tap water. Accessed 23.10.2013, ndb.nal.usda.gov
- USDA National Nutrient Database for Standard Reference, Release 26. Basic Report 14209, Coffee, brewed from grounds, prepared with tap water. Accessed 23.10.2013, ndb.nal.usda.gov
- Ruxton CHS (2008) The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks. Nutrition Bulletin 33, 15-25.