When a star U Conn basketball player took the advice of his sports nutritionist, Nancy Rodriguez, RD, and started drinking enough to consistently void a light-colored urine, he was amazed at how much better he felt all day. Unfortunately, too many athletes and exercise enthusiasts overlook the power of this essential nutrient.
The Body Cannot Function
Without Sufficient Water Supply
Perhaps it’s your turn to give water a try? This article offers droplets of information to enhance your water IQ, optimize your water balance, and help you feel and perform better.
You don’t have to drink plain water to get adequate water into your body. All fluids count, as do foods that have a high water content. For example, oatmeal is 84 percent water; low-fat milk is 90 percent; coffee is 99 percent; lettuce is 96 percent; tomatoes are 95 percent; broccoli is 89 percent; low-fat vanilla yogurt is 79 percent; and ice cream consists of 60 percent water.
Water is the solvent for biochemical reactions. Your body cannot function without sufficient water supply, as noted by the fact that athletes die from dehydration.
Your body needs water to moisten food (saliva), digest food (gastric secretions), transport nutrients to and from cells (blood), discard waste (urine), and dissipate heat (sweat). Water is a major component of the cells in muscles and organs. About 60 percent of a young male’s body weight is water, as is about 50 percent of a young woman’s body weight.
Different body parts have different water contents. For example, blood is approximately 93 percent water, muscle is about 73 percent water, and body fat is about 10 percent water. Water constantly moves between the inside and the outside of cells. About 4 to 10 percent of the water in your body gets replaced every day.
Note: Bioelectrical impedance (BIA) methods of measuring body fat actually measure body water. From that, a formula estimates the ratio of water to muscle and fat. Hence, if you use a Tanita Scale or Omron device, be sure to maintain adequate hydration. If you are dehydrated, you’ll end up with an inaccurate (higher) estimate of body fatness.
Your body produces about 8 to 16 oz. (250-500 ml) water per day during normal metabolic processes. During a marathon, a runner’s muscles can produce that much water over 2 to 3 hours. When muscles burn glycogen, they simultaneously release about 2.5 units water for each one unit of muscle glycogen, which helps protect against dehydration.
Coffee is a popular source of water. Although once thought to have a diuretic effect, current research indicates that coffee (in amounts normally consumed) hydrates as well as water over a 24-hour period. That is, after drinking coffee, you may urinate sooner, but you will not urinate more than you consume. Army research on caffeine and dehydration confirms coffee is an acceptable source of fluids for athletes, even during exercise in the heat. Hence, coffee and other caffeinated beverages such as tea or cola count towards your water intake.
An increased concentration of particles in your blood triggers the sensation of thirst. If you are a 150-pound athlete, you’ll start to feel thirsty once you’ve lost about 1.5 to 3 pounds of sweat (1 to 2 percent of your body weight). You are seriously dehydrated when you have lost 5 percent of your body weight.
Body water absorbs heat from the working muscles and sweat dissipates the heat. That is, the evaporation of a liter (about 36 ounces) of sweat from the skin represents loss of about 580 calories. Sweat keeps you from overheating during exercise and in hot environments.
To determine how much water you lose when you sweat, weigh yourself (with little or no clothing) before and after an hour of hard exercise with no fluid intake. The change in body weight reflects sweat loss. A 1-pound drop in weight equates to a loss of 16 ounces of sweat. A 2-pound drop equates to 32 ounces, that’s one quart. Drink accordingly during your workouts to prevent that loss.
When you sweat, you lose water from both inside and outside the cells. The water outside the cells is rich in sodium, an electrolyte that works in balance with potassium, an electrolyte inside the cells. Sweat contains about 7 times more sodium than potassium, hence sodium is the more important electrolyte to replace during extended exercise.
Most athletes who lose more than 2 percent of their body weight (3 pounds for a 150-pound athlete) lose both their mental edge and their ability to perform optimally in hot weather. Yet, during cold weather, you are less likely to experience reduced performance, even at 3 percent dehydration. 3 to 5 percent dehydration does not seem to affect muscle strength or performance during short intense bouts of anaerobic exercise such as weight lifting. But distance runners slow their pace by ~2 percent for each percent body weight lost by dehydration. Sweat loss of more than 10 percent body weight is life-threatening.
Adequate fluid intake can reduce problems with constipation and urinary tract infections. There is no scientific validation of theories that excessive water intake will improve weight loss, remove toxins, or improve skin tone.
Should you plan to drink eight glasses of water a day? No scientific evidence supports that rule, so you can simply drink in response to thirst. You can also monitor the volume of your urine. If your urine is scanty, dark and smelly, you should drink more. If you have not urinated during your work or school day (8:00 a.m. to 3:00 p.m.), you are severely under-hydrated.
Is bottled water better for you than tap water? Doubtful. According to the Center for Science in the Public Interest, nearly half of bottled waters come from municipal water supplies, not from the mountain streams pictured on the labels. This suggests standard municipal tap water is high quality. Rather than spending money on bottled water, turn on your tap. This will help stop the flood of 95 million plastic water bottles that get discarded each day, of which only 20 percent get recycled. Drink plenty of water, but also think “green.”
Nancy Clark, MS, RD, CSSD (Board Certified Specialist in Sports Dietetics) counsels both casual and competitive athletes at her office in Newton, MA (617-795-1875). Her “Sports Nutrition Guidebook” and food guides for new runners, marathoners and soccer players offer additional information. They are available at www.nancyclarkrd.com and www.sportsnutritionworkshop.com.
Armstrong, L., A. Pumerantz, M. Roti, et al. 2005. Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. Int J Sport Nutr Exerc Metab 15:252-265
Koslo, J. “Water, hyrdration and health: What dietetics practitioners need to know,” in SCAN’s Pulse, Academy of Nutrition and Dietetics, 2012 31:1 (Winter)
National Academy of Sciences. Institute of Medicine. Food and Nutrition Board.
Dietary Reference Intakes for Water. http://www.nal.usda.gov/fnic/DRI//DRI_Water/73-185.pdf
Wilmore, J and D. Costill. Physiology of Sport and Exercise, Human Kinetics, 1994.
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