Nutritional Health for Women
Water is essential for life and activity. Water is necessary for transporting nutrients in the blood, digesting and excreting nutrients, providing the structure to your body cells, regulating temperature, lubricating joints and organs, and protecting the brain and spinal cord.
Water must be replaced in large amounts daily and is the number one nutrient needed to survive. Athletic and physical activity requires water; sweating requires more. Dehydration is the term used to describe low water levels in the body. Signs of dehydration include thirst, weight loss, weakness, fatigue, loss of appetite, dry mouth, small amounts of dark-colored urine, headaches, poor concentration, overheating, and, ultimately, whole body collapse.
Water or juices in plentiful amounts is the best fluid source for your body. Water can also be absorbed by the body in foods (soups, melons, and vegetables). It is recommended that at least eight, 8 ounce water or juice drinks are consumed each day, in addition to drinking that makes up for sweat lost during a workout. (For specifics on fluid recommendations during exercise, see chapter 14, "Exercise Fuel.") Caffeine, alcohol, and some stimulants found in "energy drinks" are diuretics and cause your body to lose water (resulting in more urination); therefore, these drinks should not be considered part of your minimum daily fluid needs.
Because the blood is full of molecules, the correct ratio of molecules to water must be maintained in order to keep the blood flowing and allow for transport of nutrients in and out of cells. Much of this transport follows gradients across cell membranes. Electrolytes facilitate these gradients via chemical interactions between molecules; thus, electrolytes maintain proper body fluid levels and transportation of essential nutrients. Electrolytes are lost through sweat, urine, and digestion and must be replenished daily. Sports drinks are formulated to replenish electrolytes. The most important electrolytes are sodium and potassium.
Sodium is necessary for maintaining water in the blood and for regulating nerve and muscle activity. It is lost in sweat and must be replenished with exercise that lasts more than 60 minutes, or sooner if exercising in high temperatures. Low sodium levels can cause drowsiness, weakness, cramping, and confusion. Endurance athletes who drink water without sodium during long events can develop serious illness. Sodium is found in many natural and most processed foods. Potassium also plays a role in muscle and nerve activation and also functions in glucose transport and glycogen storage. Potassium is lost in sweat; low potassium can cause muscle weakness and fatigue, and in severe cases, affect heart rhythm. Potassium is found in fresh fruits and vegetables.
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From The Active Woman's Health and Fitness Handbook by Nadya Swedan. Copyright © 2003 by Nadya Swedan. Used by arrangement with Perigee, a member of Penguin Group (USA) Inc.
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