Beat the Heat -- Stay Hydrated!
Last reviewed by Faculty of Harvard Medical School on August 28, 2012
By Julie Redfern, L.D., R.D.N.
Hot weather will be here soon. Along with trying to stay cool, you need to be sure you drink enough fluids. People often blame the heat when they start to get headaches, light-headedness and fatigue. These are often the first signs of dehydration, even if you are not thirsty.
The warm weather encourages people to be outside working, exercising or just enjoying the sun. All of these activities speed up the loss of body water, with dehydration close behind. Even minimal dehydration (2% to 3%) can negatively impact your physical and mental performance.
Don't wait for the dry mouth, flushed skin, headaches, lightheadedness or fatigue. You should prevent dehydration by drinking fluids throughout the day.
A good way to know if you are not drinking enough is to stay aware of the volume and color or your urine. If you notice a decrease in volume or the color is darker, its a good bet youre dehydrated.
Many factors can make you dehydrate more quickly than expected. Medications and supplements that promote increase in urination (diuretics) hasten dehydration. Huge amounts of water move out of the body through the skin with sweating, and from the lungs during exercise or illness with fever. Women who are pregnant and lactating require more fluids.
If replenishing lost body fluids is essential to preventing dehydration, does it matter what type of fluid we consume?
Fluids are considered to be any food or beverage thats liquid at room temperature, such as water, ice, soup, beverages, ice cream, sherbets, popsicles and gelatin. Water is the best fluid for hydration; it has no calories, sugar, salt, carbonation, coloring or preservatives. No other drink can even come close to that claim! And water is cheap, despite the huge commercial bonanza that bottled water has become.
Water is an essential nutrient for life. Our bodies are made up of more than 70% water. Water is necessary for so many of our basic functions, such as regulating body temperature, removing wastes, moisturizing our skin, lubricating our joints, and carrying oxygen to our cells.
Water is indeed everywhere. Water is a component of most foods we eat, especially fruits and vegetables. For example, 1 cup of fruit contains ½ cup fluid. However, many people dont drink water as their main choice of beverage. In addition to bottled water, theres a wide variety of other beverages marketed to us every day, such as:
Hundred-percent fruit juice contains some vitamins, minerals, and a lot of sugar. In fact, a 16-ounce glass of fruit juice contains about 220 calories and 25 grams of sugar. Fructose, or fruit sugar, reduces the rate at which we absorb fluid and can actually make you thirstier, leading to over consumption of calories from juice.
Sports drinks often contain fructose or sucrose syrups, flavorings, salt, citric acid, sodium, potassium and colorings. The electrolytes, sodium and potassium, are helpful for endurance-type exercise or activity, but not necessary for everyday exercise. Sports drinks dont hydrate you any better than water, but, the calories are less than in juices or soda. There are roughly 30 grams of sugar and 100 calories in 16 ounces of sports drink.
Energy drinks contain vitamins, amino acids, a lot of sugar, and caffeine. Advertised as providing more energy, this really equates to more calories and caffeine. Added caffeine can be temporarily energizing, but often leads to a rapid dip in energy and can be potentially habit forming. About 8 ounces of energy drink equals about 115 calories and 80 milligrams of caffeine. As a comparison , 8 ounces of coffee has 135 milligrams of caffeine.
Fitness waters are waters sprinkled with an assortment of nutrients, sometimes herbs, flavorings and sweeteners. These enhanced waters dont usually contain enough vitamins or minerals to make any impact on your health, and they can be costly. Additionally, there is no current credible scientific evidence that added herbs affect energy levels or improve health. These beverages can still count toward your fluid goals, but can contain 10 to 100 or more calories for 16 ounces.
Carbonated beverages such as regular or diet sodas can be high in sugar or artificial sweeteners, and caffeine. Colas are also high in phosphates that bind with calcium and weaken bones. Regular soda can contain up to 200 or more calories for 16 ounces.
Coffee, tea and lattes are also very popular. They often contain added sugars and fats along with the caffeine, and can add up to as many as 450 calories for 16 ounces. Current studies show that caffeinated beverages may not be dehydrating, as once thought. Limited amounts can count toward your overall hydration goal. However, since most caffeinated products provide very few nutrients, it is typically advised to keep intake low.
Flavored waters are beverages with a touch of flavoring with the bonus of zero calories. These beverages are great for people who prefer flavor in their beverage but wish not to have added calories.
Every persons hydration needs vary, so the standard prescription of eight, 8-ounce glasses per day of fluid may not be enough for you. Rather than count cups of fluid, its more important to be in sync with your sensation of thirst and to be aware of the early signs of dehydration! During exercise and illness, your fluid needs are likely to increase dramatically.
Julie Redfern, R.D., L.D N. is a registered dietitian in the Nutrition Consultation Service at Brigham and Women's Hospital. She specializes in nutrition counseling for the obstetrics and gynecology department. She is a graduate of the University of Vermont and completed her dietetic internship at the University of Cincinnati Medical Center. Michelle McAndrews is a dietetic intern at the Brigham and Women's Hospital.