Why Sodium-Potassium Balance Is Critical for Better Hydration By Donna P. Feldman, MS, RDN Sodium and potassium go together like yin and yang. They are the two primary electrolytes in your body, working together to maintain fluid balance in cells, blood plasma and extra-cellular fluid. Potassium is found primarily inside cells, and sodium is the main electrolyte in extra-cellular fluid. Although athletes don’t need a thorough understanding of all the complex aspects of electrolyte biochemistry, a basic understanding of the sodium-potassium balance is critical for better hydration. Potassium Facts The recommended daily intake is 4.7 grams. That’s 4,700 milligrams. But most people get much less than that from their diet. Potassium is a key regulator of blood pressure. Humans evolved on a high-potassium diet, full of plant foods, and our kidneys are well adapted to excrete excess intake of this mineral. Most potassium is lost in urine. Very little is lost in sweat. Sodium Facts Humans evolved to conserve sodium because primitive diets were very low sodium. The absolute minimum daily sodium intake needed to support health, assuming no losses in sweat, is a mere 180 milligrams per day. Excess sodium intake can raise blood pressure. The recommended daily limit on sodium intake is now 1,500 milligrams, the amount in about 2/3rd teaspoon of salt. Sodium loss in urine and sweat is adapted to intake. In other words, the more salt you eat, the more sodium in your sweat. Potassium Intake for Athletes First, regardless of your activity level, you should focus on high potassium foods for general good health. Muscle function, bone strength and nerve signaling all depend on adequate potassium. Potassium from plant foods is the best form, so pick several high potassium foods every day, such as: Bananas, Potatoes, Tomatoes and tomato juice, Oranges and orange juice, Dates, Raisins, Soy beans, tofu and edamame, Legumes and refried beans, Sweet Potatoes, Greens, such as spinach, kale and beet greens, Broccoli, Whole grain foods, Other fruits and vegetables. Sodium Intake for Athletes With training and acclimatization, your body will adjust to your typical sodium intake. If your typical sodium intake is modest, sodium losses in sweat will adjust down, with no adverse effects. But what happens when circumstances are extreme? You might travel to an event where the temperature soars, causing you to sweat much more than usual. If race day temperatures will be hot, with high humidity, and you typically sweat heavily, you should hydrate with sports drinks that contain electrolytes during the event. Altitude and very dry humidity can also cause fluid loss, even if you don’t perceive so much sweat on your skin. Again, go for sports drinks to rehydrate, or use salty snacks or special sports foods that contain sodium. If you normally avoid eating salty processed foods and snack foods, you could add some salt temporarily ahead of race day. You don’t need large amounts of sodium. Salt foods a bit or add some salty snacks like pretzels or bouillion. Some athletes actually drink pickle juice for the sodium content. If that doesn’t appeal to you, stick with pretzels. A mere 1/2-ounce of salted pretzels has roughly the same amount of sodium as 8 ounces of an electrolyte beverage. If you drink water during the race, but don’t replace the lost sodium, hyponatremia, or low blood sodium, can be the unwelcome result. Hyponatremia Most research shows that hyponatremia, or low blood sodium, is typically not due to low salt intake. Rather it’s caused by excessive sodium loss, possibly aggravated by excessive consumption of plain water. For example, competing in an extreme athletic event, such as a marathon, in high heat and humidity, can put you at risk, because you’re losing much more sodium than normal in sweat. People who work in extreme heat conditions, such as wild land fire fighters, also need to pay attention to salt intake. Again, these are unusual situations that put people at risk. Hyponatremia can come on quickly. Symptoms include: Abdominal bloating, Swollen fingers and toes, Swollen ankles and wrists. Extreme: brain swelling, fatigue, throbbing headache, confusion, loss of coordination. Rules of Thumb for Electrolytes Eat plenty of high potassium foods everyday, whatever your training level. Eat modest sodium. Maintain adequate hydration. Replace each pound lost as sweat with about 2 cups of fluid. When training or competing in high temperatures and extreme conditions, boost sodium intake with electrolyte replacement beverages or extra salt on your food. Donna P. Feldman, MS, RDN, is a registered dietitian nutritionist in Colorado, specializing in child nutrition, eating disorders, vegetarian/vegan diets, sports nutrition and food allergies. She owns Nutrition Strategy Advisors, LLC, publishes blogs and podcasts at buff.ly/17IWsW8, and co
Posted on: Fri, 05 Jul 2013 13:04:06 +0000
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