Some runners sweat so much they end up crusted with salt; they wonder if they need to eat extra salt to replace what lost in sweat. Other runners avoid salt like the plague; they see no need to add it to their food because the typical diet already contains way too much. And then there are marathoners and triathletes who read about hyponatremia (low blood sodium). They wonder if they should start eating salty foods as a part of their daily sports diet. Perhaps you, too, have wondered about the role of salt, or more correctly, sodium (the part of salt associated with high blood pressure) in your diet.
This article can help you figure out if you should shake it or leave it.
Salt is made up of two electrically charged particles, sodium and chloride, also called electrolytes. In your body, sodium helps keep the right amount of water inside your cells, outside your cells, and in your blood. During exercise, if excessive water intake dilutes the sodium outside the cells, too much water seeps into cells and they swell, including the cells in the brain. The symptoms progressively appear and the runner feels weak, groggy, nauseous, incoherent, and then may experience stumbling, seizures, coma, and death. Athletes at risk of developing hyponatremia include slow marathoners, triathletes and others who exercise for more than four hours and are highly vigilant about hydration, to the extent they drink more fluid than they lose in sweat. Over time, they accumulate a large enough intake of water to dilute the blood sodium. Consuming sodium-containing sports drinks helps, but does not protect against hyponatremia because a sports drink offers far more water than sodium. The typical sports drink may have only one fifth the concentration of normal blood serum. While dehydration is the far more common concern than overhydration, all runners can avoid either problem by knowing their sweat rates. To learn your sweat rate, weigh yourself naked before and after you exercise. A one pound drop equates to losing 16 ounces of sweat and means you should target drinking 16 ounces of fluid during similar exercise bouts. Having knowledge about your sweat rate takes the guesswork out of drinking during long runs, and reduces the risk of health problems associated with consuming too much or too little water.
The average male's body contains about 75,000 milligrams of sodium, the equivalent of eleven tablespoons of salt. When you exercise, you lose some sodium via sweat. The amount you lose depends upon:
How much salt you sweat. Some runners have saltier sweat than other. Salty sweaters tend to end up with a crust of salt on their skin after a hard workout. Other runners, in comparison, have a low sodium content in their sweat - and no white salt stains on their skin or running clothes. The amount of sodium in sweat averages about 500 milligrams sodium per pound of sweat (and ranges from 220 to 1,100 milligrams). If you lose two pounds of sweat per hour for four hours of sweaty running, your sodium losses can become significant (4,000 milligrams of sodium). You should eat salty foods to replace the losses.
How much you exercise in the heat. If you are not used to exercising in heat, you may lose 1,100 milligrams of sodium per pound of sweat. But if you are acclimatized, you may lose only 300 milligrams. This means, if you are training in the winter for a marathon that happens on an exceptionally warm spring day, you might need extra sodium during the marathon.
The kidneys regulate sodium balance. That is, if you overconsume 200 milligrams sodium, your body will get rid of those 200 mgs via urine, unless you have salt-sensitive high blood pressure. In that case, the body retains too much salt. This results in retaining extra fluid in the blood, and blood pressure rises. As you age, your sensitivity to sodium increases, as does blood pressure and the associated risks of stroke, heart and kidney disease. An estimated 2-5% of people aged 25-34 years have high blood pressure, as do 31-36% of people aged 55-65 years. Of these, about 1/3 to 1/2 are salt-sensitive. To reduce your risk of developing high blood pressure, you should not only eat a low sodium diet but also boost your intake of calcium, magnesium and potassium, three minerals that help counter the negative affects of sodium. Instead of simply subtracting salty foods, you should also: consume extra fruits, vegetables and lowfat dairy foods for potassium, magnesium and calcium; exercise (and lose weight if you have weight to lose); limit your intake of alcohol and fatty meats; moderate your salt intake by eating less processed food. Having parents with low blood pressure also helps...
For non-athletes, the body only needs 500 milligrams sodium and the dietary guidelines recommend no more than 2,400 milligrams of sodium per day. Most runners easily consume 3,000 to 5,000 milligrams of sodium daily, mostly via processed foods. Sodium enhances food's flavor and helps prevent food spoilage. Most runners consume adequate sodium, even without adding salt to their food. For example, you get sodium via bread (150 milligrams per slice), cheese (220 milligrams per ounce), eggs (60 milligrams per egg), and yogurt (125 milligrams per 8 ounces). Runners who are extreme sweaters likely need more sodium, but generally consume more, particularly if they eat fast foods. Just two slices of cheese pizza (1,200 milligrams) or a hamburger (1,400 milligrams) can easily replace sodium losses; no sweat!
Run The Planet thanks Nancy Clark for the permission to reprint the article "Salt and Runners: Shake it or Leave it?" by Nancy Clark. Text © 2005 by Nancy Clark. Nancy Clark, MS, RD, is the Director of Nutrition Services and author of "Nancy Clark's Sports Nutrition Guidebook" and "Nancy Clark's Food Guide for Marathoners: Tips for Everyday Champions". She offers nutrition consultations to casual exercisers and competitive athletes at her private practice located at Healthworks, the premier fitness center in Chestnut Hill (Usa/Massachusetts). Books and sports nutrition teaching materials are available at www.nancyclarkrd.com. Illustration © 2005 by Run The Planet.