Some athletes, due to their activity and sweat production, are at risk of having too little sodium in their blood stream during training and competition. Although high salt (sodium) diets have been linked to a number of health risks, for endurance athletes, the opposite may be true: sodium requirements may be high.
Since sodium is lost in sweat, it is important for individuals who exercise for several hours, at high intensity, or in the heat to get adequate sodium before, during, and after exercise. This is even more critical during ultra-endurance competition.
Sodium Loss During Exercise
Sodium losses range from 300 to 2,000+ milligrams (mg) per hour depending upon heat, exercise intensity, and individual physiology. It is reasonable to estimate that the body loses 1,000 mg of sodium per hour of cycling in warm (80° F) conditions.
Example: If the body loses about 1,000 mg of sodium per hour of cycling through sweat, then after four hours of cycling about 4,000 mg of sodium may be lost. In temperate (70° F) weather conditions this may take five or six hours. In high heat (over 90°F) conditions; such sodium losses can occur in just a couple of hours.
How Much Sodium do Athletes Need?
The 2005 Dietary Guidelines for Americans recommends consuming less than 2,300 milligrams of sodium per day. This will be inadequate to meet the demands of many aerobic-endurance athletes.
For aerobic-endurance athletes, it is reasonable to plan on an intake of 500 to 600 mg of sodium per hour while cycling in the heat. This can be from a combination of foods and fluids. This amount of sodium exceeds that typically available in commercial sports drinks. It can be difficult to replace the 1,000+ mg of sodium that may be lost per hour of cycling. Consuming over 1,000 mg of sodium per hour may cause blood sodium levels to rise too rapidly and is not recommended.
Good ways to increase sodium intake include: add salt to a maltodextrin-based sports drink (see Table 2), consume salty snacks (pretzels, saltine crackers, etc.), or carry salt with you to sprinkle on food while cycling. Ingesting 5,000 mg to 6,000 mg of salt during the 24 hours before a long ride/event in the heat may also help.
It is preferable to eat salty foods or drinks rather than ingest salt tablets. Studies have shown that salty foods and drinks appropriately stimulate thirst and prevent the unintentional ingestion of dangerously high amounts of sodium.
If riding intensely on extremely hot days (95+°F) sodium losses can be more than double the 1,000 mg per hour starting point.
If you have high blood pressure, heart disease, or any other medical condition that extra salt may affect, please contact your physician for advice.