26 June 12 Tweaking Sodium Intake with Heavy Sweating

Basic public health guidelines for sodium intake (1500 mg - 2300 mg) are not necessarily appropriate for those engaged in high intensity activities, especially in hot and/or humid climates. We need more water and sodium with profuse sweating. But how do we set our sodium goal in a tracker so that we don't go too high or too low?

There is no one correct answer to this question. Consider setting your sodium goal to the higher baseline of 2300 mg if you exercise regularly, have not been prescribed a low sodium diet for a medical condition, and do not have high blood pressure. On days that you sweat profusely with exercise, simply go above your sodium goal. A healthy body can tolerate a large variation in sodium intake on a day to day basis.

Estimating Sweat Losses

Benardot (Advanced Sports Nutrition, 2nd edition) estimates that 585 mg of sodium (about 1/4 teaspoon of salt) is lost with 1 lb of sweat loss. The easiest way to determine how much sweat you are losing is to weigh yourself dry and naked before and after activity. After activity, take off your wet clothes and towel off and then weigh yourself. How much weight did you lose? This captures net sweat loss above and beyond hydration during activity. As a general rule, for every pound of body weight lost, replace with about 20 fl oz (about 21/2 cups) of water and 585 mg sodium. Since this is after activity, sodium can simply come from meals and snacks, it does not have to come from an electrolyte replacement beverage.

Alert. Losing more than 2% of your starting body weight from sweat is dangerous. If you find that you are losing that much weight from sweat (despite consuming fluids during activity), consider increasing your hydration goals before and during activity. Most endurance aerobic athletes will not replenish 100% of their losses during activity but the goal is to replenish as adequately as possible. Excessive loss of body water (dehydration) can compromise mental faculties and increase the risk of heat stroke.

Have a Plan

If you are exercising continuously for an hour or more, then use electrolyte replacement drinks to help replenish sodium along with water during activity. These drinks are diluted enough to allow electrolyte replacement with minimal gastric distress. It is important to replace both water and sodium with prolonged and heavy sweating to avoid dropping the concentration of sodium in your blood. Other important electrolytes that are lost in sweat include chloride, potassium, bicarbonate, calcium, magnesium, phosphate, and sulphate.

If you are engaged in stop and go activities, then you have the luxury of choosing to replace electrolytes and water with more concentrated sources since you have the time to sit and digest without cramping. For instance, an 8 fl oz bottle of regular V-8 Juice contains 420 mg sodium and 470 mg potassium.

An eating plan that includes a variety of fruits, vegetables, whole grains, fish/seafood and/or lean meat, nuts/seeds, and lean dairy or dairy substitute will also help you replenish nutrients during rest.

Additional Resources

Dan Benardot: Advanced Sports Nutrition, 2nd Edition.
Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition & Athletic Performance. Be sure to click on the PDF link to see the entire position statement.
Katherine Isacks, MPS, RD, CDE
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Disclaimer: The information provided here does not constitute medical advice. If you are seeking medical advice, please visit your healthcare provider or medical professional.

Tags:

Exercise/Fueling for Exercise Nutrients/Salt/Sodium

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