Electrolyte Capsules

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Maintaining your electrolyte levels, primarily sodium chloride, is critical in an ultramarathon. Many runners find electrolyte capsules an important part of their hydration approach and never having any problems. Ideally, the capsules will disintegrate in the stomach, mix with water and be absorbed by the small intestine, but this may not always be the case.

1 Advantages

Electrolyte capsules have a number of advantages for replenishing electrolytes lost in sweat.

  • They are a convenient and easy to carry in a race.
  • Some electrolyte capsules contain more than just sodium and chloride, adding Magnesium, potassium and calcium to the mix. However, the capsules usually only contain small quantities of other electrolytes and their value mid-race is dubious.
  • Anti-acid (AKA buffering agent) is also present in some capsules. This may help limit stomach acidity, but it could also interfere with digestion.

2 Disadvantages

Electrolyte capsules can be opened and mixed with a sports drink, but most runners swallow them intact.

  • These capsules must be taken with water. Without sufficient water in the stomach, the capsules could form a concentrated salt solution that leads to nausea and even vomiting.
  • Capsules take time to dissolve in the stomach. My reading indicates this time is typically 5 to 15 minutes, but can be as long as 4 hours. If the water you take with the capsule is absorbed before the capsule dissolves, there will be a concentrated salt solution formed, leading to nausea and potentially vomiting.
  • Taking a capsule bypasses your sense of taste, which I believe limits some important biofeedback mechanisms. Instead of relying on your sense of tastes and what appeals, runners taking electrolyte capsules must calculate an appropriate intake, which is non-trivial.
  • Most recommendations for electrolyte capsule usage recommend taking them in a timed basis, rather than in proportion to the amount you are drinking. The can result in a significant lack of electrolytes over time. For example, a fit but un-heat acclimated male runner can sweat out 700-1800mg of sodium per hour in summer (From The Science Of Hydration.) Taking two capsules per hour (the upper recommended intake) would give 700mg (s-caps) or 400mg (salt stick), leaving a significant deficit. (The human body has about 15,000mg of sodium in the blood.)

3 Recommendations

While dehydration can be dangerous, low blood sodium (Hyponatremia) kills far more runners. It is critical that you ensure adequate electrolytes while running ultramarathons, and can be important for shorter distances.

  • Opening the electrolyte capsules and mixing with your sports drink will prevent any problems with the capsules dissolving and will allow your intake of electrolytes to balance your water intake.
  • Some runners will chew the capsule in their mouth to ensure that the electrolytes are quickly dissolved, but I’ve found this quite unpleasant.
  • My personal approach is to always carry some electrolyte capsules for emergencies in my Portable Pharmacy, but to rely primarily on other sources.
  • I will add table salt to my sports drink at 1/4 teaspoon per quart of liquid, use electrolyte drink tablets such as Nuun, drink soup/broth or eat salty foods.
  • Note that different gel packets contain widely different electrolyte levels. See Hydration 101 for some notable high-electrolyte Gels.