The Great Salt Debate

Last week’s Q&A session with Dr Alan McCubbin was a great insight into sodium, hydration requirements and the current body of scientific literature. Let’s review what we learnt and what we can take away from it. All images are courtesy of Alan. 

My takeaways from the session with Alan were as follows:

1. Sodium intake is required when replacing 60-70% of sweat loss. 

2. You do not need to replace 100% of sweat loss during sessions.

3. If you are not replacing 60-70% of fluid loss, you may not require exogenous sodium as your blood sodium levels will rise due to lower volumes of fluid due to sweat loss.

Courtesy Dr Alan McCubbin

4. Replacement of fluids and sodium may only be required for events lasting circa 3-4 hours.

5. The caveat to this is that a lot of sessions are not over this duration yet the vent that the athlete is training for might be 3+ hours long. Therefore, training your hydration strategy and ability in shorter duration sessions would make sense to prepare for the longer full events.

Duration of session and event combined with an athlete's ability to consume 60-70% of fluid losses will dictate body mass deficits. Courtesy Dr Alan McCubbin

6. At Fuelin, our fluid intake recommendations are built around 60-70% of your average sweat rate. The fluid intake recommendations that our Fuelin athletes receive in their daily session cells are in line with what the best available scientific research is suggesting.

Specific fluid requirements provided based on the athletes actual sweat rate data
(Actual athlete app screen)

7. Sodium replacement should be based on your sweat sodium concentration. This is a tricky one unless you get your sweat sodium tested. As a general rule, your sweat sodium will be on average 20-80mmol/L (460-1840mg/L). 

8. If you do not have access to testing, assume the lower end of normal and adjust accordingly based on taste, thirst, any gastrointestinal complaints or cramping.

9. Sweat sodium concentration should be a measure of whole-body sweat sodium, not a single measurement site concentration. It is important to check with the company testing your sweat sodium concentration to ensure the calculator is the correct one.

10. The currently available research recommends that sodium intake should be 30-65% of your whole body sweat sodium concentration.
This would equate to 140-550 mg/L (30%) up to 280-1100mg/L (60%). As you can see, if you are on the lower end of sodium concentration in your sweat, you may not require a large amount of extra sodium to be consumed.

Fluid replenishment and sweat sodium concentration impact need for sodium replenishment.
Courtesy Dr Alan McCubbin

11. Fuelin currently recommends starting at 50-60% of your whole body sweat sodium concentration and adjusting based on taste, thirst, any gastrointestinal complaints, cramping and perceived performance. 

12. Sodium intake helps drive thirst, by taking in more sodium, you drink more and this may be one factor that reduces cramping and thus helps improve performance.

13. Understanding your own sweat rate is KEY to building an effective hydration strategy. It will provide you with an effective and accurate range of fluid requirements in differing temperatures for specific sessions ie bike or run. 

14. At Fuelin, the sweat rate tests that you perform are used to calculate your specific fluid requirements for your specific sessions at specific temperatures in your specific zone. The more measurements you take, the better the accuracy of that recommended fluid intake range.

Detailed analysis of individual athletes sweat rate, fluid & sodium intake, fluid and sodium requirements is provided in app. Actual athlete screen image.

15. What appears to be beneficial to athletes in terms of improving performance through optimal hydration strategy could be summarized as follows:

Consuming 60-70% of fluids based on your average sweat rate.
Consuming 50-60% of your total body sweat sodium concentration.
Increasing & maximizing your carbohydrate intake to your max capacity (BIKE 90-120g/hr and RUN 50-90g/hr)

16. The definition of performance and the studies investigating it are poorly defined and studied at this point in time. More research is required before any definitive decisions can be made on sodium and its role in improving performance. Thus, if an athlete follows the above-outlined steps, they will likely improve the issues that they are suffering from. 

These are my thoughts at least on what is still a very complicated topic and one that will continue to be debated for many years to come.

You can watch the Q&A session with Dr Alan McCubbin here

Scott Tindal
May 6, 2024
Back to all articles