- When you become dehydrated while training your blood sodium (salt) levels go up, not down
- Consuming salt has little impact on your blood sodium levels
- Mild dehydration of between 0-2% body weight loss is optimal for training performance
- Overhydration can inhibit performance and can be dangerous
- If you are at risk of more than 2% dehydration, the best way to get water into your system quickly is to drink a hypotonic drink with just a little salt and a little carbohydrate
Sodium is one of the most important minerals in the body. We get it from the foods we eat and it is vital in the regulation of fluid movement between the blood and cells in the body. Unbalance your body’s sodium and it will not only play havoc with your athletic performance... it could also kill you.
The general population is a little afraid of sodium. This is because scientists have linked high sodium diets to high blood pressure and increased risk of heart disease and stroke.
To the athlete however, sodium is seen as a friend. The salt in sweat contains sodium and it is generally believed that when training, you need to replace what is lost to maintain performance and recover. In fact, if we are to believe the thousands of brands that sell high sodium sports drinks, not replacing that sodium will cause a significant drop in performance.
Marketing hype aside, the research tells us a different story:
1. Dehydration from training causes your blood sodium levels go UP not DOWN
In 2005, a group of scientists led by hydration fanatic, Dr. Tim Noakes, pooled together data from 2,153 competing endurance athletes.
Here’s a snapshot of the data:
Each dot is a post-endurance race measurement of serum (blood) sodium vs. the body weight change (loss or gain of water) in 2,153 athletes competing in a variety of different endurance sporting events.
Post-race serum (blood) sodium concentrations rise (moving from left to right in this figure) with increasing levels of weight loss (dehydration) This means that, dehydration (right side of the figure, -ve weight change) causes the blood sodium levels to rise, whereas fluid retention or overdrinking (Positive weight change) causes the blood sodium concentration to fall.
Open/white dots indicate athletes with Hyponatremia, a serious health condition caused by low sodium levels.
You can see from the line on this graph that there is a trend for sodium levels to be higher in those who are the most dehydrated (lost more body weight over their race).
2. Sodium levels vary greatly between individuals - regardless of hydration level - and consuming salt doesn’t impact this
Another observation from this data set is that there is a great amount of variability between individuals. This means that it’s hard to predict if you’re low or high on sodium even when very dehydrated.
To add to this, two studies on training athletes have shown that consuming sodium has little impact on blood sodium levels. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001428/]
Drinking a salty sports drink to replace sodium lost in sweat will not work because:
- Blood sodium levels go up not down when you’re dehydrated
- Consuming sodium has minimal impact on blood sodium levels
...But don’t throw away your sports drink just yet. There is a good reason to have a little salt (and carbohydrate) in your sports drink.
Regardless of the science, many people report anecdotally that drinking a salty sports drink does seem to make them feel better when training - especially in the heat. Here’s why I think this is:
1. Dehydration of between 0-2% is optimal for performance
A 2017 meta analysis focused on athletic performance and water intake found that fluid intake is vital to maintaining optimal performance [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5357466/]. Interestingly, they also found that maintaining between 1-3% dehydration status (body weight loss) was also an indicator of high performance
On top of this, in Noakes’ data above, he found that those who overhydrated (gained body weight over their race) were more likely to suffer from hyponatremia (white dots in the chart above), which is a rare but dangerous drop in blood sodium.
In practical terms, I think a safe range you should try to maintain for optimal physical performance is 0-2% dehydration. In looking at sweat rates, especially when training hard and/or the heat, you may need to get water into your system quickly to maintain this, and salty water may be more effective. Read on...
2. Drinks with added salt and carbohydrates will help get water into your system faster
One thing that rehydration scientists have known for centuries is that “Dilute hypotonic glucose-sodium solutions are highly effective oral rehydration solutions.” [https://pubmed.ncbi.nlm.nih.gov/9694418/] What this essentially means is that a drink containing a little salt and a little carbohydrate will cause the water in the drink to pass into the blood quicker.
MY CONCLUSION: HOW TO HYDRATE FOR OPTIMAL PERFORMANCE
- Aim to stay between 0-2% body weight loss through dehydration if you want to perform at your best.
- If there is a risk that you will lose more than 2% body weight through dehydration when training, drink water with a little sodium and carbohydrate to get it into your system faster.
- Sip this drink regularly, never deny thirst and don’t over-hydrate.
WHY I CONDUCTED THIS RESEARCH
This article is a summary of the research I collected to develop our Hydra+ product. Hydra+ was designed to be versatile so that you can adjust it depending on your training needs to keep your dehydration level between 0-2%. Diluting it with 16oz water will create a hypotonic drink focused on getting water into your system fast when training for longer durations. Using 8oz of water will get electrolytes and carbs into your system faster - ideal for high intensity shorter duration training.
Here are other benefits of using Hydra+:
- Made using real food sources of carbohydrates and electrolytes
- Contains electrolytes at levels matched to those lost in sweat (other than sodium as high levels aren’t needed)
- Made using no unnecessary additives to keep Hydra+ as close to real food as possible