Salt, which primarily consists of sodium, is essential for hydration - as a general rule in the body, water goes where there’s salt. Getting too much sodium concentration in the brain for example is bad for neurons, the cells draw in water and swell causing literal swelling of brain tissue. Too little sodium and the brain draws in water from extracellular space that results in reduced brain function.
So when it comes to salt and hydration, it’s all about getting the balance right and there’s not a one size fits all approach - there are a number of factors that you have to consider; your blood pressure, the amount of cardiovascular exercise you’re doing and how much salt you’re already consuming in your diet.
That being said, there’s a huge benefit to getting that balance right, so let’s take a closer look at 3 key insights on salt and hydration.
Why hydrating with sodium is more effective than water alone
There are a number of ways our body knows that we’re dehydrated and induce thirst, primarily there are two sets of neurons in the brain, some that detect sodium levels and others that detect low blood pressure. When they’re activated they set off a cascading effect in the body that releases hormones and make us either feel thirsty directly, or crave salty foods that when eaten cause another cascading effect of hormone release that then makes us feel thirsty. Either way, the body finds a way to let you know when you need to hydrate.
There is a negative effect on the body though of drinking too much water without enough sodium - we’ve all seen elite endurance athletes who get to the end of a long event and seem confused where they are or unable to speak through a basic interview. Beyond the physical exhaustion, their brains are typically sodium deprived at this point due to the loss of sodium from perspiration, even though they’ve been hydrating consistently throughout the race.
Adding a small amount of salt to water allows the body to replace the sodium lost and results in better overall physical and mental performance. Regular table salt is perfectly okay to use in order to do this however some athletes and performance coaches recommend using more fancy salts like pink Himalayan salt and there may be some merit to this as these salts also contain minerals like potassium and magnesium which are also incredibly beneficial to the balance of sodium levels in the body.
How much salt is the right amount of salt to stay hydrated and healthy?
The research on salt intake is difficult to navigate, primarily because studies rarely look further than ‘high salt intake’ vs ‘low salt intake’ when analyzing the diets of the participants in the study. They simply do not distinguish between person A on a high salt intake but doesn’t eat carbs and person B who is on high salt intake and eats large amounts of both carbs and fats - you can see the problem.
There is one study that does give us a broad scope for what is considered healthy and will keep you hydrated throughout the day - the paper is called "Urinary Sodium and Potassium Excretion and the Risk of Cardiovascular Events" and was published back in 2011. It looked at the amount of sodium passed in the urine which is a strong indicator for the amount that has been ingested, and then measured those numbers against serious and fatal hospitalisations for cardiovascular events such as strokes, heart attacks etc.
The results showed that at around 2 grams of sodium intake per day there were decreased risks of these serious events, this decrease of risk continued to around 4.5 to 5 grams of sodium a day, then beyond that number from 5 grams up there was again a dramatic increase in risks.
Again, it’s important to come back to the fact that many other factors are very important when determining the amount of sodium that can be ingested daily but this study is a good place to start.
Balancing caffeine, salt and water
A lot of people, especially the athletes that I’ve trained with consume a lot of coffee or energy drinks. Before a workout or a game it’s a great way to activate the sympathetic nervous system but there is a trade off. Caffeine is a diuretic and causes the excretion of fluids from the body, in part because it causes the excretion of sodium.
There is a general rule of thumb that you can follow to ensure that you stay hydrated when drinking coffee and making sure the body is staying hydrated. For every 200ml coffee or caffeinated beverage you drink, consume 350ml more water with a pinch of table salt in it to replace the sodium you’ve lost due to the diuretic effects of the caffeine.
This will help retain cognitive function throughout your workout and ensure you’re staying well hydrated.