Sodium is the main electrolyte lost in sweat and this electrolyte should be the focus for athletes when considering which sports drink they want to use to hydrate.
But what about other electrolytes that get mentioned a lot like potassium, magnesium and calcium, how important are they?
We do lose all three of these in our sweat too, just in much smaller quantities than sodium, as we'll discuss here...
The importance of sodium for hydration and performance
Sodium is the main electrolyte in the extracellular fluid (the fluid outside the cells) from which your sweat is directly drawn.
As well as maintaining fluid balance, sodium plays an important role in the absorption of nutrients in the gut, maintaining cognitive function, nerve impulse transmission and in muscle contraction. (You can learn more about why sodium's important to maintaining your performance here).
Sweat sodium concentration (i.e. how salty your sweat is) varies significantly from person-to-person because of differences in the ability of the CFTR ducts in our sweat gland to reabsorb sodium.
Cystic fibrosis transmembrane conductance regulator (CFTR): The duct in our sweat glands which sweat passes through on its journey to the skin. During sweat’s movement through the CFTR duct, sodium is reabsorbed in varying degrees between individuals. The reason for this difference in reabsorptive ability is believed to be largely genetic.
When it comes to other electrolytes like potassium, magnesium and calcium, athletes seem to be less sure on where they stand and what they should be consuming.
Potassium, magnesium and calcium are worth talking about because, alongside sodium, we do also lose them in our sweat, just in far smaller proportions.
A few studies have tried to quantify exactly how much of each we lose when sweating and - whilst the numbers are a little varied (most likely due to the differences in sampling technique, sample sites, timing, and experimental conditions) - the research generally agrees that the losses are minimal in healthy adults.
Do you need potassium in your sports drink?
Potassium is the most abundant positively charged ion in the intracellular fluid (that’s the fluid inside our cells), followed by magnesium.
It plays a role in several bodily functions, including regulating fluid balance (alongside sodium), facilitating the transmission of nerve signals and assisting in muscle contractions.
Potassium levels in the body are regulated in much the same way as sodium is, with dietary intake being balanced predominantly by excretion through urine and - to a lesser extent - through losses in our sweat.
Potassium sweat losses are reported to be in the region of 5 mmol/L, the equivalent to about 200 milligrams per litre of sweat (mg/L; or mg/32oz for those using the Imperial system!).
Compare that to the average sweat sodium concentration of just under 1,000 mg of sodium per litre of sweat from the thousands of Sweat Tests we’ve conducted, with some individuals losing far greater amounts (>2,000 mg/L!).
The imbalance of sodium and potassium across the fluid compartments is maintained by the sodium-potassium pump. Maintenance of this distribution of electrolytes between the intracellular and extracellular fluid is critical for cell function and electrical communication throughout the body.
Because of the relatively small losses of potassium that occurs through sweat, it’s unlikely that these losses alone would be substantial enough to cause a decline in performance in most cases.
On the whole, it’s thought that potassium losses only become impactful if you sweat heavily on a regular basis and your diet is chronically low in potassium.
Before you panic that this could be you, you'd have to be completely avoiding foods like potatoes, sweet potatoes, bananas, oranges, mushrooms, and lots of other fruits and vegetables in order for your diet to be dangerously low in potassium.
That being said, there may be instances where people who have extremely high sweat rates (and therefore drink very high volumes of fluid to replace these) could run the risk of diluting their potassium levels - a condition called hypokalaemia - so some level of potassium supplementation may be warranted in these cases.
Some early research on rats did suggest that a potassium-containing beverage may be useful for enhancing recovery by aiding intracellular rehydration. But, a later study in humans - which saw participants drink beverages containing either potassium or sodium when dehydrated after exercise - showed that the rehydration rate was actually slowest in the potassium-only group and lent further support to the importance of sodium in staying hydrated.
Do you need magnesium in your sports drink?
As mentioned before, magnesium is held in the intracellular fluid and is needed for more than 300 biochemical reactions in the body. Dietary magnesium mainly comes from dark green, leafy vegetables but other good sources include fruits, nuts and whole grains.
Although there can be a decline in blood plasma magnesium concentration during exercise, it's most likely due to the redistribution of it amongst fluid compartments rather than through sweat loss.
Sweat losses of magnesium have been found to be much smaller than those of potassium - somewhere in the region of 0.1-0.5 mmol/L. So the upper range being equivalent to only around 12 milligrams of magnesium per litre of sweat (Jeukendrup & Baker, 2014). Not a lot at all!
A depletion of potassium and/or magnesium has previously been linked to exercise-associated muscle cramping, but there's been little to no experimental data to support this (Shirreffs, 2003).
Do you need calcium in your sports drink?
Calcium is essential to maintaining total body health. Your body needs it every day, not just to keep your bones and teeth strong, but to also ensure proper functioning of muscles and nerves (Piste et al., 2012).
The loss of calcium in sweat is...you guessed it...low.
In the scientific literature you can find a range of 0.1 to 1.3 mmol/L (Hoshi et al, 2001; Shireffs & Maughan, 1997). Jeukendrup & Baker report an average of ~0.5 mmol/L (Just ~20 mg/L).
So, because the calcium loss you'll experience through sweating is insignificant, much like magnesium, the evidence for its inclusion in sports drinks is limited.
How much potassium, magnesium and calcium do Precision Fuel & Hydration electrolytes contain?
Firstly, any water (tap or bottled) that you drink, unless labelled 'distilled', will contain traces of all the electrolytes discussed here.
When you mix PH 500, PH 1000 or PH 1500 as directed - i.e. 1 tablet or packet per 500ml (16oz) of plain water - you get a solution containing 250mg of potassium, 48mg of calcium and 24mg of magnesium per litre. (See our blog on the importance of thinking about the relative concentration of your drinks).
The one exception to this is US customers using our low-calorie effervescent tablets, your drinks contain slightly different quantities: 260mg of potassium, 40mg of calcium and 20mg of magnesium.
Our Electrolyte Capsules contain 250mg of sodium per capsule, 125mg of potassium and trace amounts of magnesium and calcium.
In other words all of our products contain the minor electrolytes discussed here in quantities in-line with human sweat losses, we made sure of that.
|Minor Electrolyte||Average loss in sweat (mg/L) (Jeukendrup & Baker, 2014)||PH 1500, 1000, 500 content (mg/L) Low-calorie effervescent tablets in the USA||PH 1500, 1000, 500 content (mg/L) Low-calorie effervescent tablets elsewhere and all-natural drink mixes everywhere|
Whilst it’s interesting to look at what we lose in our sweat in real detail - and good to know that Precision Fuel & Hydration supplements provide you with what you’re losing - let’s end by taking a step back and remembering the bigger picture: Sodium is the electrolyte that really matters when it comes to staying hydrated. Most healthy athletes needn't worry too much at all about looking for magnesium, potassium or calcium in their sports drinks, nor taking specific supplements.
As discussed, sodium is the focus for Precision Hydration's electrolyte supplements and it is the most important electrolyte lost in your sweat.
Stronger sodium-based electrolyte drinks (ideally with >1000mg of sodium per litre) are ideal for preloading to ensure you're hydrated before exercise and are often used by athletes who have particularly salty sweat or high sweat losses during exercise. They can also be a useful to help you rehydrate quickly if you need to perform again quickly after your latest session.
As an example, PH 1500 contains 3x more sodium than most off-the-shelf sports drinks out there.
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