Salt Isn't the Villain: Electrolytes and Training

Most confusion about salt comes from treating one word as one question. There are really two. The first is a public-health question: across a whole population, does eating less sodium lower blood pressure and heart-disease risk? The answer is broadly yes, which is why the World Health Organization recommends adults keep sodium under about 2 grams a day, roughly 5 grams of salt. Most of that excess comes from processed and restaurant food, not the salt cellar.

The second is a performance question: when you sweat during exercise, you lose sodium, so should you replace it? Here the answer is that it depends on how much and how long you sweat. These two questions have different answers because they are about different situations. Advice built for lowering a nation's blood pressure was never designed to tell an athlete how to fuel a three-hour ride in the heat.

Sodium is not a guilty pleasure, it is a core electrolyte, meaning a mineral that carries an electrical charge in your body fluids. It is the main mineral in the fluid outside your cells, and it does jobs you cannot train without. It sets how much water your body holds, it is central to the nerve signals that fire your muscles, and it works with potassium to keep those signals firing rep after rep.

Because sodium governs where water goes, it is tightly tied to hydration. Drink a large amount of plain water while sodium is low and you can actually struggle to hold onto that fluid, because the body sheds water to keep its sodium concentration in range. This is why fluid and sodium are best thought of together, not as separate checkboxes.

• Fluid balance: sodium determines how much water stays in your blood and tissues.
• Nerve signalling: the electrical impulses that tell muscles to contract depend on sodium moving across cell membranes.
• Muscle function: working with potassium, sodium keeps contractions firing without the signal fading.
• Fluid retention when it counts: some sodium alongside fluid helps you actually keep what you drink during long efforts.

Sweat is not just water, it is salty water. How salty depends on the person. The American College of Sports Medicine notes that both sweat rate and sweat sodium content vary widely between individuals, which is why one-size electrolyte advice falls apart. Some people are light, low-sodium sweaters who barely need to think about it. Others are heavy, salty sweaters who finish a session with white salt stains on their kit and clearly lose a lot.

The practical point is that you should calibrate to yourself, not to a label. If you train an easy hour indoors, you lose little and normal food replaces it without thought. If you do long sessions, train in heat, or notice heavy salty sweat and cramping, deliberately replacing sodium starts to matter. The gap between those two people is real and large, so copying someone else's electrolyte routine is a poor guide.

For a typical gym session of an hour or so, in a normal room, water and your usual meals cover your electrolytes completely. You do not need a coloured sachet to survive some squats. The marketing implies otherwise, but the physiology does not back it for short, moderate efforts.

Where sodium replacement genuinely earns its keep is longer and hotter. Sessions past 60 to 90 minutes, training or racing in heat, back-to-back sessions in a day, and heavy salty sweaters are the clear cases. In those settings, taking in some sodium with your fluid helps you hold onto that fluid and can support performance and comfort, and it lowers the odds of finishing badly depleted. You can get sodium from a sports drink, an electrolyte tablet, or simply salted food and a normal drink, whatever you will actually use.

There is a serious condition at the other end of this, and it catches people out because it looks like the opposite of what they fear. Exercise-associated hyponatremia is dangerously low blood sodium, and the expert consensus is clear that its main cause is drinking too much fluid, not eating too little salt. When you pour in more water than you lose, you dilute the sodium in your blood, and in endurance events this has occasionally been fatal.

The consensus also makes an uncomfortable point for the salt-tablet crowd: because sports drinks contain far less sodium than blood, they do not reliably prevent this problem in someone who is overdrinking. In other words, more sodium is not a permission slip to drink without limit. The safest general approach in long events is to drink to thirst rather than on a rigid schedule, and to add sodium as support, not as an antidote to overdrinking.