Why Electrolytes Matter More Than Water in the Heat — And How to Get Them from Food

When a heatwave hits, the standard advice is always the same: drink more water. It’s not wrong, but it’s incomplete — and for some people, drinking nothing but plain water on the hottest days can actually leave them feeling worse, not better. The reason has nothing to do with how much you drink and everything to do with what you lose when you sweat.

Sweat isn’t just water. It carries dissolved minerals out of your body with every drop, and those minerals — electrolytes — are what keep your muscles firing, your heart beating steadily, and your nervous system communicating. Replace the fluid but not the minerals, and you can end up diluting what’s left, which is how some people manage to drink litres of water on a hot day and still feel dizzy, foggy, and drained by the afternoon.

What electrolytes actually do

Electrolytes are minerals that carry an electrical charge once dissolved in the body’s fluids. That charge is what allows them to drive the processes that keep you upright and functioning. Four matter most.

Sodium is the one you lose most heavily in sweat. It governs fluid balance, helps transmit nerve signals, and plays a direct role in muscle contraction. When sodium drops too low — often because someone is drinking heavily but not replacing salt — the result can be nausea, headache, confusion, and in serious cases a condition called hyponatraemia.

Potassium works as sodium’s counterweight, managing fluid balance inside the cells and keeping the heart’s rhythm steady. Low potassium shows up as weakness, cramping, and fatigue, which is why a potassium-poor diet makes hot weather feel harder than it should.

Magnesium is involved in more than 300 reactions in the body. It helps muscles relax after they contract, supports steady energy production, and tempers the kind of nervous irritability and restlessness that creep in when you’re depleted. It’s also one of the most commonly under-consumed minerals in the modern diet, heat or no heat.

Calcium is known for bones, but it’s just as essential for muscle and nerve function. It works alongside magnesium and potassium, and when the balance between them slips, muscles are the first thing to complain.

When these minerals fall out of balance, the symptoms are easy to mistake for ordinary tiredness: light-headedness, a dull headache, muscle cramps, irritability, and a heart that feels like it’s working harder than it should. On a hot day, when sweat losses are high, that slide happens faster than most people realise.

Why the heat raises the stakes

During heavy exertion or extreme heat, the body can lose anywhere from half a litre to well over a litre and a half of fluid per hour. Sodium, potassium and other minerals go out with it. If you top yourself back up with plain water alone, the concentration of electrolytes in your blood gets diluted further rather than restored — and that’s precisely the scenario that produces the nausea-and-headache combination so many people blame on “too much sun.”

Some people carry more risk than others. Older adults feel thirst less reliably and dehydrate more easily. Anyone exercising or working outdoors loses minerals at a much higher rate. Heavy coffee drinkers and people on certain medications, particularly diuretics, lose more through urine on top of what they sweat out. For all of them, the “just drink water” rule is the riskiest version of the advice.

How to get more electrolytes from food — naturally

The good news is that you don’t need a shelf of coloured powders to stay balanced. Food does the job, and usually better, because it delivers minerals alongside the carbohydrates and fluid that help the body actually absorb and use them.

For potassium, reach for bananas, potatoes (especially with the skin on), sweet potatoes, avocados, spinach, tomatoes, oranges, white beans, and dried apricots. A baked potato with skin quietly outperforms most sports drinks on potassium alone.

For magnesium, the best sources are pumpkin and sunflower seeds, almonds, cashews, dark chocolate above 70%, legumes, leafy greens, and wholegrains. A small handful of seeds or nuts as a daytime snack covers far more ground than most people expect.

For calcium, look to yoghurt, kefir, cheese, broccoli, kale, sesame seeds, tofu, and tinned sardines eaten with the bones.

For sodium, this is the one to stop fearing on hot, sweaty days. If you’re perspiring heavily, lightly salting your food isn’t a vice — it’s replacing exactly what you’ve lost. A salted broth, a handful of olives, or a pickle does real work after a long hot afternoon.

A simple routine for hot days

Start the morning with a glass of water with a pinch of sea salt and a squeeze of lemon — it’s the cheapest natural electrolyte drink there is, and it sets you up better than plain water. Snack on fruit and nuts instead of sweets, and build your meals around vegetables and leafy greens rather than around refined carbohydrates. After a long stretch of sweating, don’t just reach for the water bottle — reach for food with salt and potassium in it too, whether that’s a potato, a bowl of broth, or a piece of fruit. Coconut water is a convenient natural source of potassium when you want something to sip.

The principle underneath all of it is simple: water gets you halfway. Your body needs minerals to put that water to use rather than flush it straight back out. A balanced plate with enough sodium, potassium, magnesium and calcium is the most reliable way to stay sharp, steady and safe when the temperature climbs — and it asks nothing more of you than paying a little attention to what’s already on the table.

This article is for general information only and is not a substitute for medical advice. If you have kidney or heart conditions, or take medication such as diuretics, speak to your doctor before making significant changes to your fluid or electrolyte intake.