Moving to Southeast Asia? 8 reasons to think about electrolytes

• Where we stand: we’re not doctors, and most healthy people adapt to the tropics without special products. We show what the research says so you can decide what’s worth doing.
• The first one to two weeks are the hardest. Your body adapts over roughly 7 to 14 days, and you lose the most salt in sweat early on.
• Humid heat is harder than dry heat, because sweat evaporates more slowly and cools you less.
• There’s no single number. How much you sweat, and how salty it is, varies enormously from person to person.
• Don’t wait until you’re parched, and don’t force litres of plain water. Both extremes carry risks.
• Local food is often salty, so many people already get plenty of sodium from their meals.
• Stomach bugs need oral rehydration salts, not a sports drink or a zero-sugar mix.
• Some medications, alcohol and health conditions change the rules. Check with your doctor if that’s you.
• Our reading of the research: an electrolyte drink is most worth considering if you sweat heavily or stay active in the heat for an hour or more. If you’re mostly in air-con and eating local food, you may not need one.

This is for the person who has just landed and can’t stop sweating. You’re not an athlete, you just live here now. If you’ve done it, you know the feeling: a shirt that’s soaked before you’ve left the house, and a body that hasn’t caught up yet.

We looked at what the research says about heat, sweat and sodium, and where electrolytes might help and where they won’t. We are not doctors, and none of this is medical advice.

We’ll be honest where the answer is “you probably don’t need anything”. We’d rather you trust us than buy something you don’t need.

Heat tolerance builds gradually. NIOSH, the US workplace health agency, says acclimatisation takes about 7 to 14 days of regular exposure, and that new arrivals are at the highest risk of heat illness. It also notes that you lose the most salt in sweat during the first few days.

A large analysis of 1,944 sweat tests found that sweat was less salty in warmer months, which the researchers used as a stand-in for heat acclimatisation. That suggests your sweat gets less salty as you adapt. NIOSH also recommends regular meals while you adjust, because food replaces electrolytes lost in sweat.

Sweat only cools you when it evaporates. The CDC notes that when humidity is high, sweat doesn’t evaporate as quickly, so your body releases heat more slowly. NIOSH lists high humidity as a risk factor because it makes sweating less effective.

That’s why a humid 31°C can leave you soaked and still overheated, in a way a dry 31°C doesn’t. It’s also part of why the first weeks here feel so punishing: you’re sweating hard and cooling less.

Sweat rate and sweat saltiness vary a lot between people, and even in the same person from one day to the next. In that large analysis, more energy burned meant more sodium lost. Body size, fitness and heat adaptation all play a part too. The CDC lists obesity among the conditions that can limit the body’s ability to cool itself, and larger people tend to produce more heat when they move.

One surprise from the same analysis: how much sodium people ate didn’t predict how salty their sweat was. So you can’t guess your own number from your diet. The only real way to know is to measure or estimate it, which is what we’re building our Sweat app to help with.

NIOSH warns that thirst lags behind dehydration when you work in the heat. But the 2015 international consensus on exercise-associated hyponatremia (dangerously low blood sodium) found that drinking too much is its main cause, and concluded that drinking when thirsty is the safest strategy during exercise.

The honest middle: sip regularly through a hot day rather than waiting until you’re parched, and don’t force litres of plain water. That kind of low blood sodium is mostly seen in long endurance events, so it’s unlikely to trouble you at a desk. It’s still a good reason not to treat “more water” as a rule.

Southeast Asian cooking is often salty. A 2013 review of six countries in the region identified table salt and salty condiments such as fish sauce and soy sauce among the main sources of sodium in local diets. It also noted that intake estimates are limited and vary by method, so we can’t give you one number. The WHO advises limiting sodium to under 2,000 mg a day for the general population.

So if you eat local food most days, you may already be getting plenty, and more isn’t automatically better. A drink makes more sense if you cook low-salt meals at home or sweat far more than usual.

Travellers’ diarrhoea is common. For anything beyond a mild case, medical references recommend an oral rehydration solution (ORS), which contains a measured mix of sodium and glucose so the gut absorbs fluid properly. Sports drinks aren’t recommended as a replacement for ORS when you have diarrhoea, and a zero-sugar electrolyte mix isn’t either, because the glucose is there for a reason.

ORS is sold in pharmacies across the region. See a doctor early, especially if it’s a child, an older adult or anyone with a health condition, or if you can’t keep fluids down.

NIOSH lists medication for high blood pressure among the things that can affect heat tolerance. The CDC adds prescription drugs and alcohol to the factors that can limit the body’s ability to cool itself, along with older age, heart disease and fever.

That’s also a reason to be careful with salty drinks. If you take blood pressure medication, or have a heart, kidney or other health condition, ask your doctor before you add extra sodium or change how much you drink.

There’s no official guideline telling healthy adults to drink electrolyte mixes in daily life, so this is our reading of the research, not a rule. A drink is most worth considering if:

• you’re in your first couple of weeks and sweating heavily;
• you’re active outdoors or in a hot gym for an hour or more, whether that’s surfing, scootering, golf or hiking;
• you cook mostly low-salt meals at home.

It’s probably not necessary if you spend most of the day in air-conditioning and eat local food. For everyone, food, regular fluids and time to adapt come first. If you do try one, match it to your day: something light for everyday sipping, something stronger for a heavy sweat session.

Heat illness is a medical issue. If someone is confused, faints, has a very high body temperature or hot, dry skin, treat it as an emergency: call local emergency services and start cooling them down. NIOSH’s guidance is that cooling is the treatment for all heat illness.

A drink, electrolyte or otherwise, is not the answer to heat stroke.

We make two products for two kinds of day. Neither replaces food, water or time to adapt, and if you eat a lot of salty local food and spend most of the day in air-conditioning, you may not need either.

Per 6 g serve, from the product labels. Daily Driver isn’t on sale yet. Neither product is an oral rehydration solution, and neither treats illness or heat illness. If you take medication or have a health condition, ask your doctor first.

• Any study of electrolyte drink mixes in recently arrived expats. Everything here is drawn from heat-acclimatisation research (mostly workers and athletes) and general health guidance.
• Much data on how non-athletes sweat in Southeast Asia. Most sweat studies are of athletes in training, not office workers or retirees.
• Any guideline saying healthy adults should drink electrolyte mixes in daily life.

Check the label for sodium per serve compared with your usual diet, sugar or sweeteners, caffeine or other stimulants (including tea extracts), magnesium (it’s in many supplements too), and a serving size you’ll realistically use.

Questions for your doctor, if you take medication or have a health condition:

• I take blood pressure medication. Does the heat, or a salty drink, change anything for me?
• I have a heart or kidney condition. How much sodium and fluid is right for me in a hot climate?
• Does my usual alcohol intake matter more in this heat?