We all love the heat… right up until we don't. There's a very British ritual of complaining it's too cold all winter, then complaining it's too hot the moment summer actually arrives. Writing this from the middle of what has been an unusually heatwave-heavy UK summer, I feel qualified to say: both complaints are valid, and neither helps you stay safe when temperatures are actually dangerous. This is because heat illness is real… and it can sneak up on you. I’ve had SO many consultations this week with people who have underestimated the current heatwave and have presented with dizziness, palpitations and swollen ankles.. so rather than giving you a generic 'drink water and stay cool' reminder, here are the things that actually matter.
Hydration is thermoregulation.
I know there will be BBQs and garden parties and cold drinks in cans.. But on particularly hot days, alcohol and caffeine both impair thermoregulation and accelerate fluid loss. As a baseline, drink water before, during, and after activity, even before you feel thirsty. If you do feel yourself overheating, you can place ice packs wrapped in a thin towel to areas where larger blood vessels run close to the skin, for example to the neck, groin, or underarms.
Monitor your salt intake.
In hot countries, I often find the food to be excessively salty - but it does serve a purpose. Heat makes our blood vessels dilate so that we can have more blood flow closer to our skin. As a result, our blood pressure drops. Couple this with losing more fluid through our sweat, and our blood pressure drops further. The salty food can help us drink more water and can therefore raise our blood pressure (I know it’s more complicated than that).
If you’re a sweaty person in hot weather, it’s also important to remember that we lose salt in our sweat. And if you don’t really use salt when cooking for fear of the effect on blood pressure, then a heat wave is a perfect excuse to add some extra salt to your food. Obviously be careful if you usually have high blood pressure, or are on medications like beta blockers, diuretics, or anti-depressants.
Heat + Humidity + Low wind = Problem.
When checking the temperature, the number on your weather app is not the whole story. What you need is the heat index. This combines temperature and humidity to show how hot it actually feels to your body. For anyone who has spent time in tropical or subtropical climates, you’d know that high humidity is the hidden danger because it slows the evaporation of sweat- your primary cooling mechanism. So even on a day that doesn't look that extreme on paper, if the humidity is high and the wind is low, your body is working significantly harder to thermoregulate.
Timing matters more than people think.
The peak danger window for outdoor activity is usually between 3pm and 5pm, when heat has been building all day and surfaces are radiating it back at you. Man-made surfaces like blacktop and concrete are particularly bad. The twilight periods (early morning and after sunset) are different physiological environments entirely. If you exercise outdoors, grassy parks and tree-lined paths are cooler environments.
Appropriate clothing helps.
Wearing light-coloured, loose-fitting, breathable fabrics like cotton, linen, or moisture-wicking synthetics are fantastic for keeping you cool. Loose weaves allow air to circulate and let sweat do its job. Similar to a wet suit when diving, tight clothing traps heat and moisture against the skin.
👋 For the new joiners: I’m Suraj, also known as Dr Sooj - a primary care doctor & health content creator. I love navigating the complex world of health and wellness and breaking down complicated concepts.
Every Sunday, I share something interesting that weaves together science and medicine with real life. The aim is to help you live happier and healthier, without any fear-mongering!
Feel free to share this newsletter on your socials, and it would be amazing if you can forward this email on to your friends & family who love learning random things about their health. You can find the subscribe link here.
If you ever have thoughts, questions, or just want to say hey, you can reply directly to this email 😀. I read every message I get!
Suraj (Doctor Sooj)
References:
1. Bouchama A, Knochel JP. Heat stroke. N Engl J Med. 2002;346(25):1978–88.
2. Casa DJ, et al. National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses. J Athl Train. 2015;50(9):986–1000.