Saunas are one of the hottest wellness trends right now, with UK Google searches at a five-year high and up 69% over the past 12 months. Public sauna numbers have soared by 1,233% since 2023, rising from 45 to more than 600 locations, according to the British Sauna Society, and a recent survey suggests the UK could become Europe’s largest sauna market by 2033.
But as the trend grows, so does the need for balanced advice. Josephine Smith, in-house practitioner at Supplement Hub, warns that frequent sauna use could deplete key minerals and increase the risk of dehydration.
What you lose in the heat
Saunas are often praised for their benefits to heart health and detoxification, but toxins are not the only thing being lost in a session.
“Saunas have a wide range of benefits for your health, and if they work for you, whether that is for relaxation or recovery, then that is great. But it is important to make sure you are replacing the essential nutrients you could be losing through sweating,” Smith said. “When you sweat, you lose key electrolytes such as sodium, potassium, magnesium and calcium, all of which play an important role in your nervous system, blood pressure and muscle function. If these levels drop, it can lead to muscle cramps, fatigue, dizziness and, most importantly, dehydration.”
Regular sauna bathing has also been linked in studies to improved cardiovascular health, including potential reductions in blood pressure and lower risk of related events when used consistently. Experts note that the heat prompts increased heart rate and blood flow, mimicking mild exercise effects for some users. However, those with pre-existing heart conditions should consult a doctor before frequent use.
Why hydration goes beyond water
Staying hydrated is the most critical requirement for frequent sauna use, particularly when sessions follow a workout.
“Staying hydrated is really important, and you should not rely on water alone. Water should make up the majority of your intake, but it is best paired with electrolytes to reduce the risk of dehydration,” Smith said. “Dehydration affects far more than just thirst. It lowers blood volume, places strain on the heart, disrupts electrolyte balance and impacts both physical and cognitive performance. Even mild dehydration can lead to fatigue, dizziness and slower recovery. Over time, it can also put stress on the kidneys, as low fluid levels force them to work harder and produce more concentrated urine, increasing the risk of kidney issues.”
Smith recommends keeping a bottle of water on hand up to an hour before a sauna session, with electrolytes added to support well-being throughout.
“Electrolyte powders and supplements can support hydration, energy, muscle recovery and overall performance by helping to replace the key minerals lost through sweat, including sodium, potassium, magnesium and calcium. For frequent sauna users, increasing both water and electrolyte intake can help maintain fluid balance, prevent cramps and support endurance.”
Practical tips for safer sauna use
Smith advises sauna users to avoid alcohol before sessions. While it may be tempting to sweat out a hangover, alcohol is a diuretic that encourages the body to lose more fluid. Combined with the heat of a sauna, this can accelerate dehydration and increase strain on the body.
For those incorporating regular sessions into their routine, Smith also recommends introducing sauna-friendly snacks to replenish lost minerals
- Sodium: Salted nuts, trail mix, crackers, popcorn, pickles, jerky
- Potassium: Bananas, melons, oranges, grapefruit, kiwi
- Magnesium: Pumpkin seeds, figs, cashews, peanuts
- Calcium: Dairy products such as milk, yoghurt and cheese; dairy-free milk with added calcium; green leafy vegetables
Smith emphasises listening to the body and adjusting intake based on session frequency and intensity. For many, combining proper hydration strategies with nutrient replenishment allows continued enjoyment of saunas without adverse effects.