Sauna and Cold Plunge Benefits: What Heat and Cold Do in the Body, and How to Start Safely

In short: Sauna heat and cold water are short, controlled stresses. Heat raises your heart rate, widens blood vessels and switches on protective proteins inside cells. Cold triggers a fast breathing and heart response and a large rise in noradrenaline, a natural alertness chemical. Both can be practised in your own routine. Because both put real load on the heart and circulation, a doctor should check your safety and set your dose first.

What is heat and cold therapy?

Heat and cold therapy means deliberately exposing your body to heat, such as a sauna, or to cold, such as a cold shower or a cold-water dip, for a short, planned time.

Both are examples of hormesis. Hormesis is the body's habit of growing stronger after a small stress it can recover from. The dose decides the result: a measured challenge prompts repair, while too much becomes plain stress. You can read more on our page about hormetic signaling.

SOMA does not run saunas or cold plunges at its centres. These are practices you do in your own routine, at home or wherever you already have access. A SOMA doctor's role is to check that they are safe for you and to set how much, how often and how long.

What does sauna heat do in the body?

A traditional Finnish sauna is usually heated to about 80 to 100°C, and sessions in Finnish practice typically last about 5 to 20 minutes.

Your heart and blood vessels respond. As your skin warms, blood vessels near the surface widen to release heat. Your heart beats faster to move more blood to the skin. During a session, the heart's workload can look similar to moderate exercise. Over repeated sessions, the body learns to handle heat more easily. This is often called a cardiovascular conditioning response.

Cells make heat shock proteins. These are protective proteins that cells produce when they get hot. They act like repair crews, helping other proteins keep their shape. A 2023 study of young men measured these proteins and immune cells before and after a series of 10 sauna sessions, and found that trained and untrained men responded differently.

You sweat, and lose fluid. A session can draw out a lot of water and salt, which matters in a hot Indian summer when you may already be low on fluid.

What does cold do in the body?

The cold shock response. When you first meet sudden cold water, you gasp, breathe fast and hard, and your heart rate and blood pressure jump. This reflex is called the cold shock response. A gasp underwater can mean inhaling water. Cold shock is an immediate danger; continued exposure adds risks of impaired movement and hypothermia, a dangerous drop in body temperature.

A large rise in noradrenaline. Noradrenaline is a chemical messenger that makes you alert and narrows blood vessels in the skin to save heat. In a laboratory study, young men sat in 14°C water for an hour. Their noradrenaline rose more than six-fold, and their energy use rose to about four and a half times its resting level.

Brown fat and cold air. Brown fat is a special type of fat whose job is to burn energy to make heat. In a separate 2009 laboratory study, prolonged exposure to mildly cold air (a 16°C room) activated brown fat in 23 of 24 healthy men. Its activity varied a lot from person to person. That study used cold air, not a brief plunge.

What reviews of cold water show. A 2025 review included 11 trials involving 3,177 adults. Inflammatory markers increased immediately and one hour after cold-water exposure. Stress measures were lower at 12 hours, but not consistently at other measured times. Individual studies reported sleep or quality-of-life improvements. Most trials were small; one large shower trial supplied most participants. These results do not establish an ideal home dose.

How do I do heat and cold practice safely at home?

These are general safety habits, not a personal plan. Your doctor sets the temperature, time and frequency for you.

For heat

• Drink water before and after. Skip a session if you are already dehydrated, unwell or have had a hot day outdoors.

• Never use a sauna after alcohol. Alcohol and heat together increase the risk of fainting, low blood pressure and heart-rhythm problems.

• Start short and below your limit. Leave at once if you feel dizzy, sick, short of breath or have chest discomfort.

• Stand up slowly at the end. Blood has pooled in your skin, so rising fast can make you faint.

For cold

• Start mild. A cool, not icy, finish to your shower is a gentler first step than plunging into ice water.

• Never do a cold plunge or open-water dip alone. Someone should be within reach who can pull you out.

• Do not put your head under. Keep your breathing slow and controlled through the first minute.

• Leave the water immediately if you feel unwell, numb or start shivering. Remove wet clothing and wrap in dry layers. Avoid hot baths or showers.

• Confusion, blue lips, collapse or breathing difficulty require emergency medical help.

Going from hot to cold can cause abrupt changes in heart rate and blood pressure. Add this only if your doctor says it suits you.

Who must check with a doctor first?

These are screening points for a doctor to consider, not a complete list:

• any heart condition, chest pain, a past heart attack, heart-valve disease or an irregular heartbeat

• blood pressure that runs high or low, or a history of fainting

• pregnancy, or trying to conceive

• older age, or frailty

• medicines that affect heat tolerance or blood pressure, such as water tablets, blood-pressure medicines, some antidepressants and some allergy medicines

• Raynaud's, where fingers and toes go white or blue in the cold, or poor circulation

• skin conditions that flare with heat or cold, or open wounds

• epilepsy, or any condition that could cause you to lose awareness in water

• regular alcohol use

For some people, the right dose of heat or cold right now is close to zero. That is a safe and valid answer.

How does a SOMA doctor decide what is right for you?

At SOMA, a doctor looks at the whole picture first. Your heart and blood vessel health, stress load, sleep and recovery decide which stressors suit you and how much. Which tests you need depends on what the doctor finds. A person in burnout gets a very different plan from a trained athlete.

If appropriate, a SOMA doctor sets the temperature, duration and frequency for your own routine, as one part of a plan built around you.

SOMA centres in Mumbai and New Delhi

SOMA doctors see patients at two centres:

• Mumbai: A-507, Kohinoor Square, N.C. Kelkar Marg, Shivaji Park, Dadar West, Mumbai 400028. Phone +91 98671 94033.

• New Delhi: E-354, Greater Kailash II, New Delhi 110048, serving Delhi NCR and Gurugram. Phone +91 87969 92001. More about the New Delhi centre.

The New Delhi centre is independently operated under licence from SOMA Longevity Sciences, and its own doctors lead care there. Both centres follow the same SOMA assessment and diagnostic standards. Online consultations are also available. Contact either centre.

Questions people ask

What are the benefits of sauna and cold plunge?

Sauna heat raises heart rate, widens blood vessels near the skin, makes you sweat and triggers protective heat shock proteins in cells. Cold water can increase circulating noradrenaline. Separately, prolonged exposure to mildly cold air activated brown fat in a laboratory study.

Is sauna or cold plunge right for me?

It depends on your heart, blood pressure, medicines, age and stress load. A doctor should check your safety first and set a starting dose. For some people the right amount is very little, or none for now.

How long should I stay in a sauna or cold water?

There is no single safe time for everyone. In Finnish practice, sauna sessions typically last about 5 to 20 minutes. Cold shock is an immediate danger; continued exposure adds risks of impaired movement and hypothermia. Start shorter and milder than you think you need, and let your doctor set your personal dose.

Do I need a home sauna or an ice bath?

No. Many people start with a cool finish to their daily shower, or use a sauna they already have access to. Steady, regular practice matters more than extreme temperatures.

Can a doctor in Mumbai or Delhi guide my heat and cold routine?

Yes. Doctors at SOMA's centres in Dadar West, Mumbai and Greater Kailash II, New Delhi check whether heat and cold practice is safe for you. They then set the dose for your own home routine after assessing safety. SOMA does not offer sauna or cold plunge at its centres.

Sources

1. Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clinic Proceedings 2018;93(8):1111–1121. https://pubmed.ncbi.nlm.nih.gov/30077204/

2. Pilch W et al. The effects of a single and a series of Finnish sauna sessions on the immune response and HSP-70 levels in trained and untrained men. International Journal of Hyperthermia 2023;40(1):2179672. https://pubmed.ncbi.nlm.nih.gov/36813265/

3. Šrámek P, Šimečková M, Janský L, Šavlíková J, Vybíral S. Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology 2000;81(5):436–442. https://pubmed.ncbi.nlm.nih.gov/10751106/

4. van Marken Lichtenbelt WD et al. Cold-activated brown adipose tissue in healthy men. New England Journal of Medicine 2009;360(15):1500–1508. https://pubmed.ncbi.nlm.nih.gov/19357405/

5. Tipton MJ, Collier N, Massey H, Corbett J, Harper M. Cold water immersion: kill or cure? Experimental Physiology 2017;102(11):1335–1355. https://pubmed.ncbi.nlm.nih.gov/28833689/

6. Cain T et al. Effects of cold-water immersion on health and wellbeing: a systematic review and meta-analysis. PLoS One 2025;20(1):e0317615. https://pubmed.ncbi.nlm.nih.gov/39879231/

7. NHS. Hypothermia. https://www.nhs.uk/conditions/hypothermia/