Cold Is a Dose, Not a Dare

I love that there is a resurgence of hot and cold therapies for health and optimization, and I am grateful to the bro-science and the influencers who have popularized one of my favorite old-world natural therapies. But — and it is a fairly big “but” — there are a few important things the old doctors and hydrotherapists knew that we should be remembering. Some people are getting hurt, and others are simply missing out on the real benefits for lack of a few simple principles. Cold is a dose, not a dare. I’ve been using hydrotherapy clinically for three decades, so I want to tell you a little of what I have learned.

The right cold dose is generally not one your body just barely recovers from — it’s one that activates the surface circulatory system with a rebound dilation, and activates quite a number of other systems internally. Done right, cold rapidly increases metabolism, decreases inflammation, raises the positive immune response, and — in the language of the old doctors — increases your vital force. It can build brown fat, which burns more calories and improves metabolism.

Cold can help treat mood disorders and uplift your spirit. Training yourself to respond well to cold stress often builds a personal sense of confidence that you can handle what the world throws at you. In one brain-imaging study of 33 healthy men and women, just five minutes in cold water up to the neck left people feeling more active, alert, attentive, and inspired — and less distressed and nervous — with the brain’s large attention and emotion networks communicating more with each other afterward. Part of that shift in mood and energy comes from the body’s own chemical messengers:

• Norepinephrine (noradrenaline) rises sharply — two to three times higher in women after brief winter swims, and more than five times higher during a longer immersion in 57°F water. It sharpens alertness, attention, and focus.
• Dopamine, a messenger of motivation and mood, rose about two and a half times in that same immersion study.
• Cortisol does not spike the way you might expect from a “stress.” In these studies it held steady or dipped — and it settled further as people adapted with regular practice. That is resilience being trained.

Cold can work the way exercise works — a brief, deliberate stress your body answers by getting stronger. The right amount of lowering of your core body temperature produces cold-shock proteins that can improve your overall health in a number of ways, including supporting brain health and DNA repair.

But — people — how much cold, how cold, how often, how you prepare for it, and what you do AFTER the cold can change what you actually get from the experience, for good or ill.

First, the temperature

The degree of cold that produces a lot of the best results can be just 55–60°F. If you are weak or ill or fragile, even that can be too much — so you approach cold the way you’d approach lifting heavy weights. Start with cool to the touch, something that feels refreshing, not scream-worthy. Thirty to sixty seconds. This is like training with a five-pound weight before you slowly graduate to a twenty-pound weight. The old medicine said you had to treat cold exposure as a training of the body, letting it get stronger and more capable over time. Sure, some of us will thrive with a near-icy plunge for one to three minutes — but many of us will be less well after that, not better.

Prepare for the cold

Make sure your core body temperature is at least 97°F — though warming up to 98 or even 99°F beforehand with a hot shower, bath, sauna, hot drink, exercise, a hot pack, or any combination is generally ideal. You want to be warm, and feel warm, before the challenge if what you are after is an optimal healing response. If you are already adapted to cold and are strong and healthy, this may be less of a concern. If you need to increase your vital force, health, and strength… warm up first.

The real secret: what you do after

And here is the real secret from the old doctors and hydrotherapists: they let the body warm itself after the cold. Lie down or sit down and give the body three or five or eight minutes to respond to the cold before warming up with a hot tub or a hot shower or a sauna. This is where the magic of the multiple-system response kicks in. Thirty seconds you finish calmly — and that your body rapidly answers by warming itself — beats five minutes you white-knuckle. If you can’t rewarm easily afterward, that wasn’t a dose. It was an overdose.

Women and cold

Women especially need to understand how to use this power differently than men. A woman’s body — with its particular hormones and nervous system — can interpret this stimulus in ways different from a man’s. In one study, men and women sat in 57°F water until their core temperature began to drop. Both cooled at the same rate, but they got there differently: women held their heat in with a stronger insulating response, while men made more heat by shivering and burning fuel — and men showed larger adrenaline and immune-signal responses. A woman’s hormones also shift through her menstrual cycle, changing her resting body temperature and how she responds to heat and cold, and menopause and hormone therapy change the picture again.

If a woman has low thyroid function, is in the second half of her cycle and needs to care for her progesterone levels, or is struggling with too little estrogen and too much cortisol, she may not respond optimally to a cold stress. The goal is a stress response that improves function — not one that overwhelms and depletes the body.

The power of contrast therapy

Having said all that, there is also the old clinical workhorse: alternating contrast therapy. Hot, then cold, then hot again — and then maybe cold again. Three to five rounds. Alternation moves blood the way a pump moves water; applied that way, it’s gentler, and more useful for more bodies than heroic cold alone can be. I have used hot and cold to treat more injuries and infections and pain conditions than I can count — and again, the different rhythms of timing and exact temperature matter. I have used this approach even in hospitals.

Not for every body, every day

And cold is not for every body, every day. Certain heart and circulation conditions, Raynaud’s, thyroid, and a few other situations change the math entirely. That is the difference between a therapy and a stunt: a therapy has contraindications, and someone needs to know the nuances — of both you and the mechanisms — not just to avoid injury, but to transform your ability to heal and thrive. I have used cold on fragile and ill people with amazing results. But there is more to know about this force of nature, whether we are using it on ourselves or on our patients.

Reach out if you want to ask questions.

— Dr. Sara Hazel