Cold Is Information: The Biophysics of Cold Therapy

Every animal that lived through an ice age carried an answer to one question: what do you do when the heat goes away? Most of us now live at 72 degrees all year, so we've stopped asking it. Neurosurgeon Jack Kruse built a whole framework around asking it again. To him, cold isn't a stress you put up with. It's environmental information, and the place that information lands is the inner mitochondrial membrane (IMM), the folded sheet inside every mitochondrion where your cells turn food and oxygen into energy, heat and water.

This piece leans into Kruse's view on purpose, because it's the most ambitious explanation of cold out there. His ideas are attributed to him and labeled with this site's evidence tiers. The mainstream physiology is laid out next to it so you can see where the two overlap and where they part ways.

The stage: the inner mitochondrial membrane

Start with what nobody argues about. The IMM holds the electron transport chain, a relay of protein complexes that pass electrons from food down to oxygen. As electrons move, protons get pumped across the membrane, building a gradient. Those protons then flow back through ATP synthase, a molecular rotor that makes ATP. At the end of the chain, cytochrome c oxidase hands electrons to oxygen and makes water. (Centralized View)

The IMM is also where cardiolipin lives. It's a four-tailed phospholipid found almost only in this membrane, and it binds and stabilizes the respiratory complexes and the curved folds (cristae) where they sit (Paradies et al. 2019). (Centralized View) DHA, the long marine omega-3, can be built into cardiolipin and other mitochondrial phospholipids, changing how the membrane behaves. (Centralized View on whether it happens; Middle Ground on what it means for performance)

If you've read Cardiolipin and DHA, you know the framing I use: these two lipids act less like fuel and more like semiconductors and structural anchors, setting the membrane's geometry, voltage and the order of the water around it. Cold, in Kruse's model, is the environmental lever that tunes all of it.

Kruse's thesis: cold is a signal, not just a stressor

Kruse laid out his ideas in a long blog series called Cold Thermogenesis, starting in 2011–2012 as an add-on to his "Leptin Rx" reset (Kruse, The Cold Thermogenesis Protocol). Here is the core of what he argues, in his terms.

1. Cold shifts the redox state and electron flow

Kruse writes that at night the interior of our cells becomes "more reduced chemically and electrically" (Cold Thermogenesis 3). He doesn't put it in exactly these words, but my reading of his series is that cold pushes cells toward that same electron-rich, night-like state. He also writes that "cold increases the strength of a magnetic field" in the cell and that more electrons mean more magnetic potential in our membranes. In his framing, a warm, carb-heavy, always-summer lifestyle phase-shifts mitochondria "to protons and away from electrons" and lowers the IMM's electric potential (Organization and Structural Failure #8). Cold is the corrective signal. (Decentralized View)

2. Tight spacing, tunneling and the "quantum" ETC

That electrons hop between redox centers in the chain by quantum tunneling is standard biophysics. Tunneling rates fall off steeply with distance, which is why the centers are packed closely. (Centralized View) Kruse takes this further. He writes that electron tunneling in the iron-sulfur clusters stops above roughly 14 angstroms, that a "summer lifestyle 24/7" expands those atomic distances, and that "leptin resistance is a synonym for the inability to tunnel electrons" (Tensegrity #9). He also argues that cytochrome c oxidase moves protons too fast for simple diffusion, so they must be delivered by proton tunneling (same post). Cold, by tightening protein structure, keeps the system in its efficient tunneling range. (Decentralized View)

3. DHA as the cold-adapted semiconductor

This is where Kruse and the cardiolipin note meet. He writes that "the ability to tunnel well is tied specifically to DHA," and that optimal tunneling requires a lot of DHA built into cell membranes, "including the MINOS of the inner mitochondrial membrane" (Organization and Structural Failure #8). In the cold series he argues that "the colder it is the more omega 3's are needed for cell membrane signaling," which is why cold-adapted, polar animals run on marine DHA (Cold Thermogenesis 5). Elsewhere he describes DHA as turning sunlight into an electrical signal that travels to the IMM, where DHA turns it back into infrared light and heat, the heat you feel as thermogenesis in the cold (Tensegrity #5). (Decentralized View)

The cold-adaptation part has a real footing. Organisms living in the cold adjust their membrane lipids, often adding more unsaturated fatty acids, to keep their membranes fluid. This is called homeoviscous adaptation. It was first described in bacteria (Sinensky 1974) and has been measured in cold-acclimated fish such as trout. (Centralized View in microbes and cold-blooded animals; Middle Ground on how much it applies to warm-blooded humans) Whether DHA's pi-electron cloud gives it a special "quantum" role in electron or proton transfer is Kruse's leap. (Decentralized View)

4. Structured water at the membrane

Kruse leans on Gerald Pollack's work on "exclusion zone" (EZ) water, a layer next to hydrophilic surfaces that pushes out solutes and carries charge separation (Zheng et al. 2006). He argues the IMM is wrapped in a water hydration shell that tunneled electrons polarize into an exclusion zone, and that this shell holds the protons fed to ATP synthase (Organization and Structural Failure #8). When cold receptors fire, he writes, the temperature change "initially alters the molecular arrangements of water" around the mitochondria (same post), and he develops water's hydrogen-bonding networks at length in Tensegrity #6. Pollack's lab results on EZ layers are Middle Ground. Kruse's application of them to the IMM is an Decentralized View.

5. Uncoupling: heat as a feature

In standard biology, uncoupling proteins (UCPs) let protons leak back across the IMM without passing through ATP synthase, so the energy comes out as heat instead of ATP. (Centralized View) Kruse treats this leak as a design feature, not a waste. He writes that cold "increases heat release from mitochondria," and that this makes you "more energy efficient," tying it to water shrinking as it's warmed by infrared light from mitochondria (Tensegrity #9). The idea that uncoupling rebalances the system and lowers oxidative stress overlaps with mainstream thinking on "mild uncoupling." His claim that it raises overall efficiency is an Decentralized View.

6. Melatonin, night and cold

Kruse argues that melatonin acts on water's coherent domains at night and governs energy flow to and from mitochondria (Time #17). Linking that to cold is my own connection, not something I found him stating: if cold and night both put cells into a reduced, repair-mode state, mitochondrial melatonin is a natural place to look. There is mainstream support for part of the picture. Researchers at the University of Pittsburgh reported in mice that mitochondria in neurons can make melatonin themselves, and that it helps block a key step toward cell death (Suofu et al. 2017). (Middle Ground on how much this matters in humans) No one has shown that cold raises mitochondrial melatonin in humans. (Decentralized View)

7. Sun plus cold, and the ancestral marine context

For Kruse, cold never works alone. His protocol tells you to do cold at sunrise or after dinner (Cold Thermogenesis Easy Start Guide), and his writing elsewhere puts heavy weight on morning sun and seafood. Putting those together under his "Epi-paleo" label is my summary of his overall approach, not a quote from one post. The picture that comes out is of humans as cold-adapted, DHA-rich coastal animals, with sunlight, seafood and cold as the three inputs that keep the IMM in its high-voltage, well-tunneling state. (Decentralized View)

8. Deuterium: the heavy passenger in the cristae

Hydrogen comes in two stable forms. Protium is a lone proton. Deuterium carries an extra neutron, so it has roughly twice the mass. Because of that extra mass, bonds and transfers involving deuterium run slower than the same steps with ordinary hydrogen. Chemists call this the kinetic isotope effect, and it is textbook physics. (Centralized View)

Now the stage. The cristae are the folds of the inner mitochondrial membrane, and their shape is not fixed: cells remodel them, and cristae shape changes how respiratory supercomplexes assemble and how efficiently they breathe (Cogliati et al., 2013). The electron transport chain pumps protons into the cristae space, and that gradient flows back through ATP synthase, a true rotary motor whose spinning has been filmed directly (Noji et al., 1997). Swapping deuterium for hydrogen measurably changes the kinetics of the isolated mitochondrial ATPase (Urbauer et al., 1984). (Centralized View)

Kruse builds on exactly that. He writes that deuterium in the matrix and the inner membrane is "ruining cristae alignment via the KIE," and describes heavy water creating "a Kinetic Isotope Effect (KIE) bottleneck at the ATPase motor" where "the motor 'stutters'" (thread, via Thread Reader; thread). He also says that cytochrome c oxidase "makes deuterium depleted water" and that water "is the perfect insulator when it doesn't have any ions in it and it doesn't have any deuterium," which in his view lets the membrane hold its charge (Mind & Matter podcast #221). On cold specifically, he writes that "cold condenses our respiratory proteins" (Is Ketosis a Cure or Tool for a Broken Mitochondria?). (Decentralized View)

Here is how I read those pieces together, and this is interpretation, not a line I found him writing word for word: cold tightens the cristae and condenses the respiratory proteins, and that physical squeeze forces heavy deuterium out of the folds. What's left is a cleaner, lighter proton current running through the ATP synthase turbine. Pair that with cold-driven fat burning, and the mitochondria make their own deuterium-light metabolic water from the inside. That is the Kruse picture: cold doesn't just burn fuel, it rinses the engine. (Decentralized View)

Where does the outside research stand? Somlyai and colleagues reported that lowering deuterium below natural levels slowed the growth of cultured cells (Somlyai et al., 1993), and Boros and colleagues have proposed that fat-burning metabolism and the TCA cycle supply deuterium-depleted water to mitochondria (Boros et al., 2016; Boros et al., 2024). Note that both Boros papers appear in Medical Hypotheses, a journal for ideas, not trials. Deuterium-depleted water as a therapy is a live but small and contested field. (Middle Ground)

Be clear on the gap: I could not find a peer-reviewed study showing that cold exposure physically pushes deuterium out of the cristae, or that cold lowers deuterium in human mitochondria at all. The mechanism is unproven in the mainstream literature. It's a testable idea, not a finding.

What mainstream science agrees on

Now the other column. None of this disproves Kruse, but it's the part with the most data behind it.

Brown fat and UCP1

Brown adipose tissue is packed with mitochondria that carry UCP1, the protein that leaks protons across the IMM to make heat instead of ATP. It's switched on by noradrenaline from the sympathetic nervous system when you get cold (Cannon & Nedergaard 2004). (Centralized View) Adults have active brown fat, and it can be recruited. In one study, 10 days of mild cold (about 15–16°C air, 6 hours a day) raised brown fat activity and non-shivering heat production, and people felt more comfortable in the cold (van der Lans et al. 2013). (Centralized View)

Noradrenaline: the cold-water surge

In a classic study, men sat up to their necks in water at 32, 20 and 14°C for an hour. At 14°C their metabolic rate rose by 350%, plasma noradrenaline by 530% and dopamine by 250%, while adrenaline didn't change (Šrámek et al. 2000). That's the mood and focus lift people feel after a plunge. (Centralized View)

Real-world cold plungers

Danish researchers studied young men who swam in winter water and used saunas. They dipped 2 to 3 times a week, usually several short dips per visit lasting a minute or two each, and most also used a sauna. Compared with 8 matched controls, the 8 winter swimmers produced more extra heat when cooled. At a comfortable temperature they had a lower core temperature and no detectable brown fat activity, and their supraclavicular skin temperature followed a different daily rhythm (Søberg et al. 2021). It was a small observational study, so it shows association, not cause. (Centralized View findings; Middle Ground on how broadly they apply)

Cold-shock proteins

Cold switches on its own protective genes. In mice, cooling raised RBM3, a "cold-shock" protein, which restored synapse regeneration and protected neurons in models of neurodegeneration (Peretti et al. 2015). A follow-up found RTN3 as a cold-induced protein that carries some of RBM3's protective effect (Bastide et al. 2017). (Centralized View in mice; Decentralized View for cold plunging in people)

The Wim Hof study

Twelve healthy volunteers trained for 10 days in a Wim Hof-style program (meditation, breathing techniques and ice-cold water immersion), then got an injection of bacterial endotoxin. Twelve untrained controls got the same injection. The trained group had much higher adrenaline, a faster rise in anti-inflammatory IL-10 that also reached higher levels, lower inflammatory markers (TNF-α, IL-6, IL-8) and fewer flu-like symptoms (Kox et al. 2014). The breathing probably did much of the work, and the sample was small. (Centralized View finding; Middle Ground on what part cold played)

The risks are real

Cold water kills people, and it's worth knowing how. The first one to three minutes bring a cold-shock response: a gasp, hyperventilation, a jump in heart rate and blood pressure. That gasp under water is a drowning risk (Tipton et al. 2017). Sudden face immersion can also set off the diving reflex at the same time as cold shock. That "autonomic conflict" can trigger arrhythmias, especially in people with heart disease (Shattock & Tipton 2012). Longer exposure brings hypothermia, and core temperature can keep falling after you get out, which is called afterdrop. (Centralized View)

Kruse's own protocol says to see a doctor first if you have a serious health condition, to stop immediately if you feel light-headed or your skin turns pale to white, and that his "Deep CT" needs a spotter and a doctor (Cold Thermogenesis 13: FAQs).

A practical, gradual protocol

This blends Kruse's step-by-step ramp with general safety guidance drawn from the cold-water research, including Tipton et al.'s 2017 review. It's general information, not medical advice. Talk to a qualified professional before you start, especially if anything on the list below applies to you.

• Start small. Kruse begins with face dunks in 50–55°F (10–13°C) water and builds up from there (Easy Start Guide). Cold showers at the end of a normal shower work too.
• Dr. Jack Kruse threads on deuterium (Thread Reader), second thread
• Mind & Matter podcast #221 with Jack Kruse
• Is Ketosis a Cure or Tool for a Broken Mitochondria? (LinkedIn)
• Ramp slowly. Move to the torso (Kruse uses ice packs on the chest), then to partial and full immersion over weeks.
• Pick temperatures and times you can control. As a general rule of thumb, not a medical prescription, 50–60°F (10–15°C) for 1 to 5 minutes is a common, conservative place to start. The experienced winter swimmers in the Søberg study usually stayed in for only a minute or two per dip.
• Breathe through the gasp. The cold-shock gasp and fast breathing peak in the first minute or so (Tipton et al. 2017). Get in slowly and let it pass before putting your head or face under.
• Never alone, never under the influence. Don't do breath-hold work in water. Have someone nearby for anything colder or longer.
• Rewarm gently. Dry off, dress warmly and move. Expect afterdrop, and skip the hot shower right away if you feel faint.
• Pair it with light and seafood. That's the Kruse twist: morning sun on your skin and eyes, and a diet built on DHA-rich seafood.
• Stop if you get chest pain, light-headedness, confusion, numbness that doesn't go away, or pale to white skin.
• Urbauer, J. L., Dorgan, L. J. & Schuster, S. M. (1984). Effects of deuterium on the kinetics of beef heart mitochondrial ATPase. Archives of Biochemistry and Biophysics 231, 498–502. https://doi.org/10.1016/0003-9861(84)90413-2
• Cogliati, S. et al. (2013). Mitochondrial cristae shape determines respiratory chain supercomplexes assembly and respiratory efficiency. Cell 155(1), 160–171. https://doi.org/10.1016/j.cell.2013.08.032
• Noji, H. et al. (1997). Direct observation of the rotation of F1-ATPase. Nature 386, 299–302. https://doi.org/10.1038/386299a0
• Somlyai, G. et al. (1993). Naturally occurring deuterium is essential for the normal growth rate of cells. FEBS Letters 317, 1–4. https://doi.org/10.1016/0014-5793(93)81479-J
• Boros, L. G. et al. (2016). Submolecular regulation of cell transformation by deuterium depleting water exchange reactions in the tricarboxylic acid substrate cycle. Medical Hypotheses 87, 69–74. https://doi.org/10.1016/j.mehy.2015.11.016
• Boros, L. G. et al. (2024). Summiting Mount Everest in deuterium depleting nutritional ketosis without supplemental oxygen. Medical Hypotheses 185, 111290. https://doi.org/10.1016/j.mehy.2024.111290

Who should not do this without a doctor (general safety guidance, not a complete medical list): anyone with heart disease, arrhythmias, high blood pressure, a history of stroke, Raynaud's, cold urticaria, epilepsy, or diabetes with neuropathy; anyone pregnant; children; and older adults.

What would test Kruse's thesis?

A bold idea earns its place by making predictions. A few that could be tested:

• If cold works through DHA and tunneling, people with higher red-cell DHA (omega-3 index) should cold-adapt faster, with more non-shivering heat, at the same dose of cold.
• If cold "tightens" the chain, measured electron-transfer rates or the ratio of oxygen use to ATP made should shift in isolated mitochondria after cold acclimation.
• If EZ water matters at the IMM, its presence near mitochondrial membranes should be shown directly by independent labs, and shown to change with temperature.
• If cold boosts mitochondrial melatonin, it should be measurable in human tissue after cold exposure.

Until data like that exists, the honest position is to treat these ideas as a framework worth exploring, not settled fact.

For more on how I weigh claims like these, see How to Read a Claim.

Sources

Dr. Jack Kruse (viewpoint sources, jackkruse.com):

• The Cold Thermogenesis Protocol
• Cold Thermogenesis 3
• Cold Thermogenesis 5: Biologic Magnetism
• Cold Thermogenesis 13: The FAQs
• Cold Thermogenesis Easy Start Guide
• Tensegrity #5: Your Magnetic Sense
• Tensegrity #6: Hydrogen Bonding Networks in Water
• Tensegrity #9: Electron Spin Meets Mitochondrial Function
• Organization and Structural Failure #8
• Time #17: Melatonin and Insulin Are Solar Metronomes

Research:

• Cannon, B. & Nedergaard, J. (2004). Brown adipose tissue: function and physiological significance. Physiological Reviews 84(1), 277–359. https://doi.org/10.1152/physrev.00015.2003
• Paradies, G. et al. (2019). Role of cardiolipin in mitochondrial function and dynamics in health and disease. Cells 8(7), 728. https://doi.org/10.3390/cells8070728
• Zheng, J.-M. et al. (2006). Surfaces and interfacial water: Evidence that hydrophilic surfaces have long-range impact. Advances in Colloid and Interface Science 127(1), 19–27. https://doi.org/10.1016/j.cis.2006.07.002
• Sinensky, M. (1974). Homeoviscous adaptation: a homeostatic process that regulates the viscosity of membrane lipids in Escherichia coli. PNAS 71(2), 522–525. https://doi.org/10.1073/pnas.71.2.522
• Suofu, Y. et al. (2017). Dual role of mitochondria in producing melatonin and driving GPCR signaling to block cytochrome c release. PNAS 114(38), E7997–E8006. https://doi.org/10.1073/pnas.1705768114
• Šrámek, P. et al. (2000). Human physiological responses to immersion into water of different temperatures. European Journal of Applied Physiology 81, 436–442. https://doi.org/10.1007/s004210050065
• van der Lans, A. A. J. J. et al. (2013). Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. Journal of Clinical Investigation 123(8), 3395–3403. https://doi.org/10.1172/JCI68993
• Søberg, S. et al. (2021). Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Reports Medicine 2(10), 100408. https://doi.org/10.1016/j.xcrm.2021.100408
• Peretti, D. et al. (2015). RBM3 mediates structural plasticity and protective effects of cooling in neurodegeneration. Nature 518, 236–239. https://doi.org/10.1038/nature14142
• Bastide, A. et al. (2017). RTN3 is a novel cold-induced protein and mediates neuroprotective effects of RBM3. Current Biology 27(5), 638–650. https://doi.org/10.1016/j.cub.2017.01.047
• Kox, M. et al. (2014). Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans. PNAS 111(20), 7379–7384. https://doi.org/10.1073/pnas.1322174111
• Tipton, M. J. et al. (2017). Cold water immersion: kill or cure? Experimental Physiology 102(11), 1335–1355. https://doi.org/10.1113/EP086283
• Shattock, M. J. & Tipton, M. J. (2012). 'Autonomic conflict': a different way to die during cold water immersion? Journal of Physiology 590(14), 3219–3230. https://doi.org/10.1113/jphysiol.2012.229864

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