A wood frog can tolerate the freezing of their blood and other tissues. (wiki, news2), but human beings can not.

Some people plan to freeze their bodies/brains after death, and some of them have done that.

Can wood frogs help us learn how to freeze our brains safely?

  • $\begingroup$ @Dexter has the correct answer. Human cells are made mainly of water, it should be fairly obvious what the problem of freezing is. Water expands as it freezes, so the cells begin to rupture due to the expanding ice crystals. Cryoprotectants used to protect cells when they are frozen in Liquid Nitrogen in a lab setting are very toxic. You have a very short window of opportunity when thawing cells to exchange the cryoprotectant with growth medium before the cells start to die. Now multiply this a billion fold and you get an idea of what it would be like when unfreezing a whole body. $\endgroup$
    – AMR
    Sep 22, 2015 at 4:49

1 Answer 1


Generally frogs are cold blooded animals (more specifically ectothermic or poikilothermic) . Wood frogs can maintain their body temperature by production of cryoprotectants which a human body cannot produce from normal metabolic processes. Such molecules depress the freezing point of tissue and avoid ice formation. Here is a scientific report on the physiology of wood frogs and what helps them survive at freezing temperatures. There are also other mechanisms which cold blooded animals use to survive such conditions.

Now for the human part. Humans are warm blooded (more specifically endothermic). We always try to maintain their body temperature (our normal body temperature is $37^{o}$). That is why we cannot tolerate freezing temperatures, because our physiology does not have a means to avoid cell damage at that temperature. The company which you mentioned uses vitrification methods which uses various artificial cryoprotectants (which wood frog makes naturally).

There is research going on in this direction already. Researchers are using extremophiles and their metabolic products in cosmetics and medicine (like this, this and this).

  • $\begingroup$ how long can a wood frog keep frozen if they live in human-controlled cold environment? $\endgroup$ Sep 22, 2015 at 5:28
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    $\begingroup$ No idea. I know for bacteria though. We can keep bacteria for many years in $-80^0$. I have recently used bacteria stored in $-80^0$ after 6 years! $\endgroup$
    – Dexter
    Sep 22, 2015 at 10:41
  • $\begingroup$ It is interesting to test how long can wood frogs keep frozen. For bacteria, Russian people are doing the similar things. [dailymail.co.uk/sciencetech/article-3243056/… $\endgroup$ Sep 22, 2015 at 15:27
  • $\begingroup$ You should specify that the body temperature provided is in Celsius to avoid a bit of confusion :P. $\endgroup$
    – John Odom
    Sep 22, 2015 at 20:03
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    $\begingroup$ @JohnOdom $37^0$ F will be frog's body temperature during hibernation :P $\endgroup$
    – Dexter
    Sep 26, 2015 at 3:38

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