My mentor’s grandma passed away without any diseases at the age of 101. He told me his grandma is very nice and optimistic. She is also humorous. Her children kept calling her to say hello and she said each of her children wanted to be the first one to know she is dead by calling her. By the way, the grandma lived herself. The grandma likes drinking black coffee. Moreover, although my mentor is tall and strong, his grandma is pretty short. Optimism, humor, drinking coffee and being short have all been linked to longevity. But we cannot ignore another reason: my mentor is from Minnesota, a north state of United States where is very cold in winter. Cold temperature may have an important influence on longevity.
Cold temperatures have been found to be related to extended lifespan of both poikilotherms and homeotherms. Like refrigerator storage of food can slower the decay, cold temperatures are believed to slowing aging in a similar way: reduce the rate of chemical reactions since life itself, in essential, is a kind of complicated chemical reactions. This hypothesis implicates that cold caused lifespan increase is a passive process. However, the truth is, life is not like food in the refrigerator and it makes active efforts to resistance cold temperature and to live longer.
Researchers from University of Michigan tried to understand how cold temperatures are associated with lifespan by adopting C. elegans, a kind of worm which is a model animal frequently used for studying aging and senescence by scientists. They discovered that instead of slowing reactions, C. elegans struggle in cold temperatures to live longer. There exist some channels in cell surface of C. elegans which are sensitive to temperature drop. Once perceiving the change of temperature, these channels will activate some signaling pathways in cells and eventually a protein called DAF-16, which is a known lifespan extending factor, will be activated. Activated DAF-16 contributes to lifespan extension.
Interestingly, cold-sensitive channels function mainly in intestine but not in other tissues. Neural system is evolved to respond environmental signals and is supposed to be a appropriate platform for cold temperature response. However, researchers in University of Michigan reported that it is intestine but not neural system in C. elegans to respond to temperature changes. In C. elegans, intestine is also the fat tissue. Thus, both intestine and fat tissues contribute to lifespan extension.
What lesson can we learn from this cold associated lifespan extension? Considering the benefits of cold are only tested in C. elegans, it is premature to draw any similar conclusions in humans. At least in mice, lowering the whole body temperature of animals is known to extend lifespan. Anyway, people have performed ice bath for multiply purposes. Maybe we should add another one: you will live longer if you keep the habit of ice bath as along as you can.
[1] A Genetic Program Promotes C. elegans Longevity at Cold Temperatures via a Thermosensitive TRP Channel. Cell 152, 806–817, February 14, 2013.
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