dr ronapatrick here today we are going to talk about the brain and metabolic effects of cold
exposure we all want to reduce stress and make our lives easier but is that always the best approach
what if the best medicine might just be a little low-dose stress this idea harnesses hormesis
a biological phenomenon where a low-dose short-duration stressor in this case cold
temperatures triggers a cascade of adaptations that protect us against future larger stressors
basically preconditioning our bodies against stress this isn't a new idea humans have used
cold exposure often with the expectation that it promotes health for centuries
but habitual cold exposure can have far-reaching beneficial effects on our bodies metabolic health
and possibly brain function many of which converge on a chemical released in response to the cold
norepinephrine produced in the adrenal glands and central nervous system it can
act as both a hormone and neurotransmitter because of norepinephrine's unique effects
cold exposure may influence aspects of physiology relevant for fighting metabolic related diseases
and parameters of brain function associated with mood neurodegeneration and depression and studies
in both mice and humans have shown that cold water immersion increases levels of pgc-1 alpha
in skeletal muscle pgc1 alpha is a protein that regulates mitochondrial biogenesis the production
of new healthy young mitochondria increased mitochondrial biogenesis is an adaptation to
exercise and is associated with greater aerobic capacity and a lower risk for developing many
diseases such as alzheimer's parkinson's and type 2 diabetes when acting as a hormone norepinephrine
causes your blood vessels to constrict which helps you retain heat but retaining heat isn't the only
way our bodies maintain their temperature we can also produce heat a process called thermogenesis
there are two types shivering thermogenesis as the name would imply involves shivering
to produce heat it relies on the energy produced by atp hydrolysis during muscle contractions to
generate heat useful but somewhat inefficient but the body also has a more efficient way
non-shivering thermogenesis is direct metabolic heat production and norepinephrine plays an
important role here too it acts on key proteins such as ucp1 in fatty tissue these proteins
disconnect the normal electrical processes within our mitochondria that produce chemical energy and
instead allow them to directly produce heat but there's a catch not all fat can do this equally
this type of thermogenesis is mostly a quality of a type of fat known as brown fat so called
for its darker coloring which reflects the overall mitochondrial density of the tissue
scientists once thought brown fat was only present in newborns to provide protection against
body heat loss but we've since found it in adults as well particularly falling cold exposure and
that is because other types of fat can take on thermogenic characteristics of brown fat
a process that also involves mitochondrial biogenesis that is regulated by you guessed
it the release of norepinephrine in response to cold how much can we increase brown fat activity
a study in which healthy young men wore a cooling suit at 50 degrees fahrenheit found that their
brown fat volume increased 45 from baseline why does this matter because the oxidative metabolism
in their brown fat increased more than twofold suggesting that cold exposure can increase energy
expenditure which could have metabolic benefits another team of researchers exposed participants
to a temperature of 63 degrees fahrenheit for two hours a day over six weeks their thermogenesis
increased by about 58 percent and they saw a mostly negligible decrease in fat of about one and
a half pounds the control group experienced none of these changes but there's further evidence to
suggest that cold induced brown fat activation affects metabolic health improving glucose and
insulin sensitivity increasing fat utilization and protecting against diet-induced obesity
one study looked at men who underwent prolonged cold exposure in a cooling vest
their energy expenditure increased 15 but only among those who had detectable brown fat roughly
one third of this increase was due to oxidation of plasma derived glucose when the men received an
infusion of glucose only those who had detectable brown fat showed a further increase in glucose use
that's important because it indicates that brown fat plays a role in glucose utilization
essentially providing an alternate pathway for glucose and in fact for healthy young people this
type of glucose uptake after cold exposure exceeds the insulin stimulated uptake rate in skeletal
muscle making brown fat an interesting potential therapeutic target for the treatment of metabolic
disorders so it's clear that acting as a hormone norepinephrine released by cold exposure can have
wide reaching positive effects on our bodies but it can also act as a neurotransmitter and
may influence brain function animal studies have found that chronic cold exposure also promotes the
release of norepinephrine from the locus ceruleus region of the brain in the brain norepinephrine
is involved in vigilance focus attention and mood low levels are associated with decreased attention
cognitive ability energy and poor mood norepinephrine depletion may even lead to
depression in fact both adhd and depression are sometimes treated with norepinephrine reuptake
inhibitors which block the reabsorption of norepinephrine increasing the levels around
our neurons but these drugs carry some risks increasing norepinephrine through cold exposure
while not completely risk-free shows promise as a way of addressing these aspects of mental health
for example in a prospective randomized controlled trial participants received 10 sessions of
whole-body cryotherapy short exposure to extremely cold air in addition to antidepressant medication
compared to the control group who are exposed to cold but not cryogenic temperatures
the participants showed marked reductions in their depressive symptoms and improvement in
their quality of life mood and acceptance of their diagnosis sounds pretty good right so how can you
try out cold exposure for yourself the most common methods are cold water immersion and cryotherapy
they differ in their ability to reduce body temperature but they both seem to induce a robust
release of norepinephrine in one study women either swam in 35.6 degree fahrenheit water for 20
seconds or underwent cryotherapy at temperatures 166 degrees fahrenheit for two minutes they did
this three times per week for 12 weeks both groups of women showed two to three-fold increases in
their circulating norepinephrine after each exposure session and temperature does matter
in a study where healthy young men underwent one hour head out immersions in three different
temperatures of water only the coldest of the three increased norepinephrine by 530 percent and
dopamine by 250 percent compared to their levels before immersion not only that but the coldest
water increased their energy expenditure by 350 percent compared to pre-emersion levels duration
matters too a separate study found that neck deep immersion in 50 degree water for up to an hour
increased norepinephrine the longer they were submerged the bigger the response so exposing
the body to cold for prolonged periods may have a more robust effect on norepinephrine release
however other studies have still found significant effects with less time one i previously mentioned
had women immersed themselves in 35.6 degree fahrenheit water for only 20 seconds and still
saw big jumps in plasma norepinephrine while we can't strictly equate all adaptive benefits
on that basis alone at the least we do know a lot can happen in even just 20 seconds which is
encouraging for those of us that just need an excuse to get our feet wet there's still a lot
to learn about cold exposure's effects on health and the mechanisms that drive them but the early
evidence is promising for a comprehensive overview of the science be sure to check out our topic
article on cold exposure at foundmyfitness.com i'm dr rhonda patrick and i'll catch you next time
you