It's a festive time of year. The time of year
where we can't stop eating, and we embrace traditions from our families, as
well as starting to embrace traditions of our own. The winter solstice has
finally taken place, and the days are slowly getting lighter again, although
not any warmer. A lot of Christmas seems to be purely cultural- but there is
actually quite a bit of scientific reasoning behind why Christmas is really
such an important time.
So, this week, I'm looking at some of the key aspects behind
the Christmas period and why they are so important from a scientific
perspective.
1.The winter solstice
It was believed that Christmas was originally a pagan
festival to celebrate the days becoming longer again. It's possible that the
Ancient Romans used to call it the Dies Natalis Solis Invicti and celebrated it
as the birthday of the sun God. The theory goes that the word of Christ
began to spread, the festival was revamped to celebrate the birth of God.
This year, the winter solstice arrived on the 21st of
December - this year's shortest day. For those in London, the sun rose at 08:04
GMT and set again at 15:53 GMT. For those who were in the Shetland Islands, the
sun rose at 09:08 GMT and set again at 14:57 GMT
The reason the days change in length and why winter days are
always shorter is due to the position of the Sun and the Earth.
The Earth revolves around the sun but also is rotating on
its own axis at the same time. This is an imaginary line that passes though the
Earth from the North Pole to the South Pole. Everything from the North pole to
the equator is the Northern Hemisphere, whilst everything from the South Pole
to the equator is the Southern Hemisphere. This means that one hemisphere of
the earth is facing away from the sun at the same time the other hemisphere is
facing the sun. This is how we get day and night. Rotation of the earth alone
would give us equal amounts of day and night.
But what's important to note is that the earth is actually
tilted by about 23.5 degrees, away from the sun. This means that as the earth
rotates itself and rotates around the sun, one hemisphere would be angled
towards the Sun, whilst the other is angled away.
So, there will be a period of time where either one of the
Earth's poles reach its maximum tilt away from the sun. Meanwhile, the other
pole will be the closest it can be to the sun. So, this means that if the North
Pole is furthest from the sun, the South pole will be closest to the sun. So,
the Northern hemisphere will be experiencing the least amount of daylight,
whilst the Southern Hemisphere experiences the most.
The Earth continues to orbit the sun, so the Northern
hemisphere is currently starting to tilt more towards the sun each day.
Minute by minute, the sun is lasting longer and longer in the sky. Its rising a
little earlier each day and letting a little later each day. It's official-
those in the Northern Hemisphere are half way though the dark.
2.The biological importance of celebrating during the
winter.
There is evidence that the winter solstice was celebrated
back in the New Stone Age, and there was both practical and biological
reasoning for this. Winter would have been a time for scarcity so at
first it doesn't seem to make much sense to have a feast in the middle of it.
But because of this scarcity, livestock would be slaughtered to avoid having to
feed them. This actually meant there would be a plentiful supply of fresh
meat for feasting. Feasting would also have been essential for survival-
as the cold would have increased the calories that these early humans would
need.
It has also been shown that celebrating together releases
Oxytocin, a hormone needed for emotional connection and regulation, as well as
physical health, whilst physical touch releases stress-relieving hormones.
Feasting, laughing and embracing would ultimately have released hormones that
would make it possible for these early humans to live and work together.
For early humans, group living was essential for survival,
meaning emotional connection was essential. Winter would have been such a time
of stress, and stress, alongside the reduced daylight would have had such an
impact on moods; this could have reduced group morale and increased tension
dramatically within the group. Celebrating together therefore would have been
on the whole, stress relieving and therefore an important part of surviving
winter. Don't suppose these early humans would have had to deal with the drama
of family get-togethers once politics and wine enter the mix.
3.Why Christmas lights feel so good.
Driving past Christmas lights always bring a smile to my
face and I know I'm not alone in this. Christmas lights give off feelings of
delight, nostalgia and peace.
There actually is a biological reason for this.
In winter, the reduced daylight affects melatonin and
serotonin. These are two hormones that are essential for mood and your body's
day-to-day functioning. Melatonin is essential for sleep-wake cycles and is
produced in the night to regulate the body's circadian rhythm, alerting the
body to when it needs to be alert, when it needs to sleep and when it needs to
eat. In winter however, the reduced sunlight and increased darkness results in
more Melatonin being produced. This means the body clock can be totally
disrupted, potentially leading to a person feeling tired but also struggling to
sleep.
Serotonin on the other hand is a hormone that is needed for
mood, sleep, appetite, memory and digestion. Low levels of it can lead to
depression and anxiety. Serotonin release is influenced by diet - with carbs
triggering its release, stress, exercise, wound healing, and also sunlight. So
similar to Melatonin release, the lack of daylight also reduces levels of
Serotonin. As well as this, the weather conditions and it getting darker
earlier contribute to reduced motivation to exercise. This also reduces Serotonin
levels. Winter can also be stressful -especially with the cost of living
crisis. Combine all this with the insomnia and tiredness caused by
reduced Melatonin, it’s no wonder that people can experience really low moods
during the winter, and happiness can be hard to find.
That's where the Christmas lights come in. The
brightness mimic sunlight and this leads to a boost in Serotonin and Melatonin
levels. This can reset circadian rhythms and have an uplifting effect on
mood. There is also a psychological aspect. Christmas lights are often
associated with positive memories and nostalgia which causes the release of the
'happiness hormone' dopamine. The release of dopamine then hijacks the pathways
in the brain that control serotonin and lead to even more serotonins being
released, further enhancing feelings of well-being. Christmas lights are for
that reason brilliant for combating Seasonal Affective Disorder, a type of
depression linked to seasonal changes. This is a great argument for why
Christmas lights should be put up as early as possible!
4.Why Christmas smells so good.
Smell has a particularly powerful effect on memory recall.
The olfactory bulb is the part of the brain that processes smell and it
connects directly to the amygdala, which is part of the brain that processes
emotions. It is also connected to the hippocampus which processes memory. This
means that smell and long-term recall are deeply linked. Olfactory pathways
form deep connections with memory centres, and this may play a role in brain
development during childhood.
The spices pine, cinnamon and cloves, along with orange oils
have very unique scents and are never really used for times outside of
Christmas. This means that smelling them instantly activates memories of past
Christmases. This also activates the emotions associated with these
Christmases. Which is why we also have scent-induced nostalgia.
As well as this, real Christmas trees release volatile
organic compounds (VOC), especially a type of compound called terpenes.
These compounds interact with the emotional centres of the brain and influence
emotional well-being. In particular, the terpene that gives the pine smell is
alpha-pinene and is linked to reduced anxiety. Christmas trees also release
Limonene, which is linked to increased alertness and mood, and Bornyl acetate,
with is associated with relaxation.
Cinnamon, clove, nutmeg and ginger also have antimicrobial
properties and activate a kind of receptor in the body called TRP receptors;
these are usually used in sensing heat. So, this activation creates a warming
sensation even without any temperature change.
Finally, how we experience smell changes in Winter. There is
a contrast between the cold outdoor air and the warmer indoor air. Cold air is
drier and carries fewer smells and therefore makes indoor smells feel intense
and warmer. This increases their impact. In other words, if your December is
predicted to be really cold, put up your Christmas tree early and embrace the
nostalgia!
5.Why we crave rich food.
In cold environments, the body has a bigger calorie demand.
This basically means that the colder you are, the more calories the body wants.
This is because the body needs to keep itself at a stable temperature.
Heat is lost faster when the environment is cold meaning the body needs to burn
more calories to produce the energy it needs. Fat and sugar have a high
amount of energy and release it quicky.
As well as this, fat and sugar trigger the release of
serotonin which increases mood. It also leads to dopamine being released, which
increases mood, and reward pathways being produced. This means that eating warm
high calorie meals in winter provides stress relief (in a stressful time) and
gives comfort, as well as regulating the metabolic system.
The release of dopamine, serotonin and reward pathways in
response to food would have evolved from a survival mechanism. For early
humans, living in times of extreme cold, a bigger calorie demand, as well as
consumption of a fuel that quickly releases energy would have been life-saving.
So, a mechanism that encouraged early humans to eat as much as they could,
would have evolved. If humans actually felt good after eating calorie- rich
food, they would be much more likely to survive and pass this mechanism on.
This mechanism still persists today. So, over the Christmas period, when
you find yourself reaching for the next mince-pie or the next chocolate,
remember to thank your early ancestors! Their survival is the reason why you
like sweetness!
That's all from me this week! Wishing everyone a happy
festive period-and a happy solstice! May your family and friendly gatherings
release Oxytocin and reduce your stress. May Christmas lights increase your
melatonin and serotonin, and your Christmas smells of memory and nostalgia.
Finally, may you get all the sweetness your body craves!
Jess x
No comments:
Post a Comment