The winters here in the UK are long, cold, and dark, stretching from November till the end of February. We all know the feeling of leaving the house on a dark morning to walk to university or go to work and then heading home at the end of the day in the dark once again. But this long, dark winter can have more of a significant impact on our minds and our bodies than we might think.
Sunlight and being outdoors does wonders for our mental and physical health, the reason for this lying with one of the thirteen vitamins known as Vitamin D. Vitamin D is essential for our bodies to produce serotonin, a neurotransmitter that works to carry messages from the nerve cells in our brain to the rest our bodies. Serotonin has a key role in our body’s functions, aiding mood, sleep, digestion, nausea, the healing of wounds, the health of our bones, and sexual desire. A lack of serotonin can cause numerous issues; however, the most common effects are mental health issues such as depression and anxiety. 90% of the serotonin in our bodies is found in the cells that line the intestines, from which it gets released into our blood stream; the remaining 10% of serotonin in our bodies is found in the brain.
Serotonin is created in our bodies from an amino acid called tryptophan, which is one of the eight essential amino acids that must be consumed through food as our bodies cannot create it. Sunlight is the best source for enabling vitamin D synthesis, as when our skin is exposed to sunlight, ultraviolet B rays hit cholesterol in our skin providing the necessary energy for vitamin D synthesis to occur. While vitamin D can be found in foods such as salmon, eggs, cheese, nuts, oats, and seeds, you would have to eat a lot of them in order for your body to produce enough serotonin from the vitamin D.
With the lack of sun during the British winter, it is highly common for British people to experience a deficiency in vitamin D and therefore a decreased production of serotonin.
Additionally, the dark, wet, and cold weather results in a reduction of motivation to do exercise. There is an established link between exercise and mental and physical health benefits. Exercise releases endorphins, which are neurotransmitters that are released by the pituitary gland and the hypothalamus in the brain. Endorphins, similar to serotonin, help to reduce pain, decrease stress, improve mood, and enhance general wellbeing. With both the decrease in sunlight and the reduction in exercise during the cold British winters, there is no wonder that our mental and physical health deteriorates, leading to a significant increase in “seasonal depression” or the “winter blues”.