Don't wait until your brain and body are feeling depressed and fatigued to take extra vitamin D! The further you live from the equator, the more likely you are to feel an energy shift as the days get shorter and your skin gets less exposure to sunlight. Some people crave carbohydrates, feel more tired than usual, and have an overall sensation of sadness or depression.
As with anything affecting your health-physical, mental, or otherwise-this seasonal shift is found on a spectrum. On one end of the spectrum, there is no real effect, but on the other is a diagnosable illness called Seasonal Affective Disorder (SAD). The Diagnostic and Statistical Manual of Mental Disorders, fifth edition, or DSM-5, classifies SAD as a recurrent major depressive disorder, with symptoms such as: feeling depressed, sad, hopeless or worthless, having low energy, trouble sleeping, and changes in appetite or weight.
Research points to a change in serotonin, the neurotransmitter in your brain which regulates many of your body's processes including: sleep, libido, mood, appetite, even memory and learning. If you are sensitive to downward fluctuations in serotonin levels, there are ways to address the fall, winter, and spring darkness and shorter days. Light boxes and intentional exposure to the sun whenever it is shining help tremendously, especially in the early part of the day. Additionally, increasing your intake of tryptophan, the amino acid which serotonin is derived from, should be helpful. You can get tryptophan from turkey and nuts (combine with some carbohydrates to aid absorption), as well as from a supplement. I always recommend organic, high quality foods and supplements. The fewer fake ingredients and chemicals your body has to process, the healthier and stronger it will be. If money is an issue, it is better to take something more expensive fewer times a day or week, than to compromise on quality. Exercise can be an effective therapy for SAD because...well, just because. There is a lot of speculation on why exercise is so effective with depression (as effective as anti-depressant medication in many studies), but no definitive answer. Psychotherapy can be helpful, as well as extreme self-care.
Which brings us back to vitamin D. Did you know that vitamin D is not a vitamin? It is actually a hormone and it is necessary for the synthesis of both dopamine and serotonin, neurotransmitters which, when low, contribute to states of depression. Since I am not a doctor, I won't recommend specific doses to take, but I will tell you that I often take 2,000-10,000 iu/day in the winter, depending on weather, sun exposure, and energy level. Internet searches, your local library or bookstore can provide you with way more information than what I have shared here. Take good care of yourself and your brain and body, as well as your friends, family, co-workers, and neighbors will all thank you!