In the fall and winter, we experience fewer hours of daylight. Its effect on nature is visually striking—beautiful yellow, orange and red leaves. In our bodies, there are equally significant changes happening as our exposure to sunlight decreases, such as changes to mood and sleep-wake cycles as well as cessation of vitamin D production.
Feel Like Hibernating
Sunlight tells our bodies when it is time to be awake and active. When exposed to sunlight, sensors in our eyes send messages along a nerve pathway to the hypothalamus in the brain. From there, factors involved in determining if we feel awake or sleepy are controlled, as well as the body’s temperature and hormones. One of the major hormones that regulate our sleep-awake cycle is melatonin, produced by the pineal gland. Nicknamed the ‘Dracula-hormone,’ melatonin is only produced during dark hours giving you a sleepy sensation. With fewer sunlight hours, and an increased use of artificial lighting during the fall our body can lose the natural day-night rhythm causing people to have trouble sleeping, or experience daytime drowsiness. Melatonin supplements can be an effective way to reset the sleep-wake cycle and promote better sleep health. Of note, melatonin should be used for short-terms only; read supplement dosage and instructions carefully before use.
During the darkest months of the year, at latitudes above 35°, there is minimal, if any, pre-vitamin D3 production in the skin. Vitamin D is an important fat-soluble vitamin in the human body involved in bone health including calcium absorption in the gut, maintenance of blood phosphate levels, bone growth and remodeling by osteoblasts and osteoclasts. Researchers are also discovering links with vitamin D deficiency and diseases including some forms of cancer, autoimmune diseases, heart disease, rickets and osteoporosis.
There are few foods in the typical North American diet that provide vitamin D. Fortified milk and salmon are the best sources. Of note, studies have found that wild salmon has 75-90% more vitamin D than farmed salmon. There are small amounts of vitamin D found in mushrooms, egg yolks and cheese. For those whose diet does not include dairy, fortified soy milk or orange juice can offer an alternative source of vitamin D. An excellent way to get vitamin D in the darkest months of the year is using a vitamin D supplement such as an omega-3 fatty acid with vitamin D.
SAD Time of Year
According to the Mood Disorder Society of Canada, two to four percent of Canadians suffer from SAD (Seasonal Affective Disorder). SAD is a type of depression that has a seasonal cycle, provoked by the decreased number of sunlight hours in a day. Common symptoms include fatigue, oversleeping, overeating, weight gain, cravings, moodiness and depression. It’s easy to understand when you recall the biology class in which it was explained how serotonin is converted into melatonin in the body—the chemicals in your body that cause happiness and sleep are metabolically linked. Research has yet to find a conclusive therapy but shows promising results for the use of light therapy, melatonin, vitamin D and omega-3 fatty acids. Other SAD coping strategies include meditation and a healthy diet focusing on nutrient-rich foods such as green vegetables, cherries, mushrooms, and raw nuts and seeds.
Holick, MF et al. Vitamin D and Skin Physiology: a D-lightful story. J Bone Min Res 2007;22(2). http://onlinelibrary.wiley.com/store/10.1359/jbmr.07s211/asset/5650221307_ftp.pdf;jsessionid=ACC42A4D4D0CAC331D111EA806162D44.d04t01?v=1&t=hle1ftr0&s=77617ad08af0b4033d24bcbe27d29da6b0d0b637
Health Canada Monograph – Melatonin http://webprod.hc-sc.gc.ca/nhpid-bdipsn/monoReq.do?id=136&lang=eng
van Strater AC, PF Bouvy. Omega-3 fatty acids in the treatment of affective disorders: an overview of the literature. Tijdschr Psychiatr 2007;49(2):85-94. http://www.ncbi.nlm.nih.gov/pubmed/17290337