Have you ever felt fatigued, drowsy, or depressed during winter?

It could be a sign of Seasonal Affective Disorder (SAD)—a wintertime condition linked to vitamin D deficiency. SAD is associated with a wide range of depressive symptoms such as a depressed mood, lack of interest in normal activities, feelings of worthlessness, disturbed sleep, fatigue, and a decreased ability to think, concentrate or make decisions.

In a recent meta-analysis of 14 studies involving 31,424 people, Stewart et al concluded that low vitamin D levels were associated with an occurrence of depressive symptoms. Specifically, the mechanisms for seasonal affective disorder include:

  • Vitamin D levels fluctuate in the body seasonally in direct relation to available sunlight.

  • Vitamin D levels in the central nervous system affect the production of both serotonin and dopamine.

  • Vitamin D and its responsive elements are found throughout the mid-brain regions, specifically in the hypothalamus, a region that regulates most neural activity.1

It is clear vitamin D deficiency during winter is the main contributor of SAD, but how can we cope without regular access to sunlight? The following recommended vitamin D-boosting strategies for winter can provide some support:

  • Go outdoors as much as possible when the sun is out

  • Use full spectrum light bulbs or light-boxes (blue light therapy).

  • Exercise, go to bed early, get at least 7 hours of sleep each night, or use medication to treat insomnia.