With another long winter upon us, it’s essential to make sure you’re getting enough vitamin D in order to prevent seasonal affective disorder (SAD). SAD can result in anxiety and depression, increased carbohydrate cravings, sleep problems and fatigue. Our main source of vitamin D is sunlight. When the skin is directly exposed to sunlight, a form of vitamin D is created that becomes active in the kidneys.

In a study from Union Memorial Hospital in Maryland, researchers compared vitamin D to broad-spectrum light therapy in the treatment of SAD. Eight subjects received vitamin D supplements while seven subjects received broad-spectrum light therapy. Each of the participants was clinically diagnosed with SAD before the onset of treatment. After one month, participants were given several standardized tests to measure changes in their symptoms.

The test results were positive for vitamin D; subjects receiving vitamin D improved in all symptoms while the light therapy group showed no significant change in depression, despite having increased vitamin D levels.

Even Down Under, changes in mood follow the change of seasons, with symptoms of anxiety and depression increasing during colder, dark winter months. At the University of Newcastle in Australia, researchers found that vitamin D improved mood during winter months. In this double-blind study, 44 healthy men and women were given 800 IU, 400 IU or a placebo for five days during late winter.

Afterward, the participants were asked to complete a questionnaire on symptoms. Their feedback indicated that vitamin D supplements significantly enhanced mood and reduced feelings of depression.

Sources: J Nutr Health Aging. 1999;3(1):5-7; Psychopharmacology (Berl). 1998 Feb;135(4):319-23