photo of vitamin D capsules
Lack of vitamin D is likely to be a contributing factor in seasonal depression.

SAD in the winter? You may need more vitamin D

2 December, 2014

Natural Health News — If you are susceptible to the winter blues a lack of vitamin D may be the culprit, according to a recent review.

Vitamin D deficiency is not just harmful to physical health – it also might impact mental health, according to a team of researchers that has found a link between seasonal affective disorder, or SAD, and a lack of sunlight.

An international research partnership US and Australian researchers conducted a review of more than 100 leading articles and found a relationship between vitamin D and seasonal depression.  Their results are reported in the journal Medical Hypotheses.

“Seasonal affective disorder is believed to affect up to 10 percent of the population, depending upon geographical location, and is a type of depression related to changes in season,” said author Alan Stewart, an associate professor in the department of counseling and human development services at Queensland University of Technology (QUT) in Australia.

“People with SAD have the same symptoms every year, starting in fall and continuing through the winter months.”

Stewart said, based on the team’s investigations, vitamin D was likely to be a contributing factor in seasonal depression.

“We believe there are several reasons for this, including that vitamin D levels fluctuate in the body seasonally, in direct relation to seasonally available sunlight,” he said. “For example, studies show there is a lag of about eight weeks between the peak in intensity of ultraviolet radiation and the onset of SAD, and this correlates with the time it takes for UV radiation to be processed by the body into vitamin D.

For mind as well as body

Vitamin D is also involved in the synthesis of serotonin and dopamine within the brain, both chemicals linked to depression, according to the researchers.

“Evidence exists that low levels of dopamine and serotonin are linked to depression, therefore it is logical that there may be a relationship between low levels of vitamin D and depressive symptoms,” said co-author Michael Kimlin, a Cancer Council Queensland Professor of Cancer Prevention Research ay QUT.

“Studies have also found depressed patients commonly had lower levels of vitamin D.”

Vitamin D levels varied according to the pigmentation of the skin. People with dark skin often record lower levels of vitamin D, according to the researchers, and therefore may be at particular risk.

According to Kimlin adequate levels of vitamin D were essential in maintaining bone health, with deficiency causing osteomalacia in adults and rickets in children. Vitamin D levels of more than 50 nanomoles per liter are recommended by the U.S. Institute of Medicine.

“What we know now is that there are strong indications that maintaining adequate levels of vitamin D are also important for good mental health,” he said. “A few minutes of sunlight exposure each day should be enough for most people to maintain an adequate vitamin D status.”