There’s a reason so many artists – songwriters, poets, painters – connect the sun with our moods; lack of sunlight has been linked to mood disorders – especially seasonal affective disorder.

Vitamin D, known as the Sunshine Vitamin, is activated in our bodies when UV rays from sunlight strike the skin. Vitamin D receptors in part of the brain have been identified as contributors to the regulation of moods. Accordingly, researchers have started to investigate the relationship between vitamin D levels and depression.

According to the CDC, one fourth of the population in 2006 did not have sufficient levels of vitamin D. Dale Archer, M.D., speculates in Psychology Today that could be because “we are not outside as much as prior generations, and when we are, we slather on the sunscreen which prohibits UVB (the rays responsible for suntans) from penetrating the skin. These same UVB rays naturally produce vitamin D.”

Simply put, most people don’t get enough vitamin D from the sun.

And although food is a great source of vitamin D, you would have to drink five or six glasses of fortified orange juice and eat salmon every day to get the amount of vitamin D you need.

Vitamin D and Depression Study Results

Despite the growing body of research on vitamin D and depression, there is no clear answer to what role vitamin D has in either preventing or treating depression.

A recent study from Oregon State University found a correlation between depression and vitamin D in young, otherwise healthy, women. The study included 185 female college students, who had their vitamin D levels measured with blood tests at different times during the school year. Additionally, the participants completed a depression symptom survey weekly for five weeks.

More than 60 percent of participants had vitamin D levels below what is considered sufficient. Most experts agree on a vitamin D blood level of at least 20 nanograms per milliliter.

The vitamin D levels varied depending on the time of year – declining in the fall, lowest in winter, and higher in the spring.

Perhaps most interestingly, the lower the women’s levels of vitamin D, the more likely they were to have clinically significant symptoms of depression, including when the researchers accounted for other factors, including the time of year, exercise and time spent out of doors.

Even so, the researchers said that their findings don’t conclusively show that low vitamin D levels were the cause of depression in their subjects. According to the researchers, the next step should be a clinical trial to see whether vitamin D supplements can help prevent or relieve depression.

What the Studies Mean to You

Despite the lack of consensus, it seems clear that a person’s level of vitamin D may play a role with depression. A blood test can be used to determine whether your own vitamin D levels are within normal ranges.

The Vitamin D Council recommends that healthy adults take 2,000 IU of vitamin D daily, even more if they get little or no sun exposure. The Institute of Medicine’s Food and Nutrition Board say 600 IU/day is enough for adults and the Endocrine Society says 2,000 IU/day is enough for most adults.

Segments of the population who are more likely to be vitamin D deficient include people with darker skin, people who spend a lot of time indoors during the day, and people that live in the northern part of the United States or in Canada.

Be sure to talk to your health care provider about how to manage your depression, including medication, alternative treatments, exercise, or nutrition including, potentially, vitamin D supplements.