Seasonal Affective Disorder (SAD) and Vitamin D. Is There a Connection? By Carolyn Wilson

Seasonal Affective Disorder (SAD) and Vitamin D. Is There a Connection? By Carolyn Wilson

What is SAD?
Seasonal Affective Disorder is a type of depression that affects half a million people in the United States. Seasonal Affective Disorder (SAD) is characterized by recurring episodes of depression year after year, beginning in late fall with symptoms typically gone by summer. A person with SAD can have alternating periods of normal or high mood the rest of the year. SAD is thought to be caused by the changes in the amount of daylight during different times of the year. SAD is more prominent in northern regions, where the winters tend to be longer and more harsh. According to, “Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-light therapy.[9] SAD is measurably present at latitudes in the Arctic region, such as Finland (64º 00´N) where the rate of SAD is 9.5%[10] Cloud cover may contribute to the negative effects of SAD.[5] .”

How do you know if you have SAD?
The most common symptoms of SAD include: fatigue, increased cravings for sweets and carbohydrates, weight gain, loss of energy, oversleeping, difficulty concentrating, anxiety or irritability, loss of interest in social interactions and in activities you normally enjoy. Other symptoms of SAD may include prolonged feelings of hopelessness, guilt, decreased sexual interest, suicidal thoughts, and physical problems (such as headaches). It is important to note that these are symptoms are also present in other forms of depression.

How is SAD treated?
Current methods for the treatment of SAD include the regular use of light therapy. It can help treat SAD because of the increased exposure to sunlight. Normal light therapy takes about 30 minutes/day throughout the fall and winter. If light therapy improves your symptoms, you'll continue until the springtime when the sunlight returns. It is important to note that symptoms may return if light therapy is discontinued too soon. Click here for additional information on light therapy. Additional treatment has included psychotherapy, and use of prescription antidepressants. Click here for more information about treatment options.

What’s the SAD/ Vitamin D connection?
We are learning more and more about how Vitamin D affects our bodies. There is hope that Vitamin D may be beneficial to those suffering from SAD. Studies are also being done to find out how Vitamin D deficiency may contribute to causing SAD. Much research still needs to be done to find out what connection Vitamin D has with SAD. sheds some light on the correlation between Vitamin D and SAD; “The cause of SAD is not known, but is believed to relate to the daily biological clock and the way it responds to sunlight. The hormones melatonin and serotonin are thought to be involved, although exactly in what manner remains unclear.”

Where does Vitamin D come from?
In order to understand why there may be a connection between Vitamin D and SAD, it is important to know exactly what Vitamin D is and how it works in our bodies. Most people don’t know that Vitamin D is not only a fat soluble vitamin, but also a hormone. Light is the primary source of Vitamin D. When ultraviolet light in sunlight contacts the skin, it creates vitamin D3 also known as Cholecalciferol.

Very few foods actually contain vitamin D. The only significant natural source of Vitamin D is fish. Natural sources include Herring, Salmon, Halibut, Cod liver oil, Catfish, Atlantic Mackerel, Oyster, ******* mushrooms, liver, butter, cream and egg yolks. Many foods are artificially fortified with vitamin D including cow’s milk, tofu, rice milk, soy milk, orange juice, cereal, yogurt and many cereals. Supplemental Sources include most multivitamins and Vitamin D supplements.

What is the function of Vitamin D?
Vitamin D functions to maintain normal blood levels of calcium and phosphorus, it aids in the absorption of calcium and supports bone formation. Additional Research suggests that it may protect us from cancer, tuberculosis, multiple sclerosis, gum inflammation, hypertension, and other autoimmune diseases. And now, studies have also shown that low levels of vitamin D are associated with SAD.

How much Vitamin D do you need?
For healthy persons, the Food and Nutrition Board reports adequate intake (AI) for vitamin D is 200, 400, or 600 IU a day, depending on your age. We require more Vitamin D as we age because the older we get the less we are able to synthesize Vitamin D. Click here to view the Dietary Supplement Fact Sheet from the Office of Dietary Supplements website. tells us, “The NIH has set the safe upper limit at 2000 IU, but acknowledges newer data supporting a UL as high as 10,000 IU/day.[32] The Institute Of Medicine is revisiting vitamin D and calcium recommendations. The report is expected in spring 2010.”

What if you don’t get enough vitamin D?
A Vitamin D deficiency can occur from a lack of sunlight; therefore, it is interesting to note that Vitamin D is known to be widely deficient in Western populations. It is also important to know that Vitamin D deficiency can also result from breastfeeding without supplementation, and not using fortified milk. tells us, “Deficiency of vitamin D can result from a number of factors: inadequate intake coupled with inadequate sunlight (UVB) exposure, disorders that limit its absorption from the gastrointestinal tract, conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders and body characteristics such as skin color and body fat. Rarely, deficiency can result from a number of hereditary disorders.”

Fortunately, a deficiency can be prevented by exposure to just 10 minutes of sunlight per day. reminds us, “However, season, geographic latitude, time of day, cloud cover, skin cover, skin color, smog, and sunscreen affect UV ray absorption and vitamin D synthesis.

According to an article written by John Jacob Cannell MD; “There is no risk of Vitamin D toxicity from prolonged exposure to the sun because once the skin makes enough vitamin D, the sun destroys the excess.” However, it increases our risk of skin cancer. Unfortunately, the use of a sunscreen prevents Vitamin D synthesis. One way around this problem is to apply sunscreen after you’ve exposed yourself to sunlight long enough to allow for Vitamin D synthesis. It is important to know that the amount of Vitamin D that we store from the summer is not enough to meet our needs during the winter. Therefore, Vitamin D supplements can be very important. Click here for more information on the truth about Vitamin Toxicity, written by John Jacob Cannell MD.

Be sure to consult with your physician before beginning a Vitamin D supplement regimen. “Treatment of a Vitamin D deficiency should be done under the care of a knowledgeable” You can ask your physician to get a test to have your Vitamin D levels checked. Click here for symptoms of Vitamin D deficiency.

Is there evidence to support the SAD/Vitamin D connection?

There has been much debate and controversy over the connection between Vitamin D and SAD. Research has focused on how low levels of Vitamin D may contribute to the cause of SAD and how Vitamin D can reduce symptoms of SAD. In an article written by John Jacob Cannell MD (Executive Director of the Vitamin D council), He presents evidence supporting a connection between Vitamin D deficiency and seasonal variations in mood. In the article he states, “We know that 15 years ago, Professor Walter E. Stumpf of the University of North Carolina, one of the great pioneers in vitamin D research, predicted a substantial role for both bright light and vitamin D in psychiatry.”

Additional support from tells us, “The body creates vitamin D when it is exposed to the sun, and during the winter vitamin D levels drop. For this reason, it seems logical that vitamin D supplements might help people with SAD...” Also, states, “Another explanation (for SAD) is that vitamin D levels are too low when people do not get enough Ultraviolet-B on their skin. An alternative to using bright lights is to take vitamin D supplements.”

In his article, Dr. Cannell also addresses the increase in depression over the last century when he suggests, “To further strengthen the case that vitamin D deficiency causes some cases of depression, evidence should exist that the incidence of depression has increased over the last century. During that time, humans have reduced their sunlight exposure via urbanization (tall buildings and pollution reduce UVB ), industrialization (working inside reduces UVB exposure), cars (glass totally blocks UVB), clothes (even light clothing blocks UVB), sun block and misguided medical advice to never let sunlight strike you unprotected skin.” Click here to view Dr. Cannells article.

Although some studies dispel this connection, I have chosen to focus on studies that support it. Dr. Cannell reports the results of a study that used Vitamin D3 (cholecalciferol) supplementation. He reports, “In a 1998 controlled experiment, Australian researchers found that cholecalciferol (400 and 800 IU), significantly enhanced positive affect when given to healthy individuals. Forty-four subjects were given 400 IU cholecalciferol, 800 IU cholecalciferol, or placebo for 5 days during late winter in a random double-blind study. Results on a self-report measure showed that vitamin D3 enhanced positive affect a full standard deviation and there was some evidence of a reduction in negative effect. The authors concluded: "vitamin D3 deficiency provides a compelling and parsimonious explanation for seasonal variations in mood."

He writes of another study done by a vitamin D scientist. He tells us, “In 1999, in an even more interesting study, vitamin D scientist, Bruce Hollis, teamed up with Michael Gloth and Wasif Alam to find that 100,000 IU of vitamin D given as a one time oral dose improved depression scales better than light therapy in a small group of patients with seasonal affective disorder. All subjects in the vitamin D group improved in all measures and, more importantly, improvement in 25(OH) D levels levels was significantly associated with the degree of improvement.

Even though results of other studies have shown no correlation between Vitamin D and SAD, it is important to know that studies are not always done correctly. For example, Dr. Cannel comments in his article, on a previous study done that tried to dispel any connection between Vitamin D and SAD. He reports, “If you are thinking that Oren, Schulkin and Rosenthal have already shown that vitamin D has nothing to do with seasonal affective disorder, I am sorry to tell you they measured the wrong vitamin D metabolite, 1,25(OH)2D3 (calcitriol), which can be high, low, or normal in almost any condition. The only lab test that should be used to measure vitamin D stores, vitamin D deficiency and vitamin D adequacy is 25(OH) D, which they did not measure.”

Although recent studies have not been conclusive, more are sure to come. We still have a lot to learn about Vitamin D.

Are you suffering from SAD?
If you suspect that you are suffering from SAD, or you have symptoms that are greatly impacting your daily life, contact a qualified mental health professional that treats SAD. They can help you find the most appropriate treatment. SAD is a manageable condition with proper treatment.

According to the American Psychiatric Association; “SAD can be misdiagnosed as hypothyroidism, hypoglycemia, infectious mononucleosis, and other viral infections, so proper evaluation is necessary. For some people, SAD may be confused with a more serious condition like severe depression or bipolar disorder.” If you are not sure if you need to seek help, you can use the feedback from the Personalized Inventory for Depression and SAD at This self-assessment is not a substitute for professional medical advice. Click here to access this automated confidential self-assessment. If you would like to seek help and need help finding the right mental health therapist, click here .

Additional studies that support the SAD/ Vitamin D connection

These studies and others are posted on the Vitamin D Council website
1. Vitamin D and depressive symptoms in women during the winter: a pilot study.
2. Vitamin D3 enhances mood in healthy subjects during winter.
3. Vitamin D and serotonin in winter
4. Vitamin D vs. broad spectrum phototherapy in the treatment of seasonal affective disorder

Articles of interest:

“Multiple health concerns surface as winter, vitamin D deficiencies arrive.”
Sunlight, health, and Vitamin D
Shedding light on vitamin D
Vitamin D: Benefits in pregnancy and beyond
The Body's Response to Sunlight
Veils and dark skin risk rickets

Sources of Reference:

Whitney and Rolfes. "Understanding Nutrition." Thompson Wadsworth. 2009

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