Insufficient levels of vitamin D can increase the risk of depression, says a new study.
In a study reported in Medical Hypotheses, researchers found that vitamin D deficiency was directly linked to seasonal affective disorder (SAD) , a type of depression related to changes in season, that appears during the same time, every year.
Symptoms of the condition include tiredness, irritation, low energy, weight gain, oversleeping, hypersensitivity, temptation to eat more carbohydrates and difficulty to adjust with others.
The symptoms usually appear in the fall and persist throughout winter. The condition, according to the Mayo Clinic in US, often progresses into major depression in spring or early summer.
Researchers from the UGA (The University of Georgia), University of Pittsburgh, US and Queensland University of Technology, Australia looked at 100 leading articles on the subject and found that SAD was more common during winter, a season when the sunlight is very less.
In majority of the cases, people with depression also had very low levels of vitamin D.
"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," Alan Stewart of the University of Georgia College of Education, said in a news release.
"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."
A deficiency of vitamin D affects production of important neurotransmitters like dopamine and serotonin, the researchers said. Dopamine performs several important functions in the body like movement, balance and is also responsible for regulating the reward and pleasure centres in the brain. Serotonin helps communicate different parts of the brain and balances mood.
"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," Michael Kimlin, a Cancer Council Queensland Professor of Cancer Prevention Research, explained.
Researchers also found that vitamin D deficiency was more common among dark skinned people.
Vitamin D can be acquired either through exposure to sunlight or through regular consumption of certain foods, including oily fish, egg yolks, cheese, beef liver, shiitake and button mushrooms.
A severe vitamin D deficiency has been known to increase the risk of bone-softening diseases in children (rickets) and adults (osteomalacia). Previous research shows that vitamin D deficiency can also increase the risk of brain strokes and early death.
How to Beat Winter Depression- Some Tips
During winter, the melatonin production goes up. Melatonin is a sleep hormone secreted by the pineal gland in the brain during darkness. This can make one sleepy and encourages to sleep longer. According to the experts NHS Choices, SAD affects one in 15 people.
Winter is here and following are some tips to fight winter depression as provided by NHS Choices:
· Eat vitamin D rich food
· Sleep only eight hours at night
· Exercise daily
· Follow healthy diet: Include more fruits, vegetables than starchy foods like pasta, potatoes and bread
· Try to overcome stress through different techniques, including yoga