What is Vitamin D?
Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous. People who are exposed to normal quantities of sunlight do not need vitamin D supplements because sunlight promotes sufficient vitamin D synthesis in the skin. Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).
What do we need vitamin D for?
- It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones.
- It is an immune system regulator.
- It may be an important way to arm the immune system against disorders like the common cold, say scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children's Hospital Boston.
- It may reduce the risk of developing multiple sclerosis. Multiple sclerosis is much less common the nearer you get to the tropics, where there is much more sunlight, according to Dennis Bourdette, chairman of the Department of Neurology and director of the Multiple Sclerosis and Neuroimmunology Center at Oregon Health and Science University, USA.
- Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
- Vitamin D helps to prevent Alzheimer's Disease, based on multiple studies.
- Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
- It can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.
- It has been shown to reduce the risk of developing rheumatoid arthritis in women.
- A form of vitamin D could be one of our body's main protections against damage from low levels of radiation, say radiological experts from the New York City Department of Health and Mental Hygiene.
- Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America.
Vitamin D and depression
On top of all the positive impact on the health, which has been mentioned before, a number of studies report also certain connection between vitamin D levels and the risk of depression. Low vitamin D levels may be related to depression rather than contributing to the disorder. In addition, an increased risk of depression may be related to several vitamin D–sensitive diseases.
- Elderly Dutch community residents with minor or major depression had vitamin D blood levels that were 14% lower than residents without depression.
- Italian women with lower vitamin D levels - less than 20 ng/mL (50 nmol/L) - had twice the risk of developing depression. For Italian men, the risk was increased 60%.
- Postmenopausal women with one vertebrae fracture had 20% more depressive symptoms than women without a fracture. Women with at least three vertebrae fractures had three-fold the rate of depression compared to women without multiple fractures. Low vitamin D levels are an important risk factor for vertebral fracture.
- Syrian women with heart disease, high blood pressure, or kidney disease were three times more likely to have depression. Syrian men with rheumatism and respiratory disease had an even greater risk of depression. There is good evidence that low vitamin D levels are a risk factor for all of these diseases.
- A lifetime history of depression may be a risk factor for later development of Alzheimer's disease. Depression may increase the risk of mild cognitive impairment that turns into Alzheimer's. Patients with Alzheimer’s and depression have more pronounced hallmarks of the Alzheimer’s brain than patients with Alzheimer’s who are not depressed. Studies indicate vitamin D deficiency may also be a risk factor in Alzheimer’s.
- One study showed that, in the United States, vitamin D deficiency occurred more often in certain people. These people were African-Americans, living in cities, obese, and depressed. People with vitamin D levels below 20 ng/mL (50 nmol/L) had an 85% increased risk of depression compared to those with vitamin D levels greater than 30 ng/mL (75 nmol/L).
A new research, completed by UT Southwestern Medical Center in 2011, positively confirmed the previous studies’ outcomes that low levels of vitamin D and depression are indeed going hand in hand. People with the lowest levels of vitamin D were more likely to report symptoms of depression, compared to people with higher blood levels of vitamin D. This relationship was strongest among people with a history of depression.
How vitamin D works
Exactly how vitamin D and depression may be linked is not exactly clear yet. Vitamin D deficiency may result in depression, or depression may increase risk for low vitamin D levels.
For example, depressed people may spend more time indoors, and are less likely to eat a healthy diet and take care of themselves, all of which could affect vitamin D levels. On the other hand, there are vitamin D receptors everywhere in the body, including the brain. These receptors need vitamin D to do their job.
Based on the proposed explanations, vitamin D may lower the risk of depression by:
- Reducing the risk of diseases that may trigger depression, such as cancer, cardiovascular disease, and multiple sclerosis.
- Vitamin D may affect neurotransmitters, inflammatory markers and other factors, which could help explain the relationship with depression.
- Reducing the production of cytokines. Cytokines are proteins that increase inflammation and have been shown to be a possible risk factor for depression.
- Vitamin D is believed to play a role in maintaining the brain’s signaling pathways and reducing inflammation. Not enough D and inflammation degrades brain cells in a way that leads to depression symptoms—feeling tired all the time, an inability to enjoy your favorite things, and even thoughts of suicide.
Yes, some of the statements above interconnect each other, and the key consideration is that vitamin D fights with inflammation, which might play a substantial role in the depression development.
There are no reported studies showing that vitamin D supplements reduce the risk of depression. However, given the evidence, it is possible that vitamin D could have a positive effect on those who suffer from depression.
Based on studies of cancer, cardiovascular disease, and influenza, vitamin D levels above 40 ng/mL (100 nmol/L) may reduce the risk of depression.
Treating vitamin D deficiency in people with depression may result in improvement in long-term health and quality of life.
According to a recent review, treating vitamin D deficiency in people with depression or other mental disorders may result in improvement in both long-term health and quality of life. Reports confirm that vitamin D has a positive effect on depression:
- Women in Washington State increased their vitamin D levels to 47 ng/mL (118 nmol/L) by taking 5000 IU of vitamin D each day during the winter. In some of these women, their depressive symptoms lessened as indicated by the decrease in their scores on a depression test.
- Overweight and obese Norwegian women took 20,000 or 40,000 IU per week of vitamin D and their symptoms of depression decreased. Their scores were also lower on a depression test.
- Based on studies of other diseases, vitamin D blood levels of 40–50 ng/mL (100–125 nmol/L) appear to reduce the severity of depression.
The Institute of Medicine recently raised its recommendations for vitamin D. The institute recommends that people aged 1 to 70 take 600 international units (IUs) of vitamin D per day, and people older than 71 should aim for 800 IUs.
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