The likelihood of having depression is significantly increased in people with deficient level of vitamin D, compared with people with adequate levels of the sunshine vitamin, says a new study.
Data from the third US National Health and Nutrition Examination Survey revealed that people with vitamin D deficiency were at a 85 percent increased risk of having current depressive episodes, compared with people with sufficient levels, according to findings published in the International Archives of Medicine .
“It is not known, whether vitamin D deficiency leads to the depression or depression leads to the vitamin D deficiency,” write the researchers from Georgia State University. “Further studies are needed in deciphering the precise role of vitamin D in psychosomatic disorders.
“Although the direction of the cause and effect relation between depression and vitamin D deficiency is not known clearly at this time, in public health perspective, the coexistence of vitamin D and depression in the US population at large is a concern,” they add.
“It is important to identify persons who are at risk for vitamin D deficiency and/or for depression and to intervene early because these two conditions have enormous negative consequences on long term health.”
D and depression
Vitamin D is somewhat of an unusual "vitamin," because it can be made in the body from sunlight and most foods do not contain vitamin D unless added by fortification. Synthesis of vitamin D in the body requires exposure to ultraviolet light and can be influenced by genetics, skin color, and sun exposure.
Reports of greater than expected vitamin D insufficiency coupled with emerging evidence that higher circulating concentrations of this nutrient may protect against cardiovascular disease have prompted a renewed interest in teasing out how environment, genetics, and behavior work independently and coordinately to influence vitamin D status. To help clarify this, researchers at Emory University studied vitamin D status in twins living in different North American locations.
"The results of the Karohl study are quite important," according to American Society for Nutrition Spokesperson Shelley McGuire, PhD. "Over the past couple decades, nutrition scientists have discovered that maintaining optimal vitamin D status is important for much more than keeping our bones strong. It's also critical for keeping our immune systems healthy and may help protect against diseases like heart disease and cancer. This study suggests that, whereas genetic differences impact winter vitamin D status, lifestyle choices and sun exposure (factors we can control) are predominant in the summer months. Additional research is still needed in more heterogeneous populations."
The authors concluded that during the winter vitamin D status is governed mainly by genetic factors. Conversely, non-genetic factors are most important during the summer. Future studies designed to better understand what these factors are will be especially useful as public health experts continue to explore ways to increase vitamin D status in different populations living under varying environmental and dietary situations.
And the World Health Organization (WHO) forecasts that within 20 years more people will be affected by depression than any other health problem; it ranks depression as the leading cause of disability worldwide, with around 120 million people affected.
This is not the first time that vitamin D has been linked to symptoms of depression. Dutch scientists reported in 2008 in the Archives of General Psychiatry that low levels of the vitamin and higher blood levels of the parathyroid hormone (PTH) were associated with higher rates of depression among 1,282 community residents aged between 65 and 95.
Furthermore, a review by Bruce Ames and Joyce McCann from the Children's Hospital and Research Center Oakland highlighted the role of the vitamin in maintaining brain health, noting the wide distribution of vitamin D receptors throughout the brain.
According to the review (FASEB Journal, Vol.22, pp. 982-1001), the vitamin has been reported to affect proteins in the brain known to be directly involved in learning and memory, motor control, and possibly even maternal and social behaviour. Depression in the elderly is highly prevalent and can increase the risk of medical illnesses, worsen the outcome of other medical illnesses, and may increase mortality.
Vijay Ganji Ph.D., R.D and his Georgia State co-workers analysed data from 7,970 US residents aged between 15and 39. Assessments of depression were performed using the National Institute of Mental Health’s Diagnostic Interview Schedule.
Results showed that people with blood levels of vitamin D of 50 nanomoles per liter or less were at an 85 percent increased risk of having current depressive episodes in persons, compared with people blood levels of at least 75 nanomoles per liter.
“The mechanism through which vitamin D plays a role in metal health is not clearly understood,” said the researchers. “Active vitamin D enhances glutathione metabolism in neurons, therefore, promotes antioxidant activities that protect them from oxidative degenerative processes.”
The researchers also not that vitamin D is involved in gene expressions for the production of neurotransmitters like dopamine.
The researchers stress however that their results do not prove that vitamin D deficiency causes depression, and called for additional studies to decipher the association between vitamin D and depression.
Source: International Archives of Medicine