Although the main functions of vitamin D include maintaining phosphorus and calcium homeostasis (and hence providing a positive effect on bone health), vitamin D plays other important roles in the body. Consequently, vitamin D deficiencies can be felt in the whole body, including the brain.

Vitamin D is an important member of fat-soluble vitamins that can be endogenously synthesized or obtained from foods that contain vitamin D or foods that are supplemented (fortified) with vitamin D.  Endogenous synthesis of vitamin D starts in human skin under the influence of ultraviolet B (UVB) radiation, which is why this vitamin is often called the sunshine vitamin. This is how vitamin D3 is formed. This vitamin undergoes further metabolism in the body, leading to the creation of its active form. Vitamin D3 can also be obtained from foods of animal origin, with fatty fish and egg yolk as major sources. In addition, it can be found in fortified foods, such as milk or cereals. On the other hand, vitamin D2 can be synthesized in mushrooms under the influence of sunlight, and it can be found in some plants. Generally, vitamin D3 is more potent than vitamin D2, meaning that it raises the levels of active forms of vitamin D in the body more efficiently.

According to scientific literature, low levels of vitamin D are implicated in conditions such as neurodegenerative diseases (Parkinson’s disease for instance), ischemic stroke, multiple sclerosis, depression, autism and cognitive decline. Thus, vitamin D appears to play an important role in the regulation of optimal brain functioning.

Vitamin D and depression

Depression is a common mood disorder, affecting more than 120 million people worldwide. As some researchers have identified, vitamin D status (more precisely its deficiency) seems to be a potent biomarker of depression. Another group of researchers investigated the association between vitamin D levels and the scores on tests used to evaluate depression symptoms. They compared these scores in more than 200 participants with low levels of vitamin D with around 100 participants who had high levels of vitamin D. It was found that participants from the first group were more prone to depression.

In addition, one interesting study identified an inverse association between prenatal levels of vitamin D and postpartum depressive symptoms. Postpartum depression represents a serious mental health issue that occurs after childbirth and is characterized by behavioral changes and disturbances in emotions. Furthermore, one study has identified lower levels of vitamin D in postmenopausal women with major depressive disorder than postmenopausal women with no record of depression.

Vitamin D and multiple sclerosis

Multiple sclerosis (MS) is a progressive neuroinflammatory condition affecting more than 2 million people worldwide, mostly young adults. It represents a complex disease of the central nervous system, and its etiology is not completely understood. Still, immune system and inflammation seem to be important determinants of this condition. It is believed that vitamin D, due to its immune-modulatory and anti-inflammatory properties, can attenuate multiple sclerosis progression. In addition, low levels of vitamin D have been reported in individuals with MS. An interesting feature of MS is that its prevalence significantly increases at geographic locations closer to the poles.

Also, there is an inverse association between sun exposure and prevalence of MS. Since vitamin D is produced under sun exposure, it might have a sustainable effect on the incidence of multiple sclerosis.  Some findings indicate that vitamin D levels at gestational stage could negatively influence the development of MS later in life. Still, other scientists believe that vitamin D intake throughout the whole lifespan is more efficient in reducing the risk of MS. According to some estimation in Caucasians, it seems that every 50 nmol/L increase in the blood levels of vitamin D leads to more than 40% decrease in the risk of MS.

One group of researchers conducted an interesting trial and investigated whether the levels of vitamin D could predict disease progression in subjects having the first event suggestive of MS. As these researchers reported, higher baseline vitamin D predicted reduced disease activity and its slower progression, as evaluated by the follow-up study lasting for several months (6, 12, and 24 months). This indicates that low levels of vitamin D in the early diagnosis of MS might represent a strong risk factor and a predictor of further disease progression and activity.

Depression is a common co-morbidity of multiple sclerosis. Thus, one study investigated the association between vitamin D levels and the depressive symptoms in this condition. Two hundred subjects with MS were included, and depressive symptoms (assessed by the relevant scale), as well as levels of vitamin D in blood, were measured. Interestingly, the prevalence of low vitamin D levels was >45%. Moreover, lower levels of vitamin D were inversely associated with depressive symptoms, suggesting the potential role of vitamin D supplementation in the amelioration of depression in MS.

Other conditions

Apart from depression and MS, vitamin D is assumed to play an important role in other conditions related to brain health. For instance, cognitive decline has been associated with lower levels of vitamin D. Also, vitamin D is now considered as an important protective factor in the development of autism and attention hyperactive disorder (ADHD). Importantly, a mother’s intake of vitamin D during pregnancy, as well as supplementation of a child especially during the first months of life, seem to be crucial for proper brain development.

Evidently, the role of vitamin D in the human body is far more complex than its impact on bone health alone. Perhaps the most important aspects of vitamin D health effects include its impact on proper brain development and functioning. An adequate intake of vitamin D is important not only in the early stages of life but throughout the whole lifespan in order to prevent conditions such as depression and multiple sclerosis. Vitamin D deficiency being a global health issue, supplementation (or a larger intake of fortified foods) is especially important in the winter months when we are less exposed to the sun.

References:

Abboud, M., Rybchyn, M.S., Rizk, R., Fraser, D.R., Mason, R.S. (2017). Sunlight exposure is just one of the factors which influence vitamin D status. Photochemical and Photobiological Sciences. 16(3): 302-313. doi:10.1039/c6pp00329j

Adibfar, A., Saleem, M., Lanctot, K.L., Herrmann, N. (2016). Potential Biomarkers for Depression Associated with Coronary Artery Disease: A Critical Review. Current Molecular Medicine. 16(2): 137-164. PMID:26812919

Kjærgaard, M., Waterloo, K., Wang, C.E., Almås, B., Figenschau, Y., et al. (2012). Effect of vitamin D supplement on depression scores in people with low levels of serum 25-hydroxyvitamin D: nested case-control study and randomised clinical trial. British Journal of Psychiatry. 201(5): 360-368. doi:10.1192/bjp.bp.111.104349

Accortt, E.E., Schetter, C.D., Peters, R.M., Cassidy-Bushrow, A.E. (2016). Lower prenatal vitamin D status and postpartum depressive symptomatology in African American women: Preliminary evidence for moderation by inflammatory cytokines. Archives of Women’s Mental Health. 19(2): 373-383. doi:10.1007/s00737-015-0585-1

Atteritano, M., Lasco, A., Mazzaferro, S., Macrì, I., Catalano, A. et al. (2013) Bone mineral density, quantitative ultrasound parameters and bone metabolism in postmenopausal women with depression. Internal and Emergency Medicine. 8(6):485-91. doi:10.1007/s11739-011-0628-1

Faridar, A., Eskandari, G., Sahraian, M.A., Minagar, A., Azimi, A. (2012). Vitamin D and multiple sclerosis: a critical review and recommendations on treatment. Acta Neurologica Belgica. 112(4): 327-333. doi:10.1007/s13760-012-0108-z

Ascherio, A., Munger, K.L., White, R., Köchert, K., Simon KC, et al. (2014). Vitamin D as an early predictor of multiple sclerosis activity and progression. JAMA Neurology. 71(3): 306-314. doi:10.1001/jamaneurol.2013.5993

Ashtari, F., Ajalli, M., Shaygannejad, V., Akbari, M., Hovsepian, S. (2013). The relation between Vitamin D status with fatigue and depressive symptoms of multiple sclerosis. Journal of Research in Medical Sciences. 2013 Mar;18(3):193-7. PMID:23930114

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