In recent weeks, southern Spain has barely seen the sun, an unusual situation as it’s been constantly raining! More than one person might already feel their mood being affected, perhaps due to more than just the inability to sit out outside or accumulating laundry from not being able to dry their clothes. Let’s explore the crucial role of vitamin D in various physiological processes, and the importance of its supplementation if you live in a location lacking adequate sunlight.
Vitamin D influences numerous health aspects primarily through mechanisms mediated by the transcription factor Vitamin D Receptor (VDR). Transcription factors modulate the expression of certain genes, influencing cellular activity and overall organism homeostasis.
1. Bone Health and Calcium Metabolism
Vitamin D is essential for regulating calcium and phosphorus homeostasis, critical elements for bone maintenance. VDR activation in intestinal cells increases calcium and phosphorus absorption; in kidneys, it promotes calcium reabsorption at the tubular level; and in bones, it enhances mineralization and modulates osteoblast and osteoclast activity (Anderson PH & Morris HA, 2012).
2. Immune System
Many immune cells possess VDR receptors, making vitamin D an important immunomodulator, strengthening innate immunity and regulating inflammatory responses. It induces the production of antimicrobial peptides like cathelicidins and defensins, enhancing defenses against pathogens. Additionally, it inhibits excessive immune cell proliferation and decreases inflammatory cytokine production (e.g., IL-6, IL-17, TNF-α), preventing exaggerated autoimmune responses (Chung C et al., 2020).
3. Cardiovascular Health
VDR activation represses the transcription of the renin gene in renal juxtaglomerular cells, reducing the activation of the renin-angiotensin axis and positively modulating blood pressure. Additionally, by lowering inflammatory cytokine production, vitamin D reduces the risk of atherosclerotic plaque formation (Latic N & Erben RG, 2020).
4. Muscle Function and Physical Performance
VDR is present in skeletal muscle cells, where vitamin D contributes to muscle protein synthesis and muscle fiber proliferation. It also regulates mitochondrial genes, improving energy efficiency and reducing oxidative damage in skeletal muscle (Girgis CM et al., 2013).
5. Mental and Neurological Health
Vitamin D participates in synthesizing and regulating neurotransmitters such as serotonin and dopamine, modulating mood and cognition (perhaps why you might feel down with all this rain!). It also protects against brain inflammatory processes by limiting activation of glial cells (microglia and astrocytes) and production of neurotoxic cytokines (Groves NJ & Burne THJ, 2017).
6. Glucose Metabolism Regulation and Type 2 Diabetes Prevention
It enhances insulin sensitivity by increasing insulin receptor expression in peripheral tissues. This positively affects systemic inflammation, benefiting various tissues (Wimalawansa SJ, 2018).
7. Reproductive Health
VDR regulates the expression of enzymes involved in hormone synthesis (testosterone, estradiol, progesterone), influencing cell proliferation and differentiation in testes and ovaries (Lerchbaum E & Obermayer-Pietsch B, 2012).
8. Cancer Prevention
VDR induces expression of cell-cycle inhibitory proteins, reducing uncontrolled proliferation. It promotes apoptosis in potentially cancerous cells by activating pro-apoptotic pathways and reduces vascular endothelial growth factor expression, limiting new blood vessel formation required for tumor growth (Feldman D et al., 2014).
9. Skin Health
Vitamin D plays a significant role in skin health, particularly in wound healing and inflammatory skin diseases (eczema, psoriasis). It controls keratinocyte proliferation and differentiation—crucial in healing processes and skin barrier function—and mitigates dermal inflammation by regulating inflammatory cytokine production and local autoimmune responses (Bikle DD, 2010).
As you can see, vitamin D plays a fundamental role in numerous processes. Thus, from UMSS, we encourage you to maintain a balanced diet rich in vitamin D, expose yourself to the sun when you have the opportunity (prudently and responsibly), and consult a healthcare professional about supplementation if you cannot meet these recommendations.
· Anderson PH, Morris HA. Vitamin D and bone health. Scand J Clin Lab Invest Suppl. 2012;72(sup243):65–72. doi:10.3109/00365513.2012.681963
· Chung C, Silwal P, Kim I, Modlin RL, Jo EK. Vitamin D–cathelicidin axis: At the crossroads between protective immunity and pathological inflammation during infection. Immune Netw. 2020;20(2):e12. doi:10.4110/in.2020.20.e12
· Latic N, Erben RG. Vitamin D and cardiovascular disease, with emphasis on hypertension, atherosclerosis, and heart failure. Int J Mol Sci. 2020;21(18):6483. doi:10.3390/ijms21186483
· Girgis CM, Clifton-Bligh RJ, Hamrick MW, Holick MF, Gunton JE. The roles of vitamin D in skeletal muscle: form, function, and metabolism. Endocr Rev. 2013;34(1):33–83. doi:10.1210/er.2012-1012
· Groves NJ, Burne THJ. The impact of vitamin D deficiency on neurogenesis in the adult brain. Front Neurosci. 2017;11:46. doi: 10.4103/1673-5374.202936
· Wimalawansa SJ. Associations of vitamin D with insulin resistance, obesity, type 2 diabetes, and metabolic syndrome. J Steroid Biochem Mol Biol. 2018;175:177–189. doi: 10.1016/j.jsbmb.2016.09.017
· Lerchbaum E, Obermayer-Pietsch B. Vitamin D and fertility: a systematic review. Eur J Endocrinol. 2012;166(5):765–778. doi:10.1530/EJE-11-0984
· Feldman D, Krishnan AV, Swami S, Giovannucci E, Feldman BJ. The role of vitamin D in reducing cancer risk and progression. Nat Rev Cancer. 2014;14(5):342–357. doi:10.1038/nrc3691
· Bikle DD. Vitamin D and the skin. J Bone Miner Metab. 2010 Mar;28(2):117-30. doi: 10.1007/s00774-009-0153-8. Epub 2010 Jan 27. PMID: 20107849.