Vitamin D is fat soluble vitamin that can be endogenously synthesized or obtained from dietary sources. Endogenous synthesis of vitamin D3 starts in human skin under the influence of UVB radiation (sunlight), and continues by the further metabolism in the liver and kidney. Besides, foods of animal origin, such as fatty fish and egg yolk contain vitamin D3. Also, many food items, such as milks and cereals can be fortified with vitamin D3. Vitamin D3 plays an important role in maintenance of calcium and phosphorus homeostasis and regulation of bone health. Still, recent studies indicate impact of vitamin D3 on other systems in human body, including cardiovascular, immune and nervous ones.
Bone metabolism is characterized by high bone loss and bone turnover during the winter, following a seasonal pattern. Randomized, placebo controlled study investigated the impact of vitamin D3 intake during winter months (from October to April) on markers of bone formation and resorpiton as well as on bone density. While 30 subjects living in southwestern Germany were assigned to receive vitamin D3 along with calcium, 25 were assigned to control group and received no supplementation. As a result, in supplemented subjects lumbar and femoral bone mass density increased significantly.
Type 2 diabetes is associated with increased risk of fractures and, thus, one study investigated impact of vitamin D3 intake on bone mass density in prediabetic subjects. 256 subjects were randomized to receive vitamin D3 for 5 years, while 255 subjects were receiving placebo. As a result, vitamin D3 supplementation showed beneficial effects in male subjects, demonstrated as lower reduction in bone mass density comparing to the placebo.
- Meier C, Woitge HW, Witte K, Lemmer B, Seibel MJ. Supplementation with oral vitamin D3 and calcium during winter prevents seasonal bone loss: a randomized controlled open-label prospective trial. J Bone Miner Res. 2004;19(8):1221-1230.
- Larsen AU, Grimnes G, Jorde R. The effect of high-dose vitamin D(3) supplementation on bone mineral density in subjects with prediabetes. Osteoporos Int. 2018;29(1):171-180.
Vitamin D3 seems to have important role in the modulation of immunity, mediated by its activity on cells of both adaptive and innate immune system. Additionally, vitamin D3 exerts beneficial effects on autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, and multiple sclerosis.
In one trial, more than 250 patients with systematic lupus erythematosus were assigned to receive either vitamin D3 or placebo for 12 months. Lower levels of vitamin D3 correlated significantly with the disease activity. At the end of treatment period, there was significant improvement in disease activity in patients treated with vitamin D3 compared to those receiving placebo.
In a exploratory study 150 patients with rheumatoid arthritis received vitamin D3 supplement 60 000 IU per week for 6 weeks, followed with 60 000 IU per month for a total duration of 3 months. As a result, there was significant improvement in the disease activity score and symptoms of rheumatoid arthritis.
An interesting systematic review and meta-analysis questioned the impact of vitamin D supplementation in early childhood on diabetes type I onset later in life. Results of this study indicated lower risk of type I diabetes in infants supplemented with vitamin D3 compared to those who received no supplementation. Thus, vitamin D3 intake at early stages of life confers protection from diabetes type I at later stages.
- Abou-Raya A, Abou-Raya S, Helmii M. The effect of vitamin D supplementation on inflammatory and hemostatic markers and disease activity in patients with systemic lupus erythematosus: a randomized placebo-controlled trial. J Rheumatol. 2013;40(3):265-272.
- Chandrashekara S, Patted A. Role of vitamin D supplementation in improving disease activity in rheumatoid arthritis: An exploratory study. Int J Rheum Dis. 2017;20(7):825-831.
- Zipitis CS, Akobeng AK. Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis. Arch Dis Child. 2008;93(6):512-7.
Studies have indicated that participants with lower levels of vitamin D3 are more prone to depression. Lower levels of vitamin D were identified in postmenopausal women with major depression in comparison with women without depression. Interestingly, lower levels of prenatal vitamin D3 were associated with higher risk of postpartum depression.
Depression is commonly present in patients with multiple sclerosis. One study evaluated the association between vitamin D3 levels and depressive symptoms in multiple sclerosis. For this purpose, two hundred subjects with multiple sclerosis were enrolled. The prevalence of vitamin D deficiency was high (more than 45 %subjects had low levels of vitamin D3). In addition, there was inverse association with the levels of vitamin D3 and depressive symptoms (lower the values of D3, higher the chance of depression).
- Atteritano M, Lasco A, Mazzaferro S, et al. Bone mineral density, quantitative ultrasound parameters and bone metabolism in postmenopausal women with depression. Intern Emerg Med. 2013;8(6):485-491.
- Accortt EE, Schetter CD, Peters RM, Cassidy-Bushrow AE. Lower prenatal vitamin D status and postpartum depressive symptomatology in African American women: Preliminary evidence for moderation by inflammatory cytokines. Arch Womens Ment Health. 2016;19(2):373-383.
- Ashtari F, Ajalli M, Shaygannejad V, Akbari M, Hovsepian S. The relation between Vitamin D status with fatigue and depressive symptoms of multiple sclerosis. J Res Med Sci. 2013;18(3):193-197.