Study under review: Vitamin D Supplementation Affects the Beck Depression Inventory, Insulin Resistance, and Biomarkers of Oxidative Stress in Patients with Major Depressive Disorder: A Randomized, Controlled Clinical Trial
Everyone feels sad sometimes. For some people, however, sadness can grow into a debilitating medical condition known as depression, or major depressive disorder (MDD). MDD is quite prevalent, affecting approximately 20% of people at some point in their lifetime, and has been linked to other physiological complications, such as increased risk of cardiovascular disease, dyslipidemia, diabetes and hypertension. Increase in oxidative stress in MDD patients has also been reported. Overall, MDD patients have been shown to have decreased lifespan and quality of life.
Vitamin D is a fat-soluble secosteroid (a steroid with an “open” ring) that enhances absorption of essential elements, such as magnesium, iron, calcium, phosphate, and zinc. Traditionally, the majority of vitamin D has been obtained from exposure to sunlight. It is also available through dietary consumption, mostly through fortified foods like milk and cereal. Vitamin D obtained from sunlight or diet requires hydroxylation (addition of a hydroxyl “–OH” group) in the liver to become biologically active.
There are two major forms of vitamin D: D2 (ergocalciferol, obtained from foods) and D3 (cholecalciferol, synthesized following exposure to sunlight). Collectively, both isoforms are termed calciferol. Calciferol is converted into calcidiol, a parahormone, in the liver, and subsequently converted into the biologically active form calcitriol in the kidneys. Calcitriol binds the nuclear vitamin D receptor, which is ubiquitously expressed, inducing transcription of various target genes. Vitamin D plays an important role in proper bone formation and maintenance of bone density, along with a possible role in the immune system. Vitamin D deficiency has been associated with a variety of diseases, including osteoporosis, neurodegenerative diseases, cardiovascular disease, and complications during pregnancy.
Serum vitamin D levels have also been negatively correlated with depressive symptoms. Recent meta-analyses have shown a connection between higher serum vitamin D levels and improved depressive symptoms in people with MDD. There are also a number of studies on the effects of various levels of vitamin D supplementation in MDD patients. Some studies suggest no benefits of vitamin D to mood symptoms of MDD; however, a meta-analysis of existing studies concluded that vitamin D supplementation of 800IU per day or more in vitamin D deficient patients has a positive impact on MDD mood symptoms.
In addition to a positive effect on mood, vitamin D supplementation has been shown to have a positive effect on glucose and cholesterol levels in pregnant women with gestational diabetes (high blood sugar during pregnancy). Recent meta-analyses have indicated that type 2 diabetes is significantly more common in MDD patients, and markers of oxidative stress are elevated in MDD patients. Since the researchers behind the current study have recently shown that high-dose vitamin D supplementation improves glucose levels, oxidative stress and inflammation in type 2 diabetes patients, in this study they wanted to investigate the effect of vitamin D supplementation on oxidative stress and blood glucose in MDD patients, as well as the effect on mood change.
Vitamin D supplementation has been shown to be beneficial in studies on depression and metabolic disorders; however, no studies have investigated effects of vitamin D supplementation on both mood and metabolic markers in a population of MDD patients. This study was designed to investigate the benefits of high-dose 8-week vitamin D supplementation in MDD patients.
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