Vitamin D, the so-called sunshine vitamin, plays a vital role in the human body. 


It’s a fat-soluble vitamin that is stored in the liver as well as fat tissues. Different from other vitamins, the body makes its own Ds instead of relying on food sources.


Let’s see how the mechanism work in the body, what are the core benefits of this vitamin and what are the signs that you are deficient.


Vitamin D Mechanism & Types of Vitamin Ds

When we are exposed to sun, especially UV-B sunlight; 7-dehydrocholesterol, a compound in the skin starts turning into Vitamin D3. So the cholesterol on our skin converts pre-vitamin D into a more efficient form D3. This is also called pro-vitamin D.


Next, all the available D3 including dietary Vitamin D3&D2 goes to the liver and kidneys and comes out as Active Vitamin so-called: calcitriol. At this point, we can start calling this vitamin a secosteroid hormone. In fact, this is quite similar to the steroid hormone.


The release of the active Vitamin triggers or activates certain genes. These genes affect muscle protein synthesis, muscle strength, muscle size, reaction time, balance, coordination, endurance, inflammation, and immunity.


The optimal functioning of these sports-related biological processes occurs when Vit. D (cholecalciferol) storage levels approach those obtained by natural, full-body, summer sun exposure. Research indicates that it impacts not only the skeletal structure but also blood pressure, immunity, mood, brain function and ability to protect ourselves from cancer.


Vitamin D


5 Benefits of Vitamin D

Vitamin D is known for helping to balance minerals like calcium, phosphorus, sodium, and magnesium for healthy bone formation and mineralization.


Although the vitamin plays a significant role in skeletal health, its benefits go well beyond bone health to all parts of the body. Because of the abundant presence of these minerals, along with vitamin receptors in the body, vitamin’s benefits are vast, directly and indirectly influencing countless physiological functions.


For example, this vitamin can act as an antioxidant, regulate the immune activity, support cardiovascular health, modulate blood sugar balance, regulate neurotransmitter synthesis and more.


1- Enhances Bone & Muscle Health 

Vitamin D helps the body to absorb calcium, phosphorus and even Vitamin K. These are all key elements for bone health. Maintenance of the calcium at optimum levels accomplished by calcitriol and parathyroid hormone working together. 


The effects of the vitamin on muscle function were reviewed recently (Girgis et al., 2013). A well-known case-control study of 55 veiled Arabic women with severe vitamin deficiency (mean 25OHD 7 nmol/l) reported weakness on all tested parameters of muscle function compared to a control group of 22 Danish women with higher levels (47 nmol/l) (Glerup et al., 2000).


Following vitamin repletion (IM vitamin D2: 100,000 IU per week for 1 month then monthly for 5 months and 400–600 IU orally daily), significant improvements in muscle function and pain at 3 and 6 months were reported in the Arabic women.


2- Preventing Diabetes & Low Blood Sugar

There is growing evidence that D vitamin deficiency could be a contributing factor in the development of both type 1 and type 2 diabetes.


First, the β-cell in the pancreas that secretes insulin has been shown to contain VDRs as well as the 1 alpha-hydroxylase enzyme. Evidence indicates that D vitamin treatment improves glucose tolerance and insulin resistance. Vitamin D deficiency leads to reduced insulin secretion. Supplementation with D vitamin has been shown to restore insulin secretion in animals.


Researchers have also found an indirect effect on insulin secretion, potentially by a calcium effect on insulin secretion. This vitamin contributes to the normalization of extracellular calcium, ensuring normal calcium flux through cell membranes; therefore, the low vitamin levels may diminish calcium’s ability to affect insulin secretion.


Other potential mechanisms associated with D vitamin and diabetes include improving insulin action by stimulating expression of the insulin receptor, enhancing insulin responsiveness for glucose transport, having an indirect effect on insulin action potentially via a calcium effect on insulin secretion, and improving systemic inflammation by a direct effect on cytokines. 


3- Anti-Cancer Properties

Early research showed that occurrence and death for certain cancers were lower among individuals in the south, where levels of sunlight exposure are relatively high than among those living in northern countries.


As we learned, sunlight leads to the production of this vitamin. Researchers hypothesized that variation in these vitamin levels might account for this association. However, additional research is required to determine whether higher vitamin levels are related to lower cancer incidence or death rates.


In studies of cancer cells and of tumors in mice, vitamin D has been found to have several activities that might slow or prevent the development of cancer, including promoting cellular differentiation, decreasing cancer cell growth, stimulating cell death, and reducing tumor blood vessel formation.


4- Boosting the Immune System

In a 2016 research, Georgetown University Medical Center found out that sunlight directly energizes T cells which plays an important role in the immune system.  This is an addition to the role of sunlight in Vitamin D production. 


Here is an interesting fact from the 1980s; this vitamin has been used (unknowingly) to treat infections such as tuberculosis before the advent of effective antibiotics. Tuberculosis patients were sent to sanatoriums where treatment included exposure to sunlight which was thought to directly kill tuberculosis.


Cod liver oil, a rich source has also been employed as a treatment for tuberculosis as well as for generally increased protection from infections.


5- Balancing Hormones and Improves Moods

We mentioned that D vitamin activates certain genes. These genes are mainly responsible for two things: regulating the immune system and release neurotransmitters such as dopamine and serotonin.


These substances are vital in brain function and development. When researchers looked into the part of the brain where depression happens, they found a bunch of cells that are vitamin D receptors.


This vitamin also found out to be a regulator of testosterone, estrogen, and progesterone. The effects are quite interesting though. In vitamin deficient man, supplementing increased the testosterone which is good news. When it comes to women hormones, overloading ladies with Vitamin actually decreased the levels of both estrogen and progesterone. 


Vitamin D test


About Vitamin D Deficiency 

There is a great amount of evidence that this vitamin’s deficiency can cause a variety of health issues including cardiovascular disease, metabolic syndrome, various types of cancer, immune disorders and adverse pregnancy outcomes.


If you have the symptoms below you should get tested for Vitamin deficiency: 


  • Weakness, chronic fatigue or depression,
  • Anxiety or trouble sleeping
  • Weak or broken bones
  • Weakened immune system
  • Inflammation and swelling




Medical News Today – What are the health benefits of D vitamin?


Dr. Axe – Vitamin D Deficiency Symptoms & Sources to Reverse It!


NCBI – Vitamin D and muscle


Vitamin D: Vital Role in Your Health


Mayo Clinic – Vitamin D


Diabetes Spectrum – Vitamin D and Diabetes


NIH – Vitamin D and Cancer Prevention


Psychological Consequences of Vitamin D Deficiency