What are the roles of vitamin D in the body?

Vitamin D is the “sunshine vitamin”. We can obtain this vitamin from a few foods, but our body is also able to synthesize vitamin D when the skin is exposed to sunshine. In this article, we focus on the important roles that vitamin D plays in the body.

Healthy bones 
Most people are aware that calcium is essential for strong and healthy bones, but did you know that even if you consume plenty of calcium, it can’t play a proper role in the body if there is not enough vitamin D? This is because vitamin D is needed to promote calcium absorption in the gut, and it is also required for the body to be able to effectively use the calcium. In addition, vitamin D is required for the proper functioning of osteoblasts and osteoclasts–the cells responsible for ongoing bone growth and remodeling (1,2).

Vitamin D deficiency can lead to bone pain, with long-term deficiency causing rickets in children and osteomalacia in adults, as well as increasing the risk of osteoporosis and bone fractures (1).

Healthy muscles
Vitamin D is important for the normal development and growth of muscle fibers. Vitamin D promotion of calcium absorption is also important to prevent hypocalcemic tetany, which is when the muscle contract involuntary, leading to cramps and spasms. Healthy and strong muscles may also reduce the risk of fractures, particularly in the elderly, as healthy muscles reduce the risk of falls (1).

Inflammation and immune function
Vitamin D plays a role in regulating the immune response and controlling inflammation. The role vitamin D plays in controlling the levels of cytokines (small messenger proteins) is thought to also impact the association between vitamin D levels and bone health (3).

There are also possible links between vitamin D deficiency and skin conditions, such as psoriasis and skin cancer, as well as increased sensitivity to infections and autoimmune diseases (4).

Blood pressure control 
Vitamin D helps regulate the renin-angiotensin-aldosterone system (and thereby blood pressure) (1), but there is conflicting evidence whether or not vitamin D supplementation is a beneficial treatment approach for high blood pressure (5).

Cell growth
Vitamin D plays important roles in controlling cell growth and proliferation, with possible links to slowing tumor growth, but the evidence is mixed for the prevention and progression of cancer. Although there is growing evidence that adequate or higher vitamin D intake can reduce the mortality rate of at least some cancers (1).

Glucose (blood sugar) metabolism
Insulin is the hormone that is absolutely essential for regulating blood glucose levels, and it has been shown that Vitamin D helps stimulate insulin secretion from the pancreatic beta cells. In addition, adequate vitamin D levels can reduce the risk of insulin resistance. Reduced insulin production and insulin resistance are characteristics of type 2 diabetes; hence why many people with diabetes also have low vitamin D levels. Research has shown that vitamin D supplementation may help lower average blood glucose levels in people with diabetes, particularly if they are also vitamin D deficient (6).

Brain processes
Vitamin D is also important for a healthy brain, by aiding in the function of the neuronal and glial tissue in the brain. This is why cognitive impairment, dementia, psychosis, and autism have all been linked with low vitamin D levels (7).

Measuring your vitamin D levels
Checking your vitamin D levels is quick and simple. It just requires a simple finger prick blood sample with our Vitamin D Test. This test measures your blood concentration of 25-OH vitamin D, which is the main indicator of vitamin D status. This test can tell you if your levels are in the healthy optimal range, or if you have mild to moderate deficiency, or if you have a severe deficiency. It can also detect vitamin D levels that are too high (vitamin D toxicity), which can occur in people who take an excessive amount of vitamin D supplements.

For more information about vitamin D, see our previous articles:

1. Vitamin D: Fact Sheet for Health Professionals (Updated August 2021). NIH.
2. Bikle DD. (2012). Vitamin D and Bone. Curr Osteoporos Rep. 10(2): 151-159.
3. Laird E, et al. (2010). Vitamin D and Bone Health; Potential Mechanisms. Nutrients. 2(7): 693-724.
4. Bouillon R, et al. (2019). Skeletal and extraskeletal actions of vitamin D: Current evidence and outstanding questions. Endocr Rev. 40(4): 1109-1151.
5. Zhang D, et al. (2020). Effect of Vitamin D on Blood Pressure and Hypertension in the General Population: An Update Meta-Analysis of Cohort Studies and Randomized Controlled Trials. Prev Chronic Dis. 17: 190307.
6. Vitamin D: A possible ally in the fight against diabetes. (2018). McMaster University.
7. Anjum I, et al. (2018). The role of vitamin D in brain health: A mini literature review. Cureus. 10(7): e2960.