What is vitamin D?
Vitamin D is the “sunshine vitamin”. It acquired this nickname due to our body’s ability to synthesize vitamin D when the skin is exposed to sunshine. Vitamin D is also naturally present in a few foods and in fortified foods (1).
Vitamin D is a fat-soluble vitamin. It is essential for strong bones, as it promotes calcium absorption and maintains adequate serum calcium and phosphate concentrations for normal bone mineralization. Vitamin D also plays roles in controlling inflammation and cell growth, glucose (blood sugar) metabolism, and neuromuscular and immune function (2).
What are the symptoms of vitamin D deficiency?
Vitamin D deficiency can cause a range of symptoms, including:
- Bone pain
- Muscle weakness, aches, and cramping
- Mood changes, e.g., depression
In children, rickets can occur as a result of long-term vitamin D deficiency (3). Rickets is now a rare disorder, which is characterized by soft and weak bones, which can cause a range of symptoms, including:
- Skeletal deformities, such as bowed legs and thick wrists or ankles
- Failure to thrive
- Physical developmental delay
- Dental abnormalities
- Delayed motor skills
- Muscle weakness
- Bone pain, particularly in the legs, pelvis, and spine
In adults and adolescents, long-term vitamin D deficiency can also lead to osteomalacia, which is also characterized by soft and weak bones. Although adult bones are completely formed, they still undergo a constant remodeling process, and vitamin D deficiency causes defective bone mineralization during this process. Osteomalacia often doesn’t have any noticeable symptoms in the early stages, but eventually can lead to serious muscle weakness and bone pain, particularly in the legs, pelvis, and spine (3).
Vitamin D acts on cells throughout the body by binding to a specific receptor located on the cell surface. These receptors are present on almost all body cells. This means that vitamin D deficiency can also increase the risk of many other health complications (4), including:
- Insulin resistance, high blood glucose, and diabetes
- Cardiovascular disease
- Inflammatory diseases
- Asthma in children
- Specific cancers
- Cognitive impairment and depression
There is even a possible link between vitamin D and COVID-19. Although evidence is a bit mixed and sparse, there may be a link between low vitamin D levels and an increased risk of serious health complications during a COVID-19 infection (5). Vitamin D deficiency is more common in obese and diabetic people, and it is these same populations that are associated with higher mortality in COVID-19 (6).
Whether or not the link between vitamin D deficiency and COVID-19 complications proves to be correct, ensuring you have adequate vitamin D levels is going to be beneficial to your overall health. Take our easy-to-use at-home Vitamin D Test to see if you have healthy vitamin D levels.
Vitamin D supplements are readily available if you are needing more, but be careful not to over-supplement, as vitamin D toxicity is possible (although very rare).
1. Vitamin D: Fact Sheet for Health Professionals (2020, October 9). NIH
2. Jones G. (2014). Vitamin D. In A. C. Ross, B. Caballero, R. J. Cousins, K. L. Tucker, & T. R. Ziegler, Modern Nutrition in Health and Disease (11th ed). Philadelphia: Lippincott Williams & Wilkins.
3. Uday S, & Högler W. (2017). Nutritional Rickets and Osteomalacia in the Twenty-first Century: Revised Concepts, Public Health, and Prevention Strategies. Curr Osteoporos Rep, 15(4), 293-302.
4. Vitamin D Fact Sheet for Health Professionals. (Updated August 2021). National Institutes of Health, Office of Dietary Supplements.
5. Rubin R. (2021) Sorting out whether vitamin D deficiency raises COVID-19 risk. JAMA. 325(4), 329-330.
6. Weir EK et al. (2020) Does vitamin D deficiency increase the severity of COVID-19? Clin Med (Lond). 20(4), e107-e108.