- Ashley Isabel Tay
Vitamin D Deficiency - Are you getting enough Sunlight?
It is estimated that 1 billion people suffers from insufficiency or deficiency in vitamin D globally and this is caused mainly by insufficient exposure to sunlight (1). Other than insufficient sunlight exposure, the common causes of deficiency is due to inadequate dietary sources and malabsorption. Over the years, the most significant factor contributing to the prevalence of vitamin D deficiency is the change in lifestyle. For example, outdoor work has been replaced with indoor jobs and the various forms of transport that has replaced walking or cycling, hence resulting in the scarce exposure to sunlight.
Vitamin D deficiency is widely recognised as 25(OH)D level below 20ng/mL and Vitamin D insufficiency is defined as 25(OH)D level between 21-29 Ng/mL.
Patients who have vitamin D below this level may be at an increased risk for muscle weakness, fragility fractures and bone pain (2). Muscle weakness associated to vitamin D deficiency is predominantly of the proximal muscle groups through the genomic and non-genomic pathways and is reversible with vitamin D supplements. Various cardiovascular risk factors has been associated to vitamin D deficiency and appears to be linked to a higher mortality. Other conditions related to vitamin D deficiency have been identified below (3):
Role of Vitamin D
The importance of vitamin D is often overlooked. Vitamin D has receptors on virtually every cell in the human body and is responsible for many roles in the body (4).This includes bone metabolism, cell growth modulation, neuromuscular and immune function and inflammation reduction. On top of all, the primary role of vitamin D is the maintenance of extracellular fluid calcium concentrations. Vitamin D also regulates blood pressure by acting on endothelial cells and smooth muscle cells.
Getting vitamin D from Sunlight
Many studies has shown that sun exposure to face, arms and legs for 10-15mins 2x per week (below erythema level - the measure of UV radiation) could provide adequate amounts of vitamin D (1,5,6,7). However, for darker skinned individuals, this could be lengthened to 30mins 2x per week. This is because vitamin D synthesis is highly dependent on concentration of melanin. As darker skin has higher melanin than lighter skin and having more melanin reduces the ability to synthesis vitamin D from the sun. Thus, darker-skinned individual will experience slower vitamin D synthesis than light-skinned individuals.
It is important to note that increasing the the time/intensity of vitamin D does not enhance vitamin D synthesis. Ultraviolet radiation (UVR) is associated with skin ageing and cancer (8,9), thus the use of sunscreen is important to protect against UVR from sunlight exposure.
Getting vitamin D from Food
Dietary sources of vitamin D include egg yolks, portobello mushrooms, fatty fish (salmon, tuna, swordfish and sardines), beef liver, cod liver oil and fortified foods such as milk (dairy and non dairy), breakfast cereal, cheese, orange juice and infant formula (10,11).
Getting vitamin D from Supplements
Patients who are vitamin D deficient are recommended to go through a treatment period of1-3 months depending on the severity of the vitamin deficiency. However, it is important to seek help from a registered dietitian or doctor for the recommended dosage as individual dosage differs according to severity of deficiency. Also, many supplementation guidelines are disease-specific (12). Thus, all specific aspects of any disease that patient is experiencing should be considered for vitamin D recommendations to identify the cause or consequence of deficiency.
The Endocrine Society Clinical Practice Guideline recommends for vitamin D supplement for18 years and over to be 6000 IU/day or 50,000 IU/week of vitamin D for 8 weeks to raise blood 25(OH)D levels to above 30 ng/ml. Followed by maintenance therapy of 1500–2000 IU/day. Again, this is a general guideline and do seek a healthcare professional for specific dosage according to your 25(OH)D levels as according to the Institute of Medicine (IOM), 25OHD levels in excess of 125 nmol/l could be associated with harm (13). Thus, dosage of supplement should be prescribed accordingly.
Overall, we hope this gives you a better understanding of any underlying issues that you are experiencing but yet can't seem to find out the root cause of it. If you do experience any of the above symptoms and is concerned about your vitamin levels, reach out to us here.
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Pludowski P., Holick M.F., Grant W.B., Konstantynowicz J., Mascarenhas M.R., Haq A. Vitamin D supplementation guidelines. J Steroid Biochem Mol Biol. 2018;175:125–135. doi: 10.1016/j.jsbmb.2017.01.021.
Ross AC, Manson JE, Abrams SA, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;96:53–8.