Vitamin D: Little Miss (well, Mrs.) Sunshine
After all our beautiful warm weather here in Sydney, winter is truly on its way. Sitting with my cup of tea in some wintery sunshine for a few minutes today has me pondering the many roles of vitamin D in our bodies.
The role of vitamin D in bone health and maintaining calcium levels is well documented but vitamin D has also been found to have important roles in enhancing the immune system, regulating blood pressure, maintaining muscle strength, and insulin sensitivity. Vitamin D deficiency has been associated with depression, and there’s a potential link of low vitamin D levels with gestational diabetes.
Vitamin D is a fat-soluble vitamin also known as calciferol, and its main active and dietary form is vitamin D3 (also known as cholecalciferol).
Almost 90% of our vitamin D comes from exposure to sunlight. The UVB component of sunlight converts 7-dehydrocholesterol (produced in the sebaceous glands of the skin) into vitamin D3. Vitamin D is primarily stored in the adipose tissue (body fat) and then mobilised when there is insufficient sun exposure.
Safe sun exposure is essential for adequate vitamin D levels and a general rule of thumb is 5 -15mins of sunlight to exposed skin (hands, face, arms) 4 to 6 times a week outside the hours of 10am to 2pm.
We also obtain Vitamin D3 from dietary sources, including:
- Cod liver oil
- Oily fish – such as salmon, mackerel, sardines, and herring.
- Meat- especially beef liver.
- Eggs- especially yolks
- Dairy products- such as cheeses, butter and margarines.
Some foods are also fortified with Vitamin D including fruit juices, milk, and some breads.
There is also a vegetarian form of Vitamin D (D2 or ergocalciferol) found in yeasts and fungi such as mushrooms.
There is a surprisingly high prevalence of suboptimal vitamin D levels in a sunny country like Australia, thought to be due for the most part to a combination of poor dietary intake and inadequate sun exposure.
Some people do require supplementation with vitamin D, and it’s best to have your blood levels tested first in order to work out the correct dose and make sure it’s safe to take with any medications you’re currently taking.
So I’ll be taking my time with that cup of tea in the morning sun- I’m busy working on my Vitamin D levels!!
Al Mheid, I., Patel, R.S., Tangpricha, V., & Quyyumi AA. (2013). Vitamin D and cardiovascular disease: is the evidence solid? Eur Heart J 2013 Dec; 34 (48): 3691-8. doi: 10.1093/eurheartj/eht166. Epub 2013 Jun 9.
Anglin, R.S., Samaan, Z., Walter, S.D., & McDonald S.D. (2013). Vitamin D deficiency and depression in adults: systematic review and meta-analysis. Br J Psychiatry 2013 Feb; 202: 100-7. doi: 10.1192/bjp.bp.111.106666.
Gropper, S.S., & Smith, J.L. (2013). Advanced Nutrition and Human Metabolism. 6th ed. Belmont, CA: Wadsworth Cengage Learning.
Hechtman, L. (2014). Clinical Naturopathic Medicine. Chatswood (NSW), Australia: Elsevier.
Higdon, J., & Drake, V.J. (2012). An Evidence-based Approach to Vitamins and Minerals. 2nd ed. Stuttgart, Germany: Thieme.
Joshi, D., Center, J.R., & Eisman, J.A. (2010). Vitamin D deficiency in adults: systematic review and meta-analysis. Austr Prescr 2010; 33: 103-6. doi: 10.18773/aust.prescr.2010.053.