By Eoin Roe
It has been a fantastic week to be living in West Cork, the sun is shining and that has got me thinking about Vitamin D.
Vitamin D is a vitamin and also a hormone that is produced in your body by exposure to UVB rays from sunlight. When the skin is exposed to UVB a molecule known as 7-dehydrocholesterol (derived from cholesterol) is converted to cholecalciferol, also known as D3. Cholecalciferol travels to the liver where it is converted to 25-hydroxyvitamin D (25OHD). The kidney then converts 25OHD to 1,25-hydroxyvitamin D (1,25OHD), also known as calcitriol, which possesses hormonal properties and regulates calcium and phosphate balance.
Vitamin D has many roles in the body and is essential for optimal health (Holick, 2016). Low vitamin D levels are linked with health conditions such as: Osteoporosis; Cancer; Depression; Muscle weakness.
Exposure to sunlight is the best way to boost your Vvitamin D production. Interestingly those with a paler complexion will produce more Vitamin D in much shorter time. A UK study in 2010 showed that 13 minutes of sun exposure at our latitude in the summer months can provide all the vitamin D we require for the day (Rhodes et al).
If you are looking to increase your Vitamin D levels you will need sun exposure without sunscreen. However excessive sun exposure carries its own health risks so you should always be careful to protect your skin after 13 minutes with a suitable sun cream, long sleeved shirt and hat so not to burn or damage your skin.
It is worth noting that UVB radiation does not pass through windows so even if you are sitting in a sunny spot at work you may still be deficient in Vitamin D.
Unfortunately we are not always blessed with such great weather so it is worth considering supplementing with vitamin D especially in the winter months. Foods that are high in Vitamin D are, fish oils, eggs, and butter but you would have to eat a large amount of them everyday to get enough.
You may also have noticed that there are different types of Vitamin D available namely Vitamin D3 (Cholecalciferol) and Vitamin D2 (ergocalciferol). The research is showing that supplementation with vitamin D3 is more beneficial for elevating the levels of calcitrol in the blood and is therefore a better supplemental form (Swanson et al, 2014).
The majority of the population in Ireland and UK will have low vitamin D levels however it is possible to have levels that are too high. The main consequence of this is too high a level of calcium within the blood known as hypocalcaemia, which is linked to: Kidney Stone; Bone pain and muscle weakness; Abnormal heart and brain function.
Extremely high levels of calcium in the blood can become life threatening. So if you are already taking in excess of 5000iU’S of Vitamin D per day and have been for more than three months it may be wise to check this with a blood test especially in the summer months.
Vitamin D supplements are widely available and probably the most convenient way to take them in a spray or drop for which is very easily absorbed by the body. In the meantime get out and enjoy the sun.
Holick M. (2016) Biological Effects of Sunlight, Ultraviolet Radiation, Visible Light, Infrared Radiation and Vitamin D for Health. Anticancer Research March 2016 vol. 36 no. 31345-1356
Rhodes LE, Webb AR, Fraser HI, Kift R, Durkin MT, Allan D, O’Brien SJ, Vail A, Berry JL. (2010) Recommended summer sunlight exposure levels can produce sufficient (> or =20 ng ml(-1)) but not the proposed optimal (> or =32 ng ml(-1)) 25(OH)D levels at UK latitudes. Journal of Dermatology 2010 May;130(5):14411-8
Swanson CM, Nielson CM, Shrestha S (2014) Higher 25(OH)D2 Is Associated With Lower 25(OH)D3 and 1,25(OH)2D3. The Journal of Clinical Endocrinology and Metabolism. 2014;99(8):2736-2744. doi:10.1210/jc.2014-1069.
