Autoimmune diseases, sun and vitamin D
Vitamin D is one of the most relevant immune response coordinators and is of paramount importance in subjects suffering of autoimmune diseases.
Other then the well known effects on bones health, Vitamin D is also involved in insulin production, blood pressure regulation, mood stability and muscle contraction, and recent studies strongly suggest that vitamin D has a protective role in the development and progression of cancer.
Many of us know that vitamin D is fabricated under the skin by the specific action of the solar UVB radiation on skin cholesterol. Other sources like some therapeutic or cosmetic UVB lamps can provide the same effect.
When we receive too much UV we can have erythema, an irritation of the skin which can vary from light to severe and can critically contribute to skin ageing in time. Eccessive and continuative exposure to sun light can be seriously dangerous at our latitude in Australia, and can lead to various form of skin cancer especially when absorbed at young age.
While the sun can be deadly dangerous is is also true that no UVB exposure means no vitamin D production.
For safety reasons any direct sun exposure without protections should be timed. For most skin types it is normally safe if limited to 5-10 minutes with UV index beetween 2.5 and 5.5 as indicated on the Arpansa daily UV forecasts.
Well, and the diet? Aren't we having vitamin D from food?
Hum... well... not really. Yes vitamin D is contained in some food, but except for cod liver oil and some few other fishes, some variety of mushrooms and fortified cereals the amount of vitamin D in food is quite small. For this reason the content of vitamin D in food alone is normally insufficient to build up and maintain convenient stores of vitamin D in our body (this is not valid if you are perfectly healthy, your blood vitamin D level is normal and you take at least 1 tablespoon of cod liver oil daily for the rest of your life).
The deficiency of Vitamin D is often due to a combination of poor sun light exposure and poor diet, and can be exacerbated by many other factors, including obesity, malabsorption, age, illness, skin color.
In certain instances the dietary contribution of vitamin D can be practically inexistent. This is often the case of people suffering of gut conditions like gut permeability, autoimmune conditions (for example celiac disease, Crohn disease), inflammatory diseases (IBS or Ulcerative Cholitis), food intolerances, fat malabsorption, or people exposed to certain medications or to prolonged dietary restrictions.
Vitamin D deficiency is very common in warm weather climate countries where people tend to cover large parts of the body, if not all, or use large amounts of sunscreen protection (the correct application of a SPF15 sunscreen cream blocks 99% of UVB). Despite regularly affecting around ⅓ of the population it is during the Australian winter, more then in summer, that deficiency in some Australian states can involve nearly 50% of the individuals.
Vitamin D deficiency in winter by state and territory, 2011–12
(from ABS)
For these and other reasons, and not dissimilar to the need of drinking water or eating regular meals, the exposure to the sun radiation can not be considered an option but a necessity aimed to maintain blood levels of vitamin D in the beneficial range.
There is a constant debate in the scientific community about what is the ideal level of vitamin D in the blood of a healthy individual, and still there is no international consensus about it. Nevertheless all the data points to a prudential value between 75 and 100 nmol/L. The benefits (if) of having more elevated values are still subject to investigations.
As a supplements vitamin D is a very safe substance but should be prescribed by a professional based on your general state of health, your tested blood levels, your lifestyle and nutritional status, your prescribed medications and illnesses you suffer of.