Vitamin D – we all know we need it… right? My experiences living in Saudi Arabia makes me think otherwise. Let’s be frank, we all love sunshine, don’t we? Whenever we get the chance we want to soak up the sun and enjoy the beautiful scenery we have around us. But when was the last time anyone has gone out for the sole purpose of getting a dose of Vitamin D? Saudi Arabia is a country which receives ample amounts of sunshine all year round. So naturally, you would expect people not be Vitamin D deficient. This couldn’t be further from the truth – let me tell you why.
Getting a Few Things Straight
Studies have shown that 80% of our vitamin D is synthesized in the skin and thus exposure to sunlight is crucial.[1] Countries closer to the equator, in theory, have a greater chance of producing vitamin D due to the high levels of UV radiation and sun intensity. But do they?!
A UV index greater than 3 includes UV-B radiation which is required for the production of vitamin D. Countries near the equator such as Saudi Arabia have UV indexes which reach level 13 (level 11 or greater is considered extreme). However, many other factors can limit vitamin D Levels; Culture is an example. This is where things get interesting.
Saudi Arabia deficient? But how?
Well, segregation, lack of green space, religious clothing, skin colour and weather could be main contributors to vitamin D deficiency in Saudi Arabia. Saudi Arabia is a very hot country, and therefore people tend to go out more at night to avoid these extreme heats. The houses in Saudi Arabia rarely have balconies and only include small windows which, consequently, could limit sunlight exposure to the residents of those homes.
Most if not all villas are gated with only a limited number containing garden space. This is a result of privacy being a sensitive cultural issue which is regarded as of high importance, potentially limiting exposure to sunlight. Moreover, women are required to wear religious dress wear which possibly shields their skin from exposure to sunlight. Traditionally, women did not leave the house as much and if they did, they would leave for a small amount of time with minimal exposure to sunlight. This is also apparent in modern Saudi Arabia where women were prohibited from driving (not anymore though). This results in women sending out drivers or their husbands to complete their daily tasks. This could make their home (which contains little to no sunlight exposure) the main place where time is spent.
This got me thinking of what else could contribute to these reasons. Perhaps Charles Darwin’s theory of evolution and all its mighty explain this weird phenomenon?
This UV index map above shows that the further away a country is from the equator, the less intense the UV radiation is. Thus, less synthesis of Vitamin D can occur through UV-B radiation as the amount of UV-B is reduced. Moreover, it shows that Saudi Arabia and the Middle East have high intensity’s of UV radiation when compared to other countries worldwide. This seems odd because many of these countries discussed all have a UV index of at least eight which should indicate that sufficient Vitamin D can be synthesised through utilising the UVB. However, these are the areas with the highest prevalence of vitamin D deficiency suggesting other factors could affect the prevalence of vitamin D deficiency.
One study has shown that Saudis have a higher prevalence of vitamin D deficiency than Non-Saudis.[2] Historically, Saudi Arabians have been living in the desert for years. They were called Bedouins and spent the majority of their time in the sun. As shown in Image Showing the UV index of Jeddah, Lebanon, Riyadh, Dubai and Iran, Saudi Arabia is near the equator in a region of high sun intensity and UV index. Consequently, this means that indigenous Saudi Arabians were exposed to significant amounts of UVR which is harmful and breaks down folate in the skin. As a result, this enabled melanin pigmentation which functions as a defence mechanism for high levels of UVR. Melanin is present in our skin and is responsible for its colour. The more melanin there is, the darker the skin colour. However, melanin also prevents the synthesis of Vitamin D from UVB.
Saudi Arabians tend to have highly or medium-pigmented skin which contains a greater amount of melanin relative to lighter skin colours which are less pigmented.[3] This may provide evidence to explain the high prevalence of vitamin D deficiency in Jeddah and the Middle East. The dark skin colour is possibly an evolutionary adaptation for indigenous Saudi Arabians who were exposed to ample sunshine, and thus the possible increase in melanin pigmentation may have protected and still allowed the production of sufficient vitamin D in the past. However, the present inadequate sunlight exposure due to the cultural reasons and the modern urbanisation of Saudi Arabia could limit exposure to sunlight and could result in the lack of Vitamin D synthesis. This effect is enhanced in darker skin colours (more melanin) as more sunlight is needed to produce the same amount of vitamin D when compared to lighter skin colours. Other studies have illustrated this with one study demonstrating that East African immigrants (highly pigmented) in Melbourne Australia displayed a high prevalence of vitamin D deficiency (87%) possibly due to high levels of melanin reducing vitamin D synthesis in the skin. This shows that Saudi Arabians skin colour could initially limit vitamin D synthesis, and in conjunction with other factors discussed, lead to a high prevalence of vitamin D deficiency.
What now?
There is no doubt that we don’t have the answers to all the reasons why people in Saudi Arabia are Vitamin D deficient. Ironically, however, the sunshine vitamin may need a little more than just sunshine. Looking at specific cases such as Saudi Arabia may provide insight into why individuals born and raised in countries near the equator experience more skeletal diseases. For instance, when they move to countries further away from the equator they are more likely to suffer from skeletal diseases compared to inhabitants of that country. What does this mean for us Stanford students? Well, depending on our skin tone, we probably need to spend different amounts of time in the sunshine to get an ample dose of Vitamin D we need to stay healthy. In a place with such cultural diversity, we should be cautious and aware of what each of us needs to ensure we don’t suffer complications. But for now, as winter approaches, get out more and eat fortified food to get the Vitamin D you need to stay healthy!
References:
[1] Holick, M.F. (2002) Sunlight and Vitamin D. J Gen Intern Med, 17(9): 733–735. doi:10.1046/j.1525-1497.2002.20731.x
[2] Ritu, G. & Gupta, A. (2014) Vitamin D Deficiency in India: Prevalence, Causalities and Interventions. Nutrients, 6(2), 729–775. doi:10.3390/nu6020729
[3] Naeem, Z. (2010) Vitamin D Deficiency- An Ignored Epidemic. International Journal of Health Sciences (Qassim) 4(1), 5-6. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068797/
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