Can Vitamin D Deficiency Occur in Equatorial and Tropical Countries?

Uma Shankari By Uma Shankari, 18th Nov 2013 | Follow this author | RSS Feed | Short URL
Posted in Wikinut>Health>Diet & Nutrition

Why Vitamin D deficiency amidst abundant sunshine? How can we ensure getting optimum levels of Vitamin D even in countries with fewer sunny days?

Is Vitamin D Deficiency on the Rise?

When my daughter rang up from Seattle to tell me she was diagnosed as deficient in Vitamin D, I blithely assumed since she was living in a place that was cloudy for major part of the year. Just a few months later, I too tested myself prior to the spinal surgery and found out I, living in tropical India, fared no better. As I looked around, many of my friends seemed to be on Vitamin D supplements. How come all of a sudden every other person happened to be short on this vitamin? Why were they deficient amidst abundant sunshine so necessary for synthesizing it in the body? Or the numbers merely indicative of more health awareness and hence the result of more regular diagnostics, perhaps? Or is the vitamin deficiency truly on the rise? And the contributory factors – Life style? Environment?

Importance of Vitamin D

The interest in this vitamin peaked amongst the health conscious when it was reported that it supports cellular functions of the body and acts as a key factor in maintaining hormonal balance and a healthy immune system, and any insufficiency could lead to all kinds of ailments from Alzheimer's, depression, cardiovascular diseases, osteoporosis to cancer and diabetes. Yet the major source of this vitamin remains the UVB radiation from the sun, the other being the edible sources such as fatty fish, especially salmon and tuna, egg yolks, mushrooms, cod liver oil, yogurt, and some cheeses.

Vitamin D assists calcium absorption from the gut. Vitamin D is also essential for the development and maintenance of bone. Old bone is removed (resorption) and new bone is created (formation). As you age, rate of formation slows down and resorption exceeds the rate of formation, which is how osteoporosis sets in. Vitamin D insufficiency leads to reduced bone mass, leading to osteoporosis and osteomalacia in adults and rickets in children.

Causes of Vitamin D Deficiency

Anything that diminishes the transmission of solar UVB radiation to the earth's surface or its penetration into the skin will affect the cutaneous synthesis of vitamin D3. The number of UVB photons that reach the earth's surface depend on the angle at which the sun reaches the earth. The zenith angle is more during the winter and in the early morning and late afternoon. This is the time when very little vitamin D3 synthesis occurs.

The skin pigment melanin markedly reduces vitamin D3 synthesis in the body. Therefore those with dark complexion or more melanin absorb lesser UVB than those with lighter skin. This is the result of centuries of evolution and adaptation to external environment. When you keep this factor in mind it is easy to see why a dark-skinned African living in temperate climates is more likely to be deficient in Vitamin D than his/her fair-skinned counterpart.

Similarly, if people following their cultural traditions of covering their bodies from head to toe were to live in Northern America, chances of their being deficient in the sunshine vitamin is enhanced. Or if they were to apply sun screen lotion with SPF 15 or higher, it would mean they are putting themselves at risk of Vitamin D deficiency, as the sunscreen lotion absorbs 99% of the incident UVB radiation.

Besides the indiscriminate and excessive use of sunscreen creams either to avoid sun tan or skin cancer, the obesity factor could be another cause for vitamin D deficiency. Since vitamin D is a fat-soluble vitamin, it gets stored in fat cells. So more the fat, lesser is the amount of vitamin D circulating in the bloodstream.

Other factors that influence the amount of UVB radiation that reaches the ground are clouds and tall buildings, ozone and aerosol pollution, altitude and reflective surfaces such as snow. Congestion in the cities and rising levels of pollution restrict penetration of UVB rays into the atmosphere.

Certain body disorders too can cause vitamin D deficiency. For example, liver/kidney disease could lead to impaired absorption of vitamin D. It is in the liver that Vitamin D from sunlight, plant sources and animal sources are all turned into 25-hydroxy (25-OH) vitamin D, also known as calcidiol. And it is in the kidney that Calcidiol is then is activated to its metabolically active and usable form (1,25-dihydroxyvitamin D) or calcitriol.


Bone Remodelling, Cause For Vitamin D Deficiency, Use Of Sunscreen, Vitamin D, Vitamin D Synthesis

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author avatar Uma Shankari
I write on society, relationships, travel, health, nutrition and fitness.
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author avatar Henry Lahore
19th Nov 2013 (#)

Between air conditioning. dark skin. and excessive clothing the lowest levels of vitamin D on the planet are now in the Middle East.

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