Vitamin in Winter

No Sun and no Sunshine

Dr M Shafi Kuchay
Srinagar, Publish Date: Dec 12 2017 10:33PM | Updated Date: Dec 12 2017 10:33PM
Vitamin in WinterFile Photo

Winter in North India has already set in. You are lucky if you get some sunshine. But I am sure you won’t get an iota of sunshine vitamin. This is because the required ultra-violet radiations (UVB photons; 290-315 nm) in sunlight that make vitamin D in your skin are almost absent in winter.

Vitamin D or sunshine vitamin is in fact a hormone that mainly controls calcium and phosphorus absorption in the intestine of your body. Therefore, this is essential for healthy bones. Long-term vitamin D deficiency causes problems in bones. When vitamin D deficiency occurs in children, it leads to weak and soft bones, deforming of bones, and short stature. This is because the bones in children are in growing phase. When vitamin D deficiency occurs in adults, it leads to bony pains, weak muscles, soft and easy to break bones. Research over years has showed that vitamin D may be beneficial to body in many other ways, like prevention of autoimmune diseases, cancers, cardiovascular diseases and prevention of various infections. However, these  diverse functions of vitamin D are not proved yet. 

There are many forms of vitamin D circulating in the blood. Serum 25(OH)D is one form that is useful for estimating vitamin D stores in your body. This form of vitamin D can easily be measured in many laboratories. The measurement of other forms of vitamin D are usually not needed.

Like many scientific questions, vitamin D has its own controversies and debates. The most important debate is about the adequate levels of vitamin D that is optimal for your body. To address this debate, broadly speaking, world scientific community is divided into two groups. For convenience, we can put them into conservative lobby and liberal lobby. The conservative lobby says that serum 25(OH)D levels up to 12.5 ng/mL is enough for bone health and levels up to 20 ng/mL is enough for over-all health of an individual. According to this lobby, levels above 50 ng/mL is not needed for any benefit to an individual. The liberal lobby, on the other hand, defines vitamin D deficiency as serum 25(OH)D levels below 20 ng/mL. According to this lobby, Levels above 30 ng/mL is required for over-all health of an individual and levels up to 100 ng/mL is generally safe.

 Even if you agree with the conservative view point, still more than 30 percent  individuals have levels below 12.5 ng/mL, and more than 75 percent individuals have levels below 20 ng/mL in any season. The proportion of deficiency is worse in winter because of lack of sunshine and indoor lifestyle. Vitamin D deficiency has been reported from India across all age groups: pregnant women, newborns, children and adolescents, young adults, and older men and women.

Why do we have so much of vitamin D deficiency in the community? The reasons are many. One of the important reasons is that it is not present in adequate amounts in most of the food items that we consume regularly. For instance, it is only present in oily fish (cod liver oil) in sufficient amounts. All other food items either have very little amounts or not at all. In developed world, many food items of regular use like milk, curd, yogurt, cereals and oils are fortified with vitamin D. These fortified foods are important sources of vitamin D in those countries. Unfortunately, vitamin D fortified foods are not yet available in our country.

Another important reason for vitamin D deficiency is our indoor lifestyle. As you know, early humans evolved near the equator, where sun exposure is intense year round, and minimally clothed people spent most of the day outdoors. Most people in the modern world have lifestyles that prevent them from acquiring sufficient vitamin D levels. As a species, we do not get as much sun exposure as we used to get thousands of years ago. The best time for vitamin D production in the skin is from 11:00 am to 3:00 pm in summers, as the sun radiation has maximum amount of UVB photons. We hardly expose our skin to sun at that time. Even if we expose face and hands to sunlight at that time, most of us use sunscreens. The skin’s vitamin D production falls drastically with as little as a 15-SPF sunscreen use (blocks more than 98 percent UVB photons).

Atmospheric pollution is another factor contributing to vitamin D deficiency. Pollution in the air hinders UVB photons in the sunlight from reaching the earth’s surface. 

Now what to do to raise your vitamin D levels in the blood. The best method of obtaining sufficient amounts of vitamin D in the body would be through regular sun-exposure. But in winter, this is simply not possible. As we have almost no vitamin D fortified foods available in our country, the only option left for us is supplementing vitamin D through pharmacological preparations. Many vitamin D preparations are commercially available. The safe dose would be 1000-2000 IU daily. You can also consume equivalent monthly dose (30,000-60,000 IU). For consuming this much of vitamin D, you do not need to get your vitamin D levels measured. This vitamin D supplementation has to be ongoing, till you find any reliable source of vitamin D, either from regular sun exposure or from fortified food items.    

The author is a Consultant Endocrinologist at Medanta-The Medicity Hospital, Gurugram, India.