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OTHERS :

Do you find yourself feeling exhausted and experiencing chronic pain even after a good night’s rest? Maybe you need a dose of the “sunshine vitamin".

Produced by the skin when it soaks up the sun’s ultraviolet (UV) rays, vitamin D has several important functions in the body, the main one being regulation of calcium and phosphorus levels in the blood, vital for maintaining healthy bones. It also helps ward off respiratory infections such as flu, cough and cold. Lack of vitamin D can suppress immunity, impede weight loss, cause bone pain, weakness, muscle pain, hair loss, and even lead to disturbed sleep. In children, low vitamin D levels can lead to the softening of bones, which can lead to bow-legs and knock knees.

A change in lifestyle—primarily lack of exposure to sunlight—is one of the main reasons why cases of vitamin D deficiency are on the rise. According to a Harvard School of Public Health study, one billion people worldwide suffer from vitamin D deficiency. In India, deficiencies can be found in 70 out of 100 people.

The two main ways to ensure you are getting adequate amounts of vitamin D are by exposing your bare skin to sunlight and by taking vitamin D supplements. While eating the right foods can be helpful, it won’t necessarily give you the right amount of vitamin D that your body needs—there isn’t enough present in food to replenish deficiencies.

Time in the sun

When it comes to sun exposure, things get tricky. While the sun is the best natural source of vitamin D, exposure to UV radiation is also one of the major causes of skin cancer. So how much sun exposure is “enough" to get an optimal dose of vitamin D but not so much that it can lead to cancer?

For starters, you need to know that the sun does not create vitamin D in your body; rather, UV radiation converts the vitamin D in your skin to its usable form. How much is produced depends on a range of factors, including:

■ Level of UV radiation: The amount of sun received at any location is dependent on the angle at which it strikes Earth. When the sun slants, the light travels through more ozone before reaching Earth’s surface, which in turn reduces UVB exposure at the surface (the three types of ultraviolet radiation—UVA, UVB and UVC—are classified according to their wavelength). UVB rays are the primary source of vitamin D.

■ Time, year and location: The level of UV radiation varies with the time of day and year. It’s weakest when the sun slants, which is during the early and later parts of the day, and during most of the day in winters. So the closer to midday you expose your skin, the better it will be for vitamin D production.

A good rule of thumb is to see if your shadow is longer than you are. If it is, you’re not synthesizing enough vitamin D. Also, the place where you live also affects your UVB-level exposure. People who live closer to the equator can synthesize vitamin D from sunlight all year round.

■ Weather conditions: Cloud cover and air pollutants absorb and scatter UV rays, and reduce the amount of UV radiation that reaches us.

■ Skin colour: Pale skin makes vitamin D more quickly than darker skin, as the latter has more melanin, which blocks absorption. If you’re fair-skinned, you’ll need 20 minutes of sun exposure to direct sunlight three-four times a week for your body to produce adequate amounts of vitamin D. Those with darker skin require 30-40 minutes of exposure three-four times a week. In winter, you may need to spend almost double this time in the sun. Prolonged sun exposure won’t raise your vitamin D levels further; it can, however, increase your risk of skin cancer.

The more skin you expose, the more it absorbs. It is not specific or dependant on any body part. But at least face, arms and shoulders should be exposed.

■ Age: Older people are less able to produce vitamin D, with middle-aged adults having just 66% of the vitamin D-production potential that children have—largely because age often reduces mobility and restricts solar exposure.

It’s important to remember that glass blocks all UVB rays, so your body won’t produce vitamin D if you are in sunlight, but behind glass.

Some foods can be a natural source of vitamin D too. Oily fish like sardines and mackerel, eggs, red meat and organ meats, for instance, contain enough amount of vitamin D to maintain levels, but not enough to take care of deficiencies.

Most people can take vitamin D supplements without any problem. Consult a doctor who may prescribe daily, weekly or monthly capsules, or vitamin injections, after a blood test to determine existing levels.

Vishakha Shivdasani is a Mumbai-based medical doctor with a fellowship in nutrition. She specializes in controlling diabetes, cholesterol and obesity.

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