When I was studying nutrition over ten years ago, we learnt that the function of vitamin D was to support the absorption of minerals like calcium and phosphorus. Nowadays, vitamin D is referred to as a hormone, as it is manufactured in our body from sunlight. Though we live in a sunshine-rich country, over 40% of Indians are estimated to be deficient in vitamin D.
Why vitamin D is important
Research suggests that maintaining adequate levels of vitamin D during pregnancy, nursing, infancy and childhood lowers the risk of the child developing Type 1 and Type 2 diabetes and auto-immune disorders. Vitamin D is also required for:
- bone and teeth mineralization
- optimal functioning of blood
- maintaining the acid-base balance
- thyroid functioning
- the maintenance of muscle strength
- brain development in children
- an efficient immune system
- an optimal functioning of cardiovascular and respiratory systems
- insulin production/regulation.
Low vitamin D levels in our body can be due to:
- Not getting at least 15 minutes of direct sun exposure daily, and remaining indoors during sunlit hours
- Covering up and applying sunscreen at all times, while outdoors
- A darker complexion (the more the melanin, the more the time needed for the skin to produce vitamin D)
- Being older than 50 years of age (capacity to produce vitamin D from sunshine reduces with age)
- Being obese or overweight
- High pollution levels in your city (smog reduces penetration of UVB rays)
- Being on a severe low-fat diet
Vitamin D deficiency can cause:
- Rickets, a disorder seen in children, where bones become soft and bend. In adults, deficiency leads to bone pain.
- Multiple sclerosis, a serious illness affecting nerve cells of the brain and spine, gradually making it difficult for a person to move, speak or see
- Type 1 & 2 diabetes
- Rheumatoid arthritis
- Auto-immune disorders in children and adults
- Asthma and respiratory infections, especially in children
- Several types of cancers
- Thyroid problems
Vitamin D test
A niggling back/joint pain may not be the only indicator of vitamin D deficiency. In fact, a lot of otherwise healthy adults and children have been found to have low vitamin D levels in blood. So if you want to test the vitamin D level in your body, get your serum D3 levels checked. If deficient in vitamin D, opt for supplementation under your doctor’s guidance.
- Of the different types of radiation from the sun, a specific wavelength of Ultra Violet B (UVB) rays are required for vitamin D production.
- Our bodies produce vitamin D when the sun’s UVB rays interact with 7-dehydrocholesterol (7-DHC) present in our skin.
- Using sunscreen reduces absorption of UVB by as much as 95% on that patch of skin.
- The best time for sun exposure is between 10:00 am and 3:00 pm, even on cloudy days.
- By exposing arms, hands, feet, neck and face to the sun, 25% of your skin’s surface will get to soak the rays.
- UVB rays do not pass through glass or clothes.
- The body can also store excess vitamin D in the liver and release the excess during periods when there is a lack of sunlight exposure (for example, during winter). But optimal exposure to the sun is important, and not overexposure.
- Overexposure can cause skinburn. The warning signs can be the skin turning a slight pinkish hue (for fair people). Constant skinburns can lead to skin cancer. The optimum limit for exposure is usually for 25% of the time it takes to turn the skin pink, after which sunscreens need to be used.
Ways to get more vitamin D
Take note: Do not stay for a long period under the sun without covering up or applying sunscreen.
The entire family can get exposed to sunshine to a minimum of twice a week without sunscreen for at least 15 minutes (or less if your skin burns easily). If you have a dark complexion, make it 20 minutes. Make this a conscious, regular practice. Make sure that you expose at least your arms, hands, neck, face and feet.
You can encourage your children to play outdoors. Many city schools lack playgrounds, so children are invariably indoors. You will have to work out a solution to expose them to the sun, at least during weekends and holidays. If your child’s school has included outdoor play, just make sure the child is not overexposed to the sun during the hottest time of the day or else your child may suffer from dehydration or sunstroke.
If you live in northern India, stock up on sunshine during spring, summer and autumn. In winter, except on foggy days, you should be able to catch some rays during peak daylight hours.
Take supplements only with your doctor’s consent and only in the dosage that is recommended.
Vitamin D sources
Unfortunately, foods are not a great source of this vitamin.
Some foods that are relatively high in vitamin D are:
- Cod liver oil
- Egg yolks
- Fatty fish like salmon, mackerel, herring, sardines
- Mushrooms (varieties like Shiitake)
Even for non-vegetarians, food intake can contribute only a maximum of 10% of our vitamin D requirement; so the main source still remains sunshine!
Smitha Suresh is a nutritionist from Chennai