CHILDREN who spend too much time indoors are at risk of health problems due to a lack of vitamin D. Vitamin D deficiency is one of the risk factors for type 1 diabetes mellitus, multiple sclerosis, cancer, hypertension and insulin resistance.
A recent study conducted by the Health Ministry and Universiti Malaya revealed a high prevalence of vitamin D deficiency among those aged 12 to 13 years of age.
The study, published in the British Medical Journal (Open Access) last year, found that 78.9 per cent of the children in the study are vitamin D deficient, 1.5 per cent are severely deficient, and 13.7 per cent are vitamin D insufficient
Today’s children spend just over an hour each weekday outdoors and fewer than five hours on weekends. In comparison, children in the 1970s and ‘80s spent more than two hours outdoors each weekday and enjoyed nine hours of outdoor play on the weekends.
The study has also identified urban residents, females, Indians, those who are obese and not doing physical activities at a higher risk of vitamin D deficiency.
Urban residents, the obese and those who do not exercise are more likely to spend time indoors; with less exposure to sunlight. The higher incidence in females could be due to the more modest dress code observed by them.
Dark-skinned individuals require more exposure to sunlight to allow synthesis of vitamin D. This is because having more melanin in the skin soaks up UV radiation in sunlight, allowing less UV radiation to be available for synthesis of vitamin D.
This explains the higher level of vitamin D levels seen in Chinese compared to Indians and Malays observed in this study.
Vitamin D is essential for calcium absorption from food to gain strong and healthy bones and teeth. It is synthesised on exposure to ultraviolet light from a cholesterol-like molecule found in abundance in the skin.
It is also important for the normal functioning of brain, muscle, colon, breast, prostate and immune cells. People who have deficient vitamin D may develop soft and brittle bones, conditions known as rickets in children and osteomalacia in adults.
Vitamin D deficiency may remain asymptomatic unless significantly low levels continue for a period of time.
Screening for Vitamin D deficiency is recommended if you are at high risk — for example, with chronic kidney disease or malabsorption; on anticonvulsant medications (for epilepsy) or on medications for acquired immune deficiency syndrome (AIDS).
These conditions may cause severe vitamin D deficiency which requires replenishing vitamin D stores with high doses over a limited period of time. But this should be done only under medical supervision as there is a risk of possible hypervitaminosis D with prolonged use.
In healthy people, they should ensure adequacy of vitamin D through exposure to sunlight and diet. When you are out in the sun, leave at least some of the skin exposed to sunlight. Wearing shorts and T-shirts exposes about 40 per cent of the skin and should be sufficient to make a week’s requirement of vitamin D in less than 15 minutes of midday’s sun.
However, those with darker skin tone, aged 70 years or older, living away from the equator, who can be outdoors only in the morning or evening, who use sunblock outdoors and who customarily wear conservative clothing, require at least three to six times longer exposure to sunlight.
Experts recommend a daily intake of 600 IU (800 IU for those older than 70 years) from dietary or supplemental sources when sunlight is unable to provide it.
Vitamin D may be obtained from food like fatty fish (tuna, mackerel, salmon), beef liver, milk, cheese, tofu and eggs. Orange juice, soy milk, cereals and yogurt are also good sources when fortified with vitamin D.
Dr Benjamin Samraj Prakash Earnest
Dr Benjamin Samraj Prakash Earnest is a senior lecturer in Internal Medicine at School of Medicine, Taylor’s University.