"Ô, Sunlight! The most precious gold to be found on earth.” – Roman Payne, exiled American novelist
A little daily dose of this freely available “gold” does wonders for our general wellbeing and is essential for vitamin D production.
Sunlight is the main source of ultraviolet (UV) radiation, even though UV rays make up only a small portion of the sun’s rays.
About 95% of the UV rays from the sun that reach the ground are UVA rays, while the remaining 5% are UVB rays.
Our skin also naturally contains a precursor (cholesterol) to vitamin D.
When the sun’s UVB rays touch the skin, they convert this precursor to a molecule called vitamin D3, which is carried to the liver and on to the kidneys to transform it to active vitamin D (calcitriol).
Vitamin D is necessary for strong bones and muscles, and preventing osteoporosis.
Without it, our bodies cannot effectively absorb calcium and phosphorus from the foods we eat, no matter how nutritious they are.
Despite Malaysia being located just north of the equator, with ample sunshine throughout the year, vitamin D deficiency is quite high among our population.
Local studies have found vitamin D deficiency to be prevalent among both Malaysian adults and children.
In a 2011 Universiti Malaya study on 380 urban Malays, more than 70% of the participants had insufficient vitamin D levels.
They tended to have darker skin, with most of the females adopting concealing dressing styles such as head scarves (hijab), long sleeves and long skirts, and worked indoors.
The authors reported that vitamin D insufficiency was also independently associated with younger age, female sex and greater abdominal obesity.
Says consultant orthopaedic surgeon Dr Yong Chee Khuen: “Apparently, the favourite pastime among Malaysians is window shopping in air-conditioned malls!
“We don’t go under the sun for many reasons: weather, sheltered transportation, metropolitan living i.e. high-rise dwellings with less open spaces, fear of getting tanned, wearing covered clothing and concerns of skin cancer risk from UVB over-exposure.
“When we were economically poorer, we walked to work and used bicycles to transport things.
“Now, we walk for exercise and we cycle for recreation.
“As we get more urbanised, we stay indoors most of the time.”
Call me Dracula
In cities like Seoul in South Korea, which have underground complexes that are connected to different buildings, people rarely go out in the sun.
The prevalence of vitamin D deficiency in 2008 was 51.8% in males and 68.2% in females.
With the current pandemic limiting outdoor activities, as well as fear of exposure to the SARS-CoV-2 virus that causes Covid-19, the medical fraternity is worried about an exacerbation of vitamin D deficiency.
“I’m no better – I call myself Dracula!” laughs Dr Yong.
“My children don’t get to see me – I leave for work early and get back when it is dark at night.”
Children who lack vitamin D develop a condition called rickets, which causes bone weakness, bowed legs and other skeletal deformities, such as stooped posture.
He explains: “Common causes of rickets are a lack of vitamin D from poor diet, low sun exposure, a genetic defect and prolonged exclusive breastfeeding as vitamin D is deficient in breast milk.
“Because the child cannot absorb calcium and phosphorus from his diet, his bones will not form properly, and will be softer and weaker as well.”
Dr Yong points out that children with vitamin D deficiency can be identified at different stages of their growth:
- During paediatric check-ups and when receiving their immunisation shots.
- During school health services provided by the Health Ministry at pre-school, Years One and Six, and Form Three.
- Indirectly from the nutritional status via height and weight measurements, and
- Directly from examination of any skeletal deformities.
Recognising the need for vitamin D, many countries, especially ones with limited sunshine, have added supplements into common food like flour, cereals and milk.
Naturally-occurring vitamin D in our diets can be obtained from fatty fish, tuna, egg yolk, beef liver and cod liver oil.
“In adults, vitamin D deficiency results in osteomalacia, which means our bones (skeletal matrix) are poorly mineralised.
“Adults may just complain of chronic muscle aches and pains.
“Often, it is clinically silent until they have a relatively trivial trip or fall close to the ground, resulting in osteoporotic fractures, ” explains Dr Yong.
On the bright side, bones will always heal – they need roughly two months to get “sticky”, another two months to unite and four more to become strong again.
He says: “Any bone takes the same amount of time to heal and the duration is only slightly faster in younger people.
“The important thing is to protect it from further damage.
“Age, being post-menopausal, diet, inactivity and lack of vitamin D can all contribute to osteoporosis.”
Like our Western counterparts, Asians, especially women, are equally vulnerable to osteoporosis, even though we live in sunny climates.
We are living longer, but not younger.
“More than a decade ago, if an adult came in with osteoporotic fractures in the weak areas, e.g. wrist joint, hip or spine, we only treated the fracture.
“Nowadays, if a patient has a trivial fall and has an atypical fracture that suggests osteoporosis, we further investigate by doing a bone scan, vitamin D test, etc.
“These tests are not normally included in executive health packages, but when there is a fracture, it can sometimes be too late.
“Just like an egg that looks nice on the outside, but cracks when it rolls off the table, ” says Dr Yong.
Hence, creating awareness is key.
Sitting under the sun
Extra vitamin D doesn’t cause any diseases as our bodies are auto-regulated to absorb only a certain amount from the sun.
Naturally, too much sunlight can be damaging, so do apply sunscreen if you’re out all day under the sun.
“Studies have shown that in light-skinned persons, full-body sun bathing until the skin turns slightly pink will result in vitamin D production of 10,000-25,000 IU (equivalent to ingesting roughly 20-50 vitamin D pills).
“Besides, vitamin D produced in the skin may last twice as long in the blood, compared with supplements ingested.
“The ones you ingest get excreted easily and the body may only absorb about 10%, ” he says.
Also, take note that taking too many vitamin D supplements over a long period of time can cause excess calcium build-up in the body (hypercalcaemia).
This can weaken the bones and damage the kidneys and the heart.
Vitamin D is a fat-soluble vitamin, meaning that it does not dissolve in water and is best absorbed in your bloodstream when paired with high-fat foods.
For this reason, it’s recommended to take vitamin D supplements with a meal to enhance absorption.
“I always encourage patients to go under the sun rather than take oral supplements unless the situation necessitates it.
“You always feel brighter and happier under the sun – it’s free!” says Dr Yong, adding that a healthy, balanced diet is also important in getting adequate doses of vitamin D.
Certain medical conditions such as Crohn’s disease, coeliac disease and cystic fibrosis, which affect the digestive track, also affect the absorption of vitamin D from the diet.
Strict vegan diets may result in vitamin D deficiency as most of the natural sources of vitamin D are animal-based.
“Mushrooms are the only good plant source of vitamin D.
“However, as farmed mushrooms are often grown in dark rooms and contain very little vitamin D, better choices would be wild-grown mushrooms or farmed mushrooms treated with UVB light, ” says Dr Yong.
He cites the case of an older patient who consulted him for terrible body aches.
Ever since the MCO was enforced last year (2020), she had stayed indoors and did not leave the house for a year!
But she said she would occasionally sit on the balcony to get some sun.
When probed further, she revealed that the balcony was shaded with glass, hence filtering out the UVB rays.
He recalls, “She had no major issues, but her blood test showed vitamin D deficiency, while the bone density test showed she had osteopenia.
“The patient quickly asked for oral supplements, but I said ‘No, there is no shortcut, get under the sun and do some weight-bearing exercises!’
“That said, older people also have thinner skin, which reduces the production of vitamin D.”
The short shadow rule
About 90% of this “sunshine” vitamin can be obtained just from sun bathing – without sunblock.
“At least 30% of our skin should be exposed.
“It’s most practical to expose a larger surface area such as the back, instead of just the upper and lower limbs.
“There is no need to expose your face, so you can use something to shield it.
“Also cover scar areas or recent injuries, ” advises Dr Yong.
For the appropriate time of day for the best vitamin D absorption, a simple method to follow is the shorter shadow rule.
Shadows are longest in the early morning and late afternoon/early evening when the sun appears low in the sky.
“The best time to get sunlight is around noon, when the sun is nearer to the earth.
“When the sun is at its highest point, its UVB rays are the most intense, so you need less time to make sufficient vitamin D.
“So, lighter-skinned people need to spend about 30 minutes, three times a week in midday sun, whereas a darker-skinned person needs 30 minutes to three hours in the sun.
“Darker-skinned people have more melanin pigment, which acts as a natural sunscreen against sunburn and skin cancer.
“Remember, if the shadow is longer than your height, it’s not effective in generating vitamin D, ” says Dr Yong.
However, any activity in the sun is encouraged, such as gardening, morning walks on working days and longer walks on weekends, and taking a walk outdoors during your lunch break, among others.
And leave your windows wide open to catch the UVB rays if you’re indoors.
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