Sunscreen, shade and a side of deficiency
Published on 18 August 2025
We live in the tropics, yet many of us are still short on vitamin D. Here’s why – and what it really means for our health.
Singapore sees sunshine all year round. Yet, vitamin D deficiency remains surprisingly widespread across all age groups.
A 2019 study found that nearly one in three indoor workers in Singapore was vitamin D deficient. More recently, a 2024 study reported that only 2.2 per cent of pregnant women here had sufficient vitamin D levels.
According to Ms Rachel Cheang, Dietitian at the National University Polyclinics (NUP), our modern living habits play a major role. “Most of us spend the bulk of our time indoors,” she said. “Even when we do go outside, we tend to avoid the sun, whether to escape the heat or to protect our skin with umbrellas, sunscreen or long sleeves.”
Sunlight is the body’s main source of vitamin D. With limited sun exposure, production drops and the risk of deficiency rises.
How much sunlight is enough?
“Generally, we recommend 15 to 30 minutes of sun exposure daily on the arms and legs,” said Ms Cheang. “It’s best to do this outside the peak UV hours, before 10am or after 3pm.”
But lifestyle is not the only factor. Some people are biologically predisposed to produce less vitamin D from sunlight. “People with darker or tanned skin require longer sun exposure,” she explained. “Melanin reduces the amount of UVB rays that reach the skin, which, in turn, reduces vitamin D synthesis.”
Older adults are also more vulnerable. “The body’s ability to produce vitamin D declines with age,” said Ms Cheang. “When you combine that with decreased mobility or time spent indoors, such as in nursing homes or long-term care facilities, deficiency becomes more likely.”
Other at-risk groups include people who are bedbound, hospitalised or living with chronic conditions such as liver or kidney disease, Crohn’s disease, coeliac disease or short bowel syndrome.
The silent deficiency
One of the challenges with vitamin D deficiency is that it often goes unnoticed. “Mild deficiency is typically asymptomatic and usually only detected through blood tests,” said Ms Cheang.
When deficiency becomes more severe or prolonged, symptoms may include fatigue, bone pain, joint stiffness and muscle weakness. In children, it can impair bone development, causing rickets – with signs such as lethargy and irritability.
“If not addressed, deficiency can compromise bone health and increase the risk of osteoporosis,” Ms Cheang warned.
Beyond bones
Vitamin D is well known for its role in calcium absorption and bone metabolism. It was once commonly recommended for preventing falls and fractures in older adults – but that guidance has shifted.
In 2024, experts highlighted that current evidence is insufficient to confirm whether vitamin D supplements, taken alone or with calcium, effectively reduce the risk of falls or fractures. While vitamin D remains important, it is not a complete solution. Successful prevention also relies on adequate calcium intake, regular physical activity, and maintaining balance and muscle strength.
Still, vitamin D supports more than just bones. “It plays a key role in immune regulation, and promotes the production of antimicrobial peptides and regulatory T cells while reducing inflammation,” said Ms Cheang. “Deficiency has been linked to increased risks of infections, autoimmune conditions and allergies.”
It also affects the brain. “Vitamin D helps reduce oxidative stress and inflammation in the brain, and regulates receptors involved in mood and cognitive function,” she said. Low levels have been associated with a higher risk of depression and other neurological issues.
Can diet help?
While sunlight is the most efficient source of vitamin D, diet can still make a difference.
“Oily fish such as salmon and tuna are excellent sources,” said Ms Cheang. “Other options include cod liver oil, egg yolk and fortified foods like breakfast cereals, milk or plant-based milk alternatives, and margarine.”
Still, it can be difficult to get enough through food alone, especially for those with dietary restrictions or allergies.
“Supplements are useful for people who can’t meet their needs through food or sun,” said Ms Cheang. “But it’s important to consult a doctor first. A blood test can confirm if supplements are necessary and determine the appropriate dosage.”
Adults under 65 who get little sun should aim for 400 to 800 IU (10 to 20 micrograms) of vitamin D a day. Those aged 65 and above may need slightly more – up to 1,000 IU daily. The safe upper limit is 4,000 IU a day. To put that into perspective: One egg yolk has about 40 IU, a cup of fortified milk or soya milk has around 100 IU, and a small serving of salmon (about 85g) can contain 400 to 600 IU.
“Vitamin D is fat-soluble, which means it can accumulate in the body over time,” said Ms Cheang. “While acute toxicity is rare, long-term excessive intake can lead to health issues.” These include nausea, kidney problems and calcium imbalance.
What you can do
Keeping your levels healthy does not require a dramatic overhaul, just small and consistent habits.
“Include vitamin D-rich foods in your diet where possible,” said Ms Cheang. “And if you’re part of an at-risk group or have concerns about your vitamin D levels, speak to your doctor. A simple blood test can provide clarity and guide next steps.”
Even small decisions, such as drinking your coffee outdoors, walking instead of taking a taxi or choosing an outdoor seat at lunch, can help. After all, Singapore has no shortage of sunshine. The trick is letting just enough in.
The D-list: Easy ways to get more sunshine in your system
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In consultation with Ms Rachel Cheang, Dietitian, NUP.
