Vitamin D deficiency is common and may have been exacerbated with the Pandemic. Dr Charu explains all about Vitamin D, why its essential for healthy living, which groups are more likely to deficient and how much time you need in sunshine to get your levels up.

The prevalence of deficiency amongst indoor workers in Singapore is estimated to be about 30% as per a study in 2019. It’s possible that the pandemic restrictions in the past 18 months have caused more people to become deficient due to working from home and staying indoors.

How does one get their Vitamin D?

The sunshine vitamin, as it is called, is primarily produced from cholesterol in the skin on direct exposure to UVB sunlight. It goes through some steps in the liver and kidneys to change to its most effective form. A small amount of Vitamin D is obtained from foods such as egg yolks, oily fish, milk and fortified foods.

What is the role of Vitamin D in health?

The best-known role of this vitamin is to ensure absorption of calcium and phosphorus from the bowel to support bone and muscle health. Poor calcium levels lead to weak bones that can fracture easily (osteomalacia or osteoporosis). Rickets, a similar disease in growing children, is no longer common since many foods began to be fortified with Vitamin D.

There is ongoing research on some interesting roles of this vitamin.  It is proposed that Vitamin D may play an anti-inflammatory role in autoimmune conditions (such as thyroid disease and rheumatoid arthritis), and in prevention of diabetes and cardiovascular disease. It may also reduce asthma exacerbations and improve respiratory immunity. Adequate Vitamin D in patients with cancer can lower the risk of metastasis and progression to advanced cancer. By contrast, Vitamin D deficiency can adversely affect pregnancy outcomes.

What symptoms could be caused by low Vitamin D?

Symptoms of deficiency can be easily overlooked; they include bone pain, fatigue, and muscle aches. Recurrent upper respiratory tract infections and poor immunity may be present. Falls, fractures and weakness are commoner in Vitamin D-deficient elderly patients.

If one frequently spends time outdoors, could they still be deficient?

 Vitamin D production in the skin depends of the time of the day, season, skin colour, amount of exposed skin, use of sunscreen and existing medical problems. Risks of skin aging and skin cancer need to be balanced carefully.

Darker-skinned races with higher melanin pigmentation have less effective Vitamin D production in the skin. Night shift and indoor workers are at higher risk; so are those who reside in temperate regions with shorter summer months.

Vulnerable groups also include the elderly, those in residential homes, pregnant women and exclusively breastfed infants. Vegans or those on very restrictive diets, poor absorbers of Vitamin D due to a bowel disease or poor converters (liver and kidney disease) should consider regular supplementation. Vitamin D is sequestered in fat – hence obese people can be prone to deficiency.

Certain medications – statins being an important one – can also affect cholesterol synthesis and Vitamin D production.

How can one improve their Vitamin D levels?

Getting out in the sun for around 20 minutes a day can help boost Vitamin D levels. However, the risks of skin aging and skin cancer need to be balanced carefully. Oral supplementation in safe amounts and fortified foods are the recommended method to treat deficiency.

As per Singapore guidelines, as a country with strong sunshine, the recommended dietary allowances of Vitamin D are 400 IU in children up to 7 years of age, 100 IU in 7-18 year olds, and 200 IU in over-18s. Pregnant and lactating women need 400 IU daily. This figure is higher in western countries with variable sunlight exposure through the year.

UK guidelines suggest a daily supplemental dose of 400 IU (10 mcg) of Vitamin D from October to March. However, darker-skinned races, indoor workers and others at high risk as mentioned above should take 400 IU as a supplement throughout the year. Babies under a year old who are exclusively breastfed or consume less than 500 mL of formula per day should also take 400 IU of Vitamin D daily. Children between 1 and 4 years old are also advised to take 400 IU of Vitamin D a day. Guidelines vary in different countries due to variation in climates.

Is routine testing required?

Routine testing is not advised unless the person belongs to a previously mentioned high-risk group or is experiencing symptoms. Doses to treat deficiency may be higher and initial monitoring may be required.

There remains a lot of controversy about ideal Vitamin D levels and research around its multisystem effects continues to evolve.


Dr Charu Narayanan is a UK trained doctor based in IMC Katong. Dr Charu has a Diploma in Practical Dermatology and approaches disease in a holistic fashion and places emphasis on prevention.

Call 65 3163 4343 or visit



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