Vitamin D is a fat-soluble vitamin that has been widely recognised for its role in maintaining bone and muscle strength. It is not a nutrient in the usual sense since, under normal conditions, it is supplied mainly by the skin. It is essential for enhancing calcium absorption in the gut and regulating calcium and phosphate concentrations in the blood to promote normal bone mineralisation.

Yet there’s more – so much more. Many medical researchers, such as Professor Bruyere (a member of the Scientific Advisory Board of the ESCEO*), Dr Michael Holick (Professor of Medicine, Physiology and Biophysics at the Boston University Medical Centre) and Professor Rebecca Mason (from University of Sydney), agree that there is accumulating evidence that adequate vitamin D also protects against certain cancers, particularly breast, prostate and colon cancer, helps to prevent auto-immune diseases, such as multiple sclerosis, Type 1 diabetes, inflammatory bowel disease and rheumatoid arthritis, plus decreases the risk of high blood pressure, Type 2 diabetes, susceptibility to infection as well as reducing overall mortality including cardiovascular mortality.

*European Society on Clinical and Economic Aspects of Osteoporosis and Osteoarthritis

“Vitamin D plays an essential role for the growth and maintenance of a healthy skeleton. Consequently, low vitamin D level could impact bone health,” says Prof Bruyere, citing osteoporosis as a common condition that can develop due to vitamin D deficiency.

If there is mild to moderate vitamin D deficiency, calcium absorption is impaired, which can result in decreased bone density and muscle strength, and an increase in fractures. Multiple studies have linked vitamin D deficiency with falls and fractures in both women and older men. If the deficiency is severe, osteomalacia (soft bones) can develop in adults as well as rickets (bone malformations such as bowed legs and knocked knees) in children.

“Moreover, many studies have suggested that low vitamin D status could increase the risk of various diseases such as cancer, osteoarthritis, sarcopenia or cardiovascular diseases,” explains Prof Bruyere, who is also currently teaching at Belgium’s University of Liege’s Department of Public Health, Epidemiology and Health Economics.

“Outside specific medical conditions, the two main reasons are low sunshine exposure and low vitamin D intake,” says Prof Bruyere.

“Despite their high level of sunshine, the proportion of Singaporeans with low vitamin D level is similar to what could be observed around the world,” he continues. “We can consider that more than 60 per cent of the general population do not have an optimal level of vitamin D and that this proportion increases with age.”

With our long working hours spent mainly in office buildings, and our propensity to slather on sunscreen, it’s actually not really surprising that we’re vitamin D deficient, if you really think about it.

The Recommended Dietary Intake (RDI) of vitamin D is 5 to 15 micrograms per day (200-600 International Units (IU)). The amount varies depending on age:

Children of all ages – 5mcg (200 IU)
Males and females 14 -50 yrs – 5mcg (200 IU)
Males and females 51-70 yrs – 10mcg (400 IU)
Males and females >70 yrs – 15mcg (600 IU)

“Most of the international guidelines suggest that infants and all subjects aged 65 years or older should receive a supplementation with vitamin D,” says Prof Bruyere. “For the rest of the population and more particularly in patients with diseases (e.g. cancer, high cardiovascular risk, endocrine or immunologic disorders), it should be a discussion between the patient and the medical doctor.”

According to Prof Bruyere, groups most vulnerable to developing vitamin D deficiency are those who have low sun exposure (these may be people who work long hours indoors or who smother themselves in sunscreen), those who have a high body mass index, the frail elderly, those who eating little fish or have a major disorder impacting vitamin D absorption. For the elderly, those in nursing homes or hospitals may be particularly at risk.

Others at risk are those who, for religious or cultural reasons, cover up and do not expose their skin to the sun and people with dark skin because melanin reduces the amount of UV radiation getting through the skin.

READ MORE: 7 Common Nutrient Deficiencies in Women

If you have some form of malabsorption, such as coeliac disease, cystic fibrosis or inflammatory bowel disease, it may be worth checking your vitamin D levels. New research is suggesting that obesity may also be a risk factor for low vitamin D levels as the vitamin is fat soluble and becomes trapped in fat tissue and is unable to perform its functions.

The best way is to take a blood sample to assess your vitamin D status, says Prof Bruyere, although it may not be the most cost effective way.

“Regarding pregnant women, an optimal vitamin D status is also recommended since it could have some positive impacts on the bone health of mother and baby,” says Prof Bruyere.

The children of mothers who are mildly vitamin D deficient are doubly at risk. Breast milk is a poor source of vitamin D – even more so if the mother has poor vitamin D status – and if the child is wrapped up constantly and kept out of the sun.

READ MORE: Prunes, Eggs And 8 Other Foods Every Pregnant Woman Should Eat

The main source of vitamin D is from sun exposure. The UV rays convert pre-vitamin D in the skin to vitamin D3. This conversion is reduced by 95 per cent when we use sunscreen and reduced by 70 per cent as the skin ages.

You can also get some vitamin D from food. “However, most diets are low in vitamin D,” explains Prof Bruyere. “Among the vitamin D-rich foods, oily fish, such as salmon, are considered to be one of the best sources. However, it is almost impossible to reach the recommended vitamin D intake from food as it would correspond to eating more than 100 g of salmon every day.”

READ MORE: 27 Easy Ways You’ve Never Thought To Cook Salmon

The challenge exists to balance the need for sun exposure against the risk of skin cancer. The current advice is to expose your skin to the sun safely, exposing only your face, arms and hands. According to a Straits Times report, the best time to get vitamin D from sunlight is at midday when the sun is overhead, as there is maximum UVB light to promote the vitamin’s formation. Prof Bruyere recommends only 10 to 30 minutes of midday direct sunlight exposure.

Those with a lighter skin tone need about 15 minutes a day, while those with darker skin tones may need one hour or more. Out in the sun, the body knows when it has enough and will stop vitamin D formation.

However,  sitting by a window indoors will not help as glass filters out UVB rays (but NOT UVA rays which penetrate deeper and are harmful to your skin).

Besides sunlight exposure and food intake, Prof Bruyere suggests taking a vitamin D supplement, with advise from your doctor of course. Typical consumer products with 800-1000IU may be useful for people who are not vitamin D deficient, but may not provide enough dosage for deficiency patients.

Luckily, the Health Sciences Authority (HSA) recently approved a new prescription treatment called D-Cure, which gives patients a boost of 25,000 IU of vitamin D3. Available in hospitals and clinics here, Prof Bruyere says that “based on clinical studies, D-Cure is clinically proven to increase patients’ vitamin D levels from deficiency to sufficiency level over a two-month period”.

“With the current doses of vitamin D recommended by scientific societies (one should not exceed a long-term dose of more than 10,000 IU/day), the risk of experiencing an adverse effect is very limited,” Prof Bruyere explains. “Once again, the need for supplementation must be discussed with the medical doctor.”

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