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Want to Boost Your Immune System?
Try Vitamin D

What is the role of vitamin D?

Vitamin D is a fat-soluble vitamin. It is both a nutrient we eat and a hormone our bodies make.1 Vitamin D has long been known to help the body absorb and retain calcium and phosphorus; both are critical for building bone.1

In the last few years, there has been substantial debate on vitamin D’s role in being an important vitamin for immunity building. However, recent studies have observed that vitamin D has numerous effects on cells within the immune system which helps the body repair cell growth, control infections and reduce inflammation.2

How does vitamin D support the immune system?

Many people have insufficient levels of vitamin D due to lifestyle, location and other reasons. People with lower vitamin D levels are likely to have less immunity and are more susceptible to the common cold.3

Here’s how vitamin D lends support to your immune health:

Vitamin D modulates innate and adaptive immune response. Vitamin D’s ability to help support normal and healthy development of immune cells extends to adaptive immunity, as well. Adaptive immunity is one that develops when a person’s immune system responds to foreign substances. T immune cells, which are crucial in combating specific foreign particles, are helped by vitamin D.4

Vitamin D reduces respiratory tract infection by 12%. Vitamin D increases the anti-inflammatory and antiviral responses of cells in the respiratory system during respiratory viral infections.5 The respiratory tract extends from the trachea in your throat to your lungs.

The immune supportive actions of vitamin D have been recognised for over a quarter of a century, but it is only in the last few years that its significance has become apparent.6 There is increasing data linking vitamin insufficiency with prevalent immune disorders.

These observations suggest that vitamin D is a key factor that links innate and adaptive immunity, and both of these functions may be compromised under conditions of vitamin D insufficiency.7

Getting enough vitamin D may play a role in helping to keep you healthy.

Can vitamin D lower the effects of COVID-19?

It has been observed that vitamin D-deficient individuals have increased COVID-19 risk.9 Those who had adequate levels of vitamin D were 51.5% less likely to have adverse effects.10

Higher immunity - lower risk of COVID-19
Some studies have indicated that vitamin D supplements can work as an immune system booster. Vitamin D supplements help enhance immune response. However, there hasn’t been conclusive evidence to indicate vitamin D can prevent the occurence or treat COVID-19.11

Can you be vitamin D deficient in Asia?

Yes! Despite South East Asia having a reputation of being a tropical and sunny region, many here are deficient in vitamin D. Although the sun is prevalent, people in the region tend to avoid it. Sun-protection behaviours such as use of sunscreen, staying in the shade or indoors, wearing of long sleeves and using umbrellas are common practices in this region, all of which can lead to vitamin D deficiency.12

Studies have found that there is a:

  • 61% prevalence of vitamin D deficiency in Malaysian women13
  • 42% vitamin D deficiency among research participants in Singapore13
  • 32.9% prevalence of vitamin D deficiency among indoor workers in SIngapore12

How do you get vitamin D?

When your skin is exposed to sunlight, it manufactures vitamin D. The sun’s ultraviolet B (UVB) rays interact with a protein called 7-DHC in the skin, converting it into vitamin D3, the active form of vitamin D.14 We get most of our vitamin D from the sun’s rays (80%–100%) and only a small amount from our diet.

Vitamin D can be found in:15

  • fatty fish and oysters
  • beef liver
  • eggs
  • fortified cereals
  • juice
  • dairy products
  • supplements

How does vitamin D deficiency affect the immune system?

Adequate vitamin D benefits overall immune function and the health of specific immune cells.16

A lack of vitamin D may result in:18

  • frequent colds and flu
  • viral and bacterial respiratory diseases
  • asthma
  • hair loss
  • fatigue

What risk factors can lead to vitamin D deficiency?

Vitamin D deficiency can be caused by specific factors, such as:19

Age: As you age, your skin's ability to make vitamin D lessens.

Lifestyle: People who are homebound, sedentary, lower their exposure to vitamin D.

Skin tone: People with tanned / darker skin are protected by melanin and therefore less able to make vitamin D than fair skinned people.20

Diet: Vitamin D is not present in most plant-based foods. Most of the natural sources of vitamin D are animal-based.

Clothing: If you wear clothing that covers most of your skin, you may be at risk for vitamin D deficiency.17

Sunscreen: Experts believe that regular use of sunscreen can cause a vitamin D deficiency.20

What is the recommended daily intake of vitamin D?

How much vitamin D you need depends on many factors. These include:21

  • age
  • ethnicity
  • season
  • medical conditions
  • diet
  • sun exposure
  • clothing20

Generally, the recommended nutrient intake (RNI) for vitamin D is:21

RNI for adults:
Men 18 - 60 years - 5 µg/day or 200 IU
Women 18 - 60 years - 5 µg/day or 200 IU

RNI for elderly
Men 60 and above - 15 µg/day or 600 IU
Women 60 and above - 15 µg/day or 600 IU

How can you get your recommended dose of vitamin D?

Even if you live in the tropics with an abundance of sunshine, you can still be deficient in vitamin D due to various factors, such as lifestyle and other reasons. If your lifestyle and diet prevent regular, sufficient sun exposure or food sources of vitamin D, it is possible to improve your levels with vitamin and mineral supplements that contain sufficient vitamin D.


  1. Harvard School of Public Health. Vitamin D.
  2. National Library of Medicine. Vitamin D and immunity.
  3. National Library of Medicine. Back to basics: Review on vitamin D and respiratory viral infections including COVID-19. Mamtha Balla,a Ganesh Prasad Merugu,b Venu Madhav Konala,c Vikram Sangani,d Hema Kondakindi,e Mytri Pokal, Vijay Gayam,f,i Sreedhar Adapa,g Srikanth Naramala,h and Srikrishna V Malayalah. Published online 2020 Oct 29. doi: 10.1080/20009666.2020.1811074
  4. Sage Journals. Vitamin D regulation of the immune system and its implications for COVID-19: A mini review. First Published May 18, 2021
  5. Cambridge University Press. Vitamin D and immune function: an overview
  6. Cleveland Clinic. Vitamin D Deficiency.
  7. National Library of Medicine. Does vitamin D deficiency increase the severity of COVID-19? E Kenneth Weir, professor of medicine,A Thenappan Thenappan, associate professor of medicine,B Maneesh Bhargava, associate professor of medicine,C and Yingjie Chen, professor of physiologyD. Clin Med (Lond). 2020 Jul; 20(4): e107–e108. doi: 10.7861/clinmed.2020-0301.
  8. Plos One Journals. Vitamin D sufficiency, a serum 25-hydroxyvitamin D at least 30 ng/mL reduced risk for adverse clinical outcomes in patients with COVID-19 infection.
  9. Mayo Clinic. Can vitamin D protect against the coronavirus disease 2019 (COVID-19)?
  10. Straits Times Singapore. Abundant sunshine in Singapore, but more than 30% here have vitamin D deficiency: Studies
  11. National Library of Medicine. An Update on Vitamin D Deficiency Status in Malaysia,lowest%20mean%20vitamin%20D%20level.
  12. Frontiers. Impact of vitamin D on immune function: lessons learned from genome-wide analysis
  13. Quah SW, Abdul Majid H, Al-Sadat N, Yahya A, Su TT, Jalaludin MY (2018) Risk factors of vitamin D deficiency among 15-year-old adolescents participating in the Malaysian Health and Adolescents Longitudinal Research Team Study (MyHeARTs). PLoS ONE 13(7): e0200736.
  14. National Library of Medicine. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Adit A Ginde 1, Jonathan M Mansbach, Carlos A Camargo Jr. PMID: 19237723 PMCID: PMC3447082 DOI: 10.1001/archinternmed.2008.560.
  15. National Library of Medicine. Vitamin D and Immune Function. Barbara Prietl, Gerlies Treiber, Thomas R. Pieber, and Karin Amrein. Published online 2013 Jul 5. doi: 10.3390/nu5072502
  16. Cleveland Clinic. What other factors can lead to vitamin D deficiency?
  17. National Library of Medicine. Effect of clothing on different dress styles on vitamin D levels in healthy young Jordanian women. AA Mishal 1. PMID: 11804019. DOI: 10.1007/s001980170021
  18. National Library of Medicine. Effect of sunscreen on Vitamin D. R E Neale 1, S R Khan 1, R M Lucas 2, M Waterhouse 1, D C Whiteman 1, C. PMID: 30945275 DOI: 10.1111/bjd.17980 M Olsen 1
  19. Mayo Clinic. Vitamin D.
  20. National Library of Medicine. BMC Public Health. 2014; 14: 597. Published online 2014 Jun 12. doi: 10.1186/1471-2458-14-597,synthesis%20than%20light%2Dskinned%20ones.
  21. Ministry of Health Malaysia. Vitamin D.