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Why do we need vitamin D?

Bone health

Vitamin D helps your body absorb calcium from food and keeps calcium levels balanced in your blood. Without enough vitamin D, even a calcium-rich diet would not fully support bone strength.

Key roles of vitamin D in bone health

  • Helps your gut absorb calcium1
  • Supports healthy calcium levels in the blood1
  • Supports the process of bone renewal1

 

What happens if you don’t get enough

  • Children: risk of rickets (soft, weak bones)1
  • Adults: higher risk of osteoporosis and fractures1

Vitamin D helps keep your muscles strong and working properly. It supports the body’s use of calcium and other minerals needed for muscle contraction and movement. Low vitamin D levels can cause muscle weakness, making physical activities and balance more difficult.

 Key roles of vitamin D in muscle health
  • Helps your muscles contract by aiding calcium absorption2
  • Supports maintain muscle strength and coordination2
  • Lowers the risk of muscle pain and weakness, especially in older adults3
  • Improves balance to help prevent fractures4

What happens when vitamin D levels are low
  • Muscle aches and weakness
  • Poor balance and coordination
  • Increased risk of falls, which can lead to fractures
  • Difficulty with everyday activities like walking or climbing stairs

Vitamin D plays a role in helping your immune system work as it should. People with low vitamin D levels may get sick more often or take longer to recover from infections.

How vitamin D supports immunity

  • Helps regulate the immune system to respond effectively to infections6
  • Supports production of antimicrobial proteins that fight bacteria and viruses6
  • Helps control inflammation to protect the body from harm7
  • Contributes to both innate (first line) and adaptive (targeted) immune responses7

What research shows

Respiratory viruses such as COVID-19 and human metapneumovirus (HMPV) can cause serious illness, especially in vulnerable groups like children, older adults and those with weakened immune systems.

  • Observational studies link adequate vitamin D levels to a reduced risk of respiratory infections, including influenza and COVID-19.8
  • Low vitamin D status is associated with more severe infections, longer hospital stays, and increased need for intensive care.8
  • Vitamin D supplementation may reduce the severity of these infections by enhancing antimicrobial defenses and modulating inflammation but is not a cure or treatment.9

Vitamin D plays a role in helping the heart and blood vessels work well. Low vitamin D levels has been associated with some heart and circulation problems, although it is not fully clear if low vitamin D causes these issues.

How low vitamin D may affect heart health

  • May contribute to higher blood pressure by causing arteries to tighten10,11
  • Could increase inflammation that damages arteries and promotes plaque buildup10
  • Often linked to a less healthy cholesterol balance – higher “bad” LDL cholesterol and lower “good” HDL cholesterol


What research shows

  • Larger clinical trials have shown mixed results, with some indicating vitamin D supplements may slightly reduce major cardiovascular events, while others show no clear benefit.12
  • Experts emphasise that moderate amounts of vitamin D are important for heart health, but very high doses do not provide extra protection.13
  • Some studies suggest that adequate vitamin D combined with regular exercise may lead to a 23% lower risk of heart disease.14,15

Vitamin D receptors are found in many parts of the brain. Some studies suggest that low vitamin D levels may be linked to poorer memory and thinking, especially in older adults.16

What research shows
  • Evidence is mixed. Vitamin D is not a treatment for dementia or Alzheimer’s.17
  • More research is needed, but maintaining healthy vitamin D levels supports overall wellbeing.

Vitamin D supports skin cell growth and repair and may play a role in reducing inflammation. Some studies also suggest that low vitamin D is linked to hair shedding.

What research shows:

  • Skin: Vitamin D helps regulate skin cell turnover and immune responses.18 Low levels may worsen inflammatory skin conditions.
  • Hair: Some studies have linked vitamin D deficiency to hair thinning, though research is still ongoing.19
  • Beauty claims (anti-aging, ultraviolet protection, oil regulation) are not strongly proven – so they should be considered possible but not guaranteed.20-22

What to read next

References

References:

  1. Holick MF. N Engl J Med 2007;357:266-281.
  2. Ceglia L. Curr Opin Clin Nutr Metab Care 2009;12:628-633.
  3. Qi P, et al. Front Nutr2024:11:1450265.
  4. Rejnmark L. Ther Adv Chronic Dis 2011;2:25–37
  5. Latham CM, et al. Front Physiol 2021;12:660498.
  6. Grant WB, et al. Nutrients 2020;12:988.
  7. Martineau AR, et al. BMJ 2017:356:i6583.
  8. Bishop EL, et al. JBMR Plus2020;5:e10405.
  9. Su ST, et al. Front Immunol 2025;16:1625769.
  10. Martineau AR, et al. BMJ 2017:356:i6583.
  11. Haider F, et al. Cureus 2023;15:e49734.
  12. Gu, JW, et al. Medicine (Baltimore)2020;99:e19200.
  13. Khanolkar S, et al. Cureus 2023;15:e42470.
  14. Singapore Heart Foundation. Exercise and Vitamin D Go Together for Better Heart Health. Available at: www.myheart.org.sg/heart-news/exercise-and-vitamin-d-go-together-for-better-heart-health/. Accessed 25 Aug 2025.
  15. Man R E K, et al. Prevalence and Determinants of Suboptimal Vitamin D Levels in a Multiethnic Asian Population Nutr 2017; 9(3):313.
  16. Eyles DW. JBMR Plus 2020;5:e10419.
  17. Chen L, Ji HF. Nutr J 2015;14:76.
  18. Umar M., et al. Skin Pharmacol Physiol 2018;31:74-86.
  19. Mostafa WZ, Hegazy RA. J Adv Res 2015;6:793-804.
  20. Samanta, Saptadip. Vitamin D and immunomodulation in the skin: a useful affirmative nexus | Explor Immunol. 30 June 2021. Available at: https://www.explorationpub.com/uploads/Article/A10039/10039.pdf. Accessed 13 February 2023.
  21. Bocheva G, et al. Int J Mol Sci 2021;22:9097.
  22. Saini K, Mysore V. J Cosmet Dermatol 2021;20:3407-3414.