Among the ‘alphabet’ vitamins, vitamin D1 ranks high in its importance because it is one of the nutrients with one of the highest rates of deficiency (together with vitamin A2 and vitamin B121) in modern society, which has significant health implications.

Factors such as decreased exposure to ultraviolet (UV) rays due to broad-spectrum sunscreens and less time spent outdoors (50-90% of vitamin D is absorbed through the skin via sunlight)3, lower dietary intakes, and and poor absorption due to common digestive issues such as celiac disease, inflammatory bowel disease (IBD), chronic pancreatic insufficiency, and cystic fibrosis, among others3, all contribute to the rising prevalence of vitamin D deficiencies.

READ MORE | Spray Vitamin Deficiencies Away With Sublingual Supplements

Down on vitamin D

We need adequate vitamin D for optimal bone health, as it regulates calcium absorption, and proper immune function.

This important vitamin also regulates the expression of genes across at least 160 pathways that have a wide variety of biologic functions4, and plays an important role in human development in the womb5, 6.

When we don’t get enough vitamin D, we can experience numerous health-related issues. For instance, vitamin D deficiency is associated with rickets in children and osteoporosis in adults, as well as cancer, cardiovascular disease, diabetes, autoimmune diseases, and depression3.

READ MORE | 5 Vitamins And Minerals That Could Boost Your Immune System

Broad health benefits

Emerging research continues to affirm vitamin D’s essential role in human health and continually expands the list of conditions and diseases that are linked to deficiency.

For example, a study7 published in 2023 that gave 60 000 IU per month of vitamin D3 to half of the 21 302 elderly (aged 60-84) participants in the study (the other half received a placebo) determined that: “Vitamin D supplementation might reduce the incidence of major cardiovascular events”.

This finding was echoed in another 2023 study8 published in the American Heart Journal, which found taking higher-than-recommended doses of vitamin D for five years reduced the risk of atrial fibrillation in older men and women.

And a meta-analysis published in 2021 in the journal Nature Reviews Endocrinology9, affirmed the need to correct severe vitamin D deficiencies, as research reviewed in the analysis showed that supplementation of individuals with vitamin D deficiency modestly delays age-related bone loss and progression to T2DM, and improves lung function” and that “vitamin D supplementation results in a modest decrease in cancer mortality”.

In relation to vitamin D’s link to reduced cancer risk, researchers from the University of Eastern Finland and Kuopio University Hospital observed fewer cases of melanoma among regular users of vitamin D supplements than among non-users. The findings were published in the journal Melanoma Research10.

And there are potential brain benefits, too, as findings from a recent large-scale study11 suggest that taking vitamin D supplements may help ward off dementia.

When researchers at the University of Calgary’s Hotchkiss Brain Institute in Canada and the University of Exeter in the UK explored the relationship between vitamin D supplementation and dementia, the team found that taking vitamin D was associated with living dementia-free for longer, and that the group who took supplements experienced 40% fewer dementia diagnoses.

READ MORE | Brighten Up Your Health With Vitamin D

Boosting vitamin D levels

Your body primarily creates vitamin D through direct sun exposure by synthesising cholesterol via the action of sunlight on a form of vitamin D contained in the skin called cholecalciferol (also known as vitamin D3), which is then stored in the body as it is a fat-soluble vitamin.

We also get vitamin D from dietary sources including egg yolks, beef liver, and fatty fish such as tuna, herring, mackerel and salmon, as well as fortified dairy and cereal products.

In supplement form, vitamin D is available in capsule or tablet form, most commonly as vitamin D3 (cholecalciferol). These products aim to increase circulating vitamin D levels.

We also have the option to use a sublingual spray to deliver vitamin D directly into the bloodstream to boost levels as it diffuses through tissues under the tongue, an area rich in blood vessels.

As vitamin D requirements are highly individualised, any recommended supplemental approaches should be determined in consultation with a qualified healthcare practitioner.

Tips to boost vitamin D levels:

  • Boost skin to the sun’s ultraviolet rays for a few minutes each day. Optimal durations vary depending on skin type.
  • Get this ultraviolet exposure as near to solar noon as possible – generally between 10h00 and 14h00.
  • Add more vitamin D-rich foods to your daily diet.
  • Supplement with vitamin D3 products if additional support is required.


  1. Knapik, J.J. Farina, E.K. Et al. Clinically-diagnosed vitamin deficiencies and disorders in the entire United States military population, 1997–2015. Nutr J. 2021; 20: 55. Published online 2021 Jun 15. doi: 10.1186/s12937-021-00708-
  2. World Health Organization. Micronutrients Overview.
  3. Omeed Sizar; Swapnil Khare; Amandeep Goyal; Amy Givler. Vitamin D Deficiency. National Library of Medicine. Bookshelf ID: NBK532266PMID: 30335299.
  4. Arash Hossein-nezhad, Avrum Spira, Michael F. Holick. Influence of Vitamin D Status and Vitamin D3 Supplementation on Genome Wide Expression of White Blood Cells: A Randomized Double-Blind Clinical Trial. PLoS One. 2013; 8(3): e58725. Published online 2013 Mar 20. doi: 10.1371/journal.pone.0058725
  5. Wagner, C.L.. Hollis, B.W. The Implications of Vitamin D Status During Pregnancy on Mother and her Developing Child. Front Endocrinol (Lausanne). 2018; 9: 500. Published online 2018 Aug 31. doi: 10.3389/fendo.2018.00500
  6. Sucksdorf, M. Brown, A.S. Et al. Maternal Vitamin D Levels and the Risk of Offspring Attention-Deficit/Hyperactivity Disorder. Journal of the American Academy of Child & Adolescent Psychiatry. Volume 60, Issue 1, January 2021, Pages 142-151.e2.
  7. Thompson, B. Waterhouse, M. English, D.R. Et al. Vitamin D supplementation and major cardiovascular events: D-Health randomised controlled trial. BMJ 2023; 381:e075230.
  8. Jyrki K. Virtanen, Sari Hantunen, Christel Lamberg-Allardt, JoAnn E. Manson, Tarja Nurmi, Matti Uusitupa, Ari Voutilainen, Tomi-Pekka Tuomainen. The effect of vitamin D3 supplementation on atrial fibrillation in generally healthy men and women –the Finnish Vitamin D Trial. American Heart Journal, 2023; DOI: 10.1016/j.ahj.2023.05.024
  9. Bouillon, R., Manousaki, D., Rosen, C. et al. The health effects of vitamin D supplementation: evidence from human studies. Nat Rev Endocrinol 18, 96–110 (2022).
  10. Emilia Kanasuo, Hanna Siiskonen, Salla Haimakainen, Jenni Komulainen, Ilkka T. Harvima. Regular use of vitamin D supplement is associated with fewer melanoma cases compared to non-use: a cross-sectional study in 498 adult subjects at risk of skin cancers. Melanoma Research, 2022; Publish Ahead of Print DOI: 10.1097/CMR.0000000000000870
  11. Maryam Ghahremani, Eric E. Smith, Hung‐Yu Chen, Byron Creese, Zahra Goodarzi, Zahinoor Ismail. Vitamin D supplementation and incident dementia: Effects of sex, APOE , and baseline cognitive status. Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, 2023; 15 (1) DOI: 10.1002/dad2.12404