Fact or fiction: The impact of vitamin D on 3 common diseases

The Bottom Line

  • Vitamin D is a popular and widely available supplement that has been studied for the treatment and prevention of a variety of diseases.
  • In children and adults with mostly mild to moderate asthma, vitamin D supplementation doesn’t appear to reduce the risk of severe asthma attacks or improve symptom control.
  • In people who are at average risk of diabetes, vitamin D supplementation doesn't appear to lower the risk of developing type 2 diabetes but may hold benefits for people with prediabetes.
  • In healthy populations, vitamin D plus calcium may not decrease the risk of lung cancer incidence or lung cancer death.
  • The decision to start or stop a taking supplement should always be made in consultation with one’s healthcare team.   

Vitamin D, vitamin D2, vitamin D3, the “sunshine” vitamin. No matter what form it’s in or what name you know it by, when it comes to discussions about vitamins and supplements, vitamin D is sure to be thrown into the mix. Asthma treatment, diabetes prevention, and lung cancer prevention are just a few of the many areas where the potential role of vitamin D has been researched (1-3). But is vitamin D an effective strategy for this diverse range of outcomes? Click on the links below to learn more about where vitamin D may work and where it falls short.  

1. Asthma   

Globally, over 260 million people live with asthma, a chronic disease characterized by tightness in the chest, coughing, wheezing, and difficulty breathing (1;4). Research suggests that compared to placebo, vitamin D supplements don’t reduce the risk of severe asthma attacks or enhance symptom control in children and adults with mostly mild to moderate asthma. This newer evidence differs from the findings of previous research. That said, the risk of serious harmful side effects doesn’t appear to increase with the use of vitamin D supplementation. More research is needed in those living with severe asthma and low vitamin D levels (1).

2. Type 2 diabetes

Globally, over 474 million people live with type 2 diabetes, a chronic disease that impacts various aspects of health, starting from the eyes and moving down to the feet (5;6). Research suggests that compared to taking a placebo on its own or in combination with calcium supplements, low dose vitamin D supplementation doesn't appear to decrease the risk of developing type 2 diabetes in people at average risk of diabetes. However, there’s good news for those living with prediabetes. More specifically, a moderate to high dose of vitamin D supplements (aka 1000 IU or more/day) has the potential to lower the risk of developing type 2 diabetes in this population. Additionally, people with prediabetes who do not live with obesity are more likely to see the benefits of vitamin D supplementation than those that do. More research is needed to determine the optimal dose of vitamin D and how often people should be taking it, as well as the influence of body mass index on the effectiveness of the strategy (2).   

3. Lung cancer

Globally, lung cancer is responsible for the greatest number of cancer-related deaths (7). A variety of vitamins and minerals have been studied to see if they can help reduce the risk of developing lung cancer. And you guessed it, this includes vitamin D! More specifically, vitamin A, vitamin C, vitamin E, calcium, vitamin D plus calcium, selenium, and the combination of vitamins A, C, E, selenium, and zinc are among those put “under the microscope”.  Research suggests that compared to placebo, none of the individual supplements or supplement combos reduce the risk of lung cancer incidence or lung cancer death in healthy populations. What’s more, some may increase the risk of lung cancer incidence and death and other minor to serious side effects. More research is needed to confirm the vitamin D-related findings (3).

While supplements are widely available and often prescribed for those with deficiencies or certain medical conditions, it doesn’t mean they are right and safe for all people. If you are interested in supplementation as a strategy, vitamin D or other wise, be sure to consult your healthcare team prior to starting or stopping, so you can discuss the best options for you and create a tailored plan.    

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Author Details


  1. Williamson A, Martineau AR, Sheikh A, et al. Vitamin D for the management of asthma. Cochrane Database Syst Rev. 2023; 2:CD011511. doi: 10.1002/14651858.CD011511.pub3.
  2. Barbarawi M, Zayed Y, Barbarawi O, et al. Effect of vitamin D supplementation on the incidence of diabetes mellitus. J Clin Endocrinol Metab. 2020; 105:dgaa335. doi: 10.1210/clinem/dgaa335. 
  3. Cortes-Jofre M, Rueda JR, Asenjo-Lobos C, et al. Drugs for preventing lung cancer in healthy people. Cochrane Database Syst Rev. 2020; 3:CD002141. doi: 10.1002/14651858.CD002141.pub3.
  4. World Health Organization. Asthma. [Internet] 2023. [cited April 2024]. Available from https://www.who.int/news-room/fact-sheets/detail/asthma
  5. International Diabetes Federation. Facts & figures. [Internet] 2023. [cited April 2024]. Available from  https://idf.org/about-diabetes/diabetes-facts-figures/
  6. World Health Organization. Diabetes. [Internet] 2023. [cited April 2024]. Available from https://www.who.int/news-room/fact-sheets/detail/diabetes
  7. World Health Organization. Lung cancer. [Internet] 2023. [cited April 2024]. Available from https://www.who.int/news-room/fact-sheets/detail/lung-cancer

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