Preventing type 2 diabetes with the “sunshine” vitamin?

The Bottom Line

  • In 2019, diabetes was one of the top 10 causes of death globally and in Canada.  
  • In people with prediabetes, vitamin D supplementation at a dose of 1000 IU or more per day may reduce the risk of type 2 diabetes.
  • Speak with your health care team about whether you should turn to this medicine cabinet staple for the prevention of type 2 diabetes.  

Diabetes. A small word with a significant impact. In 2019, diabetes was responsible for 1.5 million deaths across the globe, making it the ninth leading cause of death worldwide (1). Closer to home, that same year, diabetes was the sixth leading cause of death in Canada (2).

Living with diabetes affects many different aspects of your health. At stake is the health of your eyes, feet, heart, kidneys, and more. Type 2 diabetes accounts for over 95% of diabetes cases. Once someone's diagnosed with type 2 diabetes, their treatment options include changes to their diet and exercise routines, quitting smoking (if needed), and working to lower their blood sugar, blood pressure, and cholesterol levels (1). However, the best defence is a good offence. So, preventing type 2 diabetes altogether is ideal.

When we talk about prevention, vitamin D throws its hat into the ring. Shocked? No need to be. Vitamin D has been studied for a host of health-related matters. For example, research has shown that vitamin D is important for developing dense, healthy bones and that vitamin D3 can help reduce the risk of acute respiratory tract infections (3-4). Vitamin D is also no stranger to diabetes-related discussions. Previous research demonstrates that certain populations with type 2 diabetes—namely those who have vitamin D deficiencies and/or who are non-obese—may be able to improve blood sugar control through the use of vitamin D supplements (5).

If vitamin D has the potential to help better the health of some folks with type 2 diabetes, can it also play a role in preventing it from developing? Let’s take a closer look at the findings of a relatively recent systematic review (6). 

What the research tells us

Similar to previous research on vitamin D as a treatment strategy for those with type 2 diabetes, when it comes to prevention, we also see effects that vary by population. The dose of vitamin D supplementation and body mass index (BMI) come into play as well.

Let’s start with the bad news. Unfortunately, taking a low dose of vitamin D via supplements doesn't appear to lower the risk of developing type 2 diabetes in people who are at average risk of diabetes.

Now for the good news. In folks with prediabetes—meaning those who have higher than normal blood sugar levels and are at a higher risk of diabetes—we see that taking a moderate to high dose of vitamin D supplements has the potential to lower the risk of developing type 2 diabetes. Here, a moderate to high dose is equal to, or more than, 1000 IU per day. When we dig even deeper into this population, we unearth that people with prediabetes who aren't obese (i.e., those with a BMI of less than 30 kg/m2) are more likely to obtain the benefits of vitamin D supplementation than their obese counterparts (i.e., those with a BMI of 30 kg/m2 or more). Further research on the influence of dosing schedules—such as the dose and frequency of supplementation—and BMI is needed to better understand their influence on the effectiveness of vitamin D in type 2 diabetes prevention (6).

While these results are positive, we do have to remember a few things. First, supplements, although widely available, can still be harmful for some people. That’s why it’s important to consult with your health care team before starting any supplements, including vitamin D. During these conversations, try to get a better sense of your risk for type 2 diabetes and whether this strategy is safe and appropriate for you. If you get the green light, be sure to ask about what dosing schedule meets your needs. Last but not least, vitamin D supplementation shouldn’t be used as a quick fix for your diabetes concerns. Lifestyle modifications such as following a healthy diet, regular physical exercise, and maintaining a healthy weight are incredibly important and shouldn’t be left behind.

Get the latest content first. Sign up for free weekly email alerts.
Author Details


  1. World Health Organization. Diabetes. [Internet] 2021. [cited February 2022]. Available from
  2. Statistics Canada. Leading causes of death, total population, by age group. [Internet] 2022. [cited February 2022]. Available from 
  3. Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ. 2017; 356:i6583. doi: 10.1136/bmj.i6583. 
  4. Cranney A, Horsley T, O'Donnell S, et al. Effectiveness and safety of vitamin D in relation to bone health. Evid Rep Technol Assess (Full Rep). 2007; 158:1-235.
  5. Wu C, Qiu S, Zhu X, et al. Vitamin D supplementation and glycemic control in type 2 diabetes patients: A systematic review and meta-analysis. Metabolism. 2017; 73:67-76. doi: 10.1016/j.metabol.2017.05.005. 
  6. 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. 

DISCLAIMER: These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (

Many of our Blog Posts were written before the COVID-19 pandemic and thus do not necessarily reflect the latest public health recommendations. While the content of new and old blogs identify activities that support optimal aging, it is important to defer to the most current public health recommendations. Some of the activities suggested within these blogs may need to be modified or avoided altogether to comply with changing public health recommendations. To view the latest updates from the Public Health Agency of Canada, please visit their website.