Episode 87 – Vitamin D


When people think about vitamin D, I think the main think that comes to mind would be bone health which is a super important one. But vitamin D is actually important for many things outside of bone health so that is what we will be going through today. 

What Are The Deficiency Rates and What Is a Good Level?

  • Around 30% of people in Australia are vitamin D deficient.  
  • Some places such as the ACT have deficiency rates near 50%. 
  • Deficiency is defined as – <50nmol/L of vitamin D on a blood test  
  • 50-150nmol/L is the healthy range, although there is a strong argument that say 80 is better than 50. And that is what I tend to aim for with my clients  
  • This also means that although ~30% of the population is deficient, it’s likely another 25-30% have sub-optimal levels. 

Bone Health 

  • Very clearly a vitamin D deficiency is linked with low bone mineral density 
  • Vitamin D is required for the absorption of calcium and phosphorous  
  • At an extreme, Vitamin D deficiency can lead to Ricketts, which involves softening and malformation of bones. 
  • Alternatively, it could contribute to osteoporosis or osteopenia 
  • Even just supplementing vitamin D at a population level without measuring levels has been shown to improve bone mineral density. People who are deficient typically get a lot of benefit, while those with high levels likely don’t get any additional benefit.   

Immune Function 

  • A 2017 meta-analysis that included 25 studies found that vitamin D supplementation reduced the rate of respiratory tract infections.  
  • Supplementation showed significantly more benefit the lower the starting vitamin D levels were, for example, those below 25nmol/L had very significant improvements from supplementation  
  • More interestingly and relevant to now, a 2021 meta-analysis on Covid and vitamin D status found that those with a vitamin D deficiency were 80% more likely to get Covid than those without 
  • So vitamin D does seem to be a pretty big player in immune function  


  • I’m aware of 5 different meta-analyses of vitamin D supplementation and depression. That’s pretty crazy considering the goal is to summarise the research effectively. 
  • One of the reasons there are so many, is because they actually have contradictory findings
  • My interpretation of the research is that: 
  •  1) Vitamin D likely can help improve depression symptoms a bit, on average. In some cases it might help, in others it might not.  
  • 2) The effect likely isn’t huge.  
  • 3) The effect is likely bigger in cases where people have quite low vitamin D levels. 
    4) One meta-analysis concluded that one reason others didn’t find a difference was because the levels of depression included in some studies were quite low at the baseline AND vitamin D status was quite high at the baseline.  

Balance and Strength 

  • Vitamin D has strong research supporting improvements in balance and strength in people above the age of 60 
  • This translates into a reduction in falls, which further reduces fracture risk beyond just having stronger bones 
  • Although, the effects are less pronounced in younger people 
  • Athletes who address a vitamin D deficiency get a little bit stronger on average, according to a 2017 systematic review on the topic.  
  • But it’s worth noting that there isn’t anywhere near as much research on this topic, so I wouldn’t draw strong conclusions. 
  • There are certain athletes who are also more likely to be vitamin D deficient e.g. basketball players train indoors, so are more likely to see less sun than athletes who train outdoors 
  • Overall, even though the evidence for performance isn’t super strong, I still think it is worth addressing  

IBS Symptoms 

  • There are plenty examples of research linking vitamin D and IBS. One example from Saudia Arabia found that 82% of participants with IBS were deficient in vitamin D, while only 30% of people without IBS had low vitamin D. 
  • But just because people with IBS are more likely to be deficient doesn’t mean that addressing the deficiency helps the IBS. 
  • As of right now, in 2023, there are only 4 randomized controlled trials looking at vitamin D supplementation and IBS. The results are mixed, but looks mildly promising.  
  • Once again it is likely an area where people who were quite low at the baseline likely would benefit more. 

Supplements vs Food vs Sun 

  • To increase vitamin D, you either take supplements, consume more through food, or get more sunlight. 
  • Getting more sunlight is typically the preferred approach, although this can be impractical for some people, and needs to be balanced with skin cancer risk. 
  • Few foods naturally contain vitamin D. Some stuff like liver, egg yolks, certain types of meats, as well as mushrooms that have been exposed to the sun contain vitamin D. But it’s rare that I actually encourage focusing on that. I’d usually focus on sunlight and/or supplements.  
  • In terms of supplements, 1000IU is the recommended dose normally. To address a deficiency quicker I go up as high as 10,000IU per day for a few weeks. Some doctors even do injections of as much as 150,000IU to address things even quicker.  

Vitamin D is linked with pretty much everything, although a lot of links are weak, and it can be hard to tell whether addressing vitamin D would actually help.

Relevant Links/ Resources

Studies Mentioned:

COVID and Vitamin D

Respiratory Tract Infections and Vitamin D – Meta Analysis

Vitamin D Supplementation and Mental Health

Vitamin D Supplementation in Major Depression

Vitamin D for Depressive Symptoms

Vitamin D and Depression

Vitamin D Supplementation to Reduce Depression in Adults

Efficacy of Vitamin D Supplementation in Depression in Adults

Vitamin D and Postural Balance

Vitamin D – Muscle Strength, Risk Of Fall and Frailty

Vitamin D and Muscle Strength in Athletes

Vitamin D Deficiency in IBS

Vitamin D Supplementation for IBS

Related Blog Posts:

Vitamin D

Vitamin D Supplements and Fracture Risk