Vitamin D shining bright

Ashleigh Caradas sheds more (sun) light on vitamin D and it long list of health benefits.

Let’s face it, we feel much better when we are in the sunshine. We flock towards balmy holiday destinations and love to find those little sunny afternoon spots to bask in. Animals love it too. It’s in our nature. And it’s not just about the brightness and warmth. Our bodies crave the sunshine so that we can make more vitamin D. 

Vit D keeps surprising us with a growing list of health benefits from cancer and osteoporosis prevention to improving gut and mental health. 

There are limited food sources of vit D (eggs, fatty fish and mushrooms to name a few) and we get most of our vit D from direct sunlight to the skin. For this reason we need to spend more time outdoors. 

Vitamin D research

Vit D is most well-known for its role in bone health and its relationship to calcium absorption. However, in recent years, vit D research has skyrocketed and the applications seem to be endless. 

It’s estimated that vit D deficiency affects up to 50% of people worldwide. With the current state of affairs and lockdowns, the threat of vit D deficiency is growing due to people spending less time outdoors. What’s more, there is a growing body of evidence around the role of vit D in offering protection against COVID-19 infections. 

COVID and vitamin D deficiency

A recent and very large population study looked at data of over 4 million people in the National Health Services. Researchers  matched 52 405 infected patients with 524 050 control individuals to assess the relationship between vitamin D levels, acquisition of supplements and positive COVID-19. Results showed a highly significant correlation between vitamin D deficiency and COVID-19 infection. 

Not only does vit D status help to prevent infection, but it has also shown promise in reducing ICU admissions in people with active COVID. One study on 103 patients with severe COVID, 52 mild cases and 206 controls showed that vitamin D deficiency was positively associated with more severe cases requiring ICU admissions. 

Another new study looked at data from hospitals and clinics across China, France, Germany, Italy, Iran, South Korea, Spain, Switzerland, the UK and US and noted that countries with the highest COVID-19 mortality rates also had lower levels of vit D in comparison to countries with lower mortality rates. The authors concluded that a good vit D status might not prevent you from contracting the virus but could prevent you from having a severe bout of the virus, or dying from the virus. 

This comes after another small study which looked at a group of 212 patients diagnosed with COVID-19 and found that patients with the most adequate vit D status had the most favourable outcomes.

Role of vitamin D in breast cancer

A 2019 review, on the role of vit D in breast cancer, looked at observational studies and found that vit D deficiency correlated with breast cancer risk and that supplemental vit D intake had an inverse relationship with this outcome. 

Vitamin D deficiencies have also been linked to various other cancers but research is still needed to make firm recommendations on whether cancer patients should supplement, or whether it can be used as a preventative measure. 

A meta-analysis of the role of vit D in mental health, in 2014, showed the relationship between vitamin D deficiency and depressive symptoms. 

Vitamin D deficiency defined

There is some controversy as to what defines a vit D insufficiency or deficiency. Because of the mounting evidence for vit D’s benefits, many experts are calling for optimal vit D ranges to be raised. 

The Institute of Medicine’s committee recommends that a serum concentration of 25-hydroxyvitamin D (25(OH)D) of 50 nmol/L is sufficient for bone and overall health in healthy individuals. Many experts are calling for vit D levels to be in the higher ranges for optimum health (as close to 50 ng/mL as possible).


Being outdoors can’t cause vitamin D toxicity but supplements can. If you’re wanting to supplement, do so short-term (as we store vitamin D) and have your blood levels checked to make sure that you need to supplement.

Ashleigh Caradas is a registered dietitian with more than 15 years’ experience in private practice. She is also a freelance health journalist, recipe developer and blogger, as well as a yoga instructor which led to incorporating stress management techniques into her practice.

MEET THE EXPERT – Ashleigh Caradas

Ashleigh Caradas is a registered dietitian with more than 15 years’ experience in private practice. She is also a freelance health journalist, recipe developer and blogger, as well as a yoga instructor which led to incorporating stress management techniques into her practice.


  • Vitamin D appears to play role in COVID-19 mortality rates. Center for Physical Genomics and Engineering and the associate director for Research Technology and Infrastructure at the Robert H. Lurie Comprehensive Cancer Center at Northwestern University, 7 May 2020.
  • Israel, et al. The link between vitamin D deficiency and covid 19 in a large population. BMJ, 2020.
  • Francisco, et al. Arch Biochem Biophys. Vitamin D Safety and Requirements. 2013
  • Enocr Pract. Vitamin D Supplementation Could Possibly Improve Clinical Outcomes of Patients Infected with Coronavirus-2019 (COVID-2019). 2020.
  • Sharmin, et al. Vitamin D and breast cancer: A systemic review and meta-analysis of observational studies. Clinger’s Nutr ASPEN. June 2019
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