Direct Link Between Vitamin D Deficiency and Chronic Inflammation

The best source of vitamin D is direct sunlight, while avoiding sunburn. Mladen Mitrinovic/Shutterstock

In a world first, genetic research from the University of South Australia (UniSA) has demonstrated a direct link between low levels of vitamin D and high levels of inflammation, a finding which will help identify people at higher risk of chronic illnesses associated with inflammation.

While inflammation is critical to the body’s healing process, if persistent, it can contribute to a range of disorders, including heart disease, type-2 diabetes and autoimmune diseases.

Analysing the genetic data of 294, 970 participants in the UK Biobank—a large-scale biomedical database and research resource that contains detailed genetic and health information from around 500,000 UK residents—the study demonstrated the link between vitamin D and C-reactive protein levels, a biomarker of inflammation.

Lead researcher Dr Ang Zhou said in a UniSA release on Monday that in response to inflammation, whether acute or chronic, high levels of C-reactive protein are generated in the liver.

“This study examined vitamin D and C-reactive proteins and found a one-way relationship between low levels of vitamin D and high levels of C-reactive protein, expressed as inflammation,” he said.

“Boosting vitamin D in people with deficiencies may reduce chronic inflammation, helping them avoid a number of related diseases.”

Research Suggests Adequate Levels of Vitamin D Enough

The UniSA study, which was supported by the National Health and Medical Research Council and published in the International Journal of Epidemiology, suggests that adequate concentrations of vitamin D could mitigate complications associated with obesity, as well as reduce the risk or severity of chronic conditions linked to inflammation, such as cardiovascular disease, type-2 diabetes and autoimmune diseases.

Maintaining adequate levels of vitamin D may reduce the risk of cardiovascular disease.   zinkevych/Adobe Stock

Professor Elina Hyppönen, senior investigator and Director of UniSA’s Australian Centre for Precision Health, said the study results address some of the controversies over what levels of vitamin D are necessary to be beneficial.

“We have repeatedly seen evidence for health benefits for increasing vitamin D concentrations in individuals with very low levels, while for others, there appears to be little to no benefit,” she said.

“These findings highlight the importance of avoiding clinical vitamin D deficiency, and provide further evidence for the wide-ranging effects of hormonal vitamin D.”

Low Sun Exposure Increases Risk of Deficiency

People who do not access adequate sun exposure are at a greater risk of vitamin D deficiency.

This includes naturally dark-skinned people, who need greater exposure to produce adequate levels of vitamin D, as well as people who cover their skin for religious reasons and chronically ill or institutionalised people who rarely go outdoors, the Australian Cancer Council reports.

Those who have previously had skin cancer or are at high risk may also avoid sun exposure and hence also be susceptible to vitamin D deficiency.

Individuals who fall into these groups may need to consult a health professional on whether a vitamin D supplement is advisable.

The Cancer Council notes that overexposure to the sun is never recommended, even if a person is deficient in vitamin D.

How Much Sun Exposure Is Necessary?

UVB radiation from the sun remains the best source of vitamin D, and while UVB levels vary according to location, time of day, time of year and cloud coverage, most people will obtain adequate vitamin D via regular incidental sun exposure.

When the UV index falls below 3, spending time outdoors in the middle of the day with some skin exposed is recommended. By yanadjan/Adobe Stock

The Cancer Council states that when the UV index is 3 or higher—during summer, for example—most people maintain sufficient vitamin D levels by spending a few minutes outside on most days of the week.

However, when the UV index drops below 3, such as in late autumn and winter in parts of southern Australia, spending time outdoors in the middle of the day with some skin exposed is recommended.

Sun protection, including sunscreen, is recommended when the UV index is 3 or higher, or when spending long periods of time outdoors.