Inflammation is the activation of the body’s immune cells in response to injury or infection.
In the short term, inflammation is necessary for proper healing. However, when it persists, it can contribute to the development of inflammatory-related health conditions such as heart disease, diabetes, and cancer, among others.
Chronic inflammation can result from ongoing infections, exposure to irritants, and autoimmune disorders. But other factors like age, stress, and diet may also play a role. Identifying chronic inflammation can be challenging, but specific inflammatory biomarkers in the blood can indicate its presence. One of which is C-reactive (CRP).
According to 2021 research, vitamin D has been shown to have a powerful anti-inflammatory effect, and deficiencies in this nutrient may contribute to chronic inflammation. Yet, the association between vitamin D and CRP is unclear. Although previous studies published in 2015 and 2020 investigated vitamin D’s influence on CRP, no evidence was found to support a causal effect.
However, new genetic research from the University of South Australia, recently published in the International Journal of Epidemiology, found an association between low vitamin D levels and elevated CRP in the blood. This discovery has researchers suggesting that boosting vitamin D in people with a deficiency may reduce chronic inflammation.
To conduct the study, scientists recruited 294,970 U.K. Biobank participants who identified as having white-British ancestry. They then analyzed the participants’ active serum 25-hydroxyvitamin D [25(OH)D] levels. They also had participants fill out health and lifestyle questionnaires and obtained blood samples for biomarker and genetic assessments.
Using linear and non-linear Mendelian randomization (MR) analyses, the investigators looked for associations between serum 25(OH)D and CRP.
The researchers found a relationship between low vitamin D levels and elevated CRP in the blood. Specifically, a one-way relationship, meaning vitamin D may be a driver for CRP levels, but not the other way around.
However, the researchers also found that only study participants with low serum 25(OH)D concentrations had elevated serum CRP. This suggests that the anti-inflammatory benefits of improving vitamin D levels are limited to people with deficiencies.
“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,” said study author Elina Hyppönen, Ph.D., a University of Australia professor and director of the Australian Centre for Precision Health, in a press release.
Hyppönen explained that vitamin D is a hormone precursor that inhibits the production of inflammatory cytokines such as interleukin-12 (IL-12).
“By doing this, it acts to modify the immune responses so that T-cell polarization moves away from an inflammatory type response (Th1) to the production of more protective T-cell phenotypes (Th2 and regulatory T-cells),” Hyppönen said.
According to the study, these actions may help to lower inflammation, thus reducing the risk or severity of many chronic diseases. Study data also indicates the prevalence of vitamin D deficiency is around 40% in some European counties. Therefore, the authors suggest that increasing vitamin D consumption across the population by adding it to widely consumed food products could be a cost-effective way to reduce chronic disease.
Although the research found an association between vitamin D and CRP, it also had some limitations. For example, participants were individuals of white-British descent. So, it is not known if these results transfer to people of other racial or ethnic groups. What’s more, CRP is not the only biomarker involved in inflammation. Other biomarkers may also indicate an inflammatory response, including tumor necrosis factor-alpha (TNF-α) and interleukin 6Trusted Source (IL-6). The scientists say further investigations should examine these biomarkers to fully understand the anti-inflammatory effects of vitamin D.
“For many of the diseases and influences, evidence for causality [is] still to be established, and we need to look further into the effects on hard outcomes such as mortality risk,” Hyppönen said. “It also looks that the prevention of severe vitamin D deficiency is the key for many of the likely benefits, and we need to develop efficient strategies to target and treat those people who are in need.”
According to experts, vitamin D deficiency is when the serum 25(OH)D levels in the blood are less than 20 ng/mL. Serum levels of 20-30 ng/mL are considered insufficient.
“Vitamin D deficiency can manifest itself in several ways, including muscle pain, weakness, depression, poor bone health, and fatigue,” Iza Correll, a licensed physician associate and founder of OVI Healthcare.
Correll added that it’s critical to correctly diagnose vitamin D deficiency because the treatment plan may vary depending on the severity.
“If a deficiency is suspected, your doctor will likely order a blood test to measure the vitamin D level in your blood. The most common diagnostic test for vitamin D deficiency is a blood test to measure the level of 25-hydroxyvitamin D in the blood,” she explained. As far as treatments go, Correll noted that “treatment for vitamin D deficiency usually involves taking supplements or, most importantly, increasing exposure to sunlight to a minimum of 10 minutes daily.” “Most people with vitamin D deficiency require 400–800 IU of vitamin D daily to bring their levels back to normal. Your doctor may also recommend increasing your intake of foods high in vitamin D, such as fatty fish, eggs, and fortified milk or cereal,” she added.