Vitamin D is a nutrient important for bone health and participates in the immune response. A new study published in BioMed Central Nutrition conducted a systematic review to investigate whether vitamin D reduces the inflammatory marker C-reactive protein.
Vitamin D is a nutrient that has an important role in calcium regulation. Vitamin D works together with calcium to maintain healthy bones and teeth, and also contributes to normal muscle, nerve and immune system functions. Vitamin D can be obtained through diet or sun exposure, however, only a few foods contain adequate amounts of vitamin D, such as cow’s milk, fortified beverages, fatty fish, and egg yolks. Low vitamin D levels are associated with several diseases including rheumatoid arthritis, metabolic syndrome, cardiovascular disease and some types of cancer. Vitamin D supplementation is often recommended for individuals with low vitamin D levels.
Low Levels of Vitamin D May Stimulate Inflammatory Response
Before disease develops, low vitamin D status is reported to stimulate a mild inflammatory response measured by elevated levels of C-reactive protein (CRP), a biomarker in the blood commonly measured to assess inflammation levels. Studies suggest that vitamin D supplementation reduces circulating C-reactive protein levels and thus, inflammation. However, other markers of inflammation, including interleukin-6 (IL-6), interleukin 10 (IL-10), and tumour necrosis factor alpha (TNFa) show inconsistent results following supplementation.
In a new study published in BioMed Central Nutrition, researchers conducted a systematic literature review using PubMed-Medline, SCOPUS, and Google Scholar and Web of Science databases to identify all randomized control trials evaluating the impact of vitamin D supplementation on C-reactive protein. Using random effects models for quantitative data, they assessed whether the literature pointed to an effect of vitamin D on reducing inflammatory response in individuals.
No Significant Decrease in C-Reactive Protein Levels
Using this method, the researchers found only 24 studies that met their inclusion criteria for a final evaluation. Pooling the data together, they showed that vitamin D supplementation did not cause a significant decrease in serum C-reactive protein levels. In addition, the inflammatory markers IL-10 and TNFa were also unaffected, while there was a modest increase in serum IL-6 following supplementation.
Therefore, the current literature suggests that vitamin D supplementation does not cause a reduction in inflammatory status. While vitamin D is known to act in the immune system, these results suggest that it may operate in supportive functions rather than regulating the inflammatory response. However, more studies should be conducted with a larger sample size and longer follow-up periods with individuals to provide a more supported conclusion on this topic.
Written by Neeti Vashi, BSc
Reference: Mazidi, M., Rezaie, P., & Vatanparast, H. (2018). Impact of vitamin D supplementation on C-reactive protein; a systematic review and meta-analysis of randomized controlled trials. BMC Nutrition, 4(1), 1.