Apparently, a lot of people are getting the flu this season, and researchers are starting to realize why. Vitamin D deficiency could be contributing to the problem.
Vitamin D inhibits inflammation that makes COVID-19 more severe
Several studies have looked at the role of vitamin D in COVID-19 infection. Some of these studies have suggested that high doses of vitamin D might have positive effects on the severity of COVID-19. However, the World Health Organization does not recommend taking this supplement for COVID-19.
In addition, studies suggest that a lack of vitamin D may increase the risk of severe COVID-19 symptoms and mortality. Although these findings are consistent with previous studies, there is some debate about the exact extent of the relationship. Some researchers believe that vitamin D may affect innate and adaptive immune responses to the virus. In other words, it might reduce cytokine production and increase IL-10, which suppresses the activation of Th1 cells.
Despite these positive results, vitamin D treatment has not been shown to reduce intensive care unit (ICU) admission rates and all-cause mortality in COVID-19 patients. Empirical treatments, such as steroids and antiretroviral drugs, have also been tested.
A recent meta-analysis found a weak association between serum 25-hydroxyvitamin D (25(OH)D) concentrations and the severity of COVID-19. This relationship was stronger in individuals with chronic obstructive pulmonary disease and asthma. The authors suggest that low 25(OH)D concentrations might serve as a biomarker for inflammatory illnesses. This could be a promising approach to protecting against pathogenic signals.
In addition to the immune system, vitamin D interacts with other systems. For example, it can regulate the activity of renin-angiotensin-aldosterone system (RAAS). RAAS is a mediator of pro-inflammatory processes, such as thrombosis and fibrosis. In turn, a low RAAS activity can exacerbate preexisting conditions.
Vitamin D induces an anti-viral effect
Various studies have investigated the effect of vitamin D metabolites on immune responses to respiratory viruses. They have shown that the activation of the innate immune system by vitamin D metabolites leads to an anti-viral effect against rhinovirus. However, several factors may affect the effects of these compounds. These factors include cell types and the metabolic pathways involved. This article reviews the effects of vitamin D metabolites on human respiratory epithelial cells infected with respiratory viruses.
The innate immune response is characterized by the production of type I IFNs. These molecules are produced upon pathogen recognition by cellular sensors. The PI3K pathway is also involved in this process. The resulting PI3K signaling leads to the generation of ROS and macrophage cytokine production. This process may lead to the accumulation of virus-infected cells and inflammation in the airway lumen, which can lead to occlusion of the airway.
A number of in vitro studies have examined the effects of vitamin D metabolites on the innate immune response to respiratory viruses. These studies have found that calcitriol induced an anti-viral effect against rhinovirus. It has been shown that calcitriol enhances the phagocytic and chemotactic capacity of macrophages, as well as the expression of CAMP and DEFB4 mRNA. These mRNAs are responsible for regulating the mammalian target of rapamycin.
These mRNAs are released by cytokines and can also be produced by epithelial cells. These molecules are considered to be primary effector defense molecules against invading microorganisms. The production of these mRNAs is regulated by vitamin D.
Trial of vitamin D supplements
Several clinical trials have investigated the protective effects of vitamin D on a range of health problems. In particular, vitamin D has been studied on how it may reduce the severity and length of acute respiratory tract infections, particularly those caused by influenza. However, results from these studies have been mixed. In some, the effects of supplementation were not apparent. In others, they were.
In the largest trial of its kind, scientists from the QIMR Berghofer Medical Research Institute in Brisbane, Australia, analyzed data from 16,000 Australians, aged 60 to 84. They found that although supplements do not prevent most people from getting a cold, they do reduce the risk of having an acute respiratory infection.
The benefits of vitamin D supplementation were especially apparent for participants who were vitamin D deficient. It also seemed to reduce the length and severity of the illness, and participants were able to manage their symptoms with less medication. But if you’re concerned about your vitamin D levels, you should talk to your doctor.
Another study, the D-Health Trial, examined the effect of vitamin D on cardiovascular and cancer mortality. It was a randomised, double-blind, placebo-controlled trial. The findings were published in The BMJ.
The D-Health Trial was a five-year trial funded by the National Health and Medical Research Council. It included 11 321 participants. It was the largest vitamin D clinical trial to date. So in essence, taking vitamin D shots may actually be a shield against a variety of Flu strains.
