Chronic cough and lack of vitamin D

A chronic cough often follows in the wake of virus infections such as colds, influenza, and COVID-19. Lack of vitamin D seems to be a major contributor, coupled with the fact that a vitamin D deficiency often increases during the disease period. Vitamin D is of vital importance to a strong immune defense and also helps to regulate inflammation. Therefore, supplementation with vitamin D may be worth considering as a way of preventing virus infections and treating complications such as chronic cough, according to two studies that are published in European Respiratory Journal.

To cough is a normal reflex that is intended to remove foreign matter such as dust and mucous from our respiratory tract. Chronic coughing and bronchitis, which is a chronic inflammation, typically occur in situations where the immune defense is not functioning optimally in its attempt to fight a cold, influenza, or COVID-19. Many people also experience problems like impaired sense of taste and permanent fatigue.
The condition known as post-COVID-19 syndrome (PCS) describes persistent or new symptoms that show more than 12 weeks after a person has been infected with COVID-19 and is not caused by other factors. It is commonly known that vitamin D regulates different inflammation markers in COVID-19 patients, thereby helping them fight the infection faster. It is also known that vitamin D supplementation can shorten the period where people cough and have reduced sense of taste. But according to the scientists behind the new study, vitamin D’s role in patients with PCS remains uncharted territory.
The scientists therefore conducted a retrospective analysis of vitamin D levels in patients with post-COVID-19-syndrome. All patients had participated earlier in a population study and had delivered several blood samples to their doctors. These blood samples were then compared with blood samples from a healthy control group.
The study revealed that PCS patients had a significant drop in their blood levels of vitamin D compared with the healthy controls. From 2019-2021, the average level of vitamin D in the PCS group went down from 58.7 nmol/L (=23.5 ng/ml) to 43.5 nmol/L (= 17.4 ng/ml).
Vitamin D levels in the blood should preferably be above 75 nmol/L, which means the PCS patients had far too little vitamin D in their system, and levels went down even further during their disease period.
According to the scientists, blood levels of vitamin D may drop for various reasons. Firstly, the acute COVID-19 infection may cause the immune defense to use more vitamin D to defend the body against the infection. Secondly, complications may occur that can increase the need for the vitamin. Finally, lack of vitamin D can become a vicious cycle in different pathological processes because most cells in the body need vitamin D.

Widespread vitamin D deficiency with other coughing types

A study from 2021 that is published in European Respiratory Journal links low vitamin D status to impaired lung function, including respiratory infections and chronic cough in children. At the time, researchers had not yet looked at vitamin D’s role in chronic cough in adults.
During the period between 2006-2008, the scientists measured levels of vitamin D in 3,914 participants of the Rotterdam study, which is a large population study. The participants were placed in the following four categories based on their vitamin D status:

• Sufficient (above 75 nmol/L)
• Insufficient (50-74 nmol/L)
• Mild/moderate deficiency (30-49 nmol/L)
• Severe deficiency (less than 30 nmol/L)

It turned out that 40 percent of the participants were more or less vitamin D-deficient. Lack of vitamin D was more widespread among the participants who suffered from chronic cough compared with those who did not have that problem.
After adjusting for confounding factors such as age, gender, BMI, smoking, use of ACE-inhibitors, asthma, and COPD (chronic obstructive pulmonary disorder), the scientists could see that vitamin D deficiency was significantly related to persistent chronic cough.
They concluded that vitamin D deficiency is common among adults with chronic cough and that the cough is not likely to improve if the deficiency is severe. It is a good idea for patients with chronic cough to have their vitamin D status measured and perhaps take vitamin D supplements to optimize levels of the nutrient in their blood.

References:

Jens Bräunlich. Vitamin D values in post-Covid syndrome patients are lower than in control groups. European Respiratory Journal 2023

Johnmary T. Arinze et al. Persistent chronic cough and vitamin D deficiency. European Respiratory Journal. 2021