Vitamin D May Help to Prevent and Treat Respiratory Infections

Did you know that upper respiratory infections are the most common illness that causes people to visit their doctor and miss work or school?
New research continues to look at the role that vitamin D may play in helping to prevent and treat respiratory infections.

Summary

Respiratory infections are any infection in the throat, sinuses, airways, or lungs. The respiratory tract is the part of the body that is involved with breathing. The most common respiratory infections include influenza, the common cold, sinus infections, bronchitis, pneumonia, and tuberculosis.
Studies have shown that there is a link between vitamin D levels and the risk of getting a respiratory infection. People who have low vitamin D levels tend to have a higher chance of developing a respiratory infection.
Respiratory infections occur more often in the wintertime. Vitamin D levels are also known to be lower in the winter. Researchers think that low vitamin D levels in the winter may be a factor that can affect someone’s chances of developing a respiratory infection.
It has been shown in many studies that people with low vitamin D levels tend to get more respiratory infections.  Some research has shown that people with high levels of vitamin D who get respiratory infections have a shorter illness duration or less severe symptoms.
Some experiments have shown that taking vitamin D supplements can help to prevent respiratory infections, but results are mixed. Some researchers recommend getting more vitamin D to protect against respiratory infections. Still, more experiments are needed for scientists and doctors to clearly understand whether or not taking a vitamin D supplement can prevent respiratory infections.
If you want to take vitamin D to prevent respiratory infections, it is unlikely to cause you any harm, as long as you take less than 10,000 IU per day. However, it’s not proven that taking vitamin D will help to prevent or treat respiratory infections.
If you have a respiratory infection, you shouldn’t take vitamin D in place of any treatment medications. Talk to your physician for more advice about taking supplements.

What are respiratory infections?

Respiratory infections are any infection in the throat, sinuses, airways, or lungs. The respiratory tract is the part of the body that is involved with breathing. There are two parts: the upper and lower respiratory tracts.
Respiratory infections are usually split up into upper or lower respiratory infections. Upper respiratory infections affect the nose, sinuses or throat. Lower respiratory infections affect the lungs and airways. Influenza, or the flu, can affect both the upper and lower respiratory tracts. Most respiratory infections are caused by a virus, but some are caused by bacteria, like tuberculosis and some forms of pneumonia¹.
The most common upper respiratory infections are:

• The common cold
• Influenza
• Tonsillitis
• Sinus infections

The most common lower respiratory infections are¹:

• Influenza
• Bronchitis
• Pneumonia
• Tuberculosis

What are the symptoms of respiratory infections?

Symptoms of respiratory infection will depend on which type of infection you have.

Symptoms will depend on which type of respiratory infection you have. The most common symptoms for all respiratory infections include²:

• Cough
• Sore throat
• Fever (especially in children)
• Headache

Upper respiratory infections, like the common cold, will also cause symptoms like runny nose, sneezing, and nasal congestion. Lower respiratory infections can also have symptoms of wheezing, a tight feeling in the chest, feeling breathless, and coughing with mucus^1,3. Respiratory infection symptoms can last up to 2 weeks⁴.

How common are respiratory infections?

Upper respiratory infections are the most common illness that causes people to visit their doctors and miss school or work¹. Adults get an average of 2-4 respiratory infections each year, while children can get up to an average of 6-10⁵. Children are more likely to get respiratory infections than adults because their immune systems aren’t well developed yet.
Respiratory infections are more common in the fall and winter seasons, although they can occur at any time. Since most respiratory infections are caused by viruses, antibiotics won’t help to treat them. Antibiotics will only work against infections caused by bacteria, like tuberculosis and some forms of pneumonia^1,6.

What are risk factors for respiratory infections?

There are some risk factors that can increase your chances of getting a respiratory infection, including^2,6:

• People with chronic diseases, like heart disease, kidney disease, or diabetes.
• People with weak immune systems, like from cancer or HIV/AIDS.
• People with other respiratory diseases, like asthma, cystic fibrosis, or chronic obstructive pulmonary disease (COPD).
• People who are morbidly obese.
• People over 65 years old and young children are more likely to develop respiratory infections.
• Spending lots of time in a hospital, nursing home, or with children.
• Smoking.

How do respiratory infections spread?

Respiratory infections are contagious and can spread when someone who is infected coughs, sneezes, or even talks. Droplets containing the virus or bacteria travel through the air and can be directly inhaled by another person through the mouth or nose. The droplets may also land on a surface and you could pick them up and then become infected after touching your eyes, nose, or mouth^4,7.
The best way to prevent getting a respiratory infection is to wash your hands and practice good hygiene. Vaccines are available for some respiratory infections, such as influenza and pneumonia^1,4.

What is the link between vitamin D and respiratory infections?

Respiratory infections occur more often in the wintertime, when vitamin D levels are known to be lower.

Vitamin D is an important part of the immune system. Some studies have shown that there is a link between vitamin D levels and the risk of getting a respiratory infection. People who have low vitamin D levels may have a higher chance of getting a respiratory infection⁸.
Vitamin D receptors are found on the surface of a cell where they receive chemical signals. By attaching themselves to a receptor, these chemical signals direct a cell to do something, for example, to act in a certain way, or to divide or die.
There are vitamin D receptors found on cells in the immune system and the respiratory tract, and vitamin D can bind to these receptors⁹. Vitamin D works in the immune system by reducing levels of inflammatory proteins called cytokines, as well as increasing amounts of antimicrobial proteins, which destroy invading germs and viruses. This combination of lowering inflammation and increasing antimicrobial defenses can help your immune system fight infections better^10,11.
Respiratory infections occur more often in the wintertime. Vitamin D levels are also known to be lower in the winter. Researchers think that low vitamin D levels in the winter may be a factor that can affect someone’s chances of developing a respiratory infection⁵.
While it is thought that having enough vitamin D may help to prevent getting a respiratory infection, more experiments need to be done to determine if taking vitamin D supplements can prevent respiratory infections, or make the duration of the illness shorter. Research hasn’t been able to show yet that low vitamin D levels are a cause of respiratory infections.

What about vitamin D and the common cold?

The common cold is an upper respiratory infection, and it is the most frequent illness that people get. Children tend to get more colds than adults, and they are more common in the fall and winter seasons. Many different viruses are known to cause colds, but the most common virus is called rhinovirus.
The rhinovirus disrupts a barrier in the cells of your respiratory tract, and this can lead to bacteria entering and causing infections. The symptoms and duration of a cold will depend on how strong the virus is, and how strong your immune system is. Having enough vitamin D can help strengthen your immune system by increasing the amounts of proteins that destroy invading viruses, like rhinovirus¹².

What does the research say in general about vitamin D and respiratory infections?

Preventing respiratory infections

Studies have shown that people who get respiratory infections tend to have lower levels of vitamin D. People with other respiratory illnesses, like asthma or COPD, have a greater increase in their risk of developing a respiratory infection if they have low levels of vitamin D¹³.
Young children are more likely to develop respiratory infections than adults. Some studies have shown that infants who have low levels of vitamin D when they are born are more likely to get a respiratory infection in their first year of life, compared to infants who are born with good vitamin D levels¹⁴. The vitamin D level of a newborn depends on their mother’s vitamin D levels, so a mother with high vitamin D levels will have a baby with high vitamin D levels¹⁵.
A study was done on young men in Finland, which found that men with low levels of vitamin D had more sick days due to respiratory infections compared to men with high levels of vitamin D¹⁶.
It has been shown in a lot of studies that people with low vitamin D levels tend to get more respiratory infections. However, more experiments are needed to determine whether or not taking a vitamin D supplement can help to protect against getting respiratory infections.

Treating and recovering from respiratory infections

Not many studies have been done about treating respiratory infections with vitamin D. Some research has shown that people with high levels of vitamin D who get respiratory infections have less severe symptoms, or a shorter duration of illness.
A study done in athletes found that those who had low levels of vitamin D had more respiratory infections that lasted longer and had more severe symptoms¹⁷.

What does recent research say about vitamin D and respiratory infections?

An experiment done in Sweden in 2012 looked at adults who had a history of getting many respiratory infections per year. The researchers gave them either 4000 IU of vitamin D per day, or a dummy pill, for 1 year. They found that¹⁸:

• People in the vitamin D group had fewer respiratory and sinus symptoms and were on fewer antibiotics throughout the year.
• The people in the vitamin D group had fewer viruses and bacteria found in their respiratory tract and noses.

The researchers conclude that supplementing with 4000 IU of vitamin D per day may help to prevent respiratory tract infections in adults.
A 2012 experiment done in Mongolia looked at classrooms of schoolchildren during the wintertime. Researchers gave children either milk fortified with 300 IU of vitamin D, or milk with no vitamin D every day for 3 months. They found that¹⁹:

• 99% of children had very low levels of vitamin D at the beginning of the study.
• Children who got the vitamin D milk had higher vitamin D levels at the end of the study.
  • Children who did not get vitamin D had double the risk of getting a respiratory infection, compared to the children who did get the vitamin D milk.

Although many of the children still didn’t reach good vitamin D levels, their chances of getting a respiratory infection were lower after getting 300 IU of vitamin D per day for 3 months.
A study published in 2009 looked at respiratory infections and vitamin D levels in adults. These researchers took information from a very large study that was done previously. Over 18,000 adults were looked at for this study. They found that⁵:

• People with the lowest vitamin D levels had a 55% higher chance of getting a respiratory infection, compared to people with the highest vitamin D levels.
• People with vitamin D levels of 30 ng/mL had the most protection against getting respiratory infections.

The researchers conclude that there is a link between vitamin D and respiratory infections, but experiments are needed to determine if vitamin D supplements can for sure help to prevent respiratory infections.
An experiment published in 2012 looked at upper respiratory infections in healthy New Zealand adults after getting vitamin D supplements. The people in the study either got an initial dose of 200,000 IU vitamin D, then another 200,000 IU 1 month later, then 100,000 IU per month for a total of 18 months; or a dummy pill with the same doses. The researchers found that²⁰:

• The people in the vitamin D group did not have fewer respiratory infections or symptoms than the people in the dummy pill group.

While there was no difference in respiratory infections in this experiment, it may be because the big monthly doses of vitamin D work differently than a daily dose would. Also, most of the people in this experiment already had average levels of vitamin D, so we can’t say for sure whether the results would be different in people with low levels of vitamin D. These researchers conclude that more experiments should be done to see if supplementing with vitamin D can help prevent respiratory infections in other populations.

Key points from the research

• People who get respiratory infections are more likely to have low levels of vitamin D.
• Vitamin D can help reduce inflammation caused by the respiratory infections and increase the number of proteins that fight against viruses.
• Respiratory infections tend to increase during the winter, which is when vitamin D levels are known to decrease in the population.
• Some experiments have shown that taking vitamin D supplements can help to prevent respiratory infections, but results are mixed.
• Some research has shown that people with high levels of vitamin D who get respiratory infections have a shorter illness duration or less severe symptoms.
• Some researchers recommend getting more vitamin D to protect against respiratory infections. Still, more experiments are needed for scientists and doctors to clearly understand whether or not taking a vitamin D supplement can prevent respiratory infections.

What does this mean for me?

Research has shown that there is a link between vitamin D and respiratory infections. People with low levels of vitamin D are more likely to get a respiratory infection, because vitamin D plays an important role in helping your immune system to fight infections and viruses.
More people get respiratory infections in the winter, and vitamin D levels are known to be lower in the winter as well. It is thought that low levels of vitamin D may be a factor that increases someone’s chances of getting a respiratory infection in the winter.
Most observational studies show that there is a link between low vitamin D levels and respiratory infections. Some experiments show that taking a vitamin D supplement can lower your risk of getting a respiratory infection, but results are mixed. More research is needed to see if taking a vitamin D supplement can help to prevent respiratory infections.
If you want to take vitamin D to prevent respiratory infections, it is unlikely to cause you any harm, as long as you take less than 10,000 IU per day. However, it’s not proven that taking vitamin D will help to prevent or treat respiratory infections.
If you have a respiratory infection, you shouldn’t take vitamin D in place of any treatment medications. Talk to your physician for more advice about taking supplements.

References

1. National Health Service. Respiratory tract infections. 2013. Web. < http://www.nhs.uk/conditions/respiratory-tract-infection/pages/introduction.aspx>
2. MedicineNet. Upper respiratory tract infections. 2013. Web. < http://www.medicinenet.com/upper_respiratory_infection/article.htm#what_is_an_upper_respiratory_infection>
3. WebMD. Symptoms of respiratory tract infections. 2009. Web. < http://www.webmd.boots.com/a-to-z-guides/tc/respiratory-tract-infection-symptoms-of-respiratory-tract-infections>
4. Centers for Disease Control and Prevention. Nonspecific Upper Respiratory Tract Infection Information Sheet. 2013. Web. < http://www.cdc.gov/getsmart/campaign-materials/info-sheets/adult-nurti.html>
5. Ginde AA, Mansbach JM & Camargo CA. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med 2009;169(4):384-390.
6. NPS. What causes respiratory tract infections (RTIs)? 2012. Web. < http://www.nps.org.au/conditions/respiratory-problems/respiratory-tract-infections/for-individuals/causes>
7. Mayo Clinic. Influenza (Flu). 2014. Web. < http://www.mayoclinic.org/diseases-conditions/flu/basics/causes/con-20035101>
8. Jolliffe DA, Griffiths CJ & Martineau AR. Vitamin D in the prevention of acute respiratory infection: systematic review of clinical studies. Journal of Steroid Biochemistry and Molecular Biology 2013;136:321-329.
9. Lang PO & Samaras D. Aging Adults and Seasonal Influenza : Does the Vitamin D Status ( H ) Arm the Body? Journal of Aging Research 2012;2012:1-9.
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13. Bergman P, Lindh AU, Bjorkhem-Bergman L & Lindh JD. Vitamin D and respiratory tract infections: a systematic review and meta-analysis of randomized controlled trials. PLoS One 2013;8(6):1-9.
14. Bozzetto S, Carraro S, Giordano G, Boner A & Baraldi E. Asthma, allergy and respiratory infections: the vitamin D hypothesis. Allergy 2012;67:10-17.
15. Magnus MC, Stene LC, Haberg SE, et al. Prospective study of maternal mid-pregnancy 25-hydroxyvitamin D level and early childhood respiratory disorders. Paediatric and Perinatal Epidemiology 2013;27:532-541.
16. Laaksi I, Ruohola JP, Tuohimaa P, et al. An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men. Am J Clin Nutr 2007;86:714-7.
17. He CS, Handzlik M, Fraser WD, et al. Influence of vitamin D status on respiratory infection influence and immune function during 4 months of winter training in endurance sport athletes. Exerc Immunol Rev 2013;19:86-101.
18. Bergman P, Norlin AC, Hansen S, et al. Vitamin D3 supplementation in patients with frequent respiratory tract infections: a randomized and double-blind intervention study. BMJ Open 2012;2(e001663):1-10.
19. Camargo CA, Ganmaa D, Frazier L, et al. Randomized trial of vitamin D supplementation and risk of acute respiratory infection in Mongolia. Pediatrics 2012;130:e561-567.
20. Murdoch DR, Slow S, Chambers ST, et al. Effect of vitamin D3 supplementation on upper respiratory tract infection in healthy adults: The VIDARIS randomized controlled trial. JAMA 2012;308(13):1333-9.

http://www.vitamindcouncil.org/health-conditions/respiratory-infections/