Vitamin D and Influenza
What is Influenza ?
Influenza, more commonly known as the flu, is a respiratory infection that is caused by a virus infecting the nose, throat, and lungs. Influenza is most common during winter and can cause fever, chills, sore throat, cough, body aches, and fatigue
What is vitamin D ?
Many studies that have been done about influenza have shown that people who have lower levels of vitamin D are more likely to get influenza. Not many studies have been done about treating influenza with vitamin D, but some research has shown a relationship between higher levels of vitamin D and shorter duration of the influenza infection.
If you want to take vitamin D to prevent influenza, 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 influenza.
What does recent research say about vitamin D and influenza?
The vitamin D group had fewer influenza symptoms compared to the dummy pill group.
Only one person in the vitamin D group had influenza when the dose was at 2,000 IU per day.
The dummy pill group had influenza symptoms mostly in the winter, whereas the people who got influenza in the vitamin D group had symptoms year round.
This experiment suggests that vitamin D, especially at higher doses, may help to protect against seasonal influenza. The researchers conclude that vitamin D supplements might be useful to prevent the flu, but that more experiments are needed.
An experiment done with Japanese schoolchildren looked at the effects of vitamin D supplements on their chances of getting influenza. The researchers gave children either 1,200 IU vitamin D per day for 3 months during the winter, or a dummy pill. They found that (2):
More children in the dummy pill group got influenza A than children in the vitamin D group.
There was a preventive effect of 1,200 IU vitamin D per day on children getting influenza A.
The researchers conclude that taking 1,200 IU of vitamin D in children can help to protect against seasonal influenza A.
In this study, there was no effect of vitamin D on influenza B, possibly because vitamin D may respond in different ways to the inflammatory proteins in the viruses.
A study done in 2011 looked at vitamin D levels and respiratory infections, like influenza, in a large group of British adults. The researchers found that (1):
For each 4 ng/ml increase in vitamin D levels in the body, there was a 7% lower chance of developing influenza.
There was a seasonal pattern of influenza which was the same as the seasonal pattern of vitamin D levels. Influenza infections decreased when vitamin D levels increased.
However, since this study was observational, the researchers couldn’t conclude for certain if higher vitamin D levels protected against the flu.
Key points from the research
People who get influenza are more likely to have low levels of vitamin D in their body
Vitamin D can help reduce inflammation caused by the influenza virus and increase the number of proteins that fight against viruses.
Influenza infections 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 reduce the chances of getting influenza.
Having high levels of vitamin D may help you to recover faster from an influenza infection, although we don’t know for sure yet if they do.
Some researchers recommend getting more vitamin D to protect against influenza. Still, more experiments are needed for scientists and doctors to clearly understand whether or not taking a vitamin D supplement can prevent influenza.