Vitamin D and Influenza

Vitamin D and Influenza

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 ?

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 influenza. People who have low vitamin D levels may have a higher chance of developing influenza.
Influenza epidemics occur in the winter, and vitamin D levels are dramatically lower in the winter as well. Since influenza is seasonal, it is thought that vitamin D might be a factor that can affect your chances of getting the flu.
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.
On the other hand, some experiments have shown that taking vitamin D supplements can reduce your chances of getting influenza in the first place. Some researchers recommend getting more vitamin D to protect against influenza, but more experiments are needed to say whether or not taking a vitamin D supplement can for sure prevent influenza.
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.
If you have influenza, you shouldn’t take vitamin D in place of your treatment medications. Talk to your physician for more advice about taking supplements (4).

What does recent research say about vitamin D and influenza?

An experiment done in the United States gave African-American women either 800 IU vitamin D per day for 2 years, then 2,000 IU per day for the 3rd year, or a dummy pill. The researchers looked at how many times those women got influenza over the 3 years. They found that (3):
  • 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.


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