It’s nothing to sneeze at.
This cold and flu season has been more active and severe than expected, largely driven by a new variant of the flu virus known as subclade K.
The Centers for Disease Control and Prevention reports that there have been at least 19 million illnesses, 250,000 hospitalizations and 10,000 deaths from the flu so far this season.
The good news is that US flu activity has decreased for the last three weeks. The bad news is that it remains elevated nationally.
To prevent the flu, experts recommend getting a flu shot, washing hands frequently and avoiding close contact with people who are sick.
Researchers are now suggesting another tool for your flu arsenal — vitamin D.
You probably know it as “the sunshine vitamin” because our bodies produce it when our skin is exposed to sunlight.
Vitamin D supports the immune system by stimulating the production of antimicrobial peptides that destroy viruses and bacteria, while suppressing excessive inflammation.
In a new study, deemed the largest of its kind, scientists from the University of Surrey in the UK found that adults with severe vitamin D deficiency were 33% more likely to be hospitalized for respiratory tract infections than those with sufficient vitamin D levels.
“Vitamin D is vital to our physical well-being,” said lead study author Abi Bournot, a Ph.D researcher at the University of Surrey.
“Not only does it keep our bones and muscles healthy, its antibacterial and antiviral properties are also thought to help reduce the risk of respiratory tract infections that can lead to hospitalization.”
The flu is a type of respiratory infection, as are bronchitis and pneumonia.
Older people face an especially higher risk of these infections due to declining lung function from aging, a naturally weakened immune system and underlying health conditions.
The National Institutes of Health suggests a daily vitamin D intake of 600 international units or 15 micrograms for people 1 to 70 years old. Infants require 400 international units, while adults over 70 should consume 800 international units (20 micrograms).
Vitamin D levels can be measured with a blood test. Bournot’s team classified severe vitamin D deficiency as below 15 nanomoles per liter.
Sufficient vitamin D was defined as levels of 75 nmol/L or greater.
Based on data from 36,200 participants, the researchers found that the hospitalization rate for respiratory tract infections decreased by 4% for each 10 nmol/L increase in vitamin D.
The study results were published in the February edition of The American Journal of Clinical Nutrition.
“Our findings of a significant association between increased vitamin D levels in our bodies and reduced hospital admission rates warrant further study,” said Andrea Darling, a postdoctoral researcher at the University of Surrey and senior study author.
“[It] points to the potential for vitamin D supplementation and consumption of vitamin D fortified foods to reduce the risk of hospitalization with respiratory infections in the future.”
The primary natural source of vitamin D for most people is the sun.
Vitamin D can also be found in fatty fish such as salmon, mackerel and tuna, fish liver oils, beef liver, egg yolks, cheese and fortified milk, cereals and orange juice.
Vitamin D supplements are widely available over the counter for a few cents per pill.
“Supplementation of the vitamin, especially in the winter months when our exposure to sunlight is limited, is an effective way of increasing vitamin D and reducing the risk of serious respiratory tract infections,” Bournot said.
“This is particularly important for older people who are at higher risk of death from such infections.”
