How Foods Can Affect Your Immunity to the Flu
Can what you eat affect a flu virus?
“You bet it can,” says Melinda Beck, Ph.D., professor of pediatrics and nutrition at the University of North Carolina at Chapel Hill. In fact, according to Dr. Beck, it’s more what you don’t eat that counts.
Dr. Beck and her multidisciplinary team of colleagues are currently building upon an earlier discovery that in mice, a diet poor in the nutrient selenium causes mutations to occur in the influenza virus, making it more dangerous. Once the virus has changed, even mice whose diets are selenium-adequate are vulnerable to the more dangerous strain.
“These observations suggest a new area for flu researchers, namely the interaction between host nutrition and viral genetics,” says Dr. Beck.
Selenium is found in plant foods, such as Brazil nuts and whole grain cereals, as well as in some meats and seafood. Its content in foods depends on the amount of selenium in the soil where the plants grow or animals graze. Selenium is incorporated into enzymes that have antioxidant properties. These enzymes are important in protecting cells from damage by free radicals that are produced during infection.
Selenium also has toxic properties if consumed in excess, so the Institute of Medicine has established a Tolerable Upper Limit for adults of 400 micrograms per day.
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| Transmission electron micrograph of human nasal epithelium infected by influenza virus (dark circular objects). Credit: Dr. Beck |
In a new project funded by the NIAID, Dr. Beck is further investigating the relationship between selenium deficiency and mutation of the influenza virus. Working with a team of virologists, immunologists, cell biologists, biochemists, and nutrition experts, she is exploring what happens at the cellular and molecular level when selenium-deficient mice as well as human epithelial cells growing in the laboratory are infected with an influenza virus.
Among other things, the team hopes to learn
- how the flu virus evolves in a selenium-deficient host,
- how the host’s cells and immune system respond to the mutated virus,
- the amount of selenium required to prevent mutations from occurring, and
- whether a diet poor in other antioxidant nutrients, such as vitamin C, could also lead to viral mutations.
In a study comparing the effect of a mutated flu virus in mice with or without adequate selenium in their diets, the researchers found that half of the selenium-deficient mice died of infection—often within a few days—while no mice with adequate selenium died. The selenium-deficient mice had large amounts inflammation-promoting chemicals in their lungs, which may account for the extensive lung damage in those animals, notes Dr. Beck. “This finding is particularly interesting,” she adds, “because deaths in humans infected with avian flu may be due to the body’s inability to control inflammation.”
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