"Man flu" seems like a lame excuse for dads to get out of doing chores, but a new study shows there may be some truth to why the flu seems to hit men worse than women.
Researchers at Johns Hopkins University knew from previous studies that estrogens have antiviral properties against HIV, Ebola and hepatitis viruses. But what they wanted to find out was how the female sex hormone affects the influenza A virus (what we commonly call the flu). And what they discovered is pretty cool.
First, let's lay down some groundwork. Viruses infect and make us sick by entering a cell and making copies of itself inside that cell. (Imagine your sick kid coming into your room and cloning himself. Talk about nightmares.) The virus spreads through the body and between people when released from infected cells. If the virus replicates less, it means the person may be less sick or less likely to spread the disease.
So how does estrogen affect the influenza A virus to replicate? The study, published in the American Journal of Physiology, looked at nasal cells (what the flu virus mainly infects) from male and female donors, exposing the cell cultures to the virus, estrogen, the environmental estrogen bisphenol A and selective estrogen receptor modulators (SERM).
Turns out estrogen, bisphenol A and SERM compound raloxifene reduced the replication of the flu virus in women's nasal cells—but not men. The estrogen triggers antiviral effects through estrogen receptor beta. According to News-Medical, receptors are protein structures that molecules bind with to induce cells to respond.
"What makes our study unique is two-fold," says lead author Dr. Sabra Klein. "First, we conducted our study using primary cells directly isolated from patients, allowing us to directly identify the sex-specific effect of estrogens. Second, this is the first study to identify the estrogen receptor responsible for the antiviral effects of estrogens, bringing us closer to understanding the mechanisms mediating this conserved antiviral effect of estrogens."
It may also explain why premenopausal women on certain types of birth control or post-menopausal women on hormone replacement might be better protected during flu season. Klein and her team see clinical potential in the finding that therapeutic estrogens used for treating infertility and menopause might also protect against the flu.
Whether you now believe in "man flu" or not, one commenter named Hecate isn't having it: "No amount of papers will change my mind, you can get your OWN hot lemony paracetamol drink ... and if you 'fancy you can manage some soup'—the can opener is in the drawer!!!"