Gut Check looks at health claims made by studies, newsmakers, or conventional wisdom. We ask: Should you believe this?

The claim:

M

en’s flu symptoms are worse than women’s, so when they complain about how much they’re suffering it’s not (just) because they’re big babies.

Tell me more:

“Man flu” has become an internet meme, complete with its own tongue-in-cheek website dedicated to the proposition that when men catch even a simple cold their symptoms are as bad as if they had influenza, and when they contract actual flu their symptoms are way worse than women’s.

A recent study tested that hypothesis. Researchers at the University of Ottawa injected lab mice with molecules from bacteria, which mimic infection with E. coli, salmonella, legionella, and related bugs. They found “an important sex difference” in how the mice’s body temperatures responded, they reported in the journal Brain, Behavior, and Immunity: At the onset of infection, males’ body temperature fell more than females’ did. That would seem to fit with the “man flu” idea that identical infections make males more miserable — in this case, chilled — than females. The male mice’s signs of inflammation were also worse than females’, and they seemed to huddle together more and have droopier eyelids.

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“My data supports the idea that the man flu isn’t just a myth,” Ottawa psychology professor Nafissa Ismail said in an interview. The findings, moreover, are consistent with animal studies going back to the 1990s finding that “the intensity of infections tends to be lower in females than in males,” Ismail and colleagues wrote, possibly because of how sex hormones testosterone in males and estrogen in females affect the immune system.

Really?

Joking aside, sex and gender differences in response to infection is a lively area of research, in part because until a few years ago neither women nor female lab animals were regularly included in biomedical studies.

The mouse results, however, fall short of proving that men’s flu symptoms are worse than women’s, or that men’s mild infections are as bad as women’s serious ones. For one thing, the experiment used bacteria, not viruses; only the latter cause cold and flu, and bacterial infections are imperfect proxies for viral ones. Also, results in a few dozen mice, while a good start, don’t necessarily reveal much about human biology.

More extensive evidence undercuts the notion of man flu. The most important is that immune organs such as the thymus as well as immune cells such as macrophages all have receptors for testosterone and estrogens, so those sex hormones can affect the immune system. In general, testosterone suppresses it slightly while estrogens rev it up, including by increasing the production of microbe-killing antibodies and inflammation-causing proteins. Result: When women catch a virus, their immune systems flood the zone.

That might suggest that men are doomed to be more miserable when they have a flu or other viral infection, as their immune systems take a lackadaisical approach to fighting it. But no. “People think that when we get sick it’s the virus that causes our symptoms, but often those symptoms are from the immune response,” said biologist Sabra Klein of Johns Hopkins Bloomberg School of Public Health. “Cells clogging our airways, proteins causing inflammation, fever, and chills — that’s all immune response to a flu virus. And it is more common in females than males for those responses to go on too long and to be too intense. Testosterone [tamps down] the immune response, so you don’t get the exaggerated response” that intensifies symptoms.

The upside of females’ more vigorous immune response is that they generally recover from infections faster than males. Might man flu be more about how long a sufferer suffers, with psychological resilience eventually crumpling in the face of day-after-day symptoms? (The male mice in the Ottawa study took an average of 48 hours to recover, compared to 24 hours for the females.)

In the absence of strong physiological data supporting the notion of man flu, “you can look at psychological differences,” said immunologist Laura Haynes of the University of Connecticut, who studies age and sex differences in response to infection. “Maybe men just get whinier.”

The verdict:

Believers in man flu do not have physiology on their side.

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  • I got Man Flu and am a woman this nearly killed me and its been 2 months now and i am still not well.

  • What about the % of body fat?

    a. lower body fat = lower body temperature.
    b. grease doesn’t hurt, muscles do.
    c. grease doesn’t swell, muscles do.

  • Tho is why females have a much higher incidence of autoimmune diseases such as lupus, MS, myasthenia gravis, rheumatoid arthritis. Graves disease and autoimmune thyroiditis.

  • This is interesting, but I think something else that should be kept in mind is where the females are in their menstrual cycle. I think there is variability in immune responses there as well.

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