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  • There's usually a laundry list of dos and don'ts that people can expect to hear when they're pregnant.

  • Don't eat fish, don't drink caffeinated beveragesand they don't always tell you why.

  • One of the most oddly specific-sounding ones is a moratorium on soft cheeses.

  • And there's actually an extremely good reason for it, although the focus shouldn't necessarily fall on Camembert.

  • A number of processed foods, including but not limited to soft cheeses, can harbor the infectious bacterium Listeriaand it's a serious danger to fetuses.

  • Listeria monocytogenes is a common bacterium found in a huge variety of places, including water, soil, raw produce, processed foodsand even feces.

  • It's actually a pretty uncommon infection in the general population, but one exception is pregnant people, for whom it's nearly 20 times more common.

  • A lot of changes happen to your body during pregnancy.

  • This includes your immune system, specifically a reduction in cell-mediated immunity.

  • This system includes multiple defense mechanisms that don't rely on antibodies.

  • Instead it's mediated by specialized cells.

  • This type of immunity is important for detecting and destroying cells in your body that may be infected with viruses or bacteria.

  • Your antibody-based immunity, on the other hand, makes those antibodies in response to viruses or bacteria in the fluid outside of your cells.

  • But your body shifts away from cell-mediated immunity during pregnancy to allow a tiny human to grow inside of you.

  • This ensures those well-meaning immune cells don't detect the fetus and treat it like an unwanted intruder.

  • Although Listeria infection is far more common in pregnant people, symptoms tend to be very mild.

  • This is because Listeria is a unique bacterium with a sneaky way of getting around that doesn't get your antibody-based immune system all riled up.

  • The bacteria basically trick the cells in your gastrointestinal tract into engulfing them.

  • Once inside a cell, Listeria multiplies and pushes against the membrane, eventually pushing straight through into neighboring cells without spending any time in the outside space.

  • This means your best defense against Listeria is your cell-mediated immunity.

  • So it makes sense that there's less of a reaction in a pregnant host.

  • But this sneaky way of spreading also means it can get across the placenta, and this is where it becomes really risky.

  • The human maternal-fetal interface is what nourishes your fetus and protects it from both your immune cells and outside infections.

  • Placental cells have direct contact with maternal blood, so the placenta is very resistant to infections, but not to pathogens like Listeria.

  • And researchers aren't totally sure why yet.

  • Although Listeria doesn't usually have much of an impact on the pregnant person, it's very dangerous to developing fetuses.

  • It can cause premature birth or pregnancy loss as well as brain damage, and is often fatal to fetuses and newborns.

  • We mostly get Listeria infections from contaminated foods, and we can take some steps to limit our exposure to it.

  • Like pasteurization, which eliminates Listeria from dairy products.

  • So although you can get it from a variety of things, unpasteurized cheese is definitely on the no-go list.

  • In some parts of the world, including the US, it's actually hard to find unpasteurized cheese.

  • But Listeria has also been found in pasteurized soft cheeses thanks to manufacturing issues.

  • Soft cheese gets a lot of attention when it comes to Listeria risk, but there's actually a wide range of dairy products, cold meats, and other processed foods that are vulnerable to contamination.

  • Recent outbreaks of Listeria have even been linked to unprocessed foods, like raw sprouts, celery, and melon.

  • Like we saidListeria is super common, and it's also behind the prohibition of stuff like hot dogs and deli meats for pregnant people.

  • So to be on the safe side, it might be a good idea to just avoid the deli counter for the duration of pregnancy!

  • Thanks for asking, and thanks especially to our patrons for supporting this episode.

  • Patrons have a chance at getting their questions answered in episodes like this one.

  • So if there's something you're itching to know, consider becoming a patron at patreon.com/scishow.

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B2 中高級

懷孕期間吃軟奶酪有危險嗎? (Are Soft Cheeses Dangerous During Pregnancy?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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