Speaker 1: Welcome to brain stuff production of iHeartRadio. Hey, brain stuff,
Speaker 1: laurin vogel bomb here. When people can't digest milk, we
Speaker 1: call that lactose intolerance. This might seem to signify that
Speaker 1: it's an unusual condition that most people are just fine
Speaker 1: consuming dairy products like milk, cheese, and ice cream, But
Speaker 1: it turns out that we pour souls who get gassy, crampy,
Speaker 1: and otherwise digestively miserable after eating dairy products are actually
Speaker 1: in the majority worldwide. It's the people who can handle
Speaker 1: milk where the weird ones. A. Lactose is the main
Speaker 1: sugar in all mammal milk, and everyone is born with
Speaker 1: the gene that codes for producing lactase, which is the
Speaker 1: enzyme in our bodies that processes lactose, so when we're babies,
Speaker 1: we all have the ability to digest milk. The human
Speaker 1: body produces lactase in the small intestine, where it breaks
Speaker 1: down lactose into glucose and glactose, which are bodies can
Speaker 1: easily absorb into our bloodstream, But for reasons unknown, the
Speaker 1: gene for lactase tends to shut off at about the
Speaker 1: time that most of us would be weaned off of
Speaker 1: breast milk and onto solid foods. Most people's bodies don't
Speaker 1: create any lactase, or very little of it by the
Speaker 1: time they're five years old or so. In the absence
Speaker 1: of lactase, the excess sugar sitting around in your small
Speaker 1: intestines causes your body to try to flush it out
Speaker 1: by secreting fluids and moving things along faster than normal.
Speaker 1: By the time the lactose reaches your colon, the mostly
Speaker 1: helpful microorganisms there eat it and poop things like carbon dioxide, hydrogen,
Speaker 1: and methane. In combination. This can lead to those unpleasant
Speaker 1: symptoms of diarrhea, gas, and cramps. Some lucky people, however,
Speaker 1: carry a genetic mutation that allows the lactase gene to
Speaker 1: keep working. Sometimes it continues for just a few more years,
Speaker 1: sometimes for a lifetime. Up to ninety percent of Americans
Speaker 1: have a functional lactase gene, so in the US it's
Speaker 1: a little unusual to be lactose intolerant. About worldwide, more
Speaker 1: than sixty percent of people lose the ability to process lactose.
Speaker 1: Because lactose intolerance is the more common condition around the globe,
Speaker 1: scientists and researchers in the field actually use the term
Speaker 1: lactase persistence for the rarer case of people who can
Speaker 1: digest dairy. Because the function of the gene is genetic,
Speaker 1: certain populations are more prone to lactase persistence than others.
Speaker 1: Northern Europeans, especially Scandinavians, tend to hang on to a
Speaker 1: functional lactase gene, along with some populations from West Africa,
Speaker 1: East Africa, and the Middle East. People from Southern Europe,
Speaker 1: the rest of Africa, much of the Americas, Central Asia,
Speaker 1: and Northern Asia are less likely to have tolerance, and
Speaker 1: it's super rare in Southeastern Asia. Based on these patterns
Speaker 1: and non genetic research, it seems that the mutations that
Speaker 1: code for keeping the lactase gene active appeared about seven thousand,
Speaker 1: five hundred years ago among cattle farming populations in Central
Speaker 1: Europe and Eastern Africa, and in camel herders in the
Speaker 1: Middle East. The theory is that the mutation was random,
Speaker 1: as all mutations are, but it became genetically advantageous in
Speaker 1: these dairy eating populations and thus spread rapidly. To this day,
Speaker 1: there are still high rates of lactase persistence in these areas.
Speaker 1: Lactase persistence might not be a necessity for survival in
Speaker 1: the modern world, but it can make life easier and
Speaker 1: perhaps more delicious. So if you can enjoy conventional ice cream, Sundays, milkshakes,
Speaker 1: and pizza with no problem, remember that you're one of
Speaker 1: the lucky ones. If you're not, remember that there are
Speaker 1: lots of dairy alternatives out there. Today's episode is based
Speaker 1: on the article are humans built to drink milk as adults?
Speaker 1: On How stuffworks dot Com? Written by Alison Cooper. Rain
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Speaker 1: how stuffworks dot Com, and is produced by Tyler Klang.
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