Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Speaker 1: Lauren Bogle Bomb here. When people can't digest milk, we
Speaker 1: call them lactose intolerant. This seems to signify that it's
Speaker 1: an unusual condition, that most people are just fine with milk,
Speaker 1: cheese and ice cream, and that lactose intolerance is something
Speaker 1: that needs to be fixed or helped. But it turns
Speaker 1: out that those poor souls who get gassy, crampy, and
Speaker 1: otherwise digestively miserable after eating dairy products are actually in
Speaker 1: the majority worldwide. It's the people who can handle milk
Speaker 1: who are the weird ones. Lactose is the main form
Speaker 1: of sugar in all mammal milk, and everyone is born
Speaker 1: with the gene that codes for the creation of lac taste,
Speaker 1: which is the enzyme that processes lactose. When we're babies,
Speaker 1: in other words, we all have the ability to digest milk.
Speaker 1: The small intestine produces lac taste. It breaks down lactose
Speaker 1: into glucose and galactose, which can be easily absorbed into
Speaker 1: the bloodstream. But for reasons unknown, the lactaste gene tends
Speaker 1: to shut off about the time we're weaned from breast milk.
Speaker 1: Most people don't create any lactaste, or very little of
Speaker 1: it by the time they're five years old or so.
Speaker 1: In the absence of lactaste, undigested lactose just sits in
Speaker 1: the colon and ferments, causing all kinds of uncomfortable side effects. Basically,
Speaker 1: your gut bacteria eat it and they excrete gas and
Speaker 1: other wastes, which you then have to excrete. Some people, however,
Speaker 1: carry a genetic mutation that allows the lactaste gene to
Speaker 1: keep working. Sometimes it continues for just a few more years,
Speaker 1: sometimes for a lifetime. Of Americans have a functional lactaste gene,
Speaker 1: so in the United States it is unusual to be
Speaker 1: lactose intolerant, but worldwide, more than six people lose the
Speaker 1: ability to process lactose. Because lactose intolerance is the more
Speaker 1: common condition around the globe, scientists and researchers in the
Speaker 1: field actually use the term lac taste persistence for people
Speaker 1: who can digest milk. Certain populations are more prone to
Speaker 1: lac taste persistence than others. In the United States, people
Speaker 1: of Caucasian descent are much more likely to be able
Speaker 1: to digest dairy and people of African American, Hispanic, and
Speaker 1: or Native American descent are not. Northern Europeans, especially Scandinavians,
Speaker 1: tend to hang onto the lactaste gene. Folks from Southern
Speaker 1: Europe are split about fifty fifty, but a full ent
Speaker 1: of Asians are lactose intolerant, hence the absence of dairy
Speaker 1: in many traditional foods from around the continent. Parts of Africa,
Speaker 1: with the history of cattle farming have populations with as
Speaker 1: much as lactaste persistence. Scientists aren't sure why some people
Speaker 1: lose the lactaste gene, but they have figured out that
Speaker 1: the genetic mutation appeared about seven thousand, five hundred years
Speaker 1: ago among dairy farming populations in Central Europe and eastern Africa.
Speaker 1: The theory is that the mutation was random, as all
Speaker 1: mutations are, but it became genetically advantageous in these dairy
Speaker 1: eating populations and thus spread rapid lee. To this day,
Speaker 1: there are still high rates of lactea persistence in those areas.
Speaker 1: Lactase persistence might not be a necessity for survival in
Speaker 1: the modern world, but it does make life more pleasurable
Speaker 1: for many people. So if you can enjoy ice cream, Sundays, milkshakes,
Speaker 1: and pizza with no problem. Remember that you're one of
Speaker 1: the lucky ones. Today's episode was written by Alison Cooper
Speaker 1: and produced by Tyler Klang. Brain Stuff is production of
Speaker 1: I Heart Radio's How Stuff Works. For more on this
Speaker 1: and lots of other topics, visit our home planet, how
Speaker 1: stuff Works dot com. And for more podcasts for my
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