Are Humans Built to Drink Milk After Childhood?

The majority of humans become lactose intolerant as they grow up. Learn how ancient herders changed our digestive gene pool in this episode of BrainStuff, based on this article: https://health.howstuffworks.com/wellness/food-nutrition/facts/humans-built-drink-milk-adults.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain stuff production of iHeartRadio. Hey, brain stuff,
laurin vogel bomb here. When people can't digest milk, we
call that lactose intolerance. This might seem to signify that
it's an unusual condition that most people are just fine
consuming dairy products like milk, cheese, and ice cream, But

(00:23):
it turns out that we pour souls who get gassy, crampy,
and otherwise digestively miserable after eating dairy products are actually
in the majority worldwide. It's the people who can handle
milk where the weird ones. A. Lactose is the main
sugar in all mammal milk, and everyone is born with
the gene that codes for producing lactase, which is the

(00:45):
enzyme in our bodies that processes lactose, so when we're babies,
we all have the ability to digest milk. The human
body produces lactase in the small intestine, where it breaks
down lactose into glucose and glactose, which are bodies can
easily absorb into our bloodstream, But for reasons unknown, the
gene for lactase tends to shut off at about the

(01:07):
time that most of us would be weaned off of
breast milk and onto solid foods. Most people's bodies don't
create any lactase, or very little of it by the
time they're five years old or so. In the absence
of lactase, the excess sugar sitting around in your small
intestines causes your body to try to flush it out
by secreting fluids and moving things along faster than normal.

(01:30):
By the time the lactose reaches your colon, the mostly
helpful microorganisms there eat it and poop things like carbon dioxide, hydrogen,
and methane. In combination. This can lead to those unpleasant
symptoms of diarrhea, gas, and cramps. Some lucky people, however,
carry a genetic mutation that allows the lactase gene to

(01:51):
keep working. Sometimes it continues for just a few more years,
sometimes for a lifetime. Up to ninety percent of Americans
have a functional lactase gene, so in the US it's
a little unusual to be lactose intolerant. About worldwide, more
than sixty percent of people lose the ability to process lactose.
Because lactose intolerance is the more common condition around the globe,

(02:14):
scientists and researchers in the field actually use the term
lactase persistence for the rarer case of people who can
digest dairy. Because the function of the gene is genetic,
certain populations are more prone to lactase persistence than others.
Northern Europeans, especially Scandinavians, tend to hang on to a
functional lactase gene, along with some populations from West Africa,

(02:35):
East Africa, and the Middle East. People from Southern Europe,
the rest of Africa, much of the Americas, Central Asia,
and Northern Asia are less likely to have tolerance, and
it's super rare in Southeastern Asia. Based on these patterns
and non genetic research, it seems that the mutations that
code for keeping the lactase gene active appeared about seven thousand,

(02:58):
five hundred years ago among cattle farming populations in Central
Europe and Eastern Africa, and in camel herders in the
Middle East. The theory is that the mutation was random,
as all mutations are, but it became genetically advantageous in
these dairy eating populations and thus spread rapidly. To this day,
there are still high rates of lactase persistence in these areas.

(03:21):
Lactase persistence might not be a necessity for survival in
the modern world, but it can make life easier and
perhaps more delicious. So if you can enjoy conventional ice cream, Sundays, milkshakes,
and pizza with no problem, remember that you're one of
the lucky ones. If you're not, remember that there are
lots of dairy alternatives out there. Today's episode is based

(03:47):
on the article are humans built to drink milk as adults?
On How stuffworks dot Com? Written by Alison Cooper. Rain
Stuff is production of by Heart Radio in partnership with
how stuffworks dot Com, and is produced by Tyler Klang.
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