Ironically, for my first illness post I’m covering something
that isn’t actually an illness but can definitely make people sick. Lactose
intolerance is the inability to digest
the sugar (lactose) in milk products.
Figure 1: Milk hates some people.
Image from Rakka on
Flickr.
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Let’s look at a list of the recognized symptoms from the Mayo
Clinic:
· Diarrhea
· Nausea, and sometimes, vomiting
· Abdominal cramps
· Bloating
· Gas
How nice of them to put the worst symptoms first! I say this
because in the popular media lactose intolerance is often joked about, laughed
off, and generally considered a simple nuisance. On the popular science nerd
sitcom Big Bang Theory, Leonard is often made fun of because his lactose intolerance
makes him gassy. The truth is that the symptoms
can range from just mild gas and bloating to full-on diarrhea and vomiting
that feels like a velociraptor is tearing apart your insides while you sweat
and cry in the bathroom in the middle of the night and wonder if you’re dying
of some weird nocturnal intestinal disease. Why nocturnal? Well, because the symptoms
are caused by lactose making it to the large intestine. The average digestion
time for food to pass through your stomach and small intestine is around 6-8
hours but many people begin feeling gas and bloating symptoms only a few hours
after eating dairy. Everyone is different. Assuming 6-8 hrs, if you eat dairy
for supper it’s going to hit your large intestine in the night. When lactose
gets to the large intestine, that’s where things get interesting… if by interesting,
I mean painful bloating, gas, and diarrhea. Which I do. So where does the gas
come from and why does lactose cause such terrible cramping and diarrhea?
Figure 2: Lactose is made up of the simple sugars glucose
and galactose.
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The human body has taken on lots of little buddies during
its evolution including bacteria, with some even becoming an integral part of
cell function (holla to the mitochondria!). In the large intestine, bacteria can breakdown the leftover undigested
lactose into usable products like short chain fatty acids, which are further
broken down for energy. Great, right? It is except the byproducts of lactose breakdown by bacteria include CO2,
H2, and methane gas. And where do those gases need to go? Out.
But the way out is generally blocked by previous, um, material so the pressure
builds up until, well, you know. The first bowel movement in an attack is
usually normal in all respects except urgency, about 3-4 on the Bristol Stool Scale.
Once that’s out of the way comes the diarrhea, which can range from a 5 to a
watery 7 on the scale.
Figure 3: Lactose in the large intestine leads to excess
water loss
due to osmosis.
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So with all of these uncomfortable symptoms, why isn’t lactose
intolerance considered an illness? Historically, lactose intolerance has been
the default setting in adult mammals. Mammals only needed to survive on milk
until they could eat solid food so after infancy lactAse production decreased.
In Europe, people realized they could drink the milk of other mammals and make
delicious products like cheese and ice cream (okay, not really ice cream way
back then). As they ate more dairy at later ages the production of lactAse
stayed higher. This is why it’s rare for people of European descent to be
lactose intolerant. Surprisingly, up to
75 percent of adult humans are lactose intolerant to some degree and the
highest rates are in people from Southeast Asia, Africa, and in Native
Americans, cultures
with traditionally low rates of dairy consumption after infancy.
In another post, I’ll tell you about the tests that can be
used to diagnose lactose intolerance and how it’s treated.
I am not a medical
doctor, none of this is intended as medical advice, and I cannot diagnose you
in the comments. If you are concerned about your health, please see your
physician.
Awesome post! I enjoyed it thoroughly. Are you open to subject suggestions?? :)
ReplyDeleteThanks! Yes, I'm definitely open to suggestions! You can email them to me (sicknessisfascinating at gmail dot com) or tweet them at me. I'd like to put a Submit an illness form on the blog but haven't figured out how to yet.
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