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Monday, June 11, 2018

Understanding Lactose

In "Bluff the Listener" segment of the most recent episode of the popular NPR show, Wait Wait, Don't Tell Me, guest Bim Adewunmi tells a story of an "extremely lactose intolerant" man becoming the spokesperson for a major ice cream company. Which would be funnier, if it didn't reveal just how much the population still doesn't understand about lactose. Let's break it down:

  1. Lactose is not milk. It's a sugar component of almost all milk (well, the real stuff from mammals, not the extracts from plants often called plant milks). 
  2. It's a disaccharide - two simple sugars connected together. It's not a complex protein, as Bim mistakenly calls it on the podcast. 
  3. An enzyme called lactase breaks this bond, creating the two simple sugars again. Lactase is produced by most mammals as infants (that includes humans), but upon maturation, most humans stop producing lactase. Thus, most people (in the world) actually can't digest lactose as adults - this is normal (the statistical definition). 
  4. Through a quirk of evolution, some humans retained the ability to produce lactase through adulthood - mostly through a founding population in Europe (documented human evolution, for realz). In fact, lactase persistence is the odd case, but it's diagnostic of how medicine is so Eurocentric. 
  5. Processed and fermented milk products usually don't have lactose because the microbes used will usually digest it already (think yogurt or long aged cheeses). And yes, you can make ice cream with lactose free milk. 
Hey, contestant, knowing basic milk chemistry should've been a big giveaway on Bim's story. 


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