Biochemist Katie Wu is lactose intolerant, but her mother won't believe her.

Katherine (Katie) Wu is a graduate student at Harvard University. Currently, she is studying how bacteria handle stressful situations so that she can someday learn to do the same. Outside of the lab, she is Co-Director of Harvard Science in the News, a graduate student organization that trains aspiring scientists to better communicate with the general public through free public lectures, online blogs, podcasts, outreach programming, and more. Additionally, she designs and teaches health science and leadership curriculum for HPREP, an outreach program for underserved and minority high school students from the Greater Boston area.

This story originally aired on Nov. 10, 2017 in an episode titled, “DNA.”

Story Transcript

For a few months in college, I subsisted almost entirely on cereal, not out of necessity but out of obsession.  Most nights I would sit down for dinner in my dining hall with three bowls in front of me.  For my appetizer, fiber-rich Raisin Bran, which, as far as I was concerned, was basically salad.  Multigrain Cheerios for my main course and Frosted Mini-Wheats for dessert. 

One night, after a particularly brutal physics midterm, I staggered into my dining hall with only one thought on my mind: Oatmeal Squares.  So I poured myself some cereal and I headed over to the fridge for my cereal accompaniment of choice – almond milk. 

That’s when disaster struck.  The almond milk was empty.  Okay. This sucked, but it was going to be okay.  I would have soy milk.  Soy milk is great.  But, of course, that was empty too.  As was the rice milk and the coconut milk and, even impossibly, this beany-tasting jar of hemp milk that I could have sworn had been in that fridge since freshman orientation.  In fact, the only thing left in the entire milk section was this half-empty carton of skim cow’s milk. 

I was horrified.  My life in a series of Kellogg’s cereal boxes flashed before my eyes.  In that moment, as I was staring at this carton of skim milk, my panicked thoughts started to drift towards my mother.  No, not because of some twisted milk-driven, Freudian impulse thing but because I’m lactose intolerant. 

And I’m not alone here.  About 75 percent of the world’s population actually can’t digest lactose after they're about two years old, around the age of weaning.  But even if you can’t digest lactose, that doesn’t necessarily mean you're lactose intolerant.  Only some people have that adverse reaction. 

So what can happen is this.  If lactose sits undigested in your colon, it can start to draw water into your gut and you get diarrhea.  If you're super lucky, you'll also have certain populations of bacteria in your gut that can ferment that lactose and create a ton of rancid gas and nausea.  It’s pretty great. 

So science tells us that lactose intolerance is kind of, definitely, a thing, but my mother, my mother believes that lactose intolerance is more a state of mind. 

So I’m my mother’s only child and I grew up way too fast for her liking.  Every developmental milestone from my first bite of solid food to my first successful parallel park was a traumatic event for her.  She desperately resisted my independence.  To her, me growing up was me growing away. 

The day I left for college, she sat me down and started talking to me about her friend’s son.  We’ll call him Allen. 

She said, “Allen is such a good boy.  When he moved out, he cried for two weeks and now he calls his mother every day twice.” 

I resisted the urge to ask her if this kid still drinks directly from his mother’s breast or if she shipped the milk out to him on cold packs? 

So, growing up, I was just so embarrassed every time someone commented on how much I looked or acted like my mother, but she ate that shit up.  One day when I was nine, she came home carrying these two massive, hideous, matching pink dresses for us to wear to a wedding.  In an attempt to reason with her, I hid in the closet in my underwear, plugged my ears and screamed bloody murder until she let me put on different clothes. 

As hard as she fought to keep me close, I fought twice as hard to run away.  Though, in her ideal world, I’m pretty sure I would still be on the other end of a twenty-five-year-old umbilical cord. 

So maybe it’s not shocking that my mom doesn’t drink the dairy-free Kool-Aid.  To her, lactose intolerance is a figment of the imagination or a millennial myth, like depression or a liberal arts education or interracial marriage.  She has this really bad history of sneaking cream into my coffee and wedging cheese into my sandwiches.  She likes to tell me that all the pain and discomfort and bloating and nausea I experience during these events are all in my head. 

Anyway, I’m standing here in this barren wasteland where nondairy milk goes to die, confronted with this impossible choice.  I know that the reasonable thing to do is just to find something else to eat, but I'd been looking forward to my Oatmeal Squares all day and, at this point, to go without them is a fate worse than death. 

I’m locked in this staring contest with this half empty carton of skim milk and, all of a sudden, I’m Alice down the rabbit hole and the milk in front of me is saying, “Drink me.” 

Maybe it’s my stomach talking, but I start to wonder if my mother is, for once, actually right and it is all in my head.  Because I haven't had dairy in like eleven years and it is technically possible for lactose intolerance to wax and wane. 

I look down at my Oatmeal Squares and, in that moment, I decide to fight, to be brave.  I will not go gentle into that good night.  I crack open the carton of skim milk. 

Twenty minutes later, it is no longer all in my head.  Instead, it is all over my clothes, all over my floor, and all over the second-floor women’s restroom.  In that moment, I have two thoughts.  My first is that whoever first looked at a cow, considered its leaky, drooping udders, and thought it was the right decision to suck the liquid from its fleshy, pink undersides had to have been the biggest idiot in the entire world. 

My second is of nauseated vindication.  Nothing has changed.  I’m still pretty damn lactose intolerant.  If anything, the years off dairy has made my body more sensitive to it and it’s punishing me for breaking fast. 

Here’s the frustrating thing.  My mother could have watched this entire ordeal unfold and she still probably wouldn’t have believed me.  All this in spite of the fact that, as someone who grudgingly cohabitated with her for eighteen years, I can tell you that she and I both know that she too gets a little tooty after ice cream. 

That’s the thing.  Biology tells us that we’re all a little more our mothers than our fathers.  We exist inside our mothers’ bodies, emerge into the world through our mothers, even get our first gut and microbes from our mothers, the same microbes that can go on to determine whether or not we put cream cheese on our bagels. 

What’s more, there's actually some DNA that we only get from our mothers.  Most of our DNA is in the nucleus.  That’s where our chromosomes are, but there's also some in the mitochondria, which you may remember from middle school biology as the powerhouse of the cell. 

Maternal mitochondrial DNA is lost during fertilization so the inheritance of this stuff is entirely matrilineal.  In reality, mitochondrial DNA is just like 0.1 percent of our genetic code.  It’s actually kind of surprising this stuff is still around at all because it’s a lot of work for the cell to remain two separate sets of DNA.  Mitochondrial DNA should have been lost to the ether long ago. 

Nevertheless, she persisted.  Mitochondrial DNA is still passed on, stable and intact, generation to generation, mother to child. 

In my quest to break free of my mother, I lost sight of who she really was.  The same woman who had scoffed at my gastrointestinal distress and denied me the luxury of a bra through the end of middle school was the same woman who indulged my voracious love for reading and bought me every book I could have ever wanted.  The same woman who, knowing I don't have a lot of time to shop for groceries, once tried to ship me a pound of grapes in a FedEx envelope, who drove in socks and flip-flops six hours just to have dinner with me the night of my college graduation.

Who, on nights when I woke up screaming, would crawl into bed with me and let me curl up on her chest and, when I grew too big to fit there, with my head resting on the left side of her body so I could just hear the sound of her beating heart.  It was the closest thing I ever had to a lullaby. 

My mother, fueled by her often misguided but always unconditional love, is an inextricable part of me.  And when I remember this, I don't have to look far to see her in myself.  I have her stocky build, I have her lopsided smile, I have her lactose intolerance for better or for worse.  I have her pride, though I know sometimes she wishes I would give that one back. 

In every cell in my body there's a small unfathomable piece that is entirely my mother: stubborn, unbroken, eternal. 

Thank you.