Whenever I go on a date or grab dinner with a new friend, something inevitably comes up:
I'm lactose intolerant.
Most people I meet assume that means I can't be within ten feet of any dairy products (which is actually more in line with a milk allergy), and everyone else cites some meme about how lactose intolerant people are sadists—so I always have something to clear up. And don't feel bad! Even other lactose intolerant people don't know what I'm about to share. I'm just ~special~ because I studied nutrition. So let's explain the difference between lactose intolerance and a milk allergy.
Lactose is a disaccharide, a sugar made up of two simpler sugars. It looks a lot like sucrose (table sugar), but it's made up of glucose bonded to galactose, whereas sucrose is glucose and fructose. Your body makes a special enzyme to break down each of these sugars, and the enzyme that breaks down lactose is called lactase (notice the "A"). If you're lactose intolerant, it just means you don't make enough lactase to digest lactose.
image: common disaccharides
If a lactose intolerant person were to drink a glass of milk, the lactose in the milk would pass through the small intestine (where most macronutrients are absorbed) and head straight for the large intestine, dragging water along with it. The bacteria in the large intestine would then go on a destructive sugar rampage, fermenting the lactose and making gasses. That means uncomfortable bloating, toots, and diarrhea. *insert poop emoji*
So how do you fight back?
Most pharmacies and grocery stores carry lactase supplements, which can be taken orally with lactose-rich foods to help you digest them (before they reach your large intestine bacteria, that is).
Research also shows that even people with low lactase production can still tolerate 0.5 to 1 cup of milk with meals. And dairy products where lactose has been converted to lactic acid, like yogurt and hard cheeses, are definitely still digestible as well. (And thank goodness—cheese is life, amirite?)
A milk allergy is much more serious than lactose intolerance—lactose intolerant people only experience symptoms when they ingest lactose, but people with milk allergies can get adverse reactions just by being around dairy.
Like other allergies, a milk allergy is an immune response to a certain protein. If you have a milk allergy, your immune system essentially thinks milk protein is a dangerous invader, and it reacts accordingly. Allergy symptoms may vary, both by intensity and type, but they can include hives, itching, coughing, wheezing, or even anaphylaxis—a life-threatening restriction of the airways.
Milk allergies can be sneaky too. Things like protein powders can contain milk protein in the form of whey and casein, so be careful!
Just So You Know
I'm not a doctor, or even a registered dietitian—I'm just a writer with a bachelor's in nutrition. So if you think you're lactose intolerant or allergic to milk, consult a registered dietitian or medical doctor! I guarantee they're smarter than me.
Anyway, now you can just let me enjoy my ice cream! (Unless I forget my lactase pills.)