if you’re lactose intolerant, why does the lactose cause bowel distress instead of passing through inertly?


I get that lactase is needed to break it down into galactose and glucose, but why does the two monosaccharides’ glycocidic linkage cause so much pain and problems during digestion if it’s isn’t broken apart?

In: 104

There are bacteria in your gut, if you don’t digest the lactose the bacteria will metabolize it instead, the by-products of the bacterial metabolism is whats causing distress.

> it’s isn’t broken apart?

It’s not broken apart *by you*… but your intestines are full of billions of bacteria that can break it down just fine!

When your own body can’t break down the lactose into a digestible form, that just means it passes through the stomach and becomes a huge pile of food for intestinal bacteria. The result is that:

* the bacteria multiply to much higher population levels than they should have, and
* all those bacteria eating all that food creates a bunch of waste products and gases

All the bacteria and their gassy excrement being generated inside your pipes is what causes the pain and bloating, not the glycocidic linkages!

Lots of common bacteria can make lactase. If you don’t break up and absorb the lactose before it reaches the bacteria in your large intestine, they’ll consume it for energy and produce carbon dioxide gas in the process. Fermenting a little lactose makes a big volume of carbon dioxide, which pushes on your guts in painful and inconvenient ways.

In addition to fermentation, if the amount of unabsorbed lactose in the gut is high enough it raises the osmotic pressure, attracting water into the bowels, so water flows in and this influx of water is what leads to diarrhea.

That’s why for me if I eat like a meal with cream it just makes me gassy and my stool smell very sour, but if I drink like a glass of milk on an empty stomach I will have diarrhea within 30 minutes.