Submitted by chemstu69 t3_11c7e1n in explainlikeimfive
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?
Even without the bacteria, lactose is osmotically active so it limits water absorption by your intestines which causes diarrhea just like sorbitol
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It's interesting to see how lactose intolerance is caused by more than just the inability to break down lactose. Our gut bacteria can play a key role in the digestion of lactose, and the by-products of their metabolism can cause distress. This is why lactose-free products are so popular, as they have been predigested for us. It's fascinating to see how our bodies work together to help us digest food!
> 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:
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.
Can this affect nlood alcohol levels?
I don't think there's a significant effect. Just because there's fermentation happening doesn't mean a lot of alcohol is being produced. It's probably similar bacteria to the first population active in sauerkraut, which produce a lot of bubbling and a negligible amount of alcohol.
Also there isn't very much lactose in milk. Even if you ferment it with a yeast that turns it into alcohol fairly efficiently, milk won't pass 2.5% ABV, which is half the strength of beer.
There is a condition called Auto-Brewery Syndrome that can cause significant amounts of ethanol to be produced by gastrointestinal flora, but I'm not sure if it has any links to lactose intolerance.
Everyone has explained the gas and bloating. The second problem is diarrhea.
That's because you can't absorb lactose through the intestine. The molecule is too big and humans don't have specific transporters for it. This means you get a high amount of lactose in your bowels.
Physics tell us things always strive to go from a high to a low concentration, essentially diluting it. If the lactose can't move from your bowels into the bloodstream, it will instead drag lots of water from the blood into the intestines.
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.
A huge family of gut bacteria are capable of fermenting lactose. They are relatives of our old Friend E.coli.
If you can't digest it they will and when they do they produce a whole lot of gas! It's being forcibly inflated by the gas that causes the discomfort and potential projectile sharting.
You body can't absorb the double sugar, so the sugar goes to the colon and the bacteria go wild.
I did not know it was osmotic though, I thought it was just the irritation from the bacteria.
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You aren't the only thing that eats it. You are full of bacteria which CAN break down, but not in the same way your lactase does... it doesn't care that it spits out a bunch of byproduct gas. That gas causes inflammation in your gut and all the symptoms you are mentioning.
Two fold: Even though you can’t digest lactose and turn it into energy or fat stores, the bacteria living in your colon can and break those carbon chemical bonds. This provides energy to the bacteria those causes that carbon to bond with oxygen and form CO2. The excess CO2 causes pain, flatulence and bloating. Second, sugar is osmotically active meaning that is draws water to itself, causing diarrhea.
Therefore, Lactose intolerance commonly leads to a combination of pain, bloating, flatulence and diarrhea.
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You do realize "lactose free" just means the manufacturer has added lactase to the product so it's been predigested for you? It still has the same amount of sugar as you would normally get.
Lactase breaks down lactose into glucose and galactose which are types of sugar.
My continuous glucose meter gives me a better reading with lactose free rather than regular dairy products, so that does for me, and both my GP and Diabetic specialist nurse are happy, win win for me, I'm not going to over analyse it.
Gullible-Flounder-79 t1_ja21ysn wrote
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.