Lactose intolerance flatulence: volume, or scent?

I’ve read in many places that one of the symptoms of lactose intolerance is flatulence.

However, these sources all seem to tiptoe around the subject as though everyone knows what they mean by “flatulence” as a symptom.

What I want to know is: If you’re lactose intolerant and you consume lactose, is the symptom supposed to be that you have BIGGER farts (i.e. with a greater volume of gas released), or is it that you have more FREQUENT farts, or is it that your farts SMELL worse?

Some or all of the above. It varies.

Pretty much all of the above. A lactose intolerant person can’t digest lactose. However, the bacteria in the colon can and will. The by-product of this digestion is gaseous and unpleasantly aromatic.

All of the above, as noted. The problem is that digestion is designed to proceed slowly and to spread the contents of a meal out over the longest possible time to ensure that the intestines have the greatest chance to break down the food and absorb all nutrients in it.

This means that any undigested lactose reaches the colon over a period of hours. The bacteria that ferment the lactose and create the gases (the smell actually seems to come from fatty acids produced as part of the process since the gases themselves are odorless) work continually on the lactose for hours and hours. The gas builds up in the intestines and releases violently - and seemingly forever.

Oh, one nitpick to Finagle I just noticed.

You want the bacteria in the colon to digest the lactose. What happens in lactose intolerance is that different types of bacteria don’t digest, but instead ferment the lactose. It’s the fermentation process that creates the gas. The bacteria in yogurt and some probiotics contain bacteria that do digest lactose and these will reduce the symptoms greatly.

Pictures Exapno Mapcase tapping his foot impatiently as he’s waiting for a fart to end.

But mostly, one does notice the smell.

I guess I’m not red-hot on the difference between digestion and fermentation as far as bacteria are concerned. I’m assuming that in both cases, microorganisms break down substances, getting energy out of the process and producing by-products. Is “fermentation” a form of digestion that produces unpleasant by-products or is the chemical process fundamentally different?

If a person with lactose intolerance ingests lactose, they’ll fart whereas otherwise they might not fart at all.
They may fart every few minutes. For hours.

There are “testimonials” about lactose-intolerant flatulence in Harris’ book.

Er…umm…not quite.

Lactose is a disaccharide, made up of a galactose and a glucose molocule. In a person who is tolerant of lactose, an enzyme, not a bacteria, in the gut called lactase breaks the bond between the sugars, turning it into two monosaccharides, which our bodies digest with ease in the small intestine.

In a lactose intollerant person, they stop making lactase in their adult years, so the gut bacteria are free to digest the latose by means of fermantation. In doing so, they make gases. Most of the gases have no odor, but some sulphur and other compunds are in there and get released, which case the smell. Oh, and it’s not really in the colon, it’s more in the small intestine. Although because of the gas, the water that normally get absorbed in the colon can’t, and so eating lactose can also cause a laxative effect. Fun all around!

Totally different. Digestion of lactose uses the enzyme lactase to break the bond between the simple sugars glucose and galactose that form the disachharide lactose. The simple sugars can be absorbed into the body with no difficulty and no symptoms.

If that were the only process, then no problem. But some bacteria use the glucose and galactose as a food source. The glucose is split into short-chain fatty acids.

More Than You Ever Wanted to Know About Short Chain Fatty Acids

And on for 23 pages.

Anyway, the fatty acids are then metabolized into other byproducts and these reactions create the carbon dioxide and hydrogen (and in some people methane) that are the gases that build up in the system. It’s like making beer in the belly.

Yes, lactase is produced in the small intestine to digest lactose. But the issue at hand is undigested lactose.

Lactose intolerance is the normal state of humanity. In many people lactase making stops at or near the age of weaning. It can occur thereafter at any age, but many children are lactose intolerant.

No. As I’ve explained, digestion and fermentation are two different things.

Cite, please? My sources tell me it’s the fatty acids that cause the smell. Where does the sulfur come from?

Absolutely not true. All the bacteria are in the colon. If you have them in the small intestine you have other problems than gas.

Nonsense. These are two different processes. Undigested lactose in the intestines causes a reverse molality that pulls water into the intestines rather than the normal removal of water as part of digestion. This has nothing to do with the gas created.

I’ll bet you dollars to donut-holes that there is sulfur in cheese somewhere. The fragrant farts I produce after I eat a whole package of string cheese have the unmistakable aroma of sulfur compounds.

BTW, I have never been diagnosed with lactose intolerance, but I’m worried that maybe I might be lactose intolerant, which would really tick me off because I like to drink between a quart and a half-gallon of nonfat milk per day. Are there “degrees” of lactose intolerance, i.e. can somebody be “just a little” lactose intolerant or “really really” lactose intolerant?

Sure there are degrees. If you make just enough lactase to digest all the lactose you take in, you won’t get symptoms. If you have just a tiny bit less than enough, then some lactose will get through. If you have a lot less than enough, then a lot of lactose will reach the colon. Unfortunately lactase production tends to decrease with age if you are LI.

BTW, Googling tells me that sulfur compounds do give cheeses distinctive flavors. They aren’t part of the breakdown of lactose, though. Maybe they form a overlay of aroma. :slight_smile:

yes there are degrees of intolerance.

me? I am pretty extreme.
if I eat a meal with milk products kinda mixed in and in small amounts then I do have some of the rankest gas you can imagine.
if I were to go chug a glass of milk or get exposed to a high amount then there is no gas…
because after about 5-10 min my stomache starts to cramp hard. then I can feel the express train on the move and between 20-30 minutes later I am on the pot.

Ill spare you the further details but a sudden dense amount of lactose will clean out my system in minutes and yes it sucks.

Probiotics (Acidolpholous) can help, note.

Needless to say this absolute nonsense and shouldn’t be in GQ.

No bacterium can ferment lactose without digesting it, and no bacterium can digest lactose in the gut without fermenting it.

When EM talks about digesting instead of fermenting he is making a nonsense statement. It’s like talking about eating without swallowing. Although they are different processes, in the case of lactose in the human gut you can never have one without the other.

And the idea that the bacteria in yoghurt digest lactose and are therefore somehow different from the gut bacteria that ferment it is equally nonsensical. Gut bacteria and yoghurt bacteria both digest lactose and both ferment it.

Digestion is simply the process of breaking food up into small pieces that can be absorbed into a living cell. Lactose won’t go into a bacterial cell as is, so it needs to be broken down into two smaller subunits.

Fermentation is simply a process that occurs within a cell to get energy out of food. It’s the actual ‘burning’ of the food as distinct from the ‘chewing’ that is digestion.

As you can see what EM is saying is nonsense. No bacterium can ferment lactose without first digesting it because in order to ferment it the lactose has to be taken into the cell, which can’t happen until it has been digested.

It is equally nonsensical to suggest that any bacterium would spend considerable energy and resources converting lactose into glucose and then not absorb it. Indeed it would be an extraordinary mutant if it could avoid absorbing and fermenting it.

EM’s idea that some bacteria ferment lactose and others ferment it is absolute bollocks. Some bacteria can neither ferment nor digest lactose and some can both ferment it and digest it. With a minor weasel exception there are not bacteria that only ferment or only digest as EM has suggested.

Once again, this is absolute nonsense from EM and highlights a total lack of understanding of a topic on which he spruiks so authoritatively.

“Although the bacterial counts of the stomach contents is generally low the walls of the stomach are usually heavily colonized with bacteria….,

The small intestine is separated into two parts, the duodenum and the ileum. The former… resembles the stomach in its microbial flora. From the duodenum to the ileum the pH gradually becomes more alkaline and bacterial numbers gradually increase. In the lower ileum bacteria are found in the intestinal cavity… Cell numbers of 10^5 –10^7 per gram are common.”

Brock, T.D., Madigan, M.T.; Biology of Microrganisms.

As you can see EM’s claim that all bacteria are in the colon is as ignorant and untrue as his claims regarding bacteria that can magically ferment lactose without digesting it and vice versa.
EM have recently thrashed out this very topic only a few days ago. After repeatedly asking him to provide references for his claims and explain what he proposes is even physiologically possible he slunk away.

You can read it all here:

Doubtless he will do the same in this thread. But this is GQ, we are supposed to be giving factiual answers, not ignorant BS.
So come on EM.

Can we have some evidence that says that any bacteria either digest or ferment lactose depending on strain?

Can you please name just one of these bacteria that merely digest lactose and don’t then go on to ferment its byproducts and product fatty acids and gases. If such bacteria exist then you should be able to name one shouldn’t you?
Can you please explain how your probiotic Lactobaccilli can manage to decompose lactose into galactose and glucose and be able to avoid fermenting the glucose so produced?

And can we please have a reference from a non-commercial source (ie some site that doesn’t make money form selling probiotics) to support your claim that probiotics help in LI? So far you have produced not one.

These are simple questions. They are perfect GQ fodder. So why can’t you answer them?

If they can the evidence hasn’t been forthcoming in that other thread where I requested references numerous times. Lots of commercial sites, Dairy Farmer’s co–opertaives etc claim that it works, but the medical/scientific literature doesn’t seem to support the idea.

Since this is GQ can you provide a reputable reference that it works?

"Background: Lactose intolerance is the most common disorder of intestinal carbohydrate digestion. Lactobacillus acidophilus BG2FO4 is a strain of lactobacilli with properties of marked intestinal adherence and high ß-galactosidase activity.

Objective: This study was designed to determine whether oral feeding of Lactobacillus acidophilus BG2FO4 leads to a lactose-tolerant state. . . .

Discussion: *ngestion of Lactobacillus acidophilus BG2FO4 for 7 d in subjects with lactose maldigestion with and without hypochlorhydria failed to result in any significant overall improvement in hydrogen production after lactose ingestion. The strategy of changing the enteric flora in the upper gastrointestinal tract to change an upper intestinal condition such as lactase deficiency does not appear to be effective.

Levri KM, Ketvertis K, Deramo M, Merenstein JH, D’Amico F; J Fam Pract. 2005 Jul;54(7):613-20.

Do probiotics reduce adult lactose intolerance? A systematic review.

CONCLUSIONS:** Probiotic supplementation in general did not alleviate the symptoms and signs of lactose intolerance in adults** in this review. Some evidence suggests that specific strains, concentrations, and preparations are effective. Further clinical trials of specific strains and concentrations are necessary to delineate this potential therapeutic relationship.

The best the medical literature seems to have is that ther might be some evidence that some specific strains work, but the evidence is only suggetsive, not conclusive.

Okay, if eating L. acidophilus doesn’t show any improvement in digestion in lactose-intolerant folks, how about eating the Lactobacillus found in yogurt?

(I’m assuming yogurt Lactobacillus is not the acidophilus species.)