# Lactose intolerance and beans
**URL:** https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313
**Category:** Factual Questions
**Created:** [September 8, 2009, 6:14pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313 "2009-09-08T18:14:33Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)
#### Post date: [September 8, 2009, 6:14pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/1 "2009-09-08T18:14:33Z")
Beans make you, you know. It happens because undigested sugars are digested by bacteria farther downstream, producing gas as a by-product. My understanding of lactose intolerance is the same, that it is actually the lack of enzymes needed to digest lactose, and the products of bacteria digesting it downstream cause extreme discomfort.
Why do people who get gas from beans (which apparently is virtually everybody) become no more than the fodder for fart jokes, but lactose intolerant people can truly suffer from it?
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### Author:  [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)
#### Post date: [September 8, 2009, 6:31pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/2 "2009-09-08T18:31:33Z")
Great username/thread combo, by the way.
Lactose is a sugar found in dairy which is composed of one molecule of galactose bound to one molecule of glucose. A particular enzymes is required to breakdown lactose for proper digestion. If not digested, the bacteria in your gut will metabolize it, making gas a a by product.
The sugar in beans is in the form of a starch, which is long chains of glucose molecules bound together. It is similar to the starch found in potatoes, but with a different pattern of bonding. Humans have problems breaking this particular bonding arrangement, leaving the beans undigested. Bacteria do their thing, cause gas production.
Lactaid provides the enzymes to metabolize lactose. (beta-galactosidase)
Beeno provides the enzymes for starch metabolism. (alpha-glactosidase)
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [September 8, 2009, 6:40pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/3 "2009-09-08T18:40:17Z")
Undigested lactose has two mechanisms for creating symptoms. One is the one you mentioned. The other is that the lactose molecules change the molality of the intestines. Rather than water being removed from the intestines, water is drawn in. This results in the continual diarrhea associated with lactose intolerance and not with bean digestion.
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### Author:  [@GilaB](https://boards.straightdope.com/u/GilaB)
#### Post date: [September 10, 2009, 6:30pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/4 "2009-09-10T18:30:33Z")
Not everybody has bean issues - I can eat them without a problem. Is it possible that some people make the appropriate enzyme to break down bean starches? Or do I just have more efficient bacteria?
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### Author:  [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)
#### Post date: [September 10, 2009, 7:06pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/5 "2009-09-10T19:06:52Z")
> [@GilaB](#):
>
> Not everybody has bean issues - I can eat them without a problem. Is it possible that some people make the appropriate enzyme to break down bean starches? Or do I just have more efficient bacteria?
Not all beans cause problems. You can prepare them in a way that breaks down the starch a lot or gets rid of a lot of the starch in a way that would make them have less side-effects.
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### Author:  [@tim-n-va](https://boards.straightdope.com/u/tim-n-va)
#### Post date: [September 10, 2009, 7:11pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/6 "2009-09-10T19:11:59Z")
On another message board I’d read that the enzyme to digest lactose is produced at the tip of the villi in the small intestines. As result, some people with celiac disease have lactose intolerance symptoms due to the villi being damaged by the gluten they consume. Is that a plausible sequence?
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### Author:  [@typoink](https://boards.straightdope.com/u/typoink)
#### Post date: [September 10, 2009, 7:20pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/7 "2009-09-10T19:20:34Z")
Aside: the first time I read the OP, I thought the question was “why don’t people make fun of people with lactose intolerance the way they make fun of bean-eaters.”
My first thought was, “people aren’t jerks,” but the obvious falseness of that made me start to wonder if the OP had a point.
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### Author:  [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)
#### Post date: [September 10, 2009, 8:57pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/8 "2009-09-10T20:57:35Z")
> [@typoink](#):
>
> Aside: the first time I read the OP, I thought the question was “why don’t people make fun of people with lactose intolerance the way they make fun of bean-eaters.”
>
> My first thought was, “people aren’t jerks,” but the obvious falseness of that made me start to wonder if the OP had a point.
Well, the point isn’t so much the making fun part, but you know that scene in Blazing Saddles wouldn’t have been nearly so funny if those cowboys had all just had a big glass of milk. 🙂
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### Author:  [@Uncertain](https://boards.straightdope.com/u/Uncertain)
#### Post date: [September 10, 2009, 11:26pm UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/9 "2009-09-10T23:26:03Z")
> [@IvoryTowerDenizen](#):
>
> The sugar in beans is in the form of a starch, which is long chains of glucose molecules bound together. It is similar to the starch found in potatoes, but with a different pattern of bonding. Humans have problems breaking this particular bonding arrangement, leaving the beans undigested. Bacteria do their thing, cause gas production.
>
> Lactaid provides the enzymes to metabolize lactose. (beta-galactosidase)
>
> Beeno provides the enzymes for starch metabolism. (alpha-glactosidase)
Is it really starch then? I thought that starch, by definition, consisted of glucose residues. Perhaps it’s some other polysaccharide, or just small alpha-galactosides.
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### Author:  [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)
#### Post date: [September 11, 2009, 12:26am UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/10 "2009-09-11T00:26:27Z")
> [@tim-n-va](#):
>
> On another message board I’d read that the enzyme to digest lactose is produced at the tip of the villi in the small intestines. As result, some people with celiac disease have lactose intolerance symptoms due to the villi being damaged by the gluten they consume. Is that a plausible sequence?
Yes, that’s correct.
> [@Uncertain](#):
>
> Is it really starch then? I thought that starch, by definition, consisted of glucose residues. Perhaps it’s some other polysaccharide, or just small alpha-galactosides.
I’m not sure what glucose residues might mean.
> **[Polysaccharide](https://en.wikipedia.org/wiki/Polysaccharides)**
>
> Polysaccharides (/ˌpɒliˈsækəraɪd/; from Ancient Greek πολύς (polús) 'many, much' and σάκχαρ (sákkhar) 'sugar') are "Compounds consisting of a large number of monosaccharides linked glycosidically". They are the most abundant carbohydrates in food. Their structures range from linear to highly branched polymers. Examples include storage polysaccharides such as starch, glycogen, and galactogen and structural polysaccharides such as hemicellulose and chitin. The term "glycan" is synonymous wi Po...
> [@](#):
>
> Starches are glucose polymers in which glucopyranose units are bonded by alpha-linkages. It is made up of a mixture of Amylose (15-20%) and Amylopectin (80-85%). Amylose consists of a linear chain of several hundred glucose molecules and Amylopectin is a branched molecule made of several thousand glucose units(every chain 24-30 glucose unit). Starches are insoluble in water. They can be digested by hydrolysis, catalyzed by enzymes called amylases, which can break the alpha-linkages (glycosidic bonds). Humans and other animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet. The formation of starches are the way that plants store glucose.
That’s a formal definition of starches, but it’s true that starch in casual speech is an all-embracing term for carbohydrates more complex than sugars.
Beans contain oligosaccharides, which are polysaccharides. There are varying structures for oligosaccharides in vegetables but you can consider them to be sugar chains that are metabolized to glucose in digestion.
Or, in short, IvoryTowerDenizen had it right. Beano is an alpha-galactosidase, meaning it breaks the alpha bonds between components of the chain. The difference between that and the beta bond in lactose that Lactaid breaks is that the beta bond curls downward and the alpha bond curls upward. For real. That directional change makes all the difference.
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### Author:  [@Uncertain](https://boards.straightdope.com/u/Uncertain)
#### Post date: [September 11, 2009, 1:56am UTC](https://boards.straightdope.com/t/lactose-intolerance-and-beans/509313/11 "2009-09-11T01:56:21Z")
> [@Exapno\_Mapcase](#):
>
> I’m not sure what glucose residues might mean.
You mean the “residue” part? It’s standard terminology for what’s left of a monomer after its incorporation into a polymer. “Glucose residue” is used in the Wikipedia article you linked to.
> **[Polysaccharide](https://en.wikipedia.org/wiki/Polysaccharides)**
>
> Polysaccharides (/ˌpɒliˈsækəraɪd/; from Ancient Greek πολύς (polús) 'many, much' and σάκχαρ (sákkhar) 'sugar') are "Compounds consisting of a large number of monosaccharides linked glycosidically". They are the most abundant carbohydrates in food. Their structures range from linear to highly branched polymers. Examples include storage polysaccharides such as starch, glycogen, and galactogen and structural polysaccharides such as hemicellulose and chitin. The term "glycan" is synonymous wi Po...
> [@](#):
>
> That’s a formal definition of starches, but it’s true that starch in casual speech is an all-embracing term for carbohydrates more complex than sugars.
It is? People refer to cellulose as starch? Chitin?
> [@](#):
>
> Beans contain oligosaccharides, which are polysaccharides.
Oligosaccharides are shorter than polysaccharides. “Oligo” means “few”, and “poly”, of course, means “many”.
> [@](#):
>
> There are varying structures for oligosaccharides in vegetables but you can consider them to be sugar chains that are metabolized to glucose in digestion.
An oligosaccharide that contains galactose would not, I believe, be metabolized to glucose in digestion. The galactose would be absorbed as galactose. Same for fructose and other monosaccharides. Some of these things are converted to glucose, or glucose phosphates, as part of their metabolism inside of cells, but that’s not digestion.
> [@](#):
>
> Or, in short, IvoryTowerDenizen had it right. Beano is an alpha-galactosidase, meaning it breaks the alpha bonds between components of the chain.
Specifically, it breaks alpha-galactosidic bonds. It won’t cleave in the middle of a “chain”, but will only cleave a galactose off the end, and it has to be the correct end. Not so good for breaking down polysaccharides, but good for small things, like the disaccharide melibiose (the alpha equivalent of lactose).
> [@](#):
>
> The difference between that and the beta bond in lactose that Lactaid breaks is that the beta bond curls downward and the alpha bond curls upward. For real. That directional change makes all the difference.
Uh, yeah, the difference is the configuration at the anomeric carbon of galactose. Is that supposed to be surprising?