Because of spam, I personally moderate all comments left on my blog. However, because of health issues, I will not be able to do so in the future.

If you have a personal question about LI or any related topic you can send me an email at I will try to respond.

Otherwise, this blog is now a legacy site, meaning that I am not updating it any longer. The basic information about LI is still sound. However, product information and weblinks may be out of date.

In addition, my old website, Planet Lactose, has been taken down because of the age of the information. Unfortunately, that means links to the site on this blog will no longer work.

For quick offline reference, you can purchase Planet Lactose: The Best of the Blog as an ebook on or Almost 100,000 words on LI, allergies, milk products, milk-free products, and the genetics of intolerance, along with large helpings of the weirdness that is the Net.

Friday, March 07, 2008

Lactose Intolerance Doesn't Cause Bad Breath

I received a question today asking me if there's a connection between lactose intolerance (LI) and bad breath.

No. There isn't. Simple and straightforward.

As always, I forgot the internet and the legions of pseudoscience. Not to mention the anti-milk crowd which wants to demonize dairy in all its forms.

A Google search on "lactose intolerance" and "bad breath" brings up a breathtaking 75,000+ hits. Many of them are copies of (or variations of: hey, if you're peddling pseudoscience why would a little plagiarism stop you?) two basic articles.

One is by Dr. Harold Katz, founder of The California Breath Clinics.

High Protein Foods
These bacteria love those proteins, and certain foods are packed with them:

Milk and Cheese and most other dairy products. (The fat content does not matter.) If you are lactose intolerant, do not eat or drink these products! Since your system cannot digest them properly, they are available to the bacteria for an extended period of time. A recent research article from the Los Angeles Times (November 1996) on lactose intolerance showed that nearly 67% of all Americans can be classified as "Lactose Intolerant". This is due to the fact that in a diverse population such as we have here, there is a predilection for Asians, Hispanics, and African-Americans to be lactose intolerant.

Fish are high in proteins. As many people eat a high fish diet, logically they make the problem worse.

The pseudoscience here is of very high quality. Lactose intolerance is the inability to digest the lactose sugar in dairy products. Dairy proteins are digested perfectly well. No dairy proteins are available for an extended time. They are absorbed by the small intestine and don't reach the colon where the bacteria are.

Other questions should be springing to mind as you read this. Meat is high is protein as well. Shouldn't meat be a prime cause of bad breath? What about plant protein? Vegetarians always say that high protein plant products can be eaten in lieu of meat. Wouldn't they cause bad breath?

While Dr. Katz's notions about diet are bizarre and obviously wrong to anyone who knows anything about nutrition and digestion, you'd have to be more aware to catch the subtlety wrong in the other theory, which can be found in articles similar to this one by Sue Spataro.
[The bad breath] is powerfully strong and people can sense it from feet away. Others may think the person has poor oral hygiene when in reality they are lactose intolerant. The oral hygiene has nothing to do with their bad breath. The bad breath is caused by the lactose rich foods sitting in the person's intestines and fermenting. The body tries to get rid of the gases that are produced as the result of fermentation by having them reabsorbed by the bloodstream and exhaled out.

The hydrogen breath test is a common way doctors make the diagnosis of lactose intolerance. This tests measures the amount of hydrogen in the breath. Normally, very little hydrogen is in the breath. But undigested lactose in the colon (large intestine) is fermented by bacteria, and various gases including hydrogen is produced. The hydrogen is absorbed by the intestines, carried through the bloodstream to the lungs, and exhaled. In the test, the patient drinks a lactose-loaded beverage, and the breath is analyzed at regular intervals. Raised levels of hydrogen in the breath indicate improper digestion of lactose. Certain foods, medications, and cigarettes can affect the test's accuracy and should be avoided before taking the test. This test is available for children and adults.

Yes, fermenting bacteria do create reactions that end in the production of extremely vile-smelling gases, mostly from volatile sulfur compounds. And it is quite true that this is the only reaction which creates hydrogen that percolates through the body and is emitted in the breath, the reason why the hydrogen breath test has become the most common test for LI.

What's not true is that the sulfur compounds do the same thing. The gases that are produced leave the body via a different exit, the process known as farting (or flatulence). Doctors would surely have noticed by now, after millions of hydrogen breath tests, if the lactose load that we drink to make the test work also caused sulfur to pour out along with the hydrogen. So would we patients. We don't, because it doesn't happen.

Notice how each theory makes use of a bit of real science to give the work a sheen of verisimilitude before venturing off into parts unknown. Katz talks about bacteria in the intestines, but ascribes to them a role unknown to other doctors. Spataro uses the hydrogen pathway to try to make a point about unnamed other gases that are not as odorless as hydrogen.

Standard medical science has nothing to say about lactose intolerance causing bad breath. A search of PubMed, the medical journal database, turns up no articles making the connection. It's a "truth" known only to the internet.

If you want real facts about bad breath - facts that nowhere mention "lactose" or "dairy" or "protein" - I recommend that American Dental Association's FAQ page on bad breath or the Mayo Clinic's Causes of Bad Breath page.

Don't get suckered by pseudoscience.

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Anonymous said...

The ADA states that "gastrointestinal disturbance" can cause bad breath and the Mayo Clinic states that "metabolic disorders" can cause bad breath. I think that lactose intolerance can be categorized as both of the above, wouldn't you?

Steve Carper said...

No, I wouldn't.

Lactose intolerance can be defined as a gastrointestinal disturbance, but the two terms are not synonyms. There are hundreds of possible gastrointestinal disturbances. The ADA is more likely speaking of vomiting, GERD, reflux or some other more proximate illness as a cause of bad breath.

And no one would characterize LI as a metabolic disorder. That's beyond reaching. Medline says:

"You can develop a metabolic disorder when some organs, such as your liver or pancreas, become diseased or do not function normally. Diabetes is an example."

In both cases, such internal diseases are well down the list of possible causes. Such a cause would be deeply pathological and very rare.

And LI as a cause would be even more unlikely.

Anonymous said...

Lactose intolerance can absolutely cause bad breath. It can, and it DOES. I was having issues with bad breath for a couple of months - I had no idea what the issue was. I go to the dentist every 6 months, never had a cavity. I floss, use mouth wash, and I don't eat sugary mints or gum. No gum disease, no braces, I don't smoke, etc etc. So why I would have bad breath was a complete mystery.

I am a member of a celiac forum (I also have celia disease, so I was curious to see if other people had lingering bad breath symptoms. Was it just my celiac disease? The only reason I even knew I had bad breath at all was because my boyfriend begrudgingly let me know. (It's not like I could smell it, or others were offended from miles away)

Anyway, after reading through the threads on the celiac forum, I found some other people were listing bad breath as a symptom of lactose intolerance (lactose intolerance is common in those with celiac)it was said that bad breath symptoms from eating dairy could last up to 3 days. Well, I certainly was eating a lot more dairy despite my lactose intolerance to try to make up for the food I couldn't eat from the celiac disease. That would make sense, so I figured I'd eliminate dairy to see what happened.

I went off dairy for a few days - no bad breath. Went back to some low lactose cheese, bad breath back. Ate gluten free pizza with a ton of cheese, terrible breath. Ate no dairy for weeks and switched to almond cheese (no lactose) and lactaid ice cream, no bad breath.

At least in my case, it is not "dairy" that is causing the bad breath, it's just the lactose. Think about it - lactose intolerance is diagnosed by a breath test. There are high levels of hydrogen released in the breath when consuming large amounts of lactose. It CAN, and DOES cause bad breath, though I can only speak for myself. I have found eliminating lactose eliminates the problem. I can still enjoy my almond cheese and lactaid products with no GI symptoms or bad breath.

Anonymous said...

I totally agree that lactose can be the culprit for bad breath... I am sure that there must b sum reason y Dr say that lactose intolerance can lead to bad breath...also the link is recently found .. So u will hav to wait until they put sum info in medical journals.. :-)

Anonymous said...

Any form of dairy caused my constant post nasal drip, which caused my halitosis. An allergic reaction to a food substance, made me suffer for 38 years. I hate my old friends/lovers who never told me the truth. I had bad breath.
Have since solved my problem, but feel so far behind. I hate my old friends.

bhs said...

I agree…it's the post nasal drip from the lactose intolerance that causes the halitosis.

Unknown said...

The internet is very good .thats what help me thanks the docters could not help me i stop eating sugar and dairy i have fresh breath all day now happy..

Sky said...

I would have to disagree with this post. From personal experience, lactose intolerance and sometimes sugar, can most definitely cause bad breath. Especially in people with high metabolism who eat huge amounts and suffer from poor digestion.

Unknown said...

Wow lactose intolerance definitely causes bad breath. After my daughter or her dad has butter, milk or ice cream I can smell the curdled milk smell from several feet away. It is disgusting & besides these moments their breath smells normal. Your science is missing something!