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.