Why Garlic Is the Bad Breath King

From the WebMD Archives

Nov. 27, 1999 (Atlanta) -- Mama mia! Who doesn't love a good lasagna, or a big bowl of pasta with a healthy helping of marinara sauce? And after indulging, who hasn't stood at the bathroom sink, trying to brush, floss, and gargle away the dreaded garlic breath? Why, oh why, we wonder, does it seem to return, to haunt us long after the last meatball has been consumed?

Researchers at the University of Minnesota, in Minneapolis, explain the basis for 'garlic breath' in a study published in the American Journal of Physiology.

"When you eat garlic you produce several sulfur-containing gases," lead researcher Fabrizis Suarez, MD, PhD, tells WebMD. "But what we found is most of the sulfur-containing gases, with exception of one, [are of oral origin]. AMS [allyl methyl sulfide] is the only one that is not metabolized by [intestine] or the liver, and this is why this gas can go back and be released in your mouth. It's coming from the [gut], not from the mouth, and that is what gives you the odor that you have after you eat garlic." Suarez is an assistant professor at the University of Minnesota and on the staff at the Minneapolis VA Medical Center.

"This paper gives us the idea that sometimes you can have halitosis -- if you want to call the odor of garlic 'halitosis' -- that can come from the intestine instead of your mouth," he says. "But in most cases, the gases [that cause] halitosis are coming from your mouth, from the bacteria that is [on] the tongue."

Suarez and colleagues tested the mouth air, lung air, and urine from five healthy volunteers (with no history of halitosis) on two separate occasions. On one day they were given 6 grams of raw garlic to eat, on the other day no garlic was eaten. On the day when no garlic was eaten, the researchers detected low levels of three sulfur-containing gases in the mouth air, indicating that the mouth usually contains low concentrations of these gases. In contrast, when garlic was eaten, the researchers found higher concentrations of those three gases, plus two other sulfur-containing gases. For all gases except allyl methyl sulfide, the concentration of gas was much higher in the mouth air than in the lung air or the urine, suggesting that they originate in the mouth.

"Conversely, AMS concentrations in mouth air remained high for the four hours after garlic ingestion and were similar to levels in the alveolar [lung] and urine samples, indicating that this gas had undergone absorption form the gut and was being released from systemic sites," write the authors. In other words, the gas was going into the blood, circulating around the body, and being excreted in the breath and urine.

The researchers also showed that, after the five subjects brushed their teeth with toothpaste containing baking soda and hydrogen peroxide, levels of the orally generated sulfur gases went down to almost nothing -- but not the levels of allyl methyl sulfide, which remained pretty high.

"If you eat garlic, it doesn't matter what you do," Suarez says. "You are always going to smell some garlic."

In an article that appeared in the journal Gastroenterology, William Hasler, MD, responds to this issue by proposing the possibility of bad breath, or halitosis, help in the form of a dietary supplement.

"Finally, the findings [of this study] raise the question as to whether a dietary supplement could be developed that assists in gut metabolism of gases such as allyl methyl sulfide so that garlic lovers could enjoy their meals in much the same manner as supplemental lactase has allowed milk-intolerant individuals to tolerate dairy products," he writes.

Allyl methyl sulfide aside, Suarez says you can decrease the amount of sulfur-containing gases, created by garlic and other culprits, in your mouth by brushing your tongue, where many bacteria live.

Suarez offers one more solution to bad breath he discovered from his new study: "We used H2O2 -- hydrogen peroxide -- you gargle with that for one minute," he says. "It is very cheap, and you can decrease the sulfur-containing gases for eight hours."