COLUMBUS, Ohio — A word to the wise: Garlic breath can last for 24 hours. But fortunately, science is here to help.
Researchers at The Ohio State University have figured out how foods like apples, mint leaves and even lettuce can prevent halitosis caused by garlic’s sulfur compounds when eaten at the same time or soon after a garlic-laden meal.
The scientists are with Ohio State’s Department of Food Science and Technology in the College of Food, Agricultural, and Environmental Sciences.
Previous research, including some done in the department, has identified such food saviors, said Sheryl Barringer, chair of the department and co-author of the current study in the Journal of Food Science.
“But for this research, we were specifically looking at why certain foods work,” she said. “What is it about them that causes the deodorization?”
The puzzle is important for two reasons.
First, garlic breath lingers. Different volatile compounds can cause odors almost immediately from residual food particles in the mouth, later as the garlic passes into the stomach, and then finally again after being digested and moving through the bloodstream and into the lungs, where foul breath can linger for up to a day.
But the findings are also important for food processors interested in how they can reduce the effects of undesirable volatile compounds, said study co-author Rita Mirondo. Mirondo is from Tanzania and is one of 23 African students who have studied at Ohio State as part of the U.S. Agency for International Development’s Innovative Agricultural Research Initiative. She conducted the research as part of her Ph.D. studies.
Barringer and Mirondo said they thought that phenolic compounds in the foods would be the key to fighting garlic breath. Phenolic compounds are a type of phytochemical — chemicals pervasive in plants — and have long been associated with health benefits in part due to their antioxidant activity.
So, the scientists decided to test foods with varying levels of phenolic compounds, including spearmint leaves (which had the most), green tea, apples and lettuce (the least).
In addition, they tested heated apples and lettuce. Heating foods removes enzymes, which also may have played a role.
And, they made juice from the raw spearmint leaves and apples, which removed much of the phenolic compounds but kept enzymes intact.
In the study, Mirondo first chewed 3 grams (about 1 ounce) of garlic purchased at a local grocery store before swallowing it and drinking a glass of water.
To get a scientific measure of garlic breath, she then exhaled into an instrument designed to quickly capture and measure the four most important volatile compounds from garlic that produce the associated aroma.
Then, in testing that lasted a couple of months, she ate more garlic followed immediately by the different test foods, which were each chewed for 30 seconds and then swallowed, to see how they mitigated bad breath. Mirondo tested her breath 1 minute after eating the foods, and then again every 10 minutes for an hour.
“That was the hardest part of the research,” Mirondo said. “The garlic was so strong, and there were times I thought, ‘Boy, I am so tired of this study.’”
The researchers found some results that surprised them.
“When we looked at the total amount of phenolic compounds in the test foods, our theory didn’t work,” Barringer said. Lettuce has a low level of phenolic compounds, but it worked reasonably well, she said. Green tea has a high level, but it didn’t work well at all.
“That was a shock to me,” Mirondo said. “Green tea worked in other studies.”
As they looked more closely, they realized that it wasn’t necessarily the amount of phenolic compounds in the foods but the type of compounds that was important.
To study the effect of specific phenolic compounds, they blended garlic with water and put it in a Pyrex bottle, treating it with different phenolics and analyzing their effect on garlic’s compounds.
“Rosmarinic acid, which is in mint, worked the best,” Barringer said. “And the mint leaves were very, very effective. So that told us a lot.”
Quercetin, found in apples, and catechin, in green tea, also performed moderately well, the study found
“So, the type of phenolics seems to be the critical element,” Barringer said. “The amount still has an effect, but is less important.”
In the end, raw mint leaves, lettuce and apple worked best to combat garlic breath, the study found. Apple juice and mint juice, which had reduced levels of phenolic compounds, were not as effective as their whole counterparts. Heated apple and heated lettuce also didn’t perform as well as raw apple and lettuce, indicating that enzymatic activity might play a supporting role in combating garlic breath, Barringer said.
Green tea showed no effect in this research, although it had in a previous study.
“We used a different kind of tea this time, so it’s possible there are different compounds in different types of green tea,” Barringer said.
“The bottom line would be, yes, there are foods you can consume — apple, mint leaves or lettuce — that would effectively combat bad breath from garlic or other foods with sulfur volatiles, such as onion or shallots,” she said.
“But you would need to eat them at the same time or fairly quickly after eating garlic — maybe have an apple for dessert,” Barringer said. “You can’t wait for an hour, and if you notice you have garlic breath, try to eat an apple to fight it.
“It’s too late at that point. You’ve already digested the garlic, and it’s moving into your lungs. It’s past the point for the compound in the apple to react with the compounds in garlic.”
In addition, companies that manufacture breath mints, sprays or other products could draw on these findings to be sure to include phenolic compounds that are most effective, Barringer said.
“They could use enzymes, too, but they’re not required,” she said.
Mirondo plans to return to Tanzania after she earns her doctorate.