Red wines made from Cabernet Sauvignon, Merlot, Pinot Noir and Shiraz make for potent bacteria killers, according to research conducted at the University of Missouri. While not all red varieties were found to be helpful in killing harmful bacteria, those that were did not affect non-harmful and helpful strains, such as those that aid digestion, called probiotic bacteria. Promising as the results may be, however, it remains unknown if the positive effects from the lab would be realized in humans by drinking red wine.
Previous studies have found that wine can kill the bacteria that causes ulcers as well as E. coli and salmonella, while grape pomace, a byproduct of winemaking, was found to kill bacteria, as well as staph. However, "the reports on their effectiveness have not been consistent," said University of Missouri food microbiologist Azlin Mustapha, who first presented her department's findings at the Institute of Food Technologists meeting in Chicago in July. "There has been anecdotal evidence of wines' effectiveness at preventing things like traveler's diarrhea," which is caused by a bacteria, Mustapha noted. "[But] we wanted to see if we can confirm these previous reports by testing a variety of red wines and grape juices on food-borne pathogens, and went one step further to see their effects on probiotic bacteria, that is, 'friendly' or health-beneficial bacteria."
Mustapha tested 11 different red wines on several strains of potentially harmful bacteria, among them Listeria, E. coli and salmonella, as well as the probiotic lactobacillus and bifido bacteria, which aid digestion, among other benefits. The scientists isolated each strain in the lab and then exposed the samples to concentrated forms of each wine. Cabernet Sauvignon, Merlot, Pinot Noir and Shiraz provided a high inhibitory effect on the growth on all strains of harmful bacteria, except for Listeria, which proved the most resilient overall, but was still inhibited. A wine made from a Grenache-Shiraz blend provided some inhibition, though not as strong, as did a Tempranillo from Rioja. Zinfandel and a wine made from cherries exhibited no inhibitory properties on the bacteria.
"The drier the wines, the higher the acidity and levels of polyphenols," which are compounds found naturally in red wines, explained Mustapha. "These polyphenols are believed to be the main compounds responsible for killing the pathogens. Cherry and Zinfandel wines are the sweeter varieties. Generally, the sweeter wines have less of an inhibitory effect on the pathogens." The wines also had no negative effect on probiotic bacteria growth.
However, Mustapha cautioned against gulping down Merlot to stop harmful bacteria from spreading in the body. Research done in test tubes, she said, is not enough to determine if a similar observed action would occur in humans.
"We plan to conduct cell-culture studies and animal studies, where we hope to determine if red wines have preventative and protective effects, or if they can act as a treatment," said Mustapha. The hope is that those tests will find if drinking red wine at the time of infection would result in suffering less-severe effects.