July 15, 2011 -- People who drink hot tea or coffee are less likely to carry the superbug known as methicillin-resistant Staphylococcus aureus (MRSA) in their noses, researchers found.
Drinking either beverage was associated with about a 50 percent relative reduction in the odds of nasal MRSA carriage, and drinking both was associated with a 67 percent reduction, according to Dr. Eric Matheson of the Medical University of South Carolina in Charleston and colleagues.
The findings, reported in the July/August issue of Annals of Family Medicine, "raise the possibility of a promising new method to decrease MRSA nasal carriage that is safe, inexpensive, and easily accessible," they wrote.
The clinical importance of the finding is not entirely clear, however, as the relationship between nasal MRSA carriage and the chances of systemic infection has not been resolved, they added.
Previous studies have shown that tea and coffee have antimicrobial properties when applied topically, and to find out whether drinking the beverages had systemic effects the researchers turned to the 2003-2004 National Health and Nutrition Examination Survey (NHANES).
The analysis included 5,555 individuals ages 2 and older, representing 182.1 million people. About half (48.6 percent) reported consuming hot tea over the past month and 60.8 percent reported drinking coffee over the past month.
Overall, 1.4 percent of the participants carried MRSA in their noses.
After adjustment for age, race, sex, poverty status, current health status, hospitalization in the past 12 months, and use of antibiotics in the past month, there were lower odds of nasal MRSA carriage among individuals who drank any amount of hot tea, coffee or both compared with those who drank none.
A separate analysis of just the adult participants provided similar results.
Consumption of iced tea, however, was not associated with nasal MRSA carriage. The reason is unclear, but it could be that iced tea has lower levels of polyphenolic compounds than hot tea, or that the volatile antimicrobial compounds in coffee and tea reach the nose in vapor form, according to the researchers.
Although the study -- cross-sectional in design -- could not establish a causal relationship between drinking coffee and tea and nasal MRSA carriage, there are some possible mechanisms to explain the finding.
"In the case of coffee, particular attention has focused on the potential antibacterial properties of trigonelline, glyoxal, methylglyoxal, and diacetyl," Matheson and colleagues wrote. "For tea, attention has focused on the antimicrobial properties of tannic acid and catechins."
In addition, they wrote, drinking both coffee and tea decrease iron absorption, which could affect the growth of S. aureus.
The authors acknowledged that the study was limited by the exclusion of some individuals because of missing data and the inability to determine when the participants last drank coffee or tea.
They noted that the study could not address the larger question of whether nasal MRSA carriage is associated with systemic infection.
"Given this debate, the benefits of any treatment for MRSA nasal carriage should be carefully balanced against the risk," they wrote.