The stomach-churning reason you should never ask for lemon in your gin and tonic

How do you take your gin and tonic? If it’s with ice and a slice, you might want to consider doing without the slice from now on.

Elle magazine recently resurfaced a 2007 study published in the Journal of Environmental Health, in which researchers investigated the level of microbial contamination of lemon slices at 21 restaurants in the US.

“In restaurants,” researchers wrote, “a lemon slice is commonly placed on the rim of a beverage glass, or afloat in the beverage, as a flavor enhancer or a decorative garnish.

Restaurant patrons should be aware that lemon slices added to beverages may include potentially pathogenic microbes

Philip Tierno, author of The Secret Life of Germs“ Although a patron might ask for this embellishment, frequently the lemon is added without the customer’s request. Our study investigated whether these lemon slices contain microbial contamination that might be ingested by restaurant patrons.”

Conducting their investigation surreptitiously, without restaurant staff being informed, researchers ordered glasses of water and soda at each of the restaurants, then swabbed the rind and the flesh of the lemon slices that came in the drinks.

Close to 70 per cent of their samples produced some sort of microbial growth, from 25 different microbial species

"The microbes found on the lemon samples in our investigation all have the potential to cause infectious diseases at various body sites, although the likelihood was not determined in this study," researchers said. "Restaurant patrons should be aware that lemon slices added to beverages may include potentially pathogenic microbes."

Elle contacted microbiologist Philip Tierno, author of The Secret Life of Germs, to ask his view on the study. "People are touching the lemon in your glass, handling it, cutting it, placing it in a container or a cup, or a glass; and then picking up those slices at a later point in time and dropping them into a drink and putting them on the rim of a glass," he said. "You can easily see how those lemon slices and lemon wedges can be contaminated."

Tierno also identified “contamination from the skin, respiratory secretions, and fecal matter," among the sources of contaminating microbes found on lemon skins.