Vinegar has been used as both a condiment and medicine for several thousand year. As such it can be generally regarded as safe. There are a very few rare reports of adverse reaction associated with vinegar ingestion, but they usually involve other factors such as concomitant injury (laceration of the oesophagus by crab shell), ingestion of an excessive amount of vinegar over a long period of time (250ml/day for 6 years) or taking it in an impure form such as a tablet with questionable quality and content.
In Austria in 1998, a young woman who had been drinking 250 ml – a whole cup – of apple cider vinegar daily for 6 years, from the time she was 22 years old, was found to have developed low potassium levels, osteoporosis and excess amounts of renin, a protein-digesting enzyme released by the kidneys which plays a role in blood pressure regulation. Whether there were other excesses in this patient’s lifestyle that also contributed to the development of these symptoms or whether it was simply due to the extreme excess of the dose over a long period of time is not clear. Suffice it to say, that drinking a cup of vinegar every day is not good for you for a number of reasons.
In Hong Kong in 2002, there was a report of a women who tried to dislodge a piece of crab shell stuck in her throat by drinking a tablespoon of rice vinegar. It didn’t work and endoscopy later revealed inflammation and second-degree caustic injury (burn). Although drinking rice vinegar is a popular folk-remedy for objects stuck in the throat in China, it is not recommended due to the increased potential for the vinegar to irritate already damaged tissues.
In 2005, the Annals of Emergency Medicine published a rather comedic, tongue in cheek article about vinegar allegedly causing laryngospasm, leading to fainting all of which spontaneously resolved, but ruined the anticipated gastronomic accolades an off-duty physician was expecting for the pickled cucumbers he prepared according to his mother-in-law’s instructions.
There was also an anecdotal report in the Journal of the American Dieticians Association in 2005 of oesophageal injury being caused by ACV tablets in one instance and a subsequent review of ACV tablets inferred that there was very great variability in the contents of the tablets on the market and quality was very unreliable. It would therefore seem logical to use the unadulterated liquid apple cider vinegar rather than play Russian roulette with the various purveyors of tablets on the market.