Vinegars are liquid products produced from the alcoholic and subsequent acetous fermentation of carbohydrate sources. They have been used as remedies in many cultures and have been reported to provide beneficial health effects when consumed regularly. Such benefits are due to various types of polyphenols, micronutrients and other bioactive compounds found in vinegars that contribute to their pharmacological effects, among them, antimicrobial, antidiabetic, antioxidative, antiobesity and antihypertensive effects. There are many types of vinegars worldwide, including black vinegar, rice vinegar, balsamic vinegar and white wine vinegar. All these vinegars are produced using different raw materials, yeast strains and fermentation procedures, thus giving them their own unique tastes and flavours. The main volatile compound in vinegar is acetic acid, which gives vinegar its strong, sour aroma and flavour. Other volatile compounds present in vinegars are mainly alcohols, acids, esters, aldehydes and ketones. The diversity of vinegars allows extensive applications in food. [Emphasis added]
That's the first I've heard vinegar has ketones. I doubt they are in very high amounts relative to MCT or ketone ester supplementation, but it would be interesting to know which vinegars may be higher in ketones and whether it's in a physiologically meaningful amount. I wonder whether the 'Mediterrean diet' is higher in vinegar than other diets. I've never seen vinegar mentioned as being a major part of it's health benefits. I'm guessing vinegar is very at the margins nutritionally speaking, but Dr. Gundry got me thinking maybe it's a more helpful player than many realize?
Here's another paper that's out of reach to lay people.
Our results support the idea that [traditional balsamic vinegar] melanoidins may have a role in oxidative damage prevention. Fe(2+)-chelating and heme-binding activities as well as mechanisms of antioxidant activity of TBV melanoidins were also compared with coffee, barley coffee and dark beer melanoidins.