Vinegar is made by fermenting wine or other sources of ethanol, resulting in an acidic liquid containing acetic acid. Acetic acid is the source of vinegar's tart, sour flavor. Common white vinegar typically contains from 4% to 7% acetic acid; pickling vinegars contain more. Vinegar may also contains other bioactive components.
This content depends on the fruit or grain from which the vinegar was made, and includes caffeic acid, chlorogenic acid, cyanidins, ferulic acid and various other polyphenols. Vinegar has been shown to have antioxidant and antibacterial properties. Vinegar has also been shown to help control blood pressure and blood sugar, assist with weight loss by increasing satiety after meals, and enhance intestinal calcium absorption.

Cancer-related effects of consuming vinegar

Kibizu, a Japanese sugarcane vinegar, has been shown to inhibit growth and induce apoptosis in human leukemia cells. Aged Japanese kurozu rice vinegar (made from brown rice) has been shown to inhibit proliferation of human lung, bladder, colon, prostate and breast cancer cells. Kurozu sediment also has been shown to extend the life spans of mice with transplanted colon cancer tumors by inhibiting tumor progression.
Generally speaking, the antioxidant capacity of a vinegar is correlated with its phenolic and flavonoid content. One study that compared the antioxidant properties of grape juice and wine vinegar found that the antioxidant capacity of red wine vinegar was up to 46% of that of red grape juice. It is not surprising that vinegars made from foods such as brown rice with known anti-cancer activities would also have anti-cancer properties.

Additional comments

The sterilization and clarification of wine vinegars (to eliminate solids) results in a reduction in polyphenol content of less than 15%, according to one study. The loss is largest for red wine vinegar. Balsamic vinegar is an aged Italian vinegar made from white grapes; it's dark brown color is in part a result of aging in wooden casks. Apple cider vinegar sold as raw or unpasteurized can be a source of bacterial contamination.
Although vinegar has been found to reduce blood sugar and have other potential benefits, ingesting vinegar as a medicinal or drinking it on a frequent basis has also been shown to have potential adverse health effects, including low grade metabolic acidosis, a reduced rate of gastric emptying (already a problem for some diabetics), throat damage and liver injury. Vinegar is best consumed with food and acetic acid capsules are to be avoided.
Vinegar consumption might interfere with digoxin, insulin, potassium-depleting diuretics or other medications with sensitivity to PH or potassium levels.

Sources of information provided in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Note that while we are continually searching for new evidence specifically concerning this food, there is not much interest in vinegar among breast cancer researchers, so few studies are available.