Tartaric acid is a white crystalline organic acid. It occurs naturally in many plants, particularly grapes and tamarinds, and is one of the main acids found in wine. It is added to other foods to give a sour taste, and is used as an antioxidant. Salts of tartaric acid are known as tartrates. It is a dihydroxy derivative of dicarboxylic acid. Tartaric acid is a muscle toxin, which works by inhibiting the production of malic acid, and in high doses causes paralysis and death. The minimum recorded fatal dose for a human is about 12 grams. In spite of that, it is included in many foods, especially sour-tasting sweets. As a food additive, tartaric acid is used as an antioxidant with E number E334, tartrates are other additives serving as antioxidants or emulsifiers. Naturally-occurring tartaric acid is chiral, meaning that it has molecules that are non-superimposable on their mirror-images. It is a useful raw material in organic chemistry for the synthesis of other chiral molecules. The naturally occurring form of the acid is L-(+)-tartaric acid or dextrotartaric acid. The mirror-image (enantiomeric) form, levotartaric acid or D-(-)-tartaric acid, and the achiral form, mesotartaric acid, can be made artificially. Tartarate is believed to play a role in inhibiting kidney stone formation. Most tartarate that is consumed by humans is metabolized by bacteria in the gastrointestinal tract -- primarily in the large instestine. Only about 15-20% of consumed tartaric acid is secreted in the urine unchanged. Tartaric acid is a biomarker for the consumption of wine and grapes (PMID:24507823). Tartaric acid is also a fungal metabolite, elevated levels in the urine (especially in children) may be due to the presence of yeast (in the gut or bladder). It can be produced by Agrobacterium, Nocardia, Rhizobium, Saccharomyces as well (PMID:7628083) (https://link.springer.com/article/10.1023/A:1005592104426). High levels of tartaric acid have been found in autistic children. In adults, tartaric acid may be due to the consumption of wine (https://www.greatplainslaboratory.com/articles-1/2015/11/13/candida-and-overgrowth-the-problem-bacteria-by-products) (PMID:15738524; PMID:24507823; PMID:7628083).