Malt vinegar is malt that has been fermented until it becomes vinegar. It can’t be included in the Paleo menu because malt is made by germinating and drying grains of barley. The first step to living a Paleo lifestyle involves purging all grains from your diet and that includes barley.
Paleo and Gluten
Barley is a grain that contains gluten and even though it’s been distilled into vinegar, it’s not enough to eliminate the gluten from the condiment. As a result, even a small amount of malt vinegar can be enough to cause leaky gut, inflammation, and digestive issues in some people, especially those who are sensitive to gluten.
If you’re still not convinced, Mark Sisson has plenty of reasons why we should avoid all grains.