Oat vary among oat varieties. Also, oats products are frequently cross-contaminated with other gluten-containing cereals during grain harvesting, transport, storage or processing. Pure oats contain less than 20 parts per million of gluten from wheat, barley, rye, or any of their hybrids. Use of pure oats in a gluten-free diet offers improved nutritional value from the rich content of oat protein, vitamins, minerals, fiber, and lipids, but remains controversial because a small proportion of people with celiac disease react to pure oats. Some cultivars of pure oat could be a safe part of a gluten-free diet, requiring knowledge of the oat
Wheat gluten (food) among adherents of Buddhism. The oldest reference to wheat gluten appears in the "Qimin Yaoshu", a Chinese agricultural encyclopedia written by Jia Sixie in 535. The encyclopedia mentions noodles prepared from wheat gluten called "bo duo". Wheat gluten was known as "mian jin" by the Song dynasty (960–1279). Wheat gluten arrived in the West by the 18th century. "De Frumento", an Italian treatise on wheat from 1745, describes the process of washing wheat flour dough in order to extract the gluten. John Imison wrote an English-language definition of wheat gluten in his "Elements of Science and Art" published in 1803.