A gluten-free diet is a diet that excludes foods containing gluten. Gluten is a protein complex found in wheat (including kamut and spelt), barley, rye and triticale. A gluten-free diet is the only medically accepted treatment for celiac disease. Being gluten intolerant can often mean a person may also be wheat intolerant as well as suffer from the related inflammatory skin condition dermatitis herpetiformis, There are a smaller minority of people who suffer from wheat intolerance alone and are tolerant to gluten.
Despite unknown benefits for non-celiacs and evidence to suggest adverse affects, a significant demand has developed for gluten-free food in the United States.
A gluten-free diet might also exclude oats. Medical practitioners are divided on whether oats are acceptable to celiac disease sufferers or whether they become cross-contaminated in milling facilities by other grains. Oats may also be contaminated when grown in rotation with wheat when wheat seeds from the previous harvest sprout up the next season in the oat field and are harvested along with the oats.
The term gluten-free generally is used to indicate a supposedly harmless level of gluten rather than a complete absence. The exact level at which gluten is harmless for people with celiac disease is uncertain and controversial. A 2008 systematic review tentatively concluded that consumption of less than 10 mg of gluten per day for celiac disease patients is unlikely to cause histological abnormalities, although it noted that few reliable studies had been conducted.
Regulation of the label, gluten-free, varies widely by country. In the United States, the FDA issued proposed regulations in 2007 limiting the use of "gluten-free" in food products to those with less than 20 parts per million of gluten. The current international Codex Alimentarius standard allows for 20 parts per million of gluten in so-called "gluten-free" foods. There is at least one website with a table containing information on "gluten-free" food manufacturers and the gluten-parts-per-million levels to which each of those manufacturers tests.