Autolyzed yeast extract is a substance that results when yeast is broken down into its constituent components. It contains some free glutamic acid, which is the chemical in MSG that triggers reactions in MSG sensitive people. It is used as a less expensive substitute for MSG, leading some health and consumer advocates to object to its use in foods. As with MSG, the industry claims that yeast extract is a natural substance with no harmful effects, and opponents claim it causes a variety of health problems. Autolyzed yeast extract is naturally produced by growing, harvesting, and concentrating yeast cells. The yeast self-digests (autolyzes), breaking down the cell walls, and creates a savory base used to formulate a multitude of different flavors. Autolyzed yeast (containing the cell walls) or autolyzed yeast extract consists of concentrations of yeast cells that are allowed to die and break up, so that the yeastsâ€™ endogenous digestive enzymes break their proteins down into simpler compounds (amino acids and peptides). Yeast autolysates are used in Vegemite (Australia), Marmite, Promite, Oxo (New Zealand, South Africa, United Kingdom, and Republic of Ireland), Cenovis (Switzerland) and Vitam-R (Germany). Bovril (United Kingdom and Republic of Ireland) switched from beef extract to yeast extract for 2005 and most of 2006, but later switched back. The general method for making yeast extract for food products such as Vegemite and Marmite on a commercial scale is to add sodium chloride (salt) to a suspension of yeast, making the solution hypertonic, which leads to the cells shrivelling up; this triggers autolysis, in which the yeast self-destructs. The dying yeast cells are then heated to complete their breakdown, after which the husks (yeast with thick cell walls) are separated. Removing the cell walls concentrates the flavors and changes the texture.