Yeast extract spread is a pungent, salty paste that is a common condiment and flavoring in Great Britain and Australia. Popular brands of yeast extract paste are Marmite (in Great Britain) and Vegemite (in Australia). Its strong, aggressively salty flavor is not for everyone and people either love it or hate it. Those who love the stuff spread it thinly on buttered toast or stir it into hot water to make a warming drink rich in vitamin B. It also works well as a seasoning for stews and soups. While true fans say there are no real substitutes for their favorite brands of yeast extract spread, there are a few passable substitutes that may work in different contexts.
Miso is a salty, fermented paste made from crushed soybeans that has a tangy and pungent flavor when eaten alone. Like yeast extract spread, it is also traditionally added to water to make a simple soup. Its flavor, however, is all its own and will be quite different from that of a yeast extract spread.
While yeast extract spreads are completely vegetarian, they have a distinctly meaty flavor -- enough so that the makers of Bovril, a British beef extract, tried replacing the beef in its product with yeast extract. While Bovril is currently made from beef once again, it and other beef extracts can also replace yeast extract spreads in soup bases or as savory seasonings.
Peanut butter, like yeast extract spread, is sticky and distinctively flavored. Its flavor, however, will be nothing like that of a yeast extract spread.
Soy sauce shares the same dark color as yeast extract spread and has a similar salty, fermented flavor profile. While too thin to be used as a spread, it can fill in for yeast extract spreads as an ingredient in stews, sauces and other savory dishes. However, the substitution occurs most often in the opposite direction: diluted yeast extract spreads are sometimes recommended as replacements for soy sauce and a British Marmite fan devised a Japanese-style fish and rice preparation using that brand of yeast extract spread in place of soy sauce.