Yeast extract spread is a pungent, salty paste that is a common condiment and flavouring in Great Britain and Australia. Popular brands of yeast extract paste are Marmite (in Great Britain) and Vegemite (in Australia). Its strong, aggressively salty flavour 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 favourite 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 flavour when eaten alone. Like yeast extract spread, it is also traditionally added to water to make a simple soup. Its flavour, 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 flavour -- 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 savoury seasonings.
Peanut butter, like yeast extract spread, is sticky and distinctively flavoured. Its flavour, however, will be nothing like that of a yeast extract spread.
Soy sauce shares the same dark colour as yeast extract spread and has a similar salty, fermented flavour 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 savoury 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.