As a wee child I was fed this in England, it is a acquired taste as it is somewhat bitter/salty and it does not look tasty . Marmite is made from yeast extract, a by-product of beer brewing. I still eat it today on toast.
' By 1912, the discovery of vitamins was a boost for Marmite, as the spread is a rich source of the vitamin B complex; With the vitamin B1 deficiency beri-beri being common during World War I, the spread became more popular. British troops during World War I were issued with Marmite as part of their rations.' Wikipedia