Yeast extract

Yeast extract is yeast broken open and concentrated, and yeast products have been known to carry histamine and tyramine since the 1960s - it is the classic example. It hides in stocks, crisps and savoury sauces under names that do not say yeast. Gardner's review narrowed the MAOI diet to what the evidence supports, and yeast extract is one of the foods it KEPT restricted: it names Marmite concentrated yeast extract by brand, alongside aged cheese, cured meats, broad bean pods, sauerkraut, soy sauce and tap beer. Staying on that short list says more than appearing on the long one.

Concentrated yeast extract is one of the four foods both reviews of the MAOI diet put under absolute restriction, with aged cheese, broad bean pods and sauerkraut. Yeast products have been known to carry tyramine since the 1960s, and concentrating them multiplies it - which is why a spoonful of spread matters where a slice of bread does not.

Yeast extract is grown, then concentrated, and yeast takes up trace metals from whatever medium it grows in. Both steps push the nickel up, and the ingredient appears in stocks, crisps, sauces and anything savoury.

Yeast extract is a flavour concentrate, and the plant-derived flavour compounds it carries are why it is flagged for salicylate. It is also rich in other amines that burden the same pathways.

Yeast extract carries mannan from the yeast cell wall, which does ferment - so low rather than none. What keeps it low is the quantity: a stock cube or a tablespoon of flakes is a small dose next to a serving of onion, the portion the FODMAP thresholds are set against.

Yeast extract is grown rather than harvested, and being a fungus does not put it outside this axis: Savage measured cultivated mushrooms, fungi too, at 58.9 to 104.1 mg of total oxalate per 100 g of dry matter. The extract is a concentrate, though, and concentrating multiplies whatever the growth medium left behind, which is why this sits low rather than at nothing. No assay of yeast or yeast extract is published; what is known is the neighbouring fungi and how the extract is made.