Unsplash/V2oskFermented foods have been a staple of human diets for thousands of years. Long before refrigeration, fermentation was a clever way to preserve food and drink, and in many cases, it added complex flavours that became culturally treasured. But while today we enjoy kombucha, sourdough, and sauerkraut as trendy (and generally safe) fermented options, many ancient counterparts weren’t quite so tame. Some of these early creations were risky—brewed in unsanitary conditions, made with toxic ingredients, or stored in a way that invited lethal bacteria. In some cases, the recipes have thankfully been lost. In others, they’ve survived, but would be downright dangerous if prepared the same way today.
Here are some of the ancient fermented foods that modern digestive systems—and health standards—probably wouldn’t survive.
Garum: the Roman fish sauce that teetered on toxic
Garum was one of the most beloved condiments in ancient Rome. Made from fermented fish guts, herbs, and salt, it was left to sit in the sun for weeks in large vats. The mixture would liquefy over time, with the resulting liquid skimmed off and bottled. It was then splashed onto everything from meat to porridge.
While the high salt content helped preserve the fish, garum production didn’t exactly meet modern hygiene standards. In many cases, it was fermented in open containers that attracted flies and bred bacteria. Today, food safety experts warn that similarly made sauces could risk botulism or histamine poisoning, especially if they’re not carefully controlled.
Although some modern chefs have tried to recreate garum, they do so under strict fermentation protocols—something ancient vendors certainly lacked.
Kiviak: fermented seabird in a seal
Still made in parts of Greenland, kiviak is a traditional Inuit dish that involves stuffing hundreds of small auks (a seabird) into a hollowed-out seal carcass. The birds are left whole, feathers and all, then the seal is stitched shut, sealed with grease, and buried under rocks to ferment for several months.
When done right, it’s a delicacy. When done wrong, it can be fatal. Improper fermentation can lead to botulism—an extremely dangerous form of food poisoning. In 2013, several people reportedly died after consuming poorly fermented kiviak at a celebratory event.
While the Inuit developed this method to preserve food through long, harsh winters, it’s a risky one for modern eaters unfamiliar with the process. According to researchers, traditional knowledge of temperature, timing, and technique makes all the difference between a treat and a tragedy.
Egyptian ‘beer bread’: the yeast bomb
Ancient Egyptians loved their beer—and they made it differently than we do today. Their version was closer to a thick, porridge-like brew made by fermenting partially baked loaves of bread in water. This bread, often crammed with wild yeasts and local grains, would be left to bubble and froth in open containers.
While it may have packed a nutritional punch and was safer than Nile water at the time, the lack of temperature control and exposure to environmental contaminants would be a nightmare for modern brewers. Mould, bacteria, and unpredictable yeast strains could easily flourish.
Some archaeologists and brewers have recreated ancient Egyptian beer, but they do so using laboratory cultures and careful monitoring. Drinking it like the ancients did—straight from an open vat in the sun—would likely lead to more than just a hangover.
Fermented mare’s milk: a Mongol staple with a sting
Known as airag (or kumis in other regions), fermented mare’s milk was a dietary staple for Mongol nomads. It had a low alcohol content, was mildly fizzy, and often relied on natural, unpasteurised bacteria to get the job done.
The problem? Fermenting raw milk can be a minefield of harmful bacteria, especially if hygiene is inconsistent. Airag was usually kept in leather bags and stirred regularly with a wooden paddle. While traditional knowledge often ensured it was drinkable, one misstep in temperature or timing could result in milk gone very wrong.
Modern versions are sometimes pasteurised, but traditional airag could harbour E. coli, listeria, or campylobacter—none of which go well with a summer picnic.
Poi: Hawaiian fermented taro with hidden hazards
Poi is a fermented paste made from pounded taro root, a sacred staple of traditional Hawaiian cuisine. Left to ferment naturally over days, poi becomes slightly sour and smooth, and remains a symbol of cultural pride.
However, taro needs to be carefully cooked or fermented—raw, it contains calcium oxalate crystals, which can irritate the mouth and digestive tract. Traditional fermentation helped break down these compounds, but poor preparation could leave them intact.
In modern kitchens, where shortcuts and substitutions might be tempting, there’s a risk of doing it improperly. Some forms of improperly stored poi can also develop harmful moulds or bacteria. Thankfully, commercial poi today is prepared under much stricter food safety standards.
Surströmming: the fermented fish that fights back
Surströmming, a Swedish delicacy, is still made and eaten today—but it’s arguably one of the most pungent foods on earth. It’s made by fermenting Baltic herring in a salty brine until the fish essentially liquefies. Cans of surströmming are sometimes banned on planes due to the risk of exploding from the pressure of gas buildup.
In ancient or unregulated settings, the fermentation process could go very wrong. Too little salt or too much heat and you’ve got a bacterial hazard. The smell alone can cause nausea, and if the fermentation goes off, it could lead to foodborne illness.
Some historians believe similar fermented fish dishes existed across medieval and Viking-age Europe, but with even less oversight. A poorly buried barrel of fish could become a lethal stew.
Hákarl: the Icelandic shark that needs a warning label
Hákarl is made by fermenting the meat of the Greenland shark, which is naturally toxic due to high levels of urea and trimethylamine oxide. Traditional Icelandic preparation involves burying the shark in sand and gravel for weeks, then hanging it to dry for several more.
Fermentation breaks down the toxins, but the result is an intensely strong, ammonia-scented meat that’s not for the faint of heart. Tourists often struggle to keep it down.
While it’s safe when prepared by those who know how, consuming under-fermented shark could cause serious poisoning. There’s a reason this fish isn’t simply grilled and served fresh—it would be downright dangerous. According to the Icelandic Food and Veterinary Authority, proper preparation is essential to avoid toxicity.
Ancient cheese: delightful or deadly?
Cheese has been around for millennia, but ancient versions didn’t have the benefit of pasteurisation or microbiological insight. Some cheeses were stored in animal stomachs, buried in clay pots, or left to ferment in caves. Without consistent temperatures or sanitisation, these could easily develop harmful bacteria or even parasites.
In 2019, researchers found the world’s oldest cheese, buried in an Egyptian tomb. The 3,200-year-old sample contained Brucella melitensis, a bacterium that causes brucellosis—an infectious disease still present in parts of the world.
While this cheese was never meant to be eaten again, it’s a powerful reminder that ancient delicacies could come with very modern consequences.
Fermentation is often celebrated as one of the great human inventions, and rightly so.
It allowed ancient people to survive harsh climates, preserve food without refrigeration, and develop unique cultural dishes that we still enjoy today. But it wasn’t without risk. Without modern sanitation, testing, and temperature control, many fermented foods walked a fine line between nourishing and deadly.
Today, most of these foods are made under safer conditions, or avoided entirely. But history is full of bold culinary experiments, and it’s only through trial, error, and the occasional trip to the afterlife that we’ve landed on the safer versions we know now. So the next time you open a jar of kimchi or sip some kombucha, spare a thought for the ancient diners who gambled a lot more for that tangy flavour.
