Is it possible to consume too much fermented food?

Kombucha, kimchi, pickles and other fermented foods are trending, but can you have too much of a good thing?

Who can eat fermented food and how much can we have? Source: Flickr/Jules

In many cultures, fermented foods and drinks are nothing new.

The Japanese regularly eat miso, pickled vegetables and natto (fermented soybeans). Kimchi and cheonggukjang (fermented soybean paste) are traditional Korean foods.

Sauerkraut and kefir are consumed throughout Eastern Europe, douchi (fermented black soy beans) features in Chinese cooking, while poi (fermented taro) is a traditional Hawaiian staple.

Don't overlook this humble vegetable. Source: Alan Benson

Centuries of history aside, fermented foods and beverages have been relishing a red hot minute in the spotlight in recent years.

With wellness seekers eagerly scoffing – or even preparing their own – fermented products (hands up if you have a kombucha SCOBY living in your fridge), SBS Food was curious to find out whether it's possible to overdo them?

The plight of the hypersensitive gut

One of the main reasons people reach for fermented foods and drinks is better digestive health, because they're packed with gut-loving prebiotics and probiotics.

But in some cases, they can trigger digestive discomfort such as bloating, burping and gas. So, what gives? Is it a case of people overdoing these foods, or are some people more sensitive to them? According to accredited practising dietitian Joanna Baker, a mild digestive disturbance is actually normal when consuming fermented foods.

"The prebiotics they contain provide fuel for our gut bacteria, but when those bacteria feed, they tend to ferment the prebiotics, creating gas and bubbles," Baker explains.

"Gas stretches the colon and its nerve endings, but in some people, those nerve endings are hypersensitive and will send messages of pain, bloating and discomfort."

"The prebiotics they contain provide fuel for our gut bacteria, but when those bacteria feed, they tend to ferment the prebiotics, creating gas and bubbles."

In contrast, people without visceral hypersensitivity might not get any gut symptoms after their kimchi fix, or they may simply notice they feel a tad gassy, and get on with their day.

Amines, histamine and FODMAPs

While irritable bowel syndrome (IBS, which goes hand-in-hand with visceral hypersensitivity) is the most common condition that can cause a person to react to fermented foods, underlying food chemical intolerances can also be at play.

For instance, some people are sensitive to amines (which fermentation produces) while others react to the histamine that's present in fermented foods.

In both cases, symptoms can range from digestive upset to headaches, congestion, hives, rashes and lethargy. An intolerance to FODMAPs (short-chain carbohydrates that aren't absorbed properly in the gut) can also be a factor in someone reacting to fermented foods, considering yoghurt, kefir, pickled vegetables and sauerkraut have a high FODMAP rating.

"Sometimes when we remove the underlying trigger, whether it be an anime or salicylate, the nerve endings in the gut calm down, then we can start reintroducing fermented foods, and people tolerate them better," says Baker. 

We're all unique (and so are our guts)

As for whether people without underlying digestive issues can overdo fermented foods, the answer is mixed.

Sharon Flynn, the creator of The Fermentary and author of Ferment for Good: Ancient Foods for the Modern Gut, says, "It's just like overdoing anything; for instance, if you overdid chocolate it's going to affect you negatively, although less so with fermented foods.

"You're more in danger of having poor health from not including these things in your diet than you are from including them."

It's just like overdoing anything; for instance, if you overdid chocolate it's going to affect you negatively.

There's also the fact that everyone's different, and as such has a different threshold.

Seon Oh, creator of Mrs Oh Fermentation kimchi, says, "I eat different fermented foods all the time and don't have any problems because my gut is exposed to different strains of bacteria. 

"But it might be that another person [without that regular exposure] has a reaction."

Slowly does it

If you're keen to add fermented foods to your diet, it's best to pace yourself. "Start with a tablespoon with each meal, then listen to your body," advises Oh. If it upsets your gut, wait a few days, then try again with a smaller serve.

Flynn suggests that milk or water kefir, sauerkraut, kimchi and even miso paste on toast are a good starting point. Her tip is to pair fermented foods with fat, for instance, a pickle with cheese.

"Eating an acid with a fat is good for digestion – think of the traditional French charcuterie plate with cornichons and capers, or how the Japanese have pickled ginger and sour rice alongside fatty tuna," she says.

If you can't handle the price tag of boutique fermented foods, there's no need for FOMO. "Rye bread, pistachios, asparagus and legumes are amazing for the gut," says Baker.

"Ultimately, you want to aim for as many different plant foods in your diet as possible, because a diverse diet creates a diverse gut microbiome."