Fermenting foods is no new innovation: It was at the base of the culinary lifestyles of even our pre-Neolithic ancestors. Though the method was primarily meant for beverages, it was soon discovered to be a novel way to store meat and vegetables.
Along the way, the earliest consumers of fermented foods noticed their gut health improve, and so began a trend which has survived the test of time. That is not to say it is without flaws. But before we get into its potential hazards, we need to understand what fermentation is and how it benefits us.
During the process of fermentation, probiotics convert carbohydrates into alcohol or acids. These in turn act as natural preservatives and give fermented foods their unique acidity. Microorganisms (a.k.a. bacteria and fungi) have metabolic genes capable of breaking down distinct types of sugar metabolites.
There are three forms of fermentation: lactic acid fermentation, ethanol fermentation and acetic acid fermentation.
In the first form, starches and sugar are broken down to produce lactic acid which protects food from microbial spoilage. Examples include yoghurt, pickles and sauerkraut.
In the process of ethanol fermentation, pyruvate molecules (products of glucose metabolism) are broken down by yeast into alcohol and carbon dioxide molecules, producing wine, beer and bread.
The third type, acetic acid fermentation, converts sugars from grains and fruits into sour-tasting wine and other condiments.
Pros & cons
In general, fermented food are high in probiotics and are also known to display antioxidant, anti-microbial, anti-fungal, anti-inflammatory, anti-diabetic, and anti-atherosclerotic activity.
“By and large fermented foods are good for people, but some show adverse effects,” says Dr Vinayak Baruah, a gastroenterologist from Mumbai. “The most common reaction by those who are averse to fermented foods is bloating. I have even come across some people who have migraines and headaches because of curd consumption.”
“This gut-brain connection is still being researched and it is too early to say anything, but evidently it triggers adverse reaction in some people,” he adds.
Bloating and migraine
Delving into the adverse reactions, Dr Baruah says the biogenic amines produced by certain bacteria during fermentation include histamines and tyramine. Some people are allergic to histamines and other amines. In their cases amines stimulate the central nervous system and increase or decrease blood flow, triggering headaches and migraines.
Other symptoms of histamine intolerance include itchiness, rhinitis (runny nose), redness of the eye, fatigue, nausea, and vomiting.
Besides bloating, headaches and histamine intolerance, people have also complained about food-borne illness, infection from probiotics, antibiotic resistance, and other reactions.
When quality is villain
“Some people are allergic to probiotics. You would be surprised at how many of these cases we interact with during a month,” says Ranchi-based nutritionist Anjali Vasudevan. “But the most common cause of fermentation-related issues is spoilage. People find it hard to distinguish between fermented foods and spoilt food. A lot of people consume spoilt food, assuming it’s fermented and end up with food poisoning.”
Several such cases have been reported in India and other parts of the world where fermented foods are a staple.
A 2022 paper by Krzysztof Skowron noted that in many parts of the world, but especially in Africa and Asia, “pathogens such as enterotoxigenic and enterohemorrhagic Escherichia coli, Shigella spp., Salmonella spp., enterotoxigenic Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus have been detected in fermented foods.”
The paper identified a combination of factors that could lead to pathogenic microorganisms or toxins in food: From poor-quality ingredients to inadequate hygiene to a lack of food and safety standards.
“Every chance we get, we insist that people consume fermented foods,” says Dr Baruah. “But we also tell them to notice the reactions. Not everyone can digest them well.”
So, the next time you pop open a bottle of kombucha, dig into kimchi or scoop up a dollop of thick curd, check if it is spoilt and then pay heed to how your body reacts in the aftermath.