By Manal Mohammed for The Conversation
Fermented foods have become very popular, thanks to claims about their nutritional properties and reported health benefits, such as improving digestion, boosting immunity and even helping people lose weight. Some of the most popular fermented foods include kefir, kombucha, sauerkraut, tempeh, natto, miso, kimchi and sourdough bread.
But though these fermented foods might offer us many health perks, most people aren’t aware that they might not work for everyone. For some people, fermented foods might cause serious health issues.
Fermented foods are loaded with microorganisms, such as live bacteria and yeast (known as probiotics). However, not all microorganisms are bad. Many, like probiotics, are harmless and are even beneficial to us.
During the process of fermentation, probiotics convert carbohydrates (starch and sugar) into alcohol and/or acids. These act as a natural preservative and give fermented foods their distinctive zest and flavour. Many factors affect fermentation, including the type of probiotic, the primary metabolites these microbes produce (such as lactic acid, or certain amino acids), and the food undergoing fermentation. For example, probiotic yogurt is produced by fermenting milk, most commonly with lactic acid bacteria that produce lactic acid.
Fermented foods contain high amounts of probiotics, which are generally considered safe for the majority of people. In fact, they’ve been shown to have anti-oxidant, anti-microbial, anti-fungal, anti-inflammatory, anti-diabetic and anti-atherosclerotic activity. However, some people might experience severe side effects after consuming fermented foods.
1. Bloating
The most common reaction to fermented foods is a temporary increase in gas and bloating. This is the result of excess gas being produced after probiotics kill harmful gut bacteria and fungi. Probiotics secrete antimicrobial peptides that kill harmful pathogenic organisms like Salmonella and E. Coli.
A recent study showed this antimicrobial effect of probiotic Lactobacilli strains found in commercial yogurt. Although bloating after eating probiotics seems to be a good sign that the harmful bacteria are being removed from the gut, some people might experience severe bloating, which can be very painful.
Drinking too much kombucha can also lead to excess sugar and calorie intake, which may also lead to bloating and gas.
2. Headaches and migraines
Fermented foods rich in probiotics – including yogurt, sauerkraut and kimchi – naturally contain biogenic amines produced [during fermentation]. Amines are created by certain bacteria to break down the amino acids in fermented foods. The most common ones found in probiotic-rich foods include histamine and tyramine.
Some people are sensitive to histamine and other amines, and may experience headaches after eating fermented foods. Because amines stimulate the central nervous system, they can increase or decrease blood flow, which can trigger headaches and migraines. One study found that low-histamine diets reduced headaches in 75% of participants. Taking a probiotic supplement might be therefore preferred.
3. Histamine intolerance
Histamine is plentiful in fermented foods. For most, our body’s specific enzymes will naturally digest them. However, some people don’t produce enough of these enzymes. This means histamine won’t be digested and will instead be absorbed into the bloodstream.
This can cause a range of histamine intolerance symptoms. The most common are itching, headaches or migraines, runny nose (rhinitis), eye redness, fatigue, hives and digestive symptoms include diarrhoea, nausea and vomiting.
However, histamine intolerance can also cause more severe symptoms, including asthma, low blood pressure, irregular heart rate, circulatory collapse, sudden psychological changes (such as anxiety, aggressiveness, dizziness and lack of concentration)...