- Manal Mohammed
- The conversation*
For decades, fermentation has been used to preserve food, increase its shelf life and improve its flavor. But many people are unaware of the health benefits of fermented foods.
Fermented foods are generally defined as “foods or beverages produced through controlled microbial growth and conversion of food components through enzymatic action”.
It can be pickled cabbage (sauerkraut), kefir yogurt drink, sourdough bread and some pickles (only lactofermented ones).
Fermented foods are rich in beneficial microbes and helpful metabolites (substances produced during fermentation by bacteria that support a healthy gut).
Several prominent research groups suggest that fermented foods may offer a variety of health benefits, encourage weight loss, and reduce the risk of some diseases.
Food-related organizations and groups such as the UK Nutritionists Association now recommend consuming fermented foods more often.
For example, fermented milk and yogurt are now being offered to children as young as six months of age to help provide a good balance of nutrients, prevent iron deficiency in populations using cow’s milk, and reduce gastrointestinal infections.
Another study showed that regular consumption of fermented foods may be especially important for low-income communities with high deprivation who are disproportionately susceptible to gastrointestinal infections from bacteria such as E. coli and listeria.
Why do fermented foods work?
During fermentation, bacteria can produce useful vitamins and metabolites.
Fermented foods potentially contain probiotic microorganisms such as lactic acid bacteria.
And, despite the short time that these bacteria spend in the intestine, they help in the digestion of food and strengthen our immune system.
The probiotics in fermented foods also strengthen the intestinal walls to prevent their contents from leaking into the blood, so fermented foods can contribute to the prevention of leaky gut syndrome.
It has also been found to contribute to the prevention and treatment of conditions such as allergies and eczema.
Consumption of kimchi and other fermented vegetables can reduce asthma and atopic dermatitis.
Other studies show the effect of fermented foods on reducing the risk of type 2 diabetes and high blood pressure. And consumption of fermented dairy products reduced the risk of bladder cancer.
Diets high in yogurt showed a reduced risk of metabolic syndrome in older Mediterranean adults, in which a range of conditions manifest together (including increased blood pressure, high blood sugar, and excess body fat).
Probiotics in fermented foods have health-promoting properties, such as lowering cholesterol; a study has shown that several strains of lactic acid bacteria have blood cholesterol lowering properties.
There appear to be other possible benefits, but more research is needed.
A recent review of studies demonstrated the anticancer properties of lactic acid bacteria present in fermented foods on a variety of intestinal, liver and breast tumor cells as they modulate tumor development.
A diet consisting of foods rich in conjugated linoleic acid, particularly cheese, may protect against breast cancer in postmenopausal women.
However, not all studies agree, and a pilot study in mice even suggested an increase in tumor growth.
Fermented foods have also been shown to improve mood and sleep.
Prebiotics, found in fermented foods, are non-digestible ingredients that selectively stimulate the growth and activity of beneficial bacteria in our gut (not to be confused with probiotics, which are living organisms).
Consuming fermented foods can make you feel happier, as the prebiotics in fermented foods boost gut health and promote the growth of many types of beneficial bacteria.
This results in healthy levels of the hormone serotonin, which helps stabilize mood, regulate feelings of well-being and happiness, regulate anxiety, and manage sleep.
Chemicals enriched by fermentation are also linked to positive mental health.
To sleep well, you need to be kind to your gut — eating fermented foods like yogurt, sauerkraut or kimchi before bedtime can help beat insomnia.
During fermentation, lactic acid bacteria produce conjugated linoleic acids which have been shown to have a blood pressure lowering effect.
If a person has hypertension, they are more likely to have more mood problems (such as anxiety and depression) than a person with normal blood pressure.
Despite the various health benefits of fermented foods listed, some people may experience side effects.
The most common reaction is a temporary increase in gas and bloating.
This is the result of excess gas produced after probiotics kill harmful intestinal bacteria and fungi.
Unfortunately, other people may experience headaches or migraines from eating sauerkraut or kimchi, and this may be related to the histamines found in large amounts in fermented foods.
While symptoms of histamine intolerance can vary, some common reactions include headache or migraine, nasal congestion or sinus problems, nausea and even vomiting (but this is relatively rare).
Over the centuries, many people have consumed fermented foods for convenience, not knowing their health benefits.
Fortunately, many fermented foods are cheap and simple to make, offering us an easy way to improve our health and well-being.
* Manal Mohammed is Professor of Medical Microbiology at the University of Westminster, London.
This article was originally published on the academic news site The Conversation and republished here under a Creative Commons license. Read the original version here (in English).
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