20 Healthiest Fermented Foods and Their Benefits - Dietitian Fit (2024)

Fermentation is a process that converts sugars (such as glucose) into byproducts, typically acids, gas or alcohol, by using microorganisms such as bacteria, yeast, or fungi under anaerobic conditions (without oxygen). This process was traditionally used to preserve food, but in modern day it is also used to improve the flavour profile and provide additional nutrition.

What are fermented foods?

Fermented foods are foods and drinks that have undergone a controlled process of microbial growth, to allow the conversion of certain food product such as sugar, into by products such as alcohol or acid. Enzymes are involved in this conversion, and the natural fermentation process helps to preserve foods, change the taste, textures and flavours, as well as providing a magnitude of health benefits. Many, but not all fermented foods, contain live probiotics.

There are various types of fermentation, including lactic acid fermentation. This converts the sugar into lactic acid, using lactic acid bacteria (LAB) - foods such as kefir, yoghurts, sourdough bread and kimchi use LAB for fermentation. Ethanol fermentation is used for wine making, beer brewing and baking, and involves yeasts, converting the sugars into ethanol and carbon dioxide.

There is also acetic acid fermentation, converting ethanol into acetic acid, to produce foods such as vinegar and kombucha, via oxidative fermentation. Other foods, such as natto (fermented soy bean), are produced from alkaline fermentation, where proteins are broken down in an alkaline environment, to by-products like amino acids.

Types of fermented foods

There are various types of fermented foods and beverages available, and depending on the fermentation process, they produce their own unique flavours, textures and benefits. These can range from fermented beans, to different types of dairy and vegetables. Most common types of fermented foods include:

• Live yoghurt: Milk is fermented with lactic acid bacterias, to give a thick tangy yoghurt that contains probiotics (live bacterias). These probiotics help in many different areas of health, though it is important that the bacterias make it through the digestive system, without being killed by the stomach acid. It is good to choose yoghurts that have “live and active culture” or similar, on the packaging. This indicates that the bacteria can survive through the digestive system not being firstly destroyed by the stomach acid, to allow fermentation to be carried out by the bacterias in the large intestine.
• Kefir: A fermented milk drink that contains a variety of bacteria and yeast, resulting in a slightly sparkling, sour tasting beverage. It also comes in a yoghurt consistency ,and can be purchased in a range of flavours.
• Sauerkraut: A mix of shredded cabbage, which has undergone lactic acid fermentation. It originates from Central and Eastern Europe and is crunchy with a tangy flavour.
• Kimchi: Similar to above, kimchi contains shredded cabbage, as well as other vegetables such as radish, onion and carrots, and is seasoned with chilli, garlic, ginger and fish sauce. It is typically spicy, and originates from Korea.
• Miso: A seasoning originating from Japan using soy beans that have been fermented with the fungus Aspergillus oryzae, which also helps to produce soy sauce and sake. It is often used in soups and sauces.
• Tempeh: Another type of fermented soy bean, however, the soy beans are fermented with a mould known as Rhizopus. It is a dense, savoury product and is said to have a nutty flavour. It is produced from soy beans itself, where as tofu is produced from soy milk.
• Kombucha: Is made by fermenting tea, with a SCOBY - symbiotic culture of bacteria and yeast. The sugars present in the tea are digested by the SCOBY, producing the end result, which is a fizzy, tangy and fairly acidic flavoured beverage.
• Sourdough Bread: A very popular type of bread, true sourdough is made using a fermented dough starter, which contains naturally occurring lactic acid bacteria and wild yeast. Unlike regular bread which uses commercial yeast, sourdough fermentation uses wild yeast and bacteria, which gives the tangy flavour. Although sourdough is a fermented food, it is not classed as a probiotic. This is because most of the beneficial microbes do not survive the baking process, as the high temperatures kill live bacteria and yeast. Despite this, sourdough can still have many health benefits, as detailed below.

Health benefits of fermented foods

There are many benefits linked to consuming fermented foods. Although fermentation of foods was originally thought to be solely for preservation, over the years fermented foods have been recognised as providing beneficial bacteria, which can improve their nutrient availability. Here are some of the key health benefits associated with a range of fermented foods.

• Aid in digestive health
  Many, but not all, types of fermented foods are probiotics, meaning that they contain live organisms when consumed, that deliver a health benefit. Probiotic foods that are fermented include kefir, yoghurt, kimchi, sauerkraut and kombucha - providing that none of these have been pasteurised during production. The probiotics are bacteria that can help to improve the diversity and range of microbes found in the gut, and can support digestive health by helping to improve stool frequency and consistency, as well as reduce symptoms such as bloating.Fermented foods are easier to digest, as they have been partially broken down. As an example, when milk is fermented with kefir grains, the lactose sugar in milk is broken down, which allows better tolerance of kefir for those who are lactose intolerant. However, not everyone will be suited to consume fermented foods, such as those with more severe lactose intolerance or cow's milk protein allergy, as well as those with histamine intolerance, as fermented foods can be high in histamine.
• Enhanced Nutrient Absorption
  The fermentation process of foods can improve the bioavailability of nutrients, such as vitamins and minerals, in some foods. As an example, fermenting soybeans into tempeh can help reduce the presence of phytic acid, which otherwise can hinder the absorption of certain minerals such as zinc, iron and calcium. Some bacterias during fermentation can also help to increase the level of certain nutrients such as folate and vitamin B12, important for energy production and red blood cell formation.
• Weight Management
  Fermented foods have been noted to help with appetite regulation, and increase feelings of satisfaction and fullness. This is because the microorganisms in fermented foods can produce short-chain fatty acids (SCFAs) via fermentation, which bacteria in the intestine use as energy, and can influence metabolic pathways, including the secretion of appetite hormones. Fermented foods can also influence and improve blood sugar control and insulin sensitivity. These factors can have an influence on managing risk of type 2 diabetes and obesity.
• Supported Immune System
  Consuming probiotics from fermented foods has been linked to the activation of immune responses, by stimulating certain white blood cells to increase the production of antibodies, and allowing better management of inflammatory related diseases such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), inflammation and diarrhoea. The promotion of the immune system can also increase the protective immune response, increasing activity of natural killer cells and macrophages, both involved in fighting off infection. And because the gut has a key role to play in the immune response, improving the gut microbiome can improve the overall functioning of the immune system.
• Reduced Inflammation
  There are various anti-inflammatory properties of fermented foods, largely due to the bioactive compounds such as lactic acid. The regular consumption of fermented foods can support a reduction of chronic inflammation, important in managing conditions such as arthritis and IBD.
• Improved Mental Health
  Ongoing research has indicated a clear link between the gut health and mental health, known as the gut-brain axis. Fermented foods, particularly those which contain probiotics, can influence the production of neurotransmitters, or chemical messengers, along the gut-brain axis, which has an influence on symptoms such as depression and anxiety. In fact, there are certain types of probiotics that can support the production of neurotransmitters like serotonin and GABA, which are key in regulating mood and cognitive function.
• Cardiovascular Health
  Fermented foods containing lactic acid bacteria can reduce LDL cholesterol and total cholesterol, whilst increasing HDL cholesterol, influencing overall cardiovascular health. There are some antihypertensive effects of the peptides produced during fermentation of milk, which can also manage the reduction of blood pressure.

Are there any dangers of fermented foods?

Although fermented foods can provide a range of health benefits, there may be some risks associated, if not prepared properly. Here are some of these dangers to be aware of, associated with fermented foods:

• Risk of contamination
  If the fermentation process is not carried out under the right conditions, there is a risk of contamination of harmful bacteria and toxins, which can lead to food poisoning. These bacterias typically include E.coli, Listeria and Salmonella.
  The risk is not only with bacterial growth, but mould can be an issue, especially if the incorrect temperatures are used.
• High salt content
  Because fermented foods often require salt (i.e. sodium) for the fermentation process, the end result can often be high in overall sodium levels. If someone frequently consumes fermented foods high in sodium, this can increase risk of hypertension. It is important for anyone who already has high blood pressure or needs to manage their sodium intake for health reasons, to be mindful of consumption of the higher sodium types of fermented products.
• High histamine levels
  For those who have histamine intolerance, fermented foods may not be suitable - this is because fermented foods can naturally contain high levels of histamine, which can trigger symptoms such as headaches and gastrointestinal discomfort.
• Digestive issues
  When consumed, fermented foods are broken down in the gut, by the bacteria present. the breakdown of fermented foods can lead to gas production, and for some can cause excessive discomfort and unpleasant side effects such as excess gas and severe bloating. Some level of gas production is normal and expected, but for some it can be excessive and uncomfortable. This may be the case for people who cannot tolerate high FODMAP foods, which are fermentable carbohydrates found in some fermented foods, typically associated with those with IBS.
• Food allergens
  It is important to be aware of ingredients used in fermented foods, if you have an allergy. Some fermented foods contain dairy or soy, which are common allergens. Therefore, digesting these foods, if you have an allergen, can be dangerous for your health. Check the label and seek out suitable allergen free alternatives if needed.

Who should not eat fermented foods?

There are a small subgroup of the population who should be cautious when it comes to consuming fermented foods. This includes:

• Those with severe intolerances or certain allergies
  Although many fermented foods such as kefir and yoghurt are lower in lactose than milk itself, those with more severe lactose intolerance may struggle with digesting fermented dairy products. However, non dairy options such as coconut milk based kefir is available. Some fermented foods can be high in histamines, which is a compound that’s released from immune cells and can cause an allergic response. Unpleasant side effects can include digestive issues and headaches, from those with histamine intolerance. Anyone who is allergic to any fermented products, such as soy and dairy, should seek allergen free alternatives.
• People with digestive disorders
  Although fermented foods can have a role in supporting digestive health, for those with digestive disorders such as IBS, IBD or Small Intestinal Bacterial Overgrowth (SIBO), fermented foods can trigger symptoms, as the probiotics can ferment and release gas in the intestines, exacerbating symptoms. Instead of all together avoiding fermented foods, people with digestive orders should very slowly trial the introduction of a range of fermented foods in small quantities, to understand their tolerance and reaction.
• People who are immunocompromised
  Anyone with a weakened immune system, such as those with cancer or having had organ transplants or HIV/AIDS, need to be cautious of any foods containing live bacteria. Although risk of infection is low, this is higher in those with a weakened immune system, as this population is more susceptible to infections from pathogens that would not typically cause illness in a person with a healthy immune system.Guidance for those who are immunocompromised is to only consume foods that are pasteurised, which would exclude foods such as kefir, kimchi, yoghurts and sauerkraut, which are generally unpasteurised to maintain balance of bacterias.
• Pregnant or breastfeeding women
  Fermented foods are generally safe for pregnant and breastfeeding women, though it is important to choose foods that are made with safe and hygienic practise, to avoid contamination.

How often should you eat fermented foods?

How often you should eat fermented foods depends on a variety of reasons for the individual, which includes their health needs and conditions, tolerance and preferences.

Many people will be able to tolerate and enjoy a small amount of fermented foods per day. For example, this can include kefir in their breakfast smoothie, and perhaps some kimchi in their evening meal. Some may be able to tolerate more than this, especially if fermented foods have been a typical part of their diet from a young age.

For others, fermented foods in large amounts can lead to digestive discomfort. So perhaps a small glass of kombucha or a few spoons of sauerkraut may be all that someone can tolerate in a day, so these people should exercise moderation. This is specifically the case for those with known gut disorders such as IBS, who may struggle with the side effects such as gas and bloating.

Can you eat fermented foods everyday?

Yes you can safely consume fermented foods every day if you would like to enjoy these in your daily diet. There is no official guidance on how often to have fermented foods, but it can be helpful to start off slow if you are new to fermented foods, to allow your digestive system to adapt. Start with small amounts a couple of times a week, and slowly increase this over weeks and months to daily consumption.Try to also add variety with different types of fermented food products, for optimal health benefits. You may not need large servings either, especially if you are consuming multiple types of fermented foods per day.

Top 20 fermented foods

Kombucha

Kombucha is a fermented tea beverage, usually made from black or green tea. It is fermented using a SCOBY, which stands for symbiotic culture of bacteria and yeast. The taste is tangy and sweet, and is usually sparkling. Sugar is needed for the fermentation process, though much of the bacteria and yeast ferment on these sugars. The yeasts present in the SCOBY convert the sugars into carbon dioxide and alcohol, and the bacterias convert the alcohol into acetic acid, and other beneficial acids.

Kombucha can have a wide variety of probiotics, which are linked to supporting gut health. As it is made from tea, it also is a good source of antioxidants, which can help to reduce oxidative stress in the body. Acetic acid, which is a byproduct of fermentation, can support our liver health.

Kombucha is a very popular drink, often used as a very low alcoholic alternative (contains less than 0.5% ABV) for those looking to reduce their alcoholic intake, when out in bars or restaurants. It is widely available in different flavours and sizes from supermarkets and health food shops.

Whilst not everyone is a fan of the slightly sharp, vinegary flavour, it is certainly one we recommend trying! Sugar is needed for the fermentation process, though it is worth comparing the levels of sugar between different brands, as some add extra sugar and flavourings post fermentation. Be aware that as kombucha is a carbonated drink, it may lead to gas and digestive discomfort for some people, especially those with gut sensitivities. As there is a small trace of alcohol in kombucha, it may not be suitable for those who avoid alcohol for religious or other reasons.

Kimchi

Kimchi is a fermented vegetable dish that originates from Korea. Typically made using nappa cabbage, as well as other vegetables including carrots, radishes and spring onions, it is combined initially with salt, followed by a mix of spices and flavourings such as garlic and red pepper flakes. It has a spicy tangy flavour, and is usually red in colour. Kimchi is a source of probiotics, particularly the bacteria known as Lactobacillus, which is linked to improving the balance of intestinal gut microbes.

As it is made from vegetables, it is a great source of fibre, as well as other nutrients, such as vitamins A, B, C and K. It contains garlic and often ginger and other spices, known for their anti-inflammatory compounds. Although it originates from Korea, kimchi can be found easily in the UK, usually in Asian markets, as well as health food stores and some large supermarkets. Be mindful that it has a spicy flavour and is high in fibre, which may cause issues for anyone who has a sensitive digestive system. It is also fairly high in sodium, so anyone who follows a low sodium diet may need to be mindful of how often they consume kimchi.

Kefir

A type of fermented milk drink which contains a range of probiotics, kefir is popular in Western Europe where it is consumed at any time of the day as a beverage. It has grown in popularity in the UK, and is now commonly found in supermarkets and health shops. It is made using kefir grains, a mix of bacteria and yeast. The yeast ferment the milk, leaving a sour drink, rich in probiotics. It can be made from various milks, including cow, goat and sheep, as well as non-dairy milks such as coconut milk. Kefir water can also be found in some specialist shops.

Kefir often contains a wider diversity and volume of probiotics compared to yoghurt and other fermented foods. It has been shown to provide anti-inflammatory and anti-oxidant properties, during in vitro studies. During the fermentation stage, lactose sugars present in milk are broken down, so small amounts of kefir can usually be tolerated by those with lactose intolerance. It is a rich source of all the nutrients found in milk such as calcium and potassium, as well as B vitamins and protein. It is important to note that as a by product of the fermentation process, kefir can contain up to 2% ABV.

Sauerkraut

A traditional fermented cabbage, which is typically found in Eastern European diets but is available readily in the UK due to it's health benefits and flavour. The cabbage is fermented by various lactic acid bacteria, which gives the acidic, tangy flavour and sharpness of sauerkraut. It is rich in probiotics, especially Lactobacillus, which can support gut health. Sauerkraut can also support digestive issues such as bloating and constipation, as well as providing a range of vitamins including A, C, E and K, as well as fibre.

As with kimchi, the fermentation process of producing sauerkraut can use high levels of salt, so it is important for anyone who needs to be mindful of their salt or sodium intake, to enjoy sauerkraut in moderation. As with all fermented foods, ensure the sauerkraut you buy is unpasteurised, as many store brought sauerkrauts will be pasteurised and stored on the shelves, instead of the fridge section. This means that many of the beneficial bacterial properties have been killed during the pasteurisation, but a live sauerkraut will be stored in the fridge.

Miso

Miso is a fermented soybean seasoning, mixed with koji (a type of fungus known as Aspergillus oryzae) and salt. It is rich in vitamins and minerals including B vitamins, zinc and copper. Some versions of miso also include rice or barley, though traditionally it is made with just soybean and koji and salt. Fermentation of miso can last for several months to years, depending on the type of miso used, and the end result is a savoury paste, with a deep umami flavour. Miso contains lactic acid bacteria, which is produced in the fermentation process, and observational studies have shown that fermented soy products such as miso and natto, are associated with a lower risk of mortality (Katagiri et al.,2020).

Another study showed that although miso is high in sodium, it was not associated with the development of high blood pressure. A review looking at fermented soy products in particular found supportive evidence for these foods to be anti-inflammatory and may help to reduce diabetes and certain cancers. Soy beans are a good source of isoflavones, belonging to the flavonoid family of polyphenols, which provide a range of health benefits, including cholesterol lowering and reduction in risk of breast and prostate cancer.

Although heating the miso to a high temperature can destroy many of the probiotics, so we recommend trying to enjoy miso paste with foods at room temperature, such as a condiment and in a sauce. If you wish to cook with miso, to retain as many of the health benefits as possible, add miso towards the end of cooking, or in low temperature cooking. There are various types of miso, including red, white and mixed miso, all with different fermentation times and flavours, so it is good to experiment with your tastes and different dishes.

Yoghurt

Made by bacterial fermentation of milk, yoghurt is easy and simple to make at home and requires minimal ingredients or skill. It uses live bacterial cultures from a small yoghurt starter, to help create a large batch of probiotic rich yoghurt. Typically, bacterias include Lactobacillus bulgaricus and Streptococcus thermophilus, with other strains for additional probiotics.

Milk is first heated to kill unwanted bacteria, and then cooled to a specific temperature before adding the live bacteria cultures. This is then kept at a warm temperature, to allow the bacteria to ferment and thicken milk, creating yoghurt. During this time, the bacteria ferment the lactose sugar found in milk, and this gives a tangy flavour to the end result. Yoghurt is a rich source of probiotics, as well as protein and fatty acids. It is a source of many nutrients, including calcium, phosphorus, potassium, vitamin A, vitamin B2, and vitamin B12.

The consumption of yoghurt products is linked to the reduced risk of osteoporosis, diabetes, and cardiovascular diseases, as well as supporting the immune response. Several studies have shown a benefit of yoghurt consumption for certain gastrointestinal conditions, including lactose intolerance, constipation, colon cancer, inflammatory bowel disease,Helicobacter pylori infection, and allergies. Probiotics found in yoghurt may even help reduce symptoms of IBS and improve overall gut health.

Although easily available in supermarkets, it is important to choose a live yoghurt, that contains bacterial cultures. Some yoghurts are pasteurised after fermentation, removing the beneficial probiotic content. Choose a plain/no added sugar yoghurt for the best benefits. Be mindful that those with lactose intolerance may struggle to tolerate a certain level of yoghurt, so alternatives are available, such as soy or coconut yoghurt, which sometimes contain added bacterial cultures.

Pickles

Pickles are mainly vegetables, that have been preserved through fermentation in a brine mad with water and salt, and sometimes vinegar. This helps to extend shelf life as well as providing a tangy, sharp and sour flavour. Cucumbers are commonly pickled, along with peppers, beetroot, lemons and carrots. The vegetables are soaked in a brine solution, which removes all oxygen, allowing the growth of lactic acid bacteria. When naturally fermented without vinegar, they are a great source of probiotic bacteria such as Lactobacillus species. However, if vinegar is used in the pickling process, this can destroy much of the bacterias.

Pickles can provide nutrients such as vitamin K and potassium, and are a good source of fibre. Often used as a condiment of snack, a range of pickles can be easily found in the UK. Be sure to choose naturally fermented pickles rather than ones made using vinegar, to obtain the probiotic benefits. Look for labels that say 'naturally fermented' or 'contains live cultures' to be sure. The live bacteria in pickles have been associated with supporting a natural resistance to infectious disease in the gastrointestinal tract, reduced risk of cancer, improved digestion, and a reduction in cholesterol levels.

Natto

Natto is a fermented soy foods fermented with Bacillus subtilis bacteria, made by cooking soaked soybean, adding bacteria and then fermenting for a period of time. It has a strong odour, sticky and stringy like texture, and can be described as an acquired taste for most. It is rich in probiotics, as well as several nutrients including protein, vitamin K2, iron and calcium.

The fermentation of natto produces an enzyme known as nattokinase, which can support cardiovascular health by breaking down blood clots. It is widely available in Japan, though it can sometimes be found in Japanese food stores in the UK, either in the fresh isle or frozen. It is often served alongside seaweed, chopped onion and mustard, and enjoyed with steamed rice. Nattokinase supplementation has been shown to reduce blood pressure. The presence of certain isoflavones such as aglycone, are linked with having an antidiabetic effect. High levels of isoflavons are related to a reduction of colon cancer risk. Natto itself has a fairly strong flavour and smell, and can be off-putting so some, so we suggest to start small, and get used to it's flavour and texture. Mix with other flavourings such as mustard, soy sauce and rice to help the flavour.

Tempeh

Tempeh is a fermented soy bean product, popular in Indonesia and Malaysia. It has a firm texture and nutty flavour. Unlike tofu, which is made from soy milk, tempeh is created from whole soy beans, which are fermented. The soybeans are soaked, partially cooked and then mixed with a fungus called Rhizopus oligosporus. It is then fermented for up to 48 hours, where the fungus binds to the soybeans, and creates a mycelium style network.

Tempeh is rich in protein and contains all of the essential amino acids. It is rich in vitamin B12, as well as iron and calcium. It is usually consumed deep fried in soups or plenty of spices, perhaps in coconut milk, and is often used as a meat substitute. Because the soybeans have been fermented, it is said to be easier to digest, and reduces the phytic acid found in soy beans, allowing better absorption of certain minerals found.There is a presence of isoflavons in tempeh, which has been linked to reducing blood sugar levels in type. diabetes, as well as reductions in body weight and overall cholesterol levels. The isoflavones in tempeh, such as genistein and daidzein, are linked to antitumour effects, involving the inhibition of cancer cell growth. Tempeh consumption has also been correlated to a reduction in dementia such as Alzheimer's disease, which may be due to the high levels of folate and vitamin B12 present in tempeh, contributing to the brain function.

Fermented cheeses

Fermented cheese are made by coagulating milk protein and fat with bacteria cultures and an enzyme known as rennet, and then aging the cheese. The bacterial cultures often include lactic acid bacteria, and the milk may come from cow, goat or sheep. Rennet is added to the milk culture to coagulate, forming curds, which are cut, heated and drained of whey. The curds are then pressed and aged, allowing bacteria and enzymes to develop the cheese flavour and texture. Many fermented cheeses contain probiotics, and they are a rich source of protein, calcium and nutrients such as vitamin B12. Because the fermentation reduces the lactose content, many of these fermented cheeses can be tolerated by those who are lactose intolerant. Cheese consumers have been shown to have higher levels of feacal short chain fatty acids (SCFA's) includingacetate, propionate and butyrate, which can support the immune response, and gut health.

Examples include fermented Cheddar and Parmesan, cottage cheese, as well as Brie and Camembert. Choose cheeses that contain live cultures or probiotics, as some cheese can be pasteurised after aging, which removes the live probiotics. Many cheeses are high in fats, calories and sodium, so it is important to be mindful of the portion sizes and frequency of consumption, within a balanced diet.

Sourdough

A type of bread made through fermenting dough, using a sourdough starter, and bacteria. Instead of commercial yeast, a sourdough uses a starter, which is a mix of flour and water, that has been left to develop wild yeast and bacteria. The starter contains lactic acid bacteria, and the wild yeast needs time to develop, until the starter is ready to be used. The starter is mixed with flour and water to create a dough, and the yeast ferments the sugars in the flour, producing carbon dioxide, which allows the bread to rise. The presence of lactic acid bacteria producing lactic acid, which gives the bread its tangy sour flavour. The sourdough is left to rise for hours to days, before baking.

The fermentation process of sourdough breaks down the gluten protein and phytic acid in the flour, allowing better absorption of bread and improved nutrient profile. Lactic acid bacteria also provide health benefits, particularly for gut health. Due to the reduction of phytic acid, better absorption of nutrients such as iron and calcium is seen, alongside nutrients like vitamins B1 and 6. Because of the production of lactic acid bacteria, sourdough is generally easier to digest for those who struggle to digest bread, due to the level of short-chain carbohydrates that the small intestine can poorly absorb. This can apply particularly for those who have IBS.

Although the baking of sourdough bread will destroy much of the probiotic bacteria, sourdough can still provide postbiotics, which are non living organisms that promote host health. Sourdough is very popular in the UK, and all the best bakeries produce their own delicious sourdough breads, baked fresh every day.

Olives

Olives are small fruits, grown from an olive tree. You can find green and black olives, which each have their own unique taste and flavour profile. Olives contain a bitter compound known as oleuropein, which is removed during the fermentation. Olives are soaked in salt water (brine), which involves lactic acid bacteria. This converts the sugars in the olives into lactic acid, which helps with the flavour and preservation of olives. Olives themselves are a rich source of antioxidants, such as vitamin E and polyphenols, which can support our cell health, preventing oxidative damage and reducing inflammation. They are also a great source of fat soluble nutrients such as vitamins A, E and K, as well as iron and magnesium. Olives are a staple part of the Mediterranean diet, and are enjoyed as snacks and appetisers, as well as in several popular dips and dishes.

Apple cider vinegar

Apple cider vinegar (ACV) is a vinegar made by fermenting apple juice. The juice from apples is fermented with bacteria and yeast, which converts the sugars into alcohol. It is further fermented by acetic acid, and turned into vinegar. ACV has many potential health benefits, such as aiding digestion and reducing blood sugar levels. It contains antioxidants which can help reduce oxidative stress, and antimicrobial properties. Research has shown that ACV can increase stomach acid production, which can help the digestion of food, as well as reducing overall blood cholesterol.

ACV is not commonly a source of probiotic bacteria, as the number of microorganisms found in ACV can vary greatly, and it is often stored at room temperature, which would not preserve living microbes. But if you have ACV made from 'the mother' (see below) and is stored in the fridge, this may contain some living beneficial probiotics in there. However it is unclear if these would be in high enough concentration to provide benefit.

ACV has gained popularity with many using it as a health supplement, but it is important to be aware that not all claims behind ACV have an evidence base, and it should not be taken in the place of prescribed medication. Be sure to always dilute ACV in water before consuming, as undiluted ACV is very acidic and can damage tooth enamel. Choose ACV that is raw and unfiltered, that contains 'the mother', which is a collection of bacteria and enzymes, providing the benefits attributed to ACV.

Curtido

Curtido is a traditional fermented cabbage dish, comparable to kimchi or sauerkraut. It is typical in Salvadoran cuisine and of other Central American countries, and is made from finely shredded cabbage, carrots, onions, and sometimes other vegetables like beets or bell peppers, which are mixed with vinegar, salt, and spices. This mixture is then left to ferment, with vinegar being added to support the fermentation process, being driven by lactic acid bacteria. After a few days to a week, the curtido is ready to consume. It is a source of probiotics, and provides plenty of nutrients due to it's vegetable content, such as fibre and vitamins A and C. The fermentation of the vegetables allows easier digestion and can support gut health. Curtido is not commonly found in the UK, though some specialist online food retailers may have small stocks.

Salgam

Salgam is a Turkish fermented beverage, made from the juice of purple carrots, parsnips, bulgur wheat and water, and is left to naturally ferment into a salty, tangy drink. A brine solution of salt and water encourages the fermentation, and bulgar wheat provides the sugars for the lactic acid bacteria to feed on, giving Salgam it's sour taste and probiotic qualities. Salgam contains a range of lactobacillus bacterias, which can support intestinal microbiota. It is often used to restore electrolyte balance in hot climates and after physical exercise. Although not readily available in the UK, it is widely enjoyed in Turkey and neighbouring regions.

Injera

Injera is a type of flatbread, a staple food in Ethiopia and Eritrea, used both as a plate and a utensil. It is made from teff flour and undergoes a fermentation process over several days. The fermentation is driven using wild yeast and lactic acid bacteria, similar to that of sourdough bread. The fermented batter is cooked on a hot griddle or flat pan, until bubbles form and the bread is cooked.

Various LAB and yeast strains have been identified in injera, with one study stating that injera is a potential source of different probiotic yeast strains. However, due to the cooking process of Injera, much of the probiotic quality can be destroyed. Teff itself is a gluten free grain that is a good source of fibre, calcium and iron. Injera can be enjoyed at Ethiopian restaurants, or made at home.

Amazake

A beverage made from steamed rice, Amazake is a traditional Japanese fermented rice drink that is enjoyed warm. It has a slight natural sweetness and is often compared to sake, but is typically low alochol or non alcoholic, depending on how it is prepared. Amazake is made from fermented rice and koji, a mould used in various Japanese fermented products. The rice is cooked and inoculated with the koji mould, which breaks the rice starches into sugars. It is left to ferment, with the longer fermentation producing a sweeter flavour.

As it is made from rice, it is naturally gluten free and vegan. It is a good source of B nutrients, as well as folic acid and fibre.In one study, the supplementation of Amazake improved defecation frequency compared to placebo, and another study even showed that 8 weeks of Amazake supplementation in those with Liver Cirrhosis improved their quality of life in terms of fatigue, muscle cramps, loss of appetite, constipation and vomiting. Though the latter study only contained 4 participants, this shows the potential of Amazake in supporting several health concerns.

Appam

Appam is a traditional South Indian savoury pancake, made from fermented rice batter and coconut milk. It is a popular breakfast dish, also served with curries. The main ingredients to make appam are rice, coconut milk, water, salt and sugar. The ric is soaked and then ground and mixed with coconut milk, allowing time to ferment. Wild yeast and lactic acid bacteria are involved in the fermentation, allowing the development of unique flavours.

Although appam is a fermented food, when the batter is cooked at high temperatures, this will destroy much of the beneficial probiotic properties.

Cottage cheese

Cottage cheese is made from curdled milk, which is drained, but some whey is retained, leaving a wet consistency. Some cottage cheese may also contain cream and salt, and some are flavoured, such as pineapple cottage cheese. It has a creamy and lumpy texture, and is made from acidifying milk with a bacterial starter culture, or adding vinegar to curdle the milk. Curds are heated and drained, separated from the whey, to produce the texture that is known as cottage cheese.

Aside from being low in calories, cottage cheese is high in protein, and provides many nutrients, from B vitamins to calcium and phosphorus. Although cottage cheese is a fermented food, not all cottage cheese contains probiotics. Be sure to look out for the label of 'live cultures' or 'probiotics' on the packaging of cottage cheese.

Fermented vegetables

Fermented vegetables undergo a process called lacto-fermentation, where naturally occurring bacteria convert the sugars into alcohol. This bacteria is primarily lactic acid bacteria, and the fermentation process helps to preserve the vegetables, change the flavour and texture, as well as providing a range of health benefits and nutrients. Many vegetables can be fermented, including carrot, cucumber, radish, beetroot and cabbage, and it mixed with salt to draw out the liquid from the vegetables, creating a brine. The vegetables are left to ferment at room temperature for a period of time, in an anaerobic environment (without oxygen) to increase the growth of lactic acid bacteria.

If vinegar is used in the fermentation process, this can destroy some of the beneficial bacterias produced by the fermentation process. So when buying fermented vegetables, be sure to look for those which do not use vinegar, and are stored in the fridge. Fermenting vegetables breaks down some nutrients such as phytic acid, which makes it easier for the body to absorb other nutrients such as calcium and iron. Fermented vegetables are also a great source of fibre and various vitamins, and can be easily found in supermarkets and health food shops.

Fermented food recipes

There are a wide range of fermented foods that you can make at home, which can be a rewarding and cost-efficient way to enjoy fermented foods regularly in your diet. Here we included some of our favourite fermented foods, sauerkraut, kimchi and yoghurt, and the methods to make each of these:

Recipe for fermented vegetables or sauerkraut:
You can ferment many vegetables not just cabbage, such as carrots, radishes and beetroot at home. Dry-salting is a method for hard and crunchy vegetables:

Ingredients:

• Large head of cabbage, or other vegetables such as carrots, radish or turnips.
• Sea salt
• Water
• Large, sterilised jar

Method:

• Grate or finely chop your vegetables.
• Mix the vegetables with salt. Recommendations are around 1tbsp salt per 1 medium cabbage, which will help draw out any juices. Once the salts have been drawn out, pack the vegetables tightly in a sterilised jar with the liquid, and add a weight to push these down, keeping the vegetables under the liquid that has been produced. If you need to add more liquid, add a little bit of water.
• Close the lid loosely and keep the jar at room temperature, away from direct sunlight. You will need to open the jar to allow gas to escape every few days. The appearance of bubbles in the jar indicate carbon dioxide being produced.
• After 4-5 days, you can taste the ferment. If you leave the ferment for longer, it will develop in flavour and sourness.
• Once you are happy with the flavour, keep the jar in the fridge and enjoy!
• You can also experiment with adding spices and herbs to the vegetables, for extra flavour and health benefits.

Recipe for homemade kimchi:

Ingredients:

• Large head of nappa cabbage
• 30g sea salt
• 4 garlic cloves, minced
• 2 tbsp gochugaru (Korean red pepper flakes)
• 1 tbsp sugar
• 2 tbsp fish sauce (optional)
• 4 spring onions, chopped
• 1 medium carrot, julienned
• Large, sterilised jar

Method:

• Cut the cabbage into quarters to remove the inner core, and then chop into small pieces. Place in a large bowl.
• Sprinkle the salt all over the cabbage and sit for 2 hours, mixing occasionally. After 2 hours, rinse the cabbage, and dry.
• In a bowl, mix together the garlic, red pepper flakes, sugar and fish sauce, until a paste forms.
• In the large bowl with the cabbage, add in the other vegetables. Then add in the paste and mix everything well until all coated.
• Add the mixed vegetables into the sterilised jar, pressing down to remove any air, and make sure that the vegetables are submerged in their juice.
• Cover lightly with a cloth or loose lid, and leave to ferment at room temperature for up to 7 days, until you have the desired taste.
• Keep in the fridge and enjoy!

Recipe for homemade yoghurt:

Ingredients:

• 1L of whole or semi skimmed milk
• 2 tbsp of a starter yoghurt, which is a plain yoghurt with live cultures

Method:

• Heat the milk in a saucepan over medium heat, stirring occasionally, until it reaches 85°C. It should be steaming but not boiling, but small bubbles may appear.
• Let the milk cool down to 45°C, which will take around 2-3 hours.
• Once cooled, add in the 2 spoons of the plain starter yoghurt, and mix well until combined
• Pour the mixture into a sterilised jar or bottle, and shut the lid. Leave at room temperature for up to 24 hours.
• Once set, you can refrigerate and then enjoy!
• Be sure to save 2 tbsp to use as a starter for your next batch.

Where to buy fermented foods?

In the UK, fermented foods can be purchased from many different shops and food outlets, including large grocery stores. These usually stock fermented foods like yoghurt, kefir and kimchi, and the world food isles will stock miso and sauerkraut. Health food stores such as Whole Foods or Planet Organic will often have a range of fermented foods available, likely more variety than supermarkets, including kombucha and tempeh.

You may need to visit more speciality stores for some fermented foods, such as Asian supermarkets for kimchi, natto, various types of miso and other fermented soy bean products. European supermarkets will have a range of kefir and sauerkraut in different flavours, to provide you with different choices.
Some farmers market or small artisan markets may offer local sellers and small producers, who sell handmade fermented foods. Online, retailers can sell fermented foods through their websites, but be sure to check for reviews on quality and enjoyment of the product, to ensure you are making the right choices, wherever you buy from.

How to eat more fermented foods?

Here are some tips on how to integrate more fermented foods into your daily diet:

• Start slowly: If you are not someone who regularly consumes fermented foods, including small portions over a few weeks can allow your body to adjust, and you can work on slowly increasing the overall amount.
• Add in different fermented foods across the week, to add diversity of bacteria and nutritional benefits.
• Think of where you can add in a fermented food into your regular meals. For example, if you enjoy cereal in the morning, top your cereal with a few spoons of yoghurt or kefir.
• If you like salads, add in kimchi or sauerkraut for some crunch and extra flavour.
• Making smoothies with kefir can be a good way to introduce the strong flavours, combined with the sweet flavours from fruits.
• Swap your regular bread for a good quality sourdough, and top with kimchi and cottage cheese for a delicious breakfast or snack choice.
• Include miso in a marinade for chicken or fish, or even in a vegetable stew.
• Use tempeh in a stir fry with lots of vegetables and a sauce made using soy sauce and miso paste.
• Make a cheeseboard with aged cheese, alongside some fermented vegetables.

Innovations and future trends in fermentation technology

Fermentation technology is continuing to grow and evolve to allow improvements in food production, whilst being conscious of health of foods and the environment. Here are some innovations and future trends to be aware of:

Personalised nutrition and functional foods

Fermented foods are being used to target a persons specific nutritional needs and health conditions, based on their genetic information. Functional foods are foods that contain bioactive compounds produced through fermentation, to enhance their health benefits such as prebiotics and antioxidant level. Fermented foods are being developed and tailored into functional foods, to help people to meet their nutritional needs and health concerns.

Precision fermentation

This is where genetically engineered organisms are being used to produce specific foods in controlled environments. Microbial hosts are used to produce functional food ingredients, such as enzymes, vitamins, antioxidants and preservatives. Precision fermentation allows plant based meat and dairy manufacturers to provide a meat/dairy-like experience, whilst being completely vegan. Examples include creating lab-grown meat alternatives, which are plant based. This includes the already popular Impossible Foods company, who produce plant-based heme protein, via fermentation of genetically engineered yeast.

Synthetic biology and metabolic engineering

Synthetic biology combines biology, engineering, and computer science to create new biological parts and systems. It has allowed researchers to engineer microbial genomes and genetic pathways, to produce a wide range of products, such as biofuels and pharmaceuticals.

Fermentation in biotechnology and pharmaceuticals

Fermentation is being used to produce vaccines, antibodies and therapeutic proteins, as well as components for gene therapy, which is helping to advance modern medicine.

Having support from a dietitian can help you with adding in fermented foods, to benefit from the multitude of health benefits. It is important to know what fermented foods may be suitable for you and fit best into your lifestyle. Book a consultation with a dietitian here.