Kefir, a probiotic superhero: What is it and why drink it?
Oct 30, 2023 by Kathy Walker
You may be surprised to learn that the average adult has about 2kg of microbes in their gut. These microorganisms are often referred to as the gut flora, or gut microbiota. Like our fingerprints, no two gut microbial populations are the same. It turns out that your gut flora plays a major role in your overall health, having an impact on many body functions, such as immune function, metabolic health (think diabetes, heart disease, stroke, and obesity), and even your mood and mental wellbeing. If you’re wondering what this has to do with a drink, bear with me. There is a connection, but we need to get to the guts of things (pun intended 😉) before we can piece it all together.
What is gut flora?
Most of the microbes living in your gut are bacterias, but there are also small amounts of fungi, viruses, and other microorganisms. It is estimated that there are about 1,000 different types of bacteria in your gut, adding up to about one hundred trillion bacteria in total. In fact, there are many more bacterial cells in your gastrointestinal tract than there are cells in the entire human body! It’s good to know that we are mostly bacteria, right?
The gut is home to both good (beneficial) and bad (pathogenic – capable of causing disease) microbes. Other microbes, known as opportunistic microbes, are relatively harmless in small numbers. However, they can be harmful if their populations are allowed to grow too large or if they are able to move to places in the body where they don’t belong. They are usually crowded out and kept under control by the beneficial microbes, but they can have a population boom if something happens to reduce the good bacteria numbers. They seize the opportunity, hence the name opportunistic, and take over the territory previously occupied by the good microbes. The key to good gut health is having a large variety of microorganisms in the gut and having adequate numbers of good microbes.
A poor and imbalanced gut microbiota is often referred to as gut dysbiosis. This can be caused by decreased numbers of good microbes, increased numbers of bad microbes, or a reduced variety of microbes. Usually, all three factors will be present. Gut dysbiosis has been linked to many diseases, such as inflammatory bowel disease, obesity, diabetes, heart disease, allergic disorders, autism, multiple sclerosis, asthma, eczema, autoimmune disorders, depression, anxiety, and cancer.
What does your gut flora do?
Your gut, or gastrointestinal tract (GIT), is basically a really long tube that passes through the middle of your body. Food and drink go in at one end and, whatever isn’t absorbed into your body, is passed out the other end as poop. The lining of your GIT forms a barrier to stop germs, toxins, and other nasties in your gut from entering your body and causing illness and disease. Your gut flora plays a vital role in keeping this barrier intact. When your gut microbiome is unhealthy, this protective barrier can be damaged and become ‘leaky’. Germs, toxins, and other nasties are able to cross your gut lining and enter your body, making you unwell and triggering inflammation. Your immune system then has the added stress of trying to deal with the invaders.
Your gut flora helps to ‘train’ your immune system as well. Your immune system is exposed to a wide variety of microbes in your gut. Through this exposure, it learns to recognize which ones are pathogenic (and should be attacked) and which ones are beneficial (and are best left alone).
The gut flora of people with depression and anxiety has been found to be less diverse than people with good mental health. They also have more of the microorganisms that cause inflammation and less of those that reduce inflammation. Your gut and brain are in constant communication, back and forth, via a system known as the gut-brain axis. Consequently, your thoughts and emotions are able to influence gut health, and the gut can affect mental health. One example of this is the experience of having an upset tummy during times of stress.
The gut-brain axis allows for two-way communication via a long nerve, called the vagus nerve. The gut microbiota and the body cells in your gut lining also produce chemicals (called neurotransmitters) that can travel to the brain and affect mental function. One of these neurotransmitters is serotonin, which acts on certain cells in the brain, contributing to feelings of happiness. It also affects your sleep, hunger, memory, mood, learning, and sexual desire. Your gut microbiota and the body cells in your gut lining, produce about 90% of the serotonin found in the body. Your gut microbes also produce another neurotransmitter known as gamma-aminobutyric acid (GABA), which helps reduce feelings of fear and anxiety.
Good microbes also help with proper digestion and absorption of your food. The ability of your body to break food down properly is reduced by an imbalanced gut flora. Food that is absorbed into your body before it has been broken down properly can also cause issues.
Some of the microorganisms in the intestine even produce vitamins, most notably vitamins K, B5 (pantothenic acid) and B7(biotin). Others play an important role in hormone production. Different bacteria in the gut can influence your appetite, hunger levels, and feelings of fullness. There are also some microbes that produce substances called short chain fatty acids (SCFAs) when they break down fibre in the gut, which some the cells in your intestine use as fuel. SCFAs have a variety of roles in the body, including:
- Activation of the vagus nerve, affecting brain functions, such as learning and memory.
- Reducing inflammation in many different areas of the body, including the brain.
- Regulating the activity of immune cells
- Supporting healthy liver function
- Regulating the hormones that influence appetite, energy balance, body weight, immunity, brain function, and mood states
- Protecting the brain from toxins and pathogens
Many beneficial microbes also release substances when they break down fibre that are harmful to the bad microbes. This helps to keep numbers of bad microbes in check.
What are probiotics?
Probiotic literally means ‘for life’. Probiotic foods and capsules contain a high amount of ‘good bacteria’, such as Lactobacillus acidophilus and Bifidobacterium bifidum, which helps to increase the numbers of beneficial microbes in your gut. Fermented foods, such as kefir, sauerkraut, kimchi, miso, yoghurt, and kombucha, are considered to be probiotic foods or drinks. Keep in mind that heating any of these fermented foods destroys the microorganisms, making them useless as a probiotic.
Different types of probiotics have been found to be helpful for different conditions. For example, studies on laboratory mice have shown that certain probiotics can increase the amount of GABA produced in the gut and reduce anxiety and depression-like behaviour.
Phew, now that we have a bit of background information, let’s dive into the world of kefir and its role in gut health!
What is kefir?
Kefir is a cultured-milk drink full of probiotic goodness, loosely resembling liquid yoghurt. In fact, one glass of home-made milk kefir can contain about the same amount of probiotic oomph as 25 good quality probiotic capsules, or more! Now that’s some bang for your buck!! It is also more economical and natural than purchasing capsules. Furthermore, kefir contains a much greater variety of microbial strains than probiotic capsules and other fermented products, such as yoghurt and sauerkraut. It is estimated that kefir contains up to 300 different species of microbes. In comparison, most yoghurts only have 1-5 different probiotic strains.
The strength or potency of a probiotic is measured in terms of colony forming units (CFUs). The CFU refers to the number of living and active microorganisms per millilitre or gram. The average CFU count of probiotic supplements ranges between 1-10 billion CFUs per dose. Kefir has been found to contain 108 CFU/g of lactic acid bacteria, 106-107 CFU/g of yeast, and 105 CFU/g of acetic acid bacteria. It is important to note that commercial kefirs have a different microbial composition to traditional kefirs. Commercial kefirs use a starter culture rather than kefir grains. The lactose and galactose levels are usually higher in commercial kefirs as well.
A quick pronunciation guide
There is something that must be cleared up before we can continue, and that is, how the heck to pronounce the word kefir properly! Kefir is pronounced keh-feer (keh as in kettle). The word kefir is thought to originate from the Turkish word keif, which roughly translates to good feeling. I’m sure most people’s guts would agree, although maybe not everyone’s tastebuds! Being a fermented milk drink, kefir has a slightly tart, sometimes tangy flavour, with an aroma of fresh yeast (vaguely beer-like). In the spirit of honesty, it is not to some people’s liking. I personally enjoy the taste, but I have seen some people absolutely baulk at their first sip and make some very strange retching faces trying to get it down. If you find the taste challenging, you could try blending it with other healthy ingredients, such as bananas, berries, mangoes, coconut milk, coconut oil, mint, cinnamon, cacao powder, or raw honey. The only way to find out is to try it and get creative!
How to make it
Kefir is super easy to make, taking less than 5 minutes a day to maintain. All that is required is a glass jar (such as a mason jar), a sieve/strainer, a spoon, a jug, kefir grains, and some milk. Unlike homemade yoghurt, there isn’t even any heating of milk required!
Fill the glass jar with about 2 cups of fresh milk.
Add 1-2 tablespoons of fresh milk kefir grains. Ensure the jar is no more than ¾ full, otherwise the kefir may overflow during fermentation.
Rest the lid on the jar, or very lightly screw on. Do not tighten the lid because gas is produced during the fermenting process and must be allowed to escape. Other cover options include tea towels, paper towel, paper coffee filters, or several layers of cheesecloth. If necessary, secure these covers with a rubber band or tie to keep out any pests, like ants or flies.
Gently swirl or agitate the contents and leave to stand at room temperature for about 24 hours. Place in a location away from direct sunlight, such as a pantry or cupboard, to ferment. You may swirl the contents again occasionally if you wish, but it is not essential.
After 24 hours has passed, you may notice that the contents have separated into curds (thick white regions) and whey (clear or pale yellow liquid). This occurs because fermentation increases the acidity of the milk. Gently stir the contents, mixing the curds and whey together, to make straining easier.
Pour the jar contents into a strainer placed over an appropriate-sized jug, to separate the kefir grains from the fermented liquid milk kefir.
The milk thickens during fermentation, so you will probably need to use a spoon (or clean hands – don’t be afraid to get hands-on with your kefir) to separate the milk kefir from the kefir grains. Wash the strainer and utensils thoroughly after use.
Store the strained liquid milk kefir in the fridge or on the counter and enjoy!
‘Ripening’ the kefir involves leaving it for another 1 or 2 days before consuming it. This continues to lower the lactose content, adds more fizz (carbonation), and increases the amount of alcohol (yes, kefir has a small amount of alcohol), and B vitamin content. Refrigeration slows down the fermentation process, compared to storing your strained kefir out of the fridge. The flavor can become a bit too strong/sour for some people if it is left to ‘ripen’ in the fridge longer than a week or so.
Add the kefir grains that were left in the strainer to the next batch of fresh milk. There is no need to rinse the grains before adding them to the fresh new milk. Rinsing of the grains was never done by traditional cultures.
Be sure to use a clean glass fermenting jar for each new batch of kefir though. You can also add a small amount of fresh kefir from the previous batch to your next batch, if you wish. This quickly increases the acidity of the fresh milk, inhibiting the growth of bad microorganisms that may be present in the fresh milk. I don’t tend to add kefir from the previous batch and have never had any issues, but it is fine to do so.
Best Strainer for Milk Kefir
I recommend using a mesh strainer with a hole size of about 2mm (1/8”). Fine mesh strainers with smaller hole sizes take a long time and can make it difficult to separate the kefir grains from the liquid kefir. On the other hand, a strainer with a very large hole size will allow small kefir grains to pass through into the strained liquid kefir.
Modern strainers are usually made from stainless steel or plastic, however bamboo or cane strainers can also be used. Just be sure to clean them thoroughly between uses. It is often stated that metal equipment should not be used in the making of kefir, although there doesn’t seem to be any evidence to support this claim. One possible reason may be related to the acidic nature of kefir, which could react with reactive metals, such as copper, iron, and brass. However, stainless steel is non-reactive, thus it does not react with the kefir in the same way. Whilst I would always opt for a glass storage container over a stainless steel one, I have used a stainless steel strainer for many years without any obvious ill effects to myself or the kefir grains.
Does it matter what milk I use?
A variety of milks can be used, including goat, sheep, cow, mare, and camel milk. The nutritional profile of each of these types of milk differs slightly. Compared to milk from other dairy animals, milk from animals belonging to the Equidae family – this includes horses, donkeys, and zebras – is said to most closely resemble human breast milk. These specialty milks tend to come with a specialty price tag as well, so budget may be an influencing factor in deciding which milk to use. Availability in your area may also be an issue.
Traditionally, kefir was made using raw goat’s milk, thus it was high in enzymes and healthy fats. These enzymes help with the breakdown and absorption of certain nutrients, especially calcium. The kefir grains would have helped reduce the likelihood of harmful microorganisms growing in the kefir. The sale of raw milk is currently banned in Australia and some other parts of the world, usually with the exception of raw ‘bath milk’, which is sold for cosmetic purposes. Pasteurization is a legal requirement to prevent the growth of bad microorganisms in milk and reduce the likelihood of anyone becoming seriously ill. This was of particular importance in the early 1900s when hygiene practices, storage, testing, and transport processes were not what they are today. Along with any bad bacteria, many enzymes, vitamins, fatty acids, beneficial bacteria, and other components in raw milk are also destroyed during heat pasteurization. Cold pressed raw milk is a method of pasteurization that uses high pressure instead of heat, producing pasteurized milk that retains more of the beneficial enzymes found in raw milk.
The next best option is organic/biodynamic, grass-fed, whole milk. Organic/biodynamic milks come from animals that have not been treated with antibiotics, growth hormones, or reproductive hormones. The animals graze freely on pastures that have not been sprayed with pesticides and herbicides. They are not allowed to be fed any genetically modified grain, corn, or soy. The use of synthetic preservatives and colorings in the milk is not allowed either. Organic/biodynamic farms must meet high animal health and welfare standards as well. Whole milk contains more vitamin D and omega-3 fats than skim or low-fat milks. Milk with a higher fat content also produces a thicker and creamier kefir.
Milk from grass-fed, pastured animals has a different nutritional profile to that from grain-fed, factory-farmed ones. Milk from pastured cows has better protein quality, and an improved fatty acid profile, with higher levels of conjugated linoleic acid (CLA) and healthy omega-3 fatty acids, compared with milk from cows housed indoors and fed a non-pasture diet. This supports brain development, reduces inflammation, and more. Additionally, the high-starch diet of grain-fed cows reduces their ability to make certain fats in the mammary gland. This is because the process of making the fats uses substances produced by gut microbes when they digest the fibre contained in pasture diets. Diets high in starch and low in fibre (such as a grain-fed diet) also increase the likelihood of the cow developing a digestive disorder known as subacute ruminal acidosis (SARA), caused by increased acidity levels in the rumen.
Some people may find A2 milk to be a better option as well. Milk contains a protein called casein, of which there are several different types, with second most common form being beta-casein. There are two main varieties of beta-casein proteins, A1 beta-casein and A2 beta-casein. A2 beta-casein is said to be broken down differently and more easily by some people than A1 beta-casein. The structure of A2 beta-casein is more similar to human breast milk. In the past, all cows produced milk that contained only A2 beta-casein. A natural mutation and selective breeding practices have led to the dominance of cows that produce only A1 beta-casein or a combination of both A1 and A2, mostly because these cows tend to produce larger quantities of milk for a lower cost than their A2-only buddies. Milk from other animal varieties, such as goats, buffalo, sheep, and camels, contains mostly A2 beta-casein. Raw goats milk is able to be legally sold in 4 Australian states – NSW, Queensland, SA, and WA.
When milk is digested, the casein is broken down into smaller pieces, however A1 and A2 beta-casein are broken down differently. One of the segments of A1 beta-casein is called beta-casomorphin-7 and it can have effects on the body similar to that of opioid drugs, such as morphine. In addition, it has been shown to slow down digestion, leading to changes in bowel function, gut microbiota, and inflammation. Populations that drink A2 milk have less people with cardiovascular disease and type-1 diabetes than those that drink A1 milk. Some studies have also shown a reduction in symptoms of digestive discomfort after switching to A2 milk.
Nutritional profile of kefir
In general, milk kefir has been found be a good source of B vitamins, with the concentration of vitamins B1 (thiamine), B2 (riboflavin), B6 (pyroxidine), biotin, B9 (folic acid), and B12 (cobalamin) often increasing even more during fermentation. It is also a good source of vitamins A, C, D, and K, as well as carotene (used to make vitamin A), calcium, phosphorous, magnesium, potassium, sodium, and many essential amino acids. Microminerals commonly found in milk kefir include copper, iron, manganese, molybdenum, and zinc. Being a fermented product, kefir is high in amines. If you have an amine sensitivity or histamine intolerance, kefir may not be recommended!
Other health benefits of kefir
- Improved bone health
- Lower cholesterol levels
- Reduced severity of allergies
- Ease symptoms of various digestive conditions, such as ulcerative colitis, IBS, constipation, diarrhoea, bloating, and cramping
- Antioxidant activity – kefir made from kefir grains has been found to have a higher antioxidant content than kefir produced from commercial starter cultures
- Blood pressure regulation
- Improved wound healing
Do kefir grains have gluten?
Kefir grains are not technically grains as we know them, meaning they are not cereal grains like wheat and spelt, therefore they do not contain gluten. They actually look somewhat like small, gelatinous cauliflower florets, with a squishy, slimy texture. They are living microorganisms of mostly bacteria and yeast, surrounded by a slimy substance called kefiran, which is composed mostly of the simple sugars glucose and galactose.
Kefir grains increase in size and quantity with each ferment, using the lactose in the milk as a food source. This makes it necessary to remove some ‘grains’ every now and then in order to maintain the correct ratio of milk to kefir grains. If you have too many kefir grains, your milk ferments too quickly. Too little and the opposite occurs. The other thing to keep in mind is that temperature has an impact on the rate of fermentation, with higher temperatures speeding up the process and lower temperatures slowing it down. The ideal temperature range is between 20-25°C (68-77°F).
The excess grains are also healthy for you, so don’t toss them out! I choose to blend them into my smoothies, but I have heard of people getting very creative with their surplus kefir grains. If you really don’t fancy consuming your extra grains, how about giving them to the chooks or sharing with your friends?
I recommend My Fermented Life as a good source of quality fresh kefir grains. Purchases can be made at https://myfermentedlife.com/doms-cultured-products/ (a genuine recommendation – I don’t receive any kickbacks).
Start slowly or you might regret it!
I recommend proceeding slowly with the quantity you consume. Start small and gradually increase the daily amount. The reason being that, as the probiotics in the kefir take up residence in your gut, they result in the death of the ‘bad’ or ‘opportunistic’ microorganisms. When these guys die, they release toxins, which your body eliminates. However, if you go too hard too fast, the toxins are released at a rate that is beyond what your body can handle. The result is something called ‘die off’ and it can cause you to feel pretty ordinary. If you have a condition of some sort, it can cause a worsening of your usual symptoms. The take-home message? Slow and steady wins the race!
Other types of kefir
These is good news for any lactose intolerant peeps too! As part of the fermentation process, lactose is used as a fuel source by the kefir grains, thus milk kefir is significantly lower in lactose than regular milk. As an added bonus, regular probiotic consumption (or supplementation) has also been shown to improve lactose intolerance. If lactose is a concern, a fermentation time of at least 24 hours, followed by a ripening period would definitely be recommended.
Although milk kefir is lower in lactose than regular milk, some of you may still prefer non-dairy options. Fortunately, there other types of kefir, such as water kefir and coconut kefir. Other non-dairy options include rice, oat, almond, or soy milk. Of course, all of these non-dairy options will have a different nutritional profile to the dairy options.
Some causes of gut dysbiosis
Many medications can have a negative impact on gut flora, including antibiotics, acid-reducing medications, pain relievers, steroids, and oral contraceptive pills. Antibiotics (meaning ‘anti life’) significantly alter your gut flora because they don’t just target the ‘bad bacteria’, they wipe out the good ones too. Populations of opportunistic microorganisms are usually kept in check by the good microorganisms, but this balance is disrupted by antibiotics, allowing the opportunistic microbial populations to increase. One type of opportunistic microorganism is Candida albicans, the yeast responsible for thrush. As some of you may know, thrush is a common side-effect after a course of antibiotics.
Some practitioners now recommend the use of probiotics whilst taking antibiotics (taken at different times of the day) to prevent the opportunistic microorganisms from getting out of hand. It is best if probiotics are commenced within 2 days of starting a course of antibiotics. Taking probiotics after completing a course of antibiotics has been shown to be less effective, possibly even delaying recovery of healthy gut flora populations.
A poor diet high in processed, sugary foods and low in vegetables and other high-fibre foods, can cause changes to our gut microbiome. Vegetables and complex carbohydrates provide a lot of roughage and fibre that good bacteria use as a food source. This results in the production of more SCFAs, providing further health benefits.
On the other hand, sugars and processed carbohydrates are the preferred food source of the bad microbes. In addition, the growth of bad bacteria can worsen sugar cravings, leading to the consumption of even more sugary foods, creating a vicious cycle of gut dysbiosis. Food preservatives have also been found to have a negative effect on some gut microbes. Additives or thickeners are sometimes added to commercial kefir to thicken it, so be sure to read the labels. Furthermore, artificial sweeteners, such as Splenda, can contribute to gut dysbiosis and promote glucose intolerance. This is ironic, given that many people (such as diabetics) use artificial sweeteners because they have issues with glucose tolerance.
Your gut flora has an impact on your response to stress. When subjected to a challenge, people with healthy gut flora produced lower levels of stress hormones (such as cortisol) than those with gut dysbiosis. In the reverse direction, stress can have a negative impact on gut health. Increased stress results in less variety of gut microbes, a larger number of bad microorganisms, and leaky gut. Perhaps it’s time to prioritise that meditation class or recommit to your daily stress-relieving exercise routine?
Inadequate or poor-quality sleep has been shown to be associated with gut dysbiosis. Supplementation with certain probiotics has also been shown to improve sleep quality and duration.
The importance of a healthy gut microbiome has led to the development of a new branch of medicine in the field of faecal transplants. Yep, you heard right! And yes, it is literally what it sounds like – a transplant of poo from a donor with healthy gut flora into a person with an unhealthy gut environment! In Australia, it is currently only performed for people with serious Clostridioides difficile infections (also referred to as Clostridium difficile, or C. difficile) and has a 90-95% cure rate. C. difficile is a bacterial infection that can cause debilitating, and sometimes fatal, diarrhoea. Research is underway regarding the use of faecal transplants for a host of other conditions as well, such as ulcerative colitis, inflammatory bowel disease, obesity, autism, cancer immunotherapy, major depressive disorders, Parkinson’s disease, liver disease, migraines, and much more. Gut dysbiosis has been associated with all of these conditions. The question is often similar to the chicken and the egg debate. Which one came first? The disease or the dysbiosis? In some of these conditions, such as diabetes and Parkinson’s disease, it has been shown that the dysbiosis arrived first. The jury is still out with some of the other diseases.
One of the greatest tools you have to maintain a healthy gut microbiome, or to improve it, is your diet. Kefir and other fermented probiotic-rich foods, offer a natural, cost-effective and simple way of recolonizing your body with beneficial microbes and improving your health. Add in adequate sleep, exercise, and stress reduction, and your gut will be host to the most amazing microbial community in no time.
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