El Kefir has become fashionable While it has gained popularity in recent years, it is actually an ancient food with a fascinating history. This fermented beverage, which originated in the Caucasus Mountains, has been consumed for centuries for its digestive, immune-boosting, and energizing properties, and today it is considered one of the most interesting probiotics in a healthy diet.
Beyond trends, kefir is a product with solid scientific basisIt harbors a huge diversity of beneficial bacteria and yeasts, key nutrients for metabolism, and bioactive compounds capable of modulating the intestinal microbiota, supporting bone health, promoting muscle recovery, and generally helping the body to function more harmoniously.
What exactly is kefir?
When we talk about kefir, we are referring to both the fermentation granules as well as the beverage obtained by letting them act on a liquid (usually milk, although it can also be water or coconut water/milk). These grains are small, whitish or yellowish masses, irregularly shaped, composed of a matrix of polysaccharides and proteins in which numerous lactic acid bacteria and various yeasts live in perfect symbiosis.
During fermentation, these microorganisms They transform the sugars in the medium (especially lactose, in the case of milk) into lactic acid, small amounts of alcohol, and carbon dioxide. The result is a slightly foamy drink with a creamy texture but more liquid than yogurt, and with a more acidic flavor and sometimes a fruity or yeasty note.
The word kefir comes from the Turkish term “keyif”which refers to the feeling of well-being experienced after consuming something pleasant. And this is no coincidence: the shepherds and farmers of the Caucasus had been preparing a drink called «ayrag"They fermented milk in goatskin bags; over time, they observed that a spongy layer formed on the inner walls of these containers, capable of producing new batches of the beverage with even better properties. These were, in essence, kefir grains."
Over the years, this ferment went from being an almost secret “treasure” of mountain communities to becoming a product of medical and scientific interest, especially in Russia and other Eastern European countries, where it was even used as dietary support in sanatoriums for various digestive and respiratory ailments.
Nutritional composition of kefir and its microbiota
The nutritional profile of kefir can vary depending on the type of milk or starting liquid, the fermentation time, and the preparation conditions, but generally speaking, it is a beverage with good nutrient density and a moderate calorie intake. A glass (about 200 ml) of store-bought whole milk kefir usually contains around 120-160 kcal, with about 10 g of protein, 10-12 g of carbohydrates and 6-8 g of fat.
According to Codex Alimentarius parameters and various studies, milk kefir typically provides approximately 2-7% protein It is high-quality and easily digestible, containing around 6% sugars (most of which are already partially fermented) and less than 10% fat, depending on the type of milk used (whole, semi-skimmed, goat, sheep, cow, etc.). The lipid fraction includes mono-, di-, and triacylglycerols in relatively low quantities, which contributes to its being a fairly well-tolerated food.
In terms of micronutrients, kefir contains an interesting combination of Group B vitamins (B1, B2, B3, B5, B6, B9, B12, and biotin), vitamin A, vitamin C, carotenes, and vitamin K, especially in its K2 form, which is key for calcium metabolism. It is also a good source of minerals such as calcium, phosphorus, magnesium, and potassium, which makes it an interesting ally for bones, the nervous system, and muscle contraction.
The true “magic” of kefir lies in its microbial population. Multiple species of bacteria have been identified in its grains. lactobacilli, lactococci, bifidobacteria and yeasts, among which Lactobacillus kefiri, L. kefiranofaciens, L. parakefiri, L. kefirgranum, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, Bifidobacterium lactis, Leuconostoc mesenteroides or yeasts such as Kluyveromyces marxianus, Saccharomyces unisporus and Saccharomyces cerevisiae, among many others.
This enormous diversity of microorganisms is responsible for kefir having a multifunctional probiotic activityNo single species is capable of offering all the beneficial effects described; it is the combination of them and their metabolites (such as the polysaccharide kefiran) that explains their immunomodulatory, antimicrobial, antioxidant or even potentially antitumor properties observed in several studies.
Types of kefir: milk, water, coconut, and powdered kefir
There is no single type of kefir; depending on the medium in which the grains are cultivated, we obtain different types. drinks with very different characteristicsAlthough they share the same fermentation philosophy and a similar probiotic base, the most common types are milk kefir, water kefir, and coconut kefir. In recent years, a dehydrated form marketed as kefir powder has gained popularity.
The essential point is that, in all cases, the grains need a source of fermentable sugars so that its microorganisms can feed and carry out the fermentation process. In the end, most of those sugars disappear because bacteria and yeasts "devour" them to produce acids, gas, and other compounds.
milk kefir
This is the most popular variety and the one most readily available in supermarkets and organic stores. It is prepared by fermenting... cow's, goat's, or sheep's milk (or even coconut milk) with the kefir grains for about 24 hours at room temperature. If the fermentation is prolonged, the flavor becomes more acidic and the drink may become slightly carbonated.
The texture of milk kefir is reminiscent of a liquid yogurtbut somewhat more fluid and with a touch of effervescence. Traditionally, the process produced a beverage with a very low alcohol content (usually below 1%), although many current commercial products are practically alcohol- and carbon dioxide-free, resulting in a consistency closer to a drinkable yogurt.
This form of kefir is rich in complete proteins, calcium, phosphorus, magnesium and fat-soluble vitaminsIt is the type of milk commonly used in studies on bone health, immunity, and digestion. It can be consumed as is or used in cooking to replace ingredients such as heavy cream, buttermilk, sour cream, or even yogurt in soups, creams, purees, breads, and pastries.
Water kefir
Water kefir uses the same grains (adapted to an aqueous medium) but the base is a solution of sugar water (sometimes enriched with dried fruits or juices). When fermented, it produces a very light, sparkling and refreshing drink, somewhat similar to homemade fizzy lemonade with a tangy note.
This version is lactose and dairy-free, making it an interesting option for people with lactose intolerance or milk protein allergyIt's also suitable for vegans. Nutritionally, it provides less protein and fat than milk, but maintains a significant probiotic content and aids hydration, especially when consumed cold in summer.
It is usually flavored with lemon juice, lime juice, fresh herbs or pieces of fruitand it is a very worthy and healthy alternative to commercial soft drinks and isotonic drinks loaded with added sugar.
Coconut kefir
Coconut kefir is made from coconut water or coconut milkWhen coconut water is used, the resulting drink is quite light, with a sweet touch and the characteristic aroma of the fruit; when the base is coconut milk, the final product is creamier and has a higher content of healthy fats, especially medium-chain triglycerides (MCTs), which the body uses quickly as a source of energy.
Since it doesn't contain dairy, this type of kefir is Suitable for vegans and lactose intolerant people It's suitable for those with severe diabetes, while maintaining a good supply of probiotics and electrolytes (especially potassium). However, the amount of protein is lower than in milk kefir, so it's best to include it as part of a balanced diet that incorporates other protein sources.
Kefir powder
In recent years, it has become popular kefir powderIt is essentially a dehydrated product (usually made from fermented milk) that can be reconstituted with water, milk, or other plant-based beverages. Its advantages are its long shelf life and ease of transport, but its probiotic and sensory profile will depend heavily on the industrial process used.
To truly reap its benefits, it's important to choose versions that indicate on the label the presence of live and active cultures and that they haven't undergone intense heat treatments that destroy microorganisms. Additionally, it's advisable to carefully check the ingredient list to avoid mixtures full of added sugars, starches, or artificial flavorings.
Differences between kefir and yogurt
Both kefir and yogurt are fermented milk productsHowever, they are not the same, neither at the microbial level nor in their effect on the gut. Yogurt is usually made with two main bacteria (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus), while kefir can contain between 10 and more than 30 different strains of bacteria and various yeasts.
Yogurt is fermented with thermophilic cultures They need heat to activate, usually in a yogurt maker or controlled industrial process. Kefir, on the other hand, is considered mesophilic: its grains work at room temperature without needing to heat the milk, which makes it much easier. make it at home without special equipment.
Another key difference is the activity of microorganismsThe bacteria in yogurt tend to have a rather transient effect: they pass through our intestines, help while they are present, but don't tend to colonize long-term. In contrast, some kefir bacteria can adhere to the intestinal mucosa and remain longer, competing with pathogens and modulating the microbiota more intensely.
In terms of taste and texture, yogurt is usually thicker, more homogeneous, and smoother, while kefir has a a more liquid texture and a more acidic flavor profile, with hints of yeast and wheyIn addition, kefir produces a very small amount of alcohol through the action of yeasts, something that does not occur in traditional yogurt.
Health benefits of kefir
Scientific interest in kefir has grown exponentially, and various studies have described a wide range of potential positive effects about the body. Although research is still ongoing and it's not possible to speak of a miracle cure, there is evidence that, within a balanced diet, its regular consumption can be very beneficial.
Strengthening the immune system
A significant part of our immune system resides in the gut, so any food that helps to balance the microbiota It has repercussions on immunity. The probiotics in kefir, along with vitamins such as folate and biotin, promote the proper functioning of immune cells and the production of immunoglobulins.
It has been observed that specific strains of kefir, such as Lactobacillus kefiri, can inhibit the growth of pathogenic bacteria such as Salmonella or certain strains of E. coli, as well as opportunistic fungi like Candida. The polysaccharide kefiran, unique to kefir, also shows antimicrobial and immunomodulatory activity in several experimental studies.
Bone health and osteoporosis prevention
Milk kefir offers a very interesting combination of calcium, phosphorus, magnesium, vitamin D and vitamin K2These are all essential nutrients for maintaining good bone mineral density. Vitamin K2, in particular, helps direct calcium to bones and teeth instead of depositing it in arteries and soft tissues.
By improving calcium absorption and providing easily digestible protein, kefir is considered a ally to reduce the risk of osteoporosisespecially in older people, postmenopausal women, or individuals with a history of low dairy intake.
Digestive health and irritable bowel
Regular consumption of kefir contributes to to restore and maintain a balanced intestinal ecosystemThis can be very helpful in disorders such as irritable bowel syndrome, Crohn's disease, mild colitis, or diarrhea associated with antibiotic use, since probiotics help in the recolonization of the "good" flora.
In addition, the lactic acid bacteria in kefir produce enzymes that aid in the digestion of certain nutrients and They accelerate intestinal transit.This helps combat functional constipation. A possible protective effect against gastritis associated with Helicobacter pylori has also been described, as it hinders the establishment of pathogenic populations in the stomach.
Lactose intolerance
One of the best-known advantages of milk kefir is that, thanks to the fermentation process, a good part of the lactose is hydrolyzed It is broken down into glucose and galactose and subsequently transformed into lactic acid. This significantly reduces the lactose content of the final beverage.
Several studies have shown that kefir can improve lactose tolerance In people with malabsorption, it reduces symptoms such as bloating, gas, and abdominal pain compared to conventional milk. However, in cases of very severe intolerance or allergy to dairy proteins, it may be more prudent to use water-based or coconut-based versions.
Allergy and inflammatory process control
Many respiratory and skin allergies have a strong inflammatory basis. The probiotics in kefir may help. modulate the inflammatory responsereducing the overactivation of the immune system. Studies in animal models show a decrease in inflammatory cells in the airways and less mucus production after administering kefir.
In humans, although the data are still preliminary, it has been observed that the inclusion of probiotics in the diet can alleviate some allergy symptoms and improve quality of life of patients, especially in combination with other dietary and medical measures.
Skin, healing and dermatological health
The gut-skin connection is becoming increasingly clear. When the microbiota is disrupted, it's not uncommon for skin problems to appear. breakouts of acne, eczema, psoriasis or dermatitisKefir, by promoting a more balanced intestinal flora and reducing systemic inflammation, can contribute to a gradual improvement in the appearance and comfort of the skin.
Kefiran and other kefir compounds have been shown in experimental studies improve wound healing and protect the connective tissue, which reinforces the idea that it not only affects "inside" but also at the level of peripheral tissues.
Lipid profile, blood pressure and heart
Effects of kefir on the fat metabolism and blood pressureCertain microorganisms and bioactive peptides generated during fermentation appear to help modestly reduce total and LDL cholesterol levels, as well as improve some parameters of mild hypertension.
Furthermore, by providing probiotics, antioxidants, and cardioprotective nutrients (such as potassium and certain B vitamins), kefir fits well within a cardioprotective dietary patternprovided that versions without added sugars are chosen and consumed in moderation.
Potential anticancer effect
In vitro and animal model studies have shown that kefir extracts can inhibit the proliferation of certain tumor cells (such as some gastric or breast cancers) and modulate enzymes involved in the activation of carcinogenic substances. It is also suggested that its antioxidant and anti-inflammatory capacity could help reduce certain risks.
It is essential to clarify that this does not make kefir a cancer treatment or a substitute for medical therapy, but it does suggest that, as part of a diet rich in fermented foods, fruits, vegetables and fiber, can contribute to long-term prevention.
Specific benefits for active people and athletes
For those who train frequently, kefir can be a excellent post-workout supplementIts protein content promotes muscle repair and regeneration, its carbohydrate fraction provides sustained energy release, and minerals such as calcium, phosphorus, and magnesium help prevent cramps and fatigue.
Furthermore, by supporting gut health and strengthening the immune system, kefir can reduce the risk of shutdowns due to mild infections during periods of intense training. Its probiotics have been linked to an improved response to physical stress and reduced low-grade inflammation after exercise.
Another interesting point is that it provides tryptophan, an amino acid related to the production of serotonin and melatoninThis can promote better quality sleep, which is key to athletic recovery and performance.
Milk comparison: cow, goat and sheep in kefir
The type of milk used to make kefir influences its digestibility, nutritional value and tasteCow's milk is the most widely used industrially, but more and more people are opting for goat or sheep kefir because of its particular characteristics.
Goat's milk contains a higher proportion of beta-casein A2 compared to the A1 beta-casein typical of many modern cattle breeds. Some studies suggest that A2 proteins are better tolerated by people with dairy-related digestive discomfort, as they generate fewer peptides such as BCM7, which are associated with problems in individuals with increased intestinal permeability.
In addition, goat's milk usually has smaller fat globules and slightly less lactose, which could also contribute to its easier digestion for many people. Meanwhile, sheep's milk tends to be richer in protein and total fat, resulting in a denser and more satiating kefir.
At the micronutrient level, goat's milk tends to provide slightly more of vitamin A, calcium and potassium than cow's milk, and often comes from less intensive production systems, something that for many consumers also adds up when choosing.
How to choose and consume kefir to get the most out of it
For the kefir to maintain its probiotic propertiesIt's crucial to check the label. Ideally, choose products that indicate the presence of live cultures, that haven't been pasteurized after fermentation, and that contain primarily milk and ferments, without long lists of additives.
It is advisable to avoid kefirs with added sugars, syrups, starches or artificial sweetenersas they significantly worsen the product's health profile. If you prefer a sweeter taste, you can always add some pureed fruit, a little honey, cinnamon, or pure cocoa at home.
As for the quantity, a serving of around a glass a day This is usually enough to provide benefits for most people. If you've never taken it before, it's a good idea to start with half portions for a few days to test your tolerance, as you may experience mild gas or bloating at first while your gut microbiota adjusts.
Kefir fits in very well with breakfasts, desserts, afternoon snacks or as a post-workout snackIt can be combined with fresh fruit, oat flakes, nuts and seeds; used as a base for smoothies; served as a creamy salad dressing (mixed with herbs and lemon); or incorporated into vegetable creams to give them a smoother and more nutritious touch.
Possible Side Effects and Precautions
In healthy people, kefir is a food safe when consumed in moderationThe most common side effects are mild digestive discomfort (gas, bloating, slightly softer stools) at the start of consumption, which usually subside within a few days if a constant intake is maintained.
Those who present with milk protein allergyIn that case, milk kefir is not suitable, and water or coconut kefir should be used instead. In situations of severe immunodeficiency or complex intestinal pathologies, it is advisable to consult a healthcare professional before introducing large quantities of probiotics.
If it is made at home, it is essential to take extra care. hygiene in the fermentation processUse suitable containers (preferably glass), do not seal them tightly when dealing with fermented products like kombucha, and avoid mold contamination. Kefir with a strange odor, colored spots, or a distinctly unpleasant taste should be discarded.
Kefir has established itself as a versatile, nutritious and very interesting fermented food To support gut, immune, bone, metabolic, and even athletic health, thanks to its unique combination of probiotics, vitamins, minerals, and bioactive compounds. Chosen and consumed sensibly, it fits seamlessly into a varied and balanced Mediterranean diet, providing that extra boost of microbial "life" that our gut microbiota so appreciates and which, ultimately, translates into greater well-being on many levels.
