Not Everything Labeled as Kefir Is True Kefir
Marketed as a "superfood" and a panacea for all ailments, kefir has made a grand entrance onto the shelves of every supermarket. Let’s clarify the real properties of this product versus those that are merely presumed.
Although it has only recently begun to enjoy a certain level of popularity, kefir is actually native to the Caucasus region, where it has been consumed for hundreds of years. Kefir is a product obtained from milk through a fermentation process. It appears as a viscous and smooth compound, slightly frothy, with an acidic taste.
Kefir is often confused with yogurt, but the two products are fundamentally different (in terms of nutrients, aroma, flavor, and consistency). While both are fermented milk products, the bacteria used to produce them are not the same. Yogurt is produced almost exclusively with Lactobacillus bulgaricus and Streptococcus thermophilus, whereas the microorganism blend used for kefir is much more complex and contains, among others, Lactobacillus, Lactococcus, and Leuconostoc, in addition to yeasts from the genera Saccharomyces and Kluyveromyces, to name a few examples. It is estimated that this blend of strains, referred to as the "starter," contains up to 50 different species, although the exact composition has not yet been precisely identified.
Like milk, kefir is rich in minerals—particularly calcium and phosphorus—and vitamins A and B. The fat content, however, depends on the type of milk used: whole or partially skimmed. The fermentation process reduces the lactose content, so even those with mild lactose intolerance can consume this product without adverse effects. However, it should be avoided by individuals with severe lactose intolerance or milk protein allergies. The fermentation process—and specifically the dual alcoholic-lactic fermentation that lactose undergoes—gives kefir a slight alcoholic content (approximately 1–2% alcohol by volume).
A recent Spanish study attempted to unravel the mystery surrounding the true composition of kefir, focusing in particular on the traditional version made from goat’s milk. Researchers highlighted the presence of a complex of peptides (protein fragments), known as the peptidome. They found 22 potentially beneficial proteins, whose levels increase during the fermentation process, peaking at 24 hours before subsequently decreasing. In particular, 11 of these peptides are molecules already known to science for their antihypertensive, antioxidant, and antimicrobial properties. Additionally, kefir contains a heteropolysaccharide, called kefiran, which has prebiotic properties.
Today, many types of kefir are easily found on the market. The list of ingredients should ideally include only milk and lactic ferment cultures. Some brands specify the bacterial strains and whether yeasts are present. There is no specific regulation regarding the ferment cultures present in kefir, so the details are left to the discretion of the manufacturer. Some brands produce kefir with fruit, and there is also a creamy version of kefir. In the former case, sugars, sweeteners, stabilizers, and thickeners are usually present, essentially resulting in a liquid yogurt. The products labeled as creamy contain cream to achieve a smoother consistency.
Alternative: Making Kefir at Home
An interesting alternative could be to prepare kefir at home. There are "starter" sachets available on the market that can be added to milk to initiate fermentation. The "starter" granules resemble flakes of milk and consist of a set of globular structures ranging in diameter from 2 to 9 mm. These globules are made up of a matrix composed of kefiran, peptides, bacteria, and yeasts. Once the "starter" is added to the milk, preferably in a glass container covered with a clean cloth, the mixture can be left to ferment at room temperature (20–22°C) for 24 hours. In a warmer environment, fermentation will occur more quickly, while in a colder one it will take longer. Once ready, you can choose to add honey or fresh fruit to your kefir. For vegans or those who cannot consume milk, there is the option of making water kefir. In this case, what ferments is a solution of water and sugar. Although it retains its probiotic properties, it lacks the mineral and vitamin content found in milk.
It is evident that kefir's probiotic capabilities are considerable, while those of yogurt are almost negligible. Some studies have demonstrated that regular consumption of kefir can have beneficial effects on the intestinal microbiota, increasing the levels of lactobacilli and bifidobacteria. Moreover, it appears to have a positive effect on glycemic control, with reductions in fasting blood glucose and improved insulin response, although the data are preliminary and further studies are needed.
However, caution is warranted regarding marketing traps. Some supermarkets and brands promote products that are not true kefir but rather simple skimmed yogurts disguised as kefir. It is crucial that consumers carefully read labels and ensure they are purchasing authentic kefir, which should contain only milk and specific lactic ferment cultures, without added sugars, stabilizers, or other additives. Authentic kefir will provide the aforementioned probiotic properties and benefits, whereas skimmed yogurt will not offer the same health advantages.
Sources:
* Bourrie BC, Willing BP, Cotter PD. The Microbiota and Health Promoting Characteristics of the Fermented Beverage Kefir. Front Microbiol. 2016 May 4;7:647. doi: 10.3389/fmicb.2016.00647. PMID: 27199969; PMCID: PMC4854945.
* Salari A, Ghodrat S, Gheflati A, Jarahi L, Hashemi M, Afshari A. Effect of kefir beverage consumption on glycemic control: A systematic review and meta-analysis of randomized controlled clinical trials. Complement Ther Clin Pract. 2021 Aug;44:101443. doi: 10.1016/j.ctcp.2021.101443. Epub 2021 Jul 13. PMID: 34280689.
