It’s hard not to have heard the benefits of kefir extolled. The superfood of the moment, highly recommended by gurus and influencers for its slimming, regularizing, antioxidant properties, capable of supporting the immune system and fighting aging. According to Silvio Garattini, president of the Mario Negri Pharmacological Research Institute, we need to clarify things about kefir, because we are talking about a healthy food, and not an elixir of long life. Speaking on Rai 1 during the program “La Volta Buona”, the pharmacologist recalled that scientific data confirms that this fermented milk has beneficial properties for the body, but there is no data demonstrating a direct impact on human longevity. In short, the picture that emerges from the research gives kefir its rightful dimension: a useful food as part of a balanced diet, but without miraculous powers.
A thousand-year legacy in the Caucasus mountains
The origins of kefir lie in the tradition of the Caucasian pastures, where for centuries local populations have used this natural method to preserve fresh milk. According to historical accounts and ethnographic studies, the traditional preparation took place inside leather bags or animal skins, in which the milk was continuously fermented together with the so-called “kefir granules”, formed by a polysaccharide that hosts colonies of bacteria and yeasts.
The legend of its alleged properties as an elixir of long life arises from empirical observations made in the 19th century on Caucasian populations by scientists such as the Russian Nobel Prize winner Ilya Ilyich Mečnikov, who believed kefir was responsible for their famous longevity. With its progressive diffusion in Western countries during the twentieth century, the product has maintained this original fame, transforming in recent years into a true phenomenon of mass consumption on the global market.
A complex microbial symbiosis
Unlike common yogurt, which is produced using selected and isolated bacterial strains, kefir comes from the fermentation of milk thanks to the presence of the aforementioned granules or nodules. These are polysaccharide and protein structures, called kefiran, which host a complex and extremely varied microbiological community. Within this matrix, lactic acid bacteria of the Lactobacillus, Lactococcus and Streptococcus genera coexist in close symbiosis, together with acetic acid bacteria and yeasts such as Saccharomyces and Kluyveromyces.
During the production process, which usually lasts between 24 and 48 hours and is carried out at room temperature, microorganisms metabolize lactose. This mechanism produces lactic acid, a modest percentage of carbon dioxide and negligible traces of ethyl alcohol. The final result is a slightly acidic, fizzy drink with a reduced lactose content compared to the starting milk, a characteristic that facilitates gastric tolerability.
The comparison
Kefir is not the only fermented milk product in our supermarkets. But it is probably the most fashionable in recent years, so much so that many are convinced that its probiotic properties have an edge over more traditional yogurts. But is it really true? A test conducted by the Maurizi Group for the magazine Il Salvagente examined 27 commercial products divided between kefir, Greek yogurt and skyr, analyzing the presence of live microorganisms within them two weeks after the expiry date.
The analyzes showed that both Greek yogurt and kefir maintain very high microbial loads, exceeding 10 billion live cells for the classes of streptococci, lactococci and lactobacilli. However, kefir recorded lower values for bifidobacteria, which stopped at around 10 million cells. The lowest values were detected in the skyr, where the presence of live bacteria was markedly lower. The data therefore indicates that, due to the supply of live cultures, kefir is an excellent option, but with slightly lower performance than that of common Greek yogurt.
Regardless of trends, in short, the impact of kefir on human health is almost certainly positive, but equally certainly limited. Research confirms that the regular intake of fermented foods can contribute to the balance of intestinal bacterial flora, support digestive processes and promote regular transit. As highlighted by Garattini, current evidence shows the usefulness of these foods in the general framework of nutrition, but in no way supports the theories that attribute to kefir the ability to prolong life expectancy. The presence of live bacteria, however numerous, does not transform a food into a drug and does not guarantee permanent colonization of the intestine. Kefir should therefore be considered a valid nutritional alternative, to be included in a varied dietary style without expecting improper therapeutic effects.