Are kefirs and yogurts superfoods?

MAINTENANCE – Fermented milks are known to be good for intestinal health. What is it really? The answers of researcher Christophe Lavelle.

Coming from the Caucasus, kefir is extolled by some nutritionists. Aggregate of living micro-organisms, bacteria and yeasts, it comes in the form of grains intended to seed milk or fruit juice: this produces a fermented drink of the same name. Beneficial for the transit and the intestinal flora, kefir is in the process of making the bifidus ringardiser. Purists make it at home from grains bought in organic shops or traded on the internet, but it is also found ready to eat on the shelves of supermarkets. What about kefir? Is he so virtuous? Answers from researcher Christophe Lavelle (CNRS, National Museum of Natural History), who is currently conducting a study on its composition.

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LE FIGARO. – What is the difference between yoghurt and kefir, milk or fruit?

Christophe LAVELLE. – In all three cases, these are “live” fermented products, obtained without chemical or heat treatment. The difference between yoghurts and milk kefir lies in the nature of their microorganisms: thermophilic bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) for yoghurt; varied set of yeasts (species of the genera Kluyveromyces andSaccharomyces) and bacteria (species of the genera Lactobacillus, Leuconostoc, Lactococcus and Acetobacter) for milk kefir. Fruit kefir exhibits a bacteria/yeast symbiosis similar to that of milk kefir. Our work consisted in particular in dissecting the genome of about twenty fruit kefirs. Their detailed composition is still being analyzed, but we can already identify a very wide variety of micro-organisms between the strains, with probably some species still unknown in the lot!

Is it legitimate to present kefir as a superfood?

The concept of superfood is to be avoided as a general rule, since there are no miracle nutrients in food. Only favorable products, and that’s already a lot. Kefir actually provides probiotics (yeasts and bacteria) useful for digestion. A few studies, conducted only on milk kefir, show that it could also promote lactose tolerance and boost the immune system. But most of this work has focused on laboratory animals, which imposes reservations about their extrapolation to human health.

The microbial symbiosis in kefir leaves little room for massive colonization by a possibly pathogenic foreign microorganism

Christophe Lavelle, researcher at the CNRS and the National Museum of Natural History

Does the exchange of ferments on the internet present a risk of contamination, or even intoxication?

Yes, there are contaminations. But no risk of poisoning. The microbial symbiosis in kefir leaves little room for massive colonization by a possibly pathogenic foreign microorganism. If the initial balance of the ferment is disturbed by contamination, it alters the taste of kefir, but nothing more.

Will the fad around kefir last?

No doubt, and so much the better! As we have analyzed, fermented products have been making a strong comeback in recent years. Easy to produce, kefir offers both the pleasure of ferment and homemade! The sweet/sparkling taste of fruit kefir is appreciated by children and can advantageously replace sodas. Here you have all the assets of a magic drink, at the same time healthy, if you don’t add too much sugar, economical because the kefir grains multiply indefinitely, and always renewed because the recipes can be varied ad infinitum.

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