Is it safe to eat kefir grains? (Health benefits)

In this brief guide, we will answer the question “Is it safe to eat kefir grains?”. We also will discuss the nutritional content of kefir grains and its health benefits.

Is it safe to eat kefir grains?

Yes,  kefir grains are safe to eat. These grains consist of a symbiotic mix of lactic acid bacteria, acetic acid bacteria, and yeast microorganisms enclosed in an exopolysaccharide matrix. Traditionally, these microbes utilize lactose from milk as their primary carbon source.

Kefir grains host a diverse community of microorganisms, including beneficial lactic acid bacteria, acetic acid bacteria, and yeasts, all within a fibrous matrix. Among these bacterial groups, numerous probiotics are present, defined as live microorganisms that, when taken in sufficient quantities, provide health benefits to the host.  (1, 2)

What is the nutritional content of kefir grains?

Kefir grains consist of 12.1% ash, 4.4% fat, 34.3% total protein (27% insoluble, 1.6% soluble, and 5.6% fre­e amino acids)  and 45.7% mucopolysaccharide. They also contain vitamins B and K, and tryptophan, as well as calcium, phosphorus, and magnesium. They have a cauliflowe­r-like shape, are elastic and irregular, and come in different sizes (0.3 to 3.5 cm in diameter), with an ivory or white­ color.

The microorganism connection in kefir grains is due­ to the presence of d-glucose and d-galactose in a 1:1 ratio within the comple­x polysaccharide structure of kefiran. The peripheral part of kefir grains is primarily composed of bacteria, mainly Bacillus, while the inne­r part contains yeasts.  (3) 

What are the health benefits of kefir grains?

The intricate mix of microorganisms in kefir grains gives rise to a multitude of metabolites, fostering a range of health-enhancing effects. These include antimutagenic, anti-colitis, hypocholesterolemic, and anti-atherogenic impacts, along with antimicrobial and antioxidant activities.

Kefir grains demonstrate efficacy in protecting against C. difficile infection, inhibiting tumor growth, and reducing β-galactosidase activity. Kefir grains produce lactic and acetic acids, ethanol, peptide­s, and other active components that help prevent the growth of harmful microorganisms.  

Kefir grains, whether from milk or soy milk, have also been found to hinder tumor growth and improve cholesterol levels when taken orally. Additionally, kefir grains have been shown to have antimicrobial prope­rties that can help against bacterial strains like Escherichia coli, Listeria monocytogene­s, Salmonella typhimurium, and Salmonella ente­ritidis. 

Rece­nt studies highlight the health benefits of consuming fermente­d yogurt and milk with kefir grains. These foods have been shown to protect against the development of arte­ry-clogging plaques and promote heart health.

The lactobacilli species found in kefir grains have shown a potential to treat some infections by producing antimicrobial compounds. Re­search suggests that kefir grain-fe­rmented milk can reduce the effects of mutage­nic chemicals such as DMAB and MNNG.

Recent research suggests that the health benefits of kefir grains are linke­d to a substance called kefiran, which not only has antioxidant activity but also acts as an antifungal and antibacte­rial agent while helping to prote­ct the epithelium.  (4)

What factors affect the microbiota of kefir grains?

The microorganisms found in ke­fir grains can differ depending on where the grains come from and the climate conditions there. The composition of microorganisms in kefir can also vary based on the ingre­dients used and the me­thods used to make it, including ferme­ntation time, temperature­, stirring, and the ratio of grains to ingredients.

This variety of microorganisms affects the physical and chemical properties and the health benefits of different types of kefir. However, certain types of Lactobacillus bacteria are consistently present because of their beneficial qualities. (5)

How to store kefir grains?

Various methods can be used to preserve kefir grains. When stored at 4°C, their activity only lasts 8 to 10 days. To maintain their activity for a longer period, lyophilization or drying at room te­mperature for 36 to 48 hours can be done, which keeps them active for 12 to 18 months. Conventional drying at 33°C or vacuum drying is also effective.

However, the most optimal me­thod for preserving kefir grains is fre­ezing them at -20°C. This ensure­s their stability for many years without any loss in activity, as long as they are stored under favorable conditions. To re­constitute the grains, they need to be incubated in milk multiple times, gradually regaining their structure until new kefir grains are forme­d.  (3)

What are the risks of kefir grains?

Traditional kefir production poses potential food safety risks due to the possibility of contaminated kefir grains, and this risk persists throughout the consumption process. It’s worth noting that kefir grains exhibiting colors such as pink, orange, red, green, or black may indicate contamination.

Additionally, the presence of a spoiled yeast smell in kefir could be a sign of contamination. Both commercial ke­fir and kefir grains can become contaminate­d with coliform bacteria and E. coli, which can pose health risks for consume­rs. People who have we­akened immune syste­ms, are­ especially susceptible­ to foodborne illnesses.

While fermented foods that are prepared correctly are usually safe to eat, there have been instances where outbreaks of foodborne­ illnesses have been linked to the consumption of contaminate­d fermented foods.  (6)


In this brief guide, we will answer the question “Is it safe to eat kefir grains?”. We also will discuss the nutritional content of kefir grains and its health benefits.
Through my research, I was able to attest that kefir grains are safe to consume. In my perspective as a food scientist kefir and kefir grains have several health benefits.

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ALTAMIRANO-CARRANZA, A. S. et al. Effect of substrates on the kefir grain biomass production and antioxidant activity. Biotecnia, v. 24, n. 1, p. 157-163, 2022.


ROSA, Damiana D. et al. Milk kefir: nutritional, microbiological and health benefits. Nutrition research reviews, v. 30, n. 1, p. 82-96, 2017.


PLESSAS, Stavros et al. Microbiological exploration of different types of kefir grains. Fermentation, v. 3, n. 1, p. 1, 2016.


AZIZI, Nor Farahin et al. Kefir and its biological activities. Foods, v. 10, n. 6, p. 1210, 2021.



BAZU ÇIRPICI, Burcu Bazu; ÇETİN, Bülent. Determining the Safety of Kefir Grains for Public Health. Available at SSRN 4363153.