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Science  |  Dossier Food – Vice or Virtue ?

Fermented drinks

Kvass is made by fermenting rye bread, and is very popular in Russia. ©Shutterstock/Davidchuk Alexey

The fruity, tangy flavour and slight fizz of Kombucha is making it more and more popular. This fermented black tea originated in the Far East,1 and supposedly heals countless ills, from acne to digestive problems or cancer. Consumers are putting their faith in it to such an extent that, according to the most recent figures from Markets and Markets,2 the global market is expected to reach 1.8 billion US dollars in 2020 (compared to 0.6 billion in 2015).

Fermented drinks may be all the rage these days but they were already part of the Neolithic diet. According to Aristea Baschali, Doctor in Medical Sciences and Head of the Department of Nutrition at the Evangelismos Private Hospital in Athens, “People were drinking them in Egypt and in the Middle East nine thousand years ago. Alcoholic fermented drinks, such as beer and wine, were more predominant in Europe and were sometimes used as medicines, but were also seen as a source of energy. Today, however, there is a growing interest in non-alcoholic drinks such as kombucha, kefir and kvass.”

Kombucha hit the scene during the hippie movement in the 1970s, and has since won fans all over the world. It was discovered in the Far East and the numerous legends regarding this drink have contributed to this current craze. According to one story, in 415 BCE, a certain Doctor Kombu cured the Emperor of Japan’s digestive troubles with a magic tea, known as ‘cha’. Two hundred years later, the Emperor of China described kombucha as an ‘elixir of life’, as he was convinced that it was the reason for his longevity. Kombucha finally reached Germany via Russia and Ukraine in the early 20th century.

Kefir has similar therapeutic attributes. It is a slightly sweet and tart yoghurt drink produced by fermenting milk.3 It originally came from the Caucasus and is particularly popular in Russia and northern Europe. Kvass, also known as ‘bread beer’, is lesser known than kombucha and kefir. It is made by fermenting rye bread, and is one of the most frequently consumed drinks in Russia.4

Originally from the Caucasus, kefir became popular in Russia in the early 20th century, when it was sold in chemist’s across the country. Today, Russia remains the largest producer of kefir – followed by Poland – but the drink has crossed the borders of eastern Europe. According to Research and Markets, the global market for kefir is expected to grow by 5.8% a year from 2016 to reach 1.27 billion dollars by 2021.

The golden brown tint of kvass has seduced Russians ever since Vladimir the Great drank it in the 10th century. Nicknamed ‘communist Coca-Cola’ during the Soviet regime, the drink saw its popularity take a nosedive with the fall of the USSR, before staging a comeback in the early years of the new millennium. A touch ironic then that in 2008, the Coca-Cola Company launched its own version of kvass.

When chemistry is involved

Whatever their history, these beverages owe their recent popularity to fermentation, a natural process known for some 12 000 years.5 Bacteria and yeast are microorganisms that bring about a natural chemical reaction. When deprived of air and immersed in liquid at room temperature, bacteria transform the sugars in food into acids, while yeasts convert sugars into alcohol or carbon dioxide. The result is that kombucha, kefir and kvass have a sour taste, are lightly sparkling and sometimes contain a little alcohol.

When making kombucha, a white, viscous membrane called the ‘mother kombucha’ is added to sweet black tea and this triggers fermentation. Although the mother kombucha is akin to a fungus, it is actually a bacteria and yeast culture known by the acronym SCOBY, which stands for Symbiotic Culture of Bacteria and Yeast. When the microorganisms that make up the SCOBY come into contact with the liquid, they proliferate and convert the sugars in the tea. After fermentation, which can take from one to two weeks, the mother kombucha is removed, the liquid is filtered and the drink is ready to consume.

As Jenny Neikell explains in her 2016 book Les bienfaits de la fermentation6 (The benefits of fermentation) the same principle applies to the preparation of kefir. However, in this process, the viscous membrane is replaced by kefir grains, which look rather similar to small white cauliflowers and which release yeast and bacteria when in contact with milk. The kefir is considered ready when these grains float to the surface. As for kvass, the rye bread should be toasted before being soaked in water mixed with sugar, yeast and various herbs.
 

Source of probiotics

Although bacteria and yeasts are often thought to be bad for you, most of them are actually harmless. In fact, many types of bacteria and yeasts are actually essential to ensure that our bodies function correctly. Such bacteria and yeasts are known as probiotics.7

Probiotics are naturally present in our intestinal flora – or intestinal microbiota – and produce the enzymes needed to break down and digest the food we eat, while also providing nutrients such as vitamin K, certain B vitamins and minerals. The fact that they are in the intestine actually stops harmful bacteria and yeasts forming there.

In this search for balance, fermented drinks seem to be valuable allies, as the bacteria and yeasts activated by the fermentation process are also probiotic. Embryette Hyde, project manager of the American Gut Project8 notes that, “These beverages are said to act like a form of pre-digestion.”

Transforming sugars makes fermented drinks acidic, which in turn creates a hostile environment for certain harmful agents and means that good bacteria and yeasts are able to multiply. Since the microorganisms have already broken down the sugars, this makes kombucha, kefir and kvass easier to digest. Moreover, the enzymes produced by bacteria and yeasts transform lipids into fatty acids, proteins into amino acids, and complex carbohydrates into simpler carbohydrates.
 

Debatable benefits

Despite this acknowledged benefit to digestion, scientists remain cautious about any of the other purported merits of these products. Embryette Hyde points out that, “Consuming fermented food increases the diversity of microorganisms found in our intestinal flora, but it is still hard to identify the precise effects on the microbiota. Further studies are necessary.”

According to Aristea Baschali,9 “The benefits credited to these drinks are mostly based on testimonies of personal experience.” She adds that, “At present, scientific studies have focused on kombucha and kefir, but the impact of these drinks on health has yet to be proven.”

This is an opinion shared by Waisundata Yashasvi Viduranga,10 Research Fellow at the Faculty of Applied Sciences at the Rajarata University of Sri Lanka: “Like all ‘probiotic’ products available on the market, these drinks can have an effect on your intestinal flora. However, they are not medicines. How effective they are depends on the composition of the ferment. In the case of kombucha, some SCOBYs are richer in probiotics than others.” According to the United Nations Food and Agriculture Organization, probiotics are only beneficial if they are consumed in sufficient quantities.11 Furthermore, there are several strains of probiotics, some more effective than others. There is no indication that a bottle of kefir, kvass or kombucha contains either the right strains, or in the right quantity.12

Kefir and kombucha have been accused of being toxic. Aristea Baschali explains that, “In the case of kefir, some studies have shown the presence of biogenic amines. If these are consumed in large quantities, they could be a health risk, especially to a weak immune system. For kombucha, over-consumption can cause some people to experience stomach ache, or even metabolic acidosis, meaning a high level of acid in the blood.”

In 1995, following two reported cases of kombucha poisoning, the US Food and Drug Administration recommended that people with a weakened immune system should not consume kombucha.13 Doctors in Los Angeles repeated this advice in 2009 when a young, HIV-positive man suffered from kombucha poisoning.14

However, the drinks are not to blame. Embryette Hyde says that, “They may magnify symptoms in particular individuals at risk, but they are not toxic in themselves.” Waisundata Yashasvi Viduranga confirms that, “As with all foodstuffs, they must be consumed as part of a balanced diet. The risks begin with excessive consumption.”

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Glossary

Microorganisms

Microscopic living creatures found in the human body, in food and in the environment. There are countless types of microorganisms, but those active in the fermentation of foodstuffs are bacteria, yeasts and fungi.

Probiotics

These are harmless living microorganisms, mainly bacteria belonging to the genera Lactobacillus, Bifidobacterium and Streptococcus, and Saccharomyces boulardii yeasts. They are naturally present in our intestinal flora, but may also be found in some foodstuffs and food supplements.

Intestinal flora

This refers to the billions of microorganisms that live along the digestive tract. Today, it is more common to speak of intestinal microbiota.

Vitamin B

The B vitamins produced by probiotics are vitamin B2, which acts on the hormonal system, and vitamin B12, which acts on the nervous system and is important in the production of red blood cells.

Vitamin K

The K vitamins produced by probiotics are vitamin K1, which affects blood coagulation and vitamin K2, which is reputed to have anticancer properties. It also helps fix calcium on bones, preventing it from blocking arteries.

Biogenic amines

These molecules originate when amino acids are degraded and so indicate the freshness of food. During the fermentation process, microorganisms break down proteins to make amino acids, which are easier for the body to assimilate. These may in turn be converted into biogenic amines. The best known is histamine, but there are many more, such as tyramide, putrescine, cadaverine and spermidine.


​Glossary

Microorganisms

Microscopic living creatures found in the human body, in food and in the environment. There are countless types of microorganisms, but those active in the fermentation of foodstuffs are bacteria, yeasts and fungi.

Probiotics

These are harmless living microorganisms, mainly bacteria belonging to the genera Lactobacillus, Bifidobacterium and Streptococcus, and Saccharomyces boulardii yeasts. They are naturally present in our intestinal flora, but may also be found in some foodstuffs and food supplements.

Intestinal flora

This refers to the billions of microorganisms that live along the digestive tract. Today, it is more common to speak of intestinal microbiota.

Vitamin B

The B vitamins produced by probiotics are vitamin B2, which acts on the hormonal system, and vitamin B12, which acts on the nervous system and is important in the production of red blood cells.

Vitamin K

The K vitamins produced by probiotics are vitamin K1, which affects blood coagulation and vitamin K2, which is reputed to have anticancer properties. It also helps fix calcium on bones, preventing it from blocking arteries.

Biogenic amines

These molecules originate when amino acids are degraded and so indicate the freshness of food. During the fermentation process, microorganisms break down proteins to make amino acids, which are easier for the body to assimilate. These may in turn be converted into biogenic amines. The best known is histamine, but there are many more, such as tyramide, putrescine, cadaverine and spermidine.

Hannah Schlaepfer
Geneva, CH

After studying political science, Hannah Schlaepfer developed a penchant for magazine and audiovisual media. She is always willing to debate politics, fashion or even sport!

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