Tea, Kombucha, and health: a review - C. Dufresne, E. Farnworth
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Food Research International 33 (2000) 409±421
www.elsevier.com/locate/foodres
Tea, Kombucha, and health: a review
C. Dufresne, E. Farnworth *
Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Blvd. West, Saint-Hyacinthe, QC, Canada J2S 8E3
Received 21 June 1999; accepted 1 December 1999
Abstract
Kombucha is a refreshing beverage obtained by the fermentation of sugared tea with a symbiotic culture of acetic bacteria and
fungi, consumed for its bene®cial eects on human health. Research conducted in Russia at the beginning of the century and tes-
timony indicate that Kombucha can improve resistance against cancer, prevent cardiovascular diseases, promote digestive func-
tions, stimulate the immune system, reduce in¯ammatory problems, and can have many other bene®ts. In this paper, we report on
studies that shed more light on the properties of some constituents of Kombucha. The intensive research about the eects of tea on
health provide a good starting point and are summarized to get a better understanding of the complex mechanisms that could be
implicated in the physiological activity of both beverages. # 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Tea; Kombucha; Health; Chemical composition; Bene®cial property; Adverse reactions; Review
1. Introduction known medicine. It was taken in China 5000 years ago
for its stimulating and detoxifying properties in the
A large amount of information has been published elimination of alcohol and toxins, to improve blood and
concerning the eects of tea and its major constituents urine ¯ow, to relieve joint pains, and to improve resis-
on human health. This beverage has been consumed in tance to diseases (Balentine, Wiseman & Bouwens,
many countries for a very long time, and today interest 1997). Tea grew rapidly in importance and was incor-
is growing because scienti®c reports indicate that tea porated into many social rituals notably in China,
could bring bene®ts for health and may help prevent Japan and England. Today, tea is the second most
chronic diseases. Tea was ®rst introduced into Eur- popular beverage in the world after water (Yang &
opean countries from China by Portuguese and Dutch Wang, 1993).
explorers as a medicinal herb (Hollman, Hertog & Another beverage known as Kombucha, is produced
Katan, 1996). Over the years, tea consumption became by the fermentation of tea and sugar by a symbiotic
associated with eating and living habits just like coee association of bacteria and yeasts forming a ``tea fun-
or soft drinks without regards to its bene®ts. The aging gus''. It also originated in China where the ``Divine
of the population and limitations of modern medicine Che'' was prized 220 BC during the Tsin Dynasty for its
have caused many people to look for new ways to detoxifying and energizing properties (Roche, 1998). In
improve their health. Doubts surrounding lifestyle and 414, Doctor Kombu brought the tea fungus to Japan
diet along with the growing interest in functional foods from Korea to cure the digestive troubles of the
and nutraceuticals have contributed to this trend. Emperor. ``Tea Kvass'' was introduced into Russia by
When we study the development of civilization and oriental merchants and then into Eastern Europe and
the role of food and folk medicine, we often discover Europe around the turn of this century. This refreshing
that many foods and beverages were used for their beverage tasting like sparkling apple cider is often pro-
assumed bene®cial eects on health. Tea is the oldest duced in the home by fermentation using a tea fungus
passed from home to home.
The composition and properties of tea are well docum-
* Corresponding author. Fax: +1-450-773-8461. ented, but scarce scienti®c information is available con-
E-mail address: farnworthed@em.agr.ca (E. Farnworth). cerning the composition and the eects of Kombucha
0963-9969/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0963-9969(00)00067-3410 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421
on health. Bene®ts have been reported by testimony of Black tea and white sugar are the best substrates for
users in dierent conditions and with variable con- the preparation of Kombucha, although green tea can
summation. The purpose of this review is to point out be used also (Reiss, 1994). Tea leaves are added to
the biological activity of both beverages, the speci®c boiling water and allowed to infuse for about 10 min
substances implicated in the biological activity, and to after which the leaves are removed. Sucrose (50 g/l) is
try to establish a better understanding of Kombucha dissolved in the hot tea and the preparation is left to
and its possible health bene®ts. A thorough knowledge cool. Tea is poured into a wide-mouthed clean vessel
of tea, its composition and eects on metabolism and and is acidi®ed by the addition of vinegar or already
health provides a starting point to understanding the prepared Kombucha. The tea fungus is laid on the tea
potential of Kombucha. surface, and the jar is carefully covered with a clean
cloth and fastened properly. The preparation is allowed
to incubate at room temperature (between 20 and
2. From tea to Kombucha: the fermentation process 30 C) for 1±8 weeks. During fermentation, a daughter
tea fungus is formed at the tea surface. The tea fungus is
Tea plants belong to the Theaceae family and come removed from the surface and kept in a small volume of
from two main varieties: Camellia sinensis var. sinensis fermented tea. The beverage is passed through cheese-
and Camellia sinensis var. assamica (Hara, Luo, Wick- cloth and stored in capped bottles at 4 C. The taste of
remashinghe & Yamanishi, 1995a). The ®rst apical the Kombucha changes during fermentation from a
leaves are picked from the evergreen shrub and can be pleasant fruit sour-like lightly sparkling ¯avour after a
processed by dierent methods. Green tea is readily few days, to a mild vinegar-like taste with prolonged
dried with or without a ®xation step to inactivate incubation (Blanc, 1996; Reiss, 1994; Sievers, Lanini,
enzymes (Hara, Luo, Wickremashinghe & Yamanishi, Weber, Schuler-Schmid & Teuber, 1995).
1995b). Black tea, the most popular form around the The microbiological composition of the tea fungus
world, is the result of the oxidation of leaf polyphenols has been investigated. Bacteria and fungus present in
through a multi-stage enzymatic process (Hara, Luo, Kombucha form a powerful symbiosis able to inhibit
Wickremashinghe & Yamanishi, 1995d). New poly- the growth of potential contaminating bacteria (Balen-
phenol molecule complexes are formed during the pro- tine, 1997; Liu, Hsu, Lee & Liao, 1996). The main acetic
cessing of black tea (Fig. 1) acid bacteria found in the tea fungus are: Acetobacter
xylinum (Balentine, 1997), A. xylinoides, Bacterium glu-
conicum (Reiss, 1994), A. aceti, A. pasteurianus (Liu et
al., 1996). Yeasts identi®ed as Schizosaccharomyces
pombe, Saccharomycodes ludwigii, Kloeckera apiculata,
Saccharomyces cerevisiae, Zygosaccharomyces bailii,
Brettanomyces bruxellensis, B. lambicus, B. custersii,
Candida and Pichia species (Balentine, 1997; Liu et al.,
1996; Mayser, Fromme, Leitzmann & GruÈnder, 1995)
have been isolated from tea fungus. Aspects of the close
association between micro-organisms that make up the
fungus and their interaction with the substrates sup-
porting fermentation have been studied (Balentine, 1997;
Sievers et al., 1995; Yurkevich & Kutyshenko, 1998).
Acetobacter xylinum has the ability to synthesize a ¯oating
cellulose network which enhances the association formed
between bacteria and fungi (Balentine et al., 1997). The
yeast cells convert sucrose into fructose and glucose and
produce ethanol (Reiss, 1994; Sievers et al., 1995). Acetic
acid bacteria convert glucose to gluconic acid and fructose
into acetic acid. Caeine and related xanthines of the tea
infusion stimulate the cellulose synthesis by the bacteria,
(Balentine et al., 1997). Acetic acid stimulates the yeast to
produce ethanol and ethanol in turn can be helpful to
acetic acid bacteria to grow and produce acetic acid (Liu et
al., 1996). Both ethanol and acetic acid have been reported
to have antimicrobial activity against pathogenic bacteria
thereby providing protection against contamination of
Fig. 1. Chemical structure of some tea constituents. the tea fungus (Liu et al., 1996).C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 411
3. Tea and its biological activity animals, and in vitro studies lead to the conclusion that
tea has potentially protective eects for a wide variety
3.1. Chemical composition of health conditions. However, the evidence is not
always clear cut.
The chemical composition of tea leaves has been
thoroughly studied. The main constituents of green 3.2.1. Epidemiologic studies
tea leaves belong to the polyphenol group accounting Epidemiologic studies have investigated the role of
for 25±35% on a dry weight basis (Balentine et al., 1997; green tea (Bushman, 1998; Imai, Suga & Nakachi,
Hara, Luo, Wickremashinghe & Yamanishi, 1995c). 1997), black tea (Blot, McLaughlin & Chow, 1997) or
Important and characteristic tea polyphenols are both in cancer prevention often without conclusive
the ¯avanols of which catechins (¯avan-3-ols) are pre- results (Yang & Wang, 1993; Yokozawa, Dong, Naka-
dominant and the major ones are: (ÿ)-epicatechin (EC), gawa, Takeuchi et al., 1998). To make sense of data
(ÿ)-epicatechin gallate (ECG), (ÿ)-epigallocatechin generated by epidemiologic studies, individual cancers
(EGC), (ÿ)-epigallocatechin gallate (EGCG), (+)-cate- must be considered. Oral and pharyngeal cancer risks
chin (C), and (+)-gallocatechin (GC) (Hara et al., tend to be lower among tea drinkers, but results are not
1995c) (Fig. 1). These compounds contribute to the bit- statistically signi®cant (Dreosti, Wargovich & Yang,
terness, astringency and sweet aftertaste of tea bev- 1997). Esophageal cancer occurrence increases sig-
erages (Hara, Luo, Wickremashinghe & Yamanishi, ni®cantly with black tea consumption in some countries
1995e). Tea contains also ¯avonols, mainly quercetin, when the beverage is drunk very hot but there is no
kaempferol, myricetin, and their glycosides (Fig. 1). In association found otherwise and one study with green
black tea, the oxidation of polyphenols during proces- tea indicates potential protective eects (Katiyar &
sing leads to the formation of catechins and gallic acid Mukhtar, 1996). Some epidemiological studies point out
complexes such as thea¯avins, thea¯avinic acids, thear- that tea has a protective eect against stomach cancer
ubigins or theasinensis, and of proanthocyanidin poly- although other studies found opposite results (Bush-
mers (Balentine et al., 1997; Hara et al., 1995d). (Fig. 1) man, 1998; Katiyar & Mukhtar, 1996). The most com-
Methylxantines are present with 2±4% as caeine and a prehensive reports showed an inverse association of
small amount of theophylline and of theobromine green tea and this type of cancer. As for esophageal
(Hara et al., 1995c). (Fig. 1). Tea contains many amino cancer, drinking very hot tea raises the risk. Most stu-
acids, but theanine, speci®c to the tea plant, is the most dies evaluating risks for colorectal cancer have con-
abundant, accounting for 50% of the total amino acids, cluded that there is no clear relationship with tea
(Fig. 1). Amino acid degradation is involved in the bio- drinking habits (Bushman, 1998). However, an inverse
genesis of the tea aroma (Balentine et al., 1997). Chlor- association with increased green tea intake and adeno-
ophyll, carotenoids, lipids, and volatile compounds are matous colon polyps was found, but the results were not
not major constituents in a tea brew but they also play statistically signi®cant (Bushman, 1998). A green tea
an important role in the development of the aroma intake seems to lower risks to develop pancreatic cancer
(Hara et al., 1995c). Volatile fractions of tea leaves have in many population studies (Bushman, 1998). Incon-
been studied in detail and more than 600 dierent sistent or non-correlate results were reported concerning
molecules have been isolated (Hara et al., 1995c,e; Shi- the impact of drinking tea on prevention of lung, breast,
moda, Shiratsuchi & Osajima, 1995; Shimoda, Shige- uterus, liver, pancreas, bladder, kidney and urinary tract
matsu, Shiratsuchi & Osajima, 1995). These include cancer (Yokozawa, Dong, Nakagawa, Kashiwagi et al.,
terpenoids and degradation products of amino acids, 1998).
carotenoids and linoleic acid (Hara et al., 1995c). Tea For large populations, green tea would be a very use-
also contains carbohydrates, vitamins E, K, A, low ful alternative to chemical preventive agents, because it
levels of B vitamins and vitamin C (in green tea only). is nontoxic and readily available (Imai et al., 1997).
Tea also provides useful amounts of potassium, man- More accurate epidemiologic studies are needed to get
ganese and ¯uoride ions to the diet (Hara, Luo, Wick- more conclusive results. Taken together, the present
remashinghe & Yamanishi, 1995f). This brief overview scienti®c information seems to indicate that black or
of the complex composition of tea leaves helps to green tea provides some protective eect against several
understand the constituents of tea in particular those cancers, particularly of the digestive tract (Blot et al.,
that may promote health. 1997).
Epidemiological studies have also been conducted on
3.2. Biological activity tea, ¯avonoids and the incidence of cardiovascular dis-
eases (Mitscher, Jung, Shankel, Dou, Steele & Pillai,
The scienti®c community has recently turned its 1997; Tijburg, Mattern, Folts, Wiesgerber & Katan,
attention to the allegation that tea is good for health. 1997). Case-control studies showed a non-signi®cant
Several epidemiological studies, experimentation with reduction for myocardial infarction for high black tea412 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421
consumption drinkers. Cohort studies do not provide inhibiting lipid peroxidation in brain tissue from
consistent conclusions about an association between tea animals with a 200 times greater activity than alpha-toco-
drinking habits and cardiovascular diseases, (Tijburg et pherol (Anon, 1997). It was also demonstrated that
al., 1997). However, a long-term study indicated a sig- catechins can act in a synergy with tocopherol and
ni®cant lower risk of dying from coronary heart disease organic acids (Antony & Shankaranaryana, 1997; Hara
and a lower incidence of strokes when people consumed et al., 1995f). In some in vitro conditions, they can
tea. Tea is a good source of ¯avonoids and therefore, exhibit a pro-oxidant eect in the presence of Cu2+ or
the epidemiological studies about the eect of ¯avonols Fe3+ and H2O2, as observed with other phenolic anti-
on the incidence of cardiovascular diseases may be use- oxidants and vitamin C (Cao et al., 1996; Yen, Chen &
ful. There was no association or an inverse association Peng, 1997). However, antioxidant properties of tea
between ¯avonol consumption and the incidence of constituents have to be demonstrated in living material
cardiovascular diseases (Tijburg et al., 1997). The serum to be relevant to human health.
lipid pro®les in a human cohort study indicated a
decrease in serum cholesterol but no eect on serum 3.2.3. Bioavailability
triglycerides or high density lipoproteins (Mitscher et al.). It is important to look at the bioavailability of ¯avo-
Many variable or confounding factors like tobacco or noids from tea including absorption, distribution,
alcohol consumption habits, diet, life style, lack of metabolism and elimination, to get a comprehensive
information about frequency of tea drinking, type of understanding of the possible impact on living organ-
tea, infusion period, pesticides used during tea leave isms. This subject has been reviewed and the ®ndings
culture, and temperature of consumption, may con- can be summarized (Hollman, Tijburg & Yang, 1997).
tribute to the inconsistency of study results. Any bene- Pure ¯avonols are poorly absorbed, but their glycosides
®cial eects of tea could be in¯uenced by other show moderate to rapid absorption in man, probably
causative factors and the development mechanism rela- because an active glucose transport occurs in the small
ted to one speci®c cancer occurrence. Epidemiologic intestine. Catechins and catechin condensation products
studies can be used to generate important information from black tea are both well absorbed in humans.
concerning human response to tea consumption but Catechins are metabolized extensively but the absorp-
more studies are required. Experimental studies con- tion and the metabolism mechanism of larger molecules
ducted in vitro and with animals bring a more accurate present in black tea remains unclear. Catechins pass
understanding of the metabolism and function of tea through glucuronidation, sulfation and O-methylation
components that could be used to explain the potential in the liver. In the colon, bacteria cleave the ring pro-
health bene®ts of tea for humans. ducing valerolactones, phenylpropionic and benzoic
acids. Polyphenols have a strong anity for proteins via
3.2.2. Experimental studies the various phenolic groups particularly when proteins
Many studies have been conducted to identify active have a high proline content such as in caseins, gelatin
compounds in tea and to elucidate their chemical and and salivary proteins. However, the addition of milk to
biological properties. Several approaches led to the tea does not aect the polyphenol concentration in
same ®ndings: catechins and ¯avonols of tea are good plasma. Tea ¯avonoids have also a strong anity for
antioxidants in the presence of reactive oxygen species iron and form insoluble complexes which reduce the
and free radicals in both aqueous and lipophilic condi- bioavailibility of non-heme iron. Absorption of ascorbic
tions (Cao, So®c & Prior, 1996; He & Shahidi, 1997; acid inhibits this complex formation. This ®nding has
Hirayama, Takagi, Hukumoto & Katoh, 1997; Huang important implications mainly for those people having a
& Frankel, 1997; Kumamoto & Sonda, 1998; Ngang, vegetarian diet.
Wolniewicz, Letourneau & Villa, 1992; Roedig-Penman Many biological activities of tea extracts can be
& Gordon, 1997; Sawai & Sakata, 1998; Vinson, Dab- attributed to the antioxidant properties of the poly-
bagh, Serry & Jang, 1995; Wiseman, Balentin & Frie, phenol fraction through its metabolism. Protection
1997; Yokozawa, Dong, Nakagawa, Kashiwagi et al., against cardiovascular diseases, atherosclerosis, cancer,
1998). In fact, tea catechins are the most powerful anti- gene mutations, bacterial growth and diabetes are
oxidants among the known plant phenols. In some lab growing concerns. Many studies have been reported
tests, EGCG is 20 times more active than vitamin C, 30 where the protective eect of tea against these diseases
times more than vitamin E and 2±4 times more than has been evaluated.
butylated hydroxyanisole (BHA) or butylated hydro-
xytoluene (BHT) (Vinson, Dabbagh et al., 1995). The 3.2.4. Atherosclerosis and cardiovascular diseases
antioxidant activity increases with the number of o- The oxidation of low density and of very low density
dihydroxy groups, although the activity also depends lipoproteins (LDL and VLDL) brings about the pro-
upon the oxidation environment. In some conditions, cate- gressive obstruction of arteries or atherosclerosis, and
chins can exibit a very high potential of protection, can lead to angina pectoris, to coronary heart disease,C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 413
or to infarction (Tijburg et al., 1997). Tea ¯avonoids, (gluthathione, ascorbic acid, alpha-tocopherol, urea,
mainly gallocatechins, protect LDL and VLDL against carotenoids, etc.). When oxygen reacts with DNA,
oxidation by aqueous and lipophilic radicals, copper oncogene production can result which can lead to can-
ions and macrophages (Vinson, Jang, Dabbagh, Serry & cer pathology through the stages of initiation, promo-
Cai, 1995; Vinson & Dabbagh, 1998; Wiseman et al., tion and progression (Mitscher et al., 1997). Cancer can
1997; Yokozawa, Dong, Nakagawa, Kim, Hattori & also be the result of suppression of the immune system
Nakagawa, 1998) and against the proliferation of vas- by the prostaglandins following persistent in¯ammatory
cular smooth muscle cells which leads to the sclerosis of episodes initiated by reactive oxygen species. Many stu-
the artery (Yokozawa, Oura, Sakanaka & Kim, 1995). dies have indicated that tea and its constituents mainly
In studies conducted with rats, a reduction of triglycer- EGCG, are antimutagenic and anti-in¯ammatory by
ides, total cholesterol, LDL-cholesterol (Yang & Koo, intercepting carcinogenic agents and by reducing oxi-
1997) and the enhancement of superoxide dismutase dant species before they can damage DNA (Halder &
(SOD) in serum and of gluthatione S-transferase (GST) Bhaduri, 1998; Katiyar & Mukhtar, 1997; Mitscher et
and catalase in the liver were observed (Lin, Cheng, Lin, al., 1997; Yang & Wang, 1993; Yen & Chen, 1995).
Lau, Juan & Lin, 1998). Increase of SOD, GST and Catechins also protect cell membranes against oxida-
catalase improve removal of the superoxide anion radi- tion, keep reactive oxygen species in con®ned zones and
cal, the peroxides and other free radicals responsible for probably block cell membrane receptors required for
LDL oxidation (Yokozawa, Dong, Nakagawa, Kashi- cancer cell growth. The initiation of carcinogenesis can
wagi et al., 1998). Tea catechins eectively reduce cho- be overcome by the repression of some catalytic activ-
lesterol absorption from the intestine, lowering the ities and of other speci®c enzymes involved in cancer
solubility of the cholesterol and enhancing the faecal initiation. This is complemented by the enhancement of
excretion of cholesterol and total lipids. In athero- detoxifying enzymes by EGCG (Bushman, 1998;
sclerosis, the in¯ammatory process is an important Katiyar & Mukhtar, 1996).
component. Tea extract induces an anti-in¯ammatory Promotion and progression of cancer pathology are
and capillary strengthening eect (Tijburg et al., 1997). retarded even at later stages by tea in a variety of can-
Green tea also inhibits the collagen-induced aggregation cers in a range of target organs as indicated in many
of rabbit platelets and the ¯avonols quercetin and myr- studies conducted with rodents (Blot et al., 1997).
icitin are strong inhibitors of ADP- and arachidonic Laboratory research agrees with epidemiologic studies
acid-induced aggregation of human platelets, preventing that tea can reduce the incidence and the multiplicity
the formation of a thrombus (Tijburg et al., 1997). Tea of esophageal and gastrointestinal cancers (Gao,
components, mainly quercetin (Tijburg et al., 1997) and McLaughlin, Blot, Ji, Dai & Fraumeni, 1994; Weisbur-
theanine (Yokogoshi, Kato, Sagesaka-Mitane, 1995), ger, Rivenson, Reinhardt, Aliaga, Braley, Pittman &
reduce blood pressure in animals and in man and thus Zang, 1998; Xu, Ho, Amin, Han & Chung, 1992). At
lower the risk for the development of cardiovascular low concentration, tea polyphenols block the nitrosa-
diseases. Tea catechins have been found in human tion reaction and the resulting mutagenicity implicated
plasma in concentrations sucient to have an anti- in many esophageal, gastric and other tumorigenesis
oxidant activity (Nakagawa, Okuda & Miyazawa, 1997) (Katiyar & Mukhtar, 1996; Yang & Wang, 1993). Tea
and they can inhibit LDL oxidation (Pearson, Frankel, extracts show an antiproliferative eect in lung and
Aeschbach & German, 1998). More human studies are other tumor development in mice and in ®broblast cells
needed to validate these data. because they inhibit cell division in the DNA damaged
cells (Landau, Wang, Ding & Yang, 1998; Lin, Juan,
3.2.5. Cancer and gene mutations Chen, Liang & Lin, 1996; Sazuka, Imazawa, Shoji,
Documentation concerning the protective eect of tea Mita, Hara & Isemura, 1997; Xu, Baily, Hernaez,
against cancer is very extensive. Some reviews are help- Taoka, Schut & Dashwood, 1996) and can induce
ful (Blot et al., 1997; Mitscher et al., 1997; Yang & apoptosis in both malignant and non-malignant tumors
Wang, 1993; Yokozawa et al., 1998). Strong evidence in mice skin (Conney, Lu, Lou, Xie & Huang, 1999).
has come from both in vitro and in vivo studies that tea Inhibition of skin tumorigenesis is also observed when
can act as a protective agent at dierent stages of cancer mice are exposed to UVB radiation. In some studies,
development and through dierent mechanisms caeine is proposed as an active ingredient along with
(Mukhtar and Almad, 1999). catechins (Chung, 1999; Huang, Xie, Wang, Ho, Lou,
Cells exhibit many strategies to reduce oxygen and use Wang et al., 1997; Katiyar & Mukhtar, 1996; Liu,
the energy for metabolism. Reactive oxygen species Wang, Crist, Wang, Lou, Huang et al., 1998; Lu, Lou,
damage molecules by reacting with cell contents via Xie, Yen, Huang & Conney, 1997; Wang, Huang, Lou,
unregulated pathways. Usually this is prevented by Xie, Reulh, Newmark et al., 1994). Topical application
compartimentalization by lipid membranes inside the or oral ingestion of green tea polyphenols by mice sig-
cell and protective tools like enzymes and antioxidants ni®cantly prevents tumor initiation by carcinogens and414 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 the conversion of benign to malignant tumors induced against Escherichia coli, Pseudomonas aeruginosa or by free radicals (Katiyar & Mukhtar, 1996; Katiyar, Aeromonas hydrophila (Toda et al., 1989). Black and Agarwal & Mukhtar, 1993; Wang, Huang, Chang, Ma, green tea extracts can also kill Helicobacter pylori asso- Ferraro, Reulh et al., 1992). Green tea extract can pro- ciated with gastric, peptic and duodenal ulcer diseases tect DNA against scission induced by gamma-ray (Diker & Hascelik, 1994). However, the tea concentra- radiation, another causative factor of mutation and tion used in these studies exceeded normal human con- carcinogenesis (Yoshioka, Akai, Yoshinaga, Hasegawa sumption levels. Tea polyphenols can selectively inhibit & Yoshioka, 1996). Tea can also protect liver, pancreas, the growth of clostridia and promote the growth of prostate and mammary gland against cancer induction bi®dobacteria in human large intestine. The bacterial and carcinoma growth in rodent studies (Katiyar & balance in intestinal micro¯ora may be important for Mukhtar, 1996; Rogers, Hafer, Iskander & Yang, 1998; the prevention of colon cancer (Okubo & Juneja, 1997). Yang & Wang, 1993). Green tea polyphenols can inhibit Antimicrobial activity against cariogenic and period- liver monooxygenase activity or cytochrome P450 ontal bacteria have been reported. Tea polyphenols dependant carcinogen metabolism (Yang & Wang, inhibit Streptococcus mutans (Sakanaka, Kim, Tani- 1993) and protect gap junctional intercellular commu- guchi & Yamamoto, 1989), S. sobrinus (Sakanaka, Sato, nication (Katiyar & Mukhtar, 1996). The anti-invasive Kim & Yamamoto, 1990) and Porphyromonas gingiva- activity observed with tea ingestion can be related to the lis, bacteria responsible for tooth decay (Kakuda, Taki- binding of catechins with a glycoprotein and the sub- hara, Sakane & Mortelmans, 1994; Sakanaka, Aizawa, sequent decreased adhesion of the malignant cells to the Kim & Yamamoto, 1996). They hinder the synthesis of extracellular matrix (Yang & Wang, 1993). EGCG can insoluble glucans by glucosyltransferases, and the inhibit tumor promotion by dierent mechanisms. It sucrose-dependant bacteria cell adherence to tooth and reduces the binding of tumor promoters, hormones, epithelium, by reducing collagenase activity (Mitscher et cytokine and growth factors by a sealing eect on the al., 1997; Sakanaka et al., 1990, 1996). Nerolidol in the cell membrane in mouse skin while ECG, EGCG and volatile fraction of green tea, and ¯uoride also present EGC inhibit TNF-a release induced by tumor promoter in green tea, contribute to the antibacterial action of tea of cancer cells in surrounding tissue in a human cancer extracts against Streptococcus mutans (Antony & Shan- cell line (Fujiki, Suganuma, Okube, Sueoka, Suga, Imai karanaryana, 1997). Polyphenols and sesquiterpenes of et al., 1999). One study suggests that EGCG can inhibit tea have a synergistic eect on the antibacterial activity the proteolytic enzyme urokinase, essential for cancer and the anticariogenic properties of tea (Kakuda et al., growth, and also hinders the proliferation of metastasis 1994). Cariogenic bacteria release lactic acid that (Jankun, Selman & Swiercz, 1997). But EGCG can also destroy tooth enamel, but tea can increase the acid inhibit directly telomerase activity in cancer cells and resistance of teeth to these injuries (Gutman & Ryu, thus block their proliferative capacity (Naasani, Seimiya 1996). Protection against caries by tea polyphenols has & Tsuruo, 1998). Quercetin is a potential suppressor of been demonstrated with rats (Antony & Shankaranar- the multi-drug resistance observed in cancer chemo- yana, 1997). therapy (Inoue, Trevanich, Tsujimoto, Miki, Miyabe, Some results indicate that tea catechins are potentially Sugiyama et al., 1996). antiviral and antiprotozoiac agents (Gutman & Ryu, The action of tea constituents against cancers is 1996). EGCG agglutinates and inhibits in¯uenza A and demonstrated in many studies with animals, but B viruses in animal cell culture (Mitscher et al., 1997). research with humans is lacking. A recent study indi- An antiviral activity has been found against HIV virus cates that tea polyphenols have chemopreventive eects enzymes and against rotaviruses and anteroviruses in on oral mucosa leukoplakia patients (Li, Sun, Han & monkey cell culture when previously treated with Chen, 1999). EGCG (Mitscher et al., 1997). 3.2.6. Antibacterial and antiviral activity 3.2.7. Diabetes and renal failure Green tea catechins have demonstrated antibacterial Diabetes is associated with a high blood glucose con- activity against both Gram-positive and Gram-negative tent. Green and black tea extracts can decrease sig- bacteria which can be harmful to humans. Tea extracts ni®cantly the blood glucose level of aged rats by inhibit enteric pathogens such as Staphylococcus aureus, reducing the glucose absorption and uptake in dierent S. epidermis, Plesiomonas shigelloides (Toda, Okubo, ways (Zeyuan, Bingying, Xiaolin, Jinming & Yifeng, Hiyoshi & Tadakatsu, 1989), Salmonella typhi, S. tiphi- 1998). It is reported that tea polyphenolics inhibit murium, S. enteritidis, Shigella ¯exneri, S. disenteriae alpha-amylase activity in saliva, reduce the intestinal and Vibrio cholerae, V. parahaemolyticus (Mitscher et amylase activity which in turn lowers the hydrolysis of al., 1997; Toda et al., 1989; Toda, Okubo, Ikigai, starch to glucose and reduces glucose assimilation (Hara Suzuki, Suzuki & Shimamura, 1991), Campylobacter et al., 1995f). It was also found that tea reduces the jejuni and C. coli (Diker et al., 1991) but are not eective glucose mucosal uptake because polysaccharides inhibit
C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 415
the glucose absorption and the diphenylamine of tea 4. Bene®cial eects of Kombucha
promotes its metabolism (Zeyuan et al., 1998). Poly-
phenols can also decrease digestive enzyme activity and 4.1. Chemical composition
reduce glucose absorption (Zeyuan et al., 1998). They
decrease uremic toxin levels and the methylguanidine of To produce Kombucha, black tea ingredients and
hemodialysis patients. (Sakanaka & Kim, 1997) Poly- sucrose undergo progressive modi®cation by the action
phenols also protect against oxidative stress associated of the tea fungus. The main metabolites identi®ed in the
with late complications in diabetes pathology and are fermented beverage are: acetic, lactic, gluconic and glu-
useful to maintain a balance between pro- and anti-oxi- curonic acids, ethanol and glycerol (Blanc, 1996; Liu et
dants in the organism (Zeyuan et al., 1998). al., 1996). Some chemical structures of important
Tea consumption is associated with an increase in ingredients reported in Kombucha are given in Fig. 2.
urine volume and electrolyte elimination, notably The presence of usnic acid in Kombucha reported once
sodium, along with a blood pressure decrease (systolic has not been con®rmed in recent studies (Blanc, 1996).
and diastolic values) in hypertensive adenine-induced Usnic acid had been previously identi®ed in lichens and
rats (Yokozawa, Oura, Sakanaka, Ishigaki & Kim, can deactivate some groups of viruses. The metabolite
1994). Green tea catechins can suppress the progression composition and concentration depends on the tea fun-
of renal failure induced in rats or in renal cell culture, gus source, sugar concentration, and the time course of
relieve the related mesangial proliferation and glo- fermentation. With 50 g/l sucrose, concentrations of
merular sclerotic lesions and reduce levels of uremic tox- ethanol and of lactic acid are optimal (Reiss, 1994).
ins in the blood (Yokozawa, Chung, Young, Li & Oura, Yeast and bacteria in the tea fungus make use of sub-
1996; Yokozawa, Dong, Chung, Oura & Nakagawa, strates by dierent and complementary ways. Yeast cells
1997; Yokozawa, Dong, Nakagawa, Kashiwagi et al., hydrolyse sucrose into glucose and fructose, and pro-
1998; Yokozawa, Dong, Nakagawa, Kim et al., 1998). duce ethanol, with a preference for fructose as a sub-
strate (Sievers et al., 1995). Acetic bacteria utilize
3.2.8. Other protective eects of tea glucose to produce gluconic acid (Sievers et al., 1995),
Theanine, the major amino acid in green tea, can and ethanol to produce acetic acid (Yurkevich & Kuty-
reduce blood pressure and hypertension in rats. Thea- shenko, 1998). The presence of lactic acid was not
nine has an equilibrating eect on the central nervous observed in these studies but has been reported in
system and suppresses the increase in activity level another. In this study, the lactic acid synthesis is attrib-
induced by caeine (Hara et al., 1995f). This amino uted to the action of lactic bacteria on ethanol and
acid acts as a neurotransmitter in brain and can pro- acetic acid (Reiss, 1994). It is also reported that the fer-
mote the synthesis of nerve growth factor as epinephrine mentation process induces the synthesis of the B com-
does in rats (Chu, Kobayashi, Juneja & Yamamoto, plex of vitamins and folic acid (Roche, 1998). The pH
1997). Green tea extract administrated to rats 1 h before value of Kombucha decreases during the fermentation
an ethanol intake promotes alcohol metabolism. The process following the increase in the organic acid con-
results suggest that caeine and EGCG act together, tent (Blanc, 1996; Riess, 1994; Sievers et al., 1995).
caeine improving the alcohol metabolism and EGCG More complex interactions probably occur but have not
detoxifying by its antioxidant action (Kakuda, Sakane, been elucidated. It is not known how the composition of
Takihara, Tsukamoto, Kanegae & Nagoya, 1996). Tea the tea itself is aected during fermentation or how it is
extracts contain the ¯avonols quercetin, kaempferol, transformed.
and myricetin, known for their antiallergic eects: they
inhibit hyaluronidase activity and histamine release 4.2. Biological activity
(Toyoda, Tanaka, Hoshino, Akiyama, Tanimura &
Saito, 1997). Green tea can impart a protective Kombucha has been consumed in many countries for
eect against environmental pollutants by the preserva- a very long time. Many bene®ts for health have been
tion of protein thiol levels and cell viability (Miyagawa, reported based on personal observation and testimo-
Wu, Kennedy, Nakatani, Othani, Sakanaka et al., 1997). nials (Greenwalt, Ledford & Steinkraus, 1998). How-
Tea has a bene®cial protective activity on several life- ever, few properties have been demonstrated by
sustaining systems in the human body and it is easy scienti®c and experimental studies. The drink has been
to conclude that drinking tea has positive eects to studied intensively since 1852, mainly in Europe, and
maintain a healthy condition and to delay action of the has been reviewed (Allen, 1998; Stadelmann, 1961).
aging process. Studies about mechanisms underlying Reported eects have been extracted from reviews and
the bene®cial properties of tea on human health are surveys on the web site: ``The Kombucha Center'' (Fer-
progressing (Weisburger, 1999). The impact of tea con- guson & Estelle, 1998; Full Circle Press, 1998) and are
sumption on longevity is not well covered by the scien- listed in Table 1. First reports coming from Russia at
ti®c literature. the beginning of this century and during World War I416 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421
stated that the ``Russian secret home remedy'' also Oncological Research Unit'' and the ``Russian Academy
called ``Wonderdrink'' helped for headaches, gastric ill- of Sciences in Moscow'' found that the daily consump-
nesses, and especially regulates intestinal activities often tion of Kombucha was correlated with an extremely
disturbed by the lifestyle in the army (Allen, 1998). high resistance to cancer. The 1960's, researches reaf-
Between 1925 and 1950, several medical studies con- ®rmed the cancer healing properties of Kombucha, its
ducted by doctors and physicians con®rmed the tradi- detoxifying eects and proposed that a long term con-
tional claims about Kombucha and reported bene®cial sumption increased the immune system performance
eects such as antibiotic properties, regulation of gas- and boosted interferon production. The Russian ®nd-
tric, intestinal and glandular activities, relief of joint ings about Kombucha properties were further sup-
rheumatism, gout and haemorrhoids, positive in¯uence ported in Switzerland, Germany and Netherlands
on the cholesterol level, arteriosclerosis, toxin excretion (Allen, 1998). A recent study reported the antibiotic
and blood cleansing, diabetes, nervousness, and aging activity of Kombucha against Helicobacter pylori,
problems (Allen, 1998). The methodology used in these Esherichia coli, Staphylococcus aureus and Agrobacter-
studies remains unclear. In 1951, an important popula- ium tumefaciens mainly related to the acetic acid pro-
tion study conducted in Russia by the ``Central duced during the fermentation (Steinkraus, Shapiro,
Hotchkiss & Mortlock, 1996). Tea extracts used at the
same concentration did not exhibit any eect. A study on
the antimicrobial activity of some organic acids indicated
that acetic acid can inhibit fungal growth and presents a
mild activity at low pH against lactic acid bacteria
(Matsuda, Yano, Maruyama & Kumagai, 1994). In the
same conditions and over a range of pH values, d and l-
lactic acid inhibit lactic acid bacteria but present no
activity against fungi while gluconic acid exhibits only
weak activities against both types of microorganisms.
Most properties of Kombucha are attributed to the
acidic composition of the beverage. Its detoxifying
Fig. 2. Chemical structure of some Kombucha constituents. property is presumably due to the capacity of glucuronic
Table 1
Reported eects of Kombucha from drinker's testimony (a: Furguson and Estelle, 1998; b: Full Circle Press, 1998) and Russian researches (c: Allen,
1998) compared to the health eects of tea demonstrated by scienti®c studies previously reviewed in this paper
Kombucha Tea
Detoxify the body [a, b]
Reduce cholesterol level [c] x
Reduce atherosclerosis by the regeneration of cellular walls [c] x
Reduce blood pressure [a, c] x
Reduce in¯ammatory problems [c] x
Alleviate arthritis, rheumatism and gout symptoms [a, b, c]
Promote liver functions [c] x
Normalize intestinal activity and balance intestinal ¯ora, cured haemorrhoids [b, c]
Reduce obesity and regulate the appetite [b, c]
Prevent/heal bladder infection and reduce kidney calci®cation [b, c]
Stimulate the glandular system [c]
Protect against diabetes [c] x
Increase the body resistance to cancer [c] x
Have an antibiotic eect against bacteria, viruses and yeasts [a, b, c] xa
Enhance the immune system and stimulate interferon production [c]
Relieve bronchitis and asthma [a, b]
Reduce menstrual disorders and menopausal hot ¯ashes [a, b]
Improve hair, skin and nail health [a, b, c]
Reduce alcoholic's craving for alcohol [a, b]
Reduce stress and nervous disturbances, insomnia [a, b, c]
Help for headaches [b, c]
Improve eyesight [a, b]
Counteract aging problems [a, c]
Enhance general metabolism [c]
a
The eects are observed at high concentrations of tea only.C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421 417
acid to bind to toxin molecules and to increase their them has been reported. But some eects of Kombucha
excretion from the organism by the kidneys or the intake are similar to those postulated for tea itself. The
intestines. Gout, rheumatism, arthritis or kidney stones report from the Russian cancer research project among
likely produced by the accumulation of toxins in the populations after World War II, associated the habit of
body may be relieved this way. Heavy metals or envir- drinking ``tea kvass'' to a low cancer incidence in de®-
onmental pollutants can also be excreted through the nite areas (Roche, 1998). This observation could be
kidneys after glucuronidation. However, the presence of linked to the anti-cancer activity identi®ed in tea alone
glucuronic acid in Kombucha and the formation of but raises questions. For a better insight, the biological
glucuronide complexes associated with its consumption activities attributed to tea and to Kombucha are com-
is much debated (Homann, 1998). A more recent study pared in Table 1. How tea composition is altered by the
indicates that the substance identi®ed in Kombucha as fermentation process has not been elucidated. Catechins
glucuronic acid is more likely 2-keto-gluconic acid are more and more recognized as responsible for the
(Roussin, 1999). High levels of glucuronides are found strong antioxidant activity, and the anti-cancer, anti-
in the urine of Kombucha drinkers and two explana- atherosclerosis, anti-in¯ammatory, and anti-diabetes
tions have been proposed. The ®rst suggests that this properties of tea extracts. It is possible that these bene-
increase is associated to an increase in glucuronic acid ®ts attributed to Kombucha relate to the catechin con-
intake alone and the second attributes it to the presence tent of tea itself. But catechin activity can also be
of a potent beta-glucuronidase inhibitor that could be modi®ed by the chemical environment in the fermented
saccharic acid 1,4-lactone which is also found in Kom- beverage. For example, it has been reported that toco-
bucha (Roussin, 1999). In fact, it is not glucuronic acid pherol and ascorbic acid exert strong synergistic eects
that plays an important role in the detoxifying process, on the antioxidant activity of tea catechins in a linoleic
but UDP-glucuronic acid, the active form, found in the acid system (Hara et al., 1995f). Synergistic anti-
liver (Homann, 1998). UDP-glucuronic acid is not microbial activity of ethanol, acetic acid, sodium chlor-
found in Kombucha but several intermediate products of ide and essential oil has been demonstrated in vitro
the glucuronic acid pathway have been found such as sac- (Kurita & Koike, 1983). These kinds of interactions can
charic acid, ascorbic acid and saccharolactone (Homann, be expected in Kombucha and merit more attention. It
1998). Much more work is needed to elucidate the agents is likely that the eects reported for Kombucha such as
and mechanisms implicated in the detoxifying process. stimulation of the immune system, digestion and liver
The action of Kombucha intake on the nervous sys- function improvement or the enhancement of general
tem could be associated with its content of the B com- metabolism may be the result of both attributes asso-
plex of vitamins (Roche, 1998). It has been observed ciated with tea and/or changes brought about by fer-
that patients suering from cancer do not have l-lactic mentation.
acid in their connective tissues and have a blood pH
higher than 7.56. Kombucha can re-equilibrate the blood
pH and the lactic acid concentration (Roche, 1998). The 6. Kombucha: between a panacea and a dangerous
laxative activity of Kombucha is also attributed to its drink
lactic acid content (Reiss, 1994). There are some indi-
cations that lactic acid bacteria can also exert immu- Although the consumption of Kombucha generally
nostimulatory eects in the host (Marteau & Rambaud, presents no adverse side eects, a few cases of health
1993) but at this time, it is not known if micro-organ- disorders have been reported. Upset stomach, some
isms present in Kombucha can colonize the human allergic reactions, particularly for those predisposed to
gastrointestinal system. Studies generally lack rigorous acid sensitivities, and renal insuciencies are usually
experimental investigation and mechanisms of action improved by ceasing or lowering consumption (Frank,
remain uncertain or unknown. 1998). Four cases of possible toxic reactions and two
The tea fungus is also used for medical purposes in cases of unexplained severe metabolic acidosis have
skin therapy. The cellulosic pellicle formed mainly by been reported apparently related to Kombucha (Srini-
Acetobacter xylinum during the fermentation of tea has vasan, Smolinske & Greenbaum, 1997). One case of
been used as a temporary skin substitute on burns and possible hepatotoxicity (Perron, Patterson & Yanofsky,
in other skin injuries (Fontana, Franco, De Souza, Lyra 1995) and one case of skin disease (Sadjadi, 1998) have
& De Souza, 1991). also been reported. Mechanisms of adverse eects have
not been elucidated. When taking Kombucha, it is
recommended to drink plenty of water to facilitate the
5. The bene®ts of tea and more? elimination of toxins and to adjust consumption to any
body reaction (Full Circle Press, 1998). Persons suer-
Tea and Kombucha are presented in the literature as ing from severe aiction should be aware of adverse
two very distinct beverages and no correlation between side-eects brought about by Kombucha consumption.418 C. Dufresne, E. Farnworth / Food Research International 33 (2000) 409±421
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