Scientific Opinion on the substantiation of health claims related to Camellia
sinensis (L.) Kuntze (tea), including catechins in green tea and tannins in
black tea, and protection of DNA, proteins and lipids from oxidative
damage (ID 1103, 1276, 1311, 1708, 2664), reduction of acid production in
dental plaque (ID 1105, 1111), maintenance of bone (ID 1109), decreasing
potentially pathogenic intestinal microorganisms (ID 1116), maintenance of
vision (ID 1280), maintenance of normal blood pressure (ID 1546) and
maintenance of normal blood cholesterol concentrations (ID 1113, 1114)
pursuant to Article 13(1) of Regulation (EC) No 1924/2006[sup]1[/sup]
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3
European Food Safety Authority (EFSA), Parma, Italy
Słowa kluczowe:
Camellia sinensis (L.) Kuntze
DNA
black tea
blood cholesterol
blood pressure
bone
catechins
dental plaque
green tea
health claims
lipids
oxidative damage
potentially pathogenic intestinal microorganisms
proteins
tannins
tea
vision
1. Charakterystyka żywności / składnika
The food constituent that is the subject of the health claims is Camellia sinensis (L.) Kuntze, catechins present in green tea, and epigallo-catechin-3-gallate.
In the wording of claim ID 1105, tannins and fluoride are named as active ingredients in tea in relation to a claimed effect on oral health. The Panel refers to its previous opinion on fluoride in the context of the evaluation of Article 13 claims (EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA), 2009); the effects of fluoride (irrespective of the source) on tooth mineralisation will not be considered further in this Opinion.
The plant Camellia sinensis (L.) Kuntze is an evergreen shrub of the Theaceae family. Tea is an extract of the dried leaves from Camellia sinensis (L.) Kuntze and it is usually prepared by infusing the leaves in hot water. The composition of the tea leaves depends on a variety of factors, including climate, season, horticultural practices, and the type and age of the plant. Many kinds of tea are produced, which can be classified into three major types according to the different levels of fermentation: green (un-fermented), oolong (semi-fermented) and black (fully fermented) (Wang et al., 2000).
The composition of tea beverages greatly depends on the type of leaves used, on the degree of fermentation and on the methods of preparation (Kaszkin et al., 2004; Astill et al., 2001). The level of fermentation, the production process, and the method for preparing the tea infusion have not been described in relation to the claims.
Green tea contains polyphenolic compounds, which include flavanols, flavandiols, flavonoids, and phenolic acids. Most of the polyphenols in green tea are catechins. Epigallo-catechin-3-gallate (EGCG) is the most abundant catechin in green tea. In black teas, the most abundant polyphenols are tannins, mainly theaflavin and thearubigin (Mukhtar and Ahmad, 2000). Tea extracts/infusions also contain variable amounts of potentially active food constituents, such as caffeine, theanine or theogallin.
Green tea catechins (including EGCG) and tannins in black tea (mainly theaflavin and thearubigin) can be measured in foods by established methods.
The Panel considers that whereas Camellia sinensis (L.) Kuntze (tea) is not sufficiently characterised in relation to the claimed effects, catechins in green tea (including EGCG) and tannins in black tea (for ID 1105) are sufficiently characterised.
2. Znaczenie oświadczenia dla zdrowia człowieka
2.1. Ochrona DNA, białek i lipidów przed uszkodzeniem oksydacyjnym (ID 1103, 1276, 1311, 1708, 2664)
The claimed effects are “antioxidant”, “natural antioxidant” and “protection of body tissues and cells from oxidative damage”. The Panel assumes that the target population is the general population. In the context of the proposed wordings, the Panel assumes that the claimed effects relate to the protection of body cells and molecules from oxidative damage caused by free radicals.
Reactive oxygen species (ROS) including several kinds of radicals are generated in biochemical processes (e.g. respiratory chain) and as a consequence of exposure to exogenous factors (e.g. radiation, pollutants). These reactive intermediates damage biologically relevant molecules such as DNA, proteins and lipids if they are not intercepted by the antioxidant network which includes free radical scavengers like antioxidant nutrients.
The Panel considers that protection of DNA, proteins and lipids from oxidative damage may be a beneficial physiological effect.
2.2. Zmniejszenie produkcji kwasu w osadzie nazębnym (ID 1105, 1111)
The claimed effects are “oral health” and “teeth”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect relates to the reduction of acid production in dental plaque.
Plaque formation is a stepwise building of a bacterial biofilm on teeth and soft tissues, i.e. a highly specific initial attachment of bacteria to host receptors (saliva, cells), followed by secondary attachment of bacteria binding to already colonising bacteria. Fermentation of carbohydrates in the mouth by acid-producing bacteria lowers plaque pH, which contributes to demineralisation of tooth tissues (Marsh and Nyvad, 2008).
The Panel considers that reduction of acid production in dental plaque is a beneficial physiological effect.
2.3. Utrzymanie prawidłowego stanu kości (ID 1109)
The claimed effect is “bone health”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel notes that the claimed effect relates to the maintenance of normal bone.
The Panel considers that the maintenance of normal bone is a beneficial physiological effect.
2.4. Zmniejszenie ilości potencjalnie patogennych mikroorganizmów jelitowych (ID 1116)
The claimed effect is “gut flora”. The Panel assumes that the target population is the general population.
Gut flora is not sufficiently defined. In the context of the proposed wording, the Panel assumes that the claimed effect refers to aspects of: “maintain healthy gut flora” and “improve the beneficial bacteria after the antibacterial drug intake”.
The numbers/proportions of bacterial groups that would constitute a “healthy gut flora” have not been established. Increasing the number of any groups of bacteria is not in itself considered as beneficial. The Panel considers that no evidence has been provided that aspects of the claimed effect, “maintain healthy gut flora” and “improve the beneficial bacteria after the antibacterial drug intake”, are beneficial to human health.
The Panel considers that “maintain healthy gut flora” in the context of decreasing potentially pathogenic intestinal microorganisms might be a beneficial physiological effect.
2.5. Utrzymanie prawidłowego wzroku (ID 1280)
The claimed effect is “eye health”. The Panel assumes that the target population is the general population.
The Panel considers that maintenance of normal vision is a beneficial physiological effect.
2.6. Utrzymanie prawidłowego ciśnienia tętniczego (ID 1546)
The claimed effect is “cardiovascular health”. The Panel assumes that the target population is the general population.
In the context of the proposed wording, the Panel notes that the claimed effect relates to the maintenance of normal blood pressure.
Blood pressure (BP) is the pressure (per unit area) exerted by circulating blood on the walls of blood
vessels. Elevated BP, by convention 140 mmHg (systolic) and/or 90 mmHg (diastolic), may compromise the normal function of the arteries.
The Panel considers that maintenance of normal blood pressure is a beneficial physiological effect.
2.7. Utrzymanie prawidłowego stężenia cholesterolu we krwi (ID 1113, 1114)
The claimed effects are “cholesterol” and “heart health”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel notes that the claimed effect relates to the maintenance of normal blood cholesterol concentrations.
Low-density lipoproteins (LDL) carry cholesterol from the liver to peripheral tissues, including the arteries. Elevated LDL-cholesterol, by convention >160mg/dL, may compromise the normal structure and function of the arteries.
The Panel considers that maintenance of normal blood cholesterol concentrations is a beneficial physiological effect.
3. Naukowe uzasadnienia wpływu na zdrowie człowieka
3.1. Ochrona DNA, białek i lipidów przed uszkodzeniem oksydacyjnym (ID 1103, 1276, 1311, 1708, 2664)
The vast majority of references provided in the list addressed other topics than Camellia sinensis (L.) Kuntze (tea) or green tea catechins, the claimed effect, or the relationship between the intake of tea/green tea catechins and the claimed effect. These include narrative reviews on polyphenols in general, in vitro testing of the antioxidant properties of different foods, compositional analyses, and
human studies investigating the effects of green tea catechins/polyphenols on cholesterol lowering, cancer prevention, photoprotection, or have been conducted in different patient populations aiming at secondary prevention or at treatment of disease conditions. The Panel considers that no scientific conclusions can be drawn from these references to substantiate the claims.
Some experimental, and generally small-scale, human studies reported that green tea or catechins in green tea are able to increase the total antioxidant activity of plasma measured by various assays including ferric reducing ability of plasma (FRAP), oxygen radical absorbance capacity (ORAC), trolox-equivalent antioxidant capacity (TEAC), and total reactive antioxidant potential (TRAP) (van Amelsvoort et al., 2001; Benzie et al., 1999; Coimbra et al., 2006; Leenen et al., 2000; Pietta et al., 1998; Serafini et al., 1996; Sung et al., 2000), to reduce the formation of malondialdehyde (colorimetric assay) (Coimbra et al., 2006), to increase the oxidation lag time of LDL ex vivo (Luo et al., 1997; van het Hof et al., 1997; Hodgson et al., 2000; Serafini et al., 2000; Ohmori et al., 2005), and to decrease DNA damage to lymphocytes measured by the comet assay (challenging with Fe2+
before electrophoresis) (Erba et al., 2005). The Panel notes that measurements of the total antioxidant activity/potential of plasma are not considered to be markers of oxidative damage, and that the formation of malondialdehyde using a colorimetric assay as well as the resistance of LDL to oxidation are not suitable markers to assess lipid peroxidation (Griffiths et al., 2002; Mayne, 2003; Dalle-Donne et al., 2006; Knasmüller et al., 2008; Dragsted, 2008). The Panel also notes that the variant of the comet assay used in the study by Erba et al. (2005) does not specifically measure DNA oxidative damage but general DNA damage independent of its origin. The Panel considers that no scientific conclusions can be drawn from these studies for the substantiation of the claimed effect.
Two randomised controlled human intervention studies (Hakim et al., 2003; Young et al., 2002) investigated the effects of green tea catechin intake on measures of oxidative damage to DNA and one acute study (Nakagawa et al., 1999) investigated the effects of green tea catechin intake on measures of oxidative damage to body lipids.
In a two times three week blinded human crossover intervention study, volunteers (eight smokers, eight non-smokers, aged 20-31 years) consumed green tea extract (18.8 mg catechins per day) incorporated into meat patties (meat patties without catechins used as control). The intervention did not significantly affect plasma oxidation lag time or urinary 8-OHdG assessed by HPLC-ECD (Young et al., 2002). The Panel notes that the evidence provided does not establish that urinary 8-OHdG reflects oxidised DNA within cells (Cooke et al., 2009).
A total of 143 heavy smokers (aged 18-79 years) were randomised to drink 4 cups per day of either decaffeinated green tea (73.5 mg/cup total catechins), decaffeinated black tea (8.11 mg/cup total catechins) or water during four months (Hakim et al., 2003). Among the 133 smokers who completed the intervention, drinking green tea resulted in a significant decrease in urinary 8-OHdG assessed by ELISA (-31%) compared with water, while no significant change was observed among smokers consuming black tea. The Panel notes that the evidence provided does not establish that urinary 8- OHdG reflects oxidised DNA within cells (Cooke et al., 2009).
The effect of green tea extract (254 mg total catechins/subject) on plasma phosphatidylcholine hydroperoxides (PCOOH by HPLC-CL) was investigated in an acute study with 18 healthy male volunteers (Nakagawa et al., 1999). The Panel notes that, although changes in plasma PCOOH measured by HPLC-CL is an acceptable marker of lipid peroxidation, no conclusions can be drawn from this study in relation to a sustained effect of green tea catechins on lipid peroxidation.
The Panel notes that no studies with appropriate endpoints to assess oxidative damage of DNA within cells or studies investigating a sustained effect of green tea catechins on lipid peroxidation have been presented to substantiate the claimed effect. The Panel also notes that no studies investigating the effect of green tea catechins on oxidative damage to proteins have been presented.
The Panel concludes that a cause and effect relationship has not been established between the consumption of catechins (including EGCG) in green tea (Camellia sinensis (L.) Kuntze) and the protection of DNA, proteins or lipids from oxidative damage.
3.2. Zmniejszenie produkcji kwasu w osadzie nazębnym (ID 1105, 1111)
Publications provided dealing with the effects, intake or bioavailability of food constituents other than Camellia sinensis (L.) Kuntze, tea, tannins in black tea or catechins in green tea (e.g., fluoride, tannic acid, gallotannins from Melaphis chinensis), with the composition of teas, or with claimed effects other than the reduction of acid production in the dental plaque or plaque acid neutralisation (e.g., dental caries, colonisation and glucan production by mutans streptococci, intra oral hydrolysis of complex carbohydrates) were not considered to be pertinent to the claim as no scientific conclusions can be drawn from these references to substantiate the claim.
In one non-controlled intervention study in humans, ten healthy young adults were monitored for tooth surface pH on the palatal aspects of the maxillary anterior and the maxillary molar dentition after drinking black tea (Simpson et al., 2001). The Panel notes the uncontrolled nature of the study, the small number of subjects, the lack of statistical analysis, the fact that pH was only measured on the teeth surface (which greatly depends on the pH of the beverage being consumed) but not acid production, and that the amount of tannins in black tea was not reported.
Two in vitro studies on the effects of green and black tea on the inhibition of growth of different bacteria were presented (Sakanaka et al., 1990; Rasheed and Haider 1998). The Panel considers that the evidence provided in in vitro studies is not sufficient to predict the occurrence of an effect of the consumption of either catechins or tannins in Camellia sinensis (L.) Kuntze on the reduction of acid production in dental plaque.
The Panel notes that no human studies which measured acid production were presented.
The Panel concludes that a cause and effect relationship has not been established between the consumption of either catechins or tannins in Camellia sinensis (L.) Kuntze and reduction of acid production in dental plaque.
3.3. Utrzymanie prawidłowego stanu kości (ID 1109)
One recent publication reviewed the health effects associated with black tea consumption by searching databases for relevant epidemiological and clinical studies published between 1990 and 2004. The number of epidemiological studies on black tea and bone health was small (n=5), and no intervention studies were found (Gardner et al., 2007). This review includes the cross-sectional, observational study including 1,256 UK women aged 65-76 years by Hegarty et al. (2000) submitted separately in the consolidated list. The Panel notes that tea intake is insufficiently characterised in the observational studies above, that the background diet of the study populations is usually not reported (nor adjusted for), and that in the majority of them only current tea consumption was considered.
Green tea contains epigallocatechin-3-gallate (EGCG). The effects of EGCG on osteoblastic bone formation using a human osteoblast (HOB)-like cell line (Vali et al., 2007) and the mRNA expressions of relevant osteogenic markers, alkaline phosphatase (ALP) activity, and mineralisation (Chen et al., 2005) were tested in vitro. The Panel considers that the evidence provided in the in vitro studies is not sufficient to predict the occurrence of an effect of the consumption of Camellia sinensis (L.) Kuntze or any of its components on maintenance of normal bone in humans.
The Panel notes that no human studies which addressed the effects of either catechins or tannins in Camellia sinensis (L.) Kuntze on bone were provided.
The Panel concludes that a cause and effect relationship has not been established between the consumption of either catechins or tannins in Camellia sinensis (L.) Kuntze and maintenance of normal bone.
3.4. Zmniejszenie ilości potencjalnie patogennych mikroorganizmów jelitowych (ID 1116)
Four references were cited to substantiate the claimed effect.
One human study (Okubo et al., 1992) reported the effects of administration of 1200 mg polyphenols on intestinal microflora metabolism over four weeks in eight volunteers (22-48 years). Volunteers received polyphenols in the form of “Sunphenon” (Taiyo Kagaku Co Ltd, Japan) which consists of about 70% polyphenols from tea. The Panel notes that the amount of catechins in the product used for this small sample size study was not reported. The Panel considers that no conclusions can be drawn from this study for the substantiation of the claimed effect.
Three references (Ahn et al., 1990 and 1991; Lee et al., 2006) related to in vitro growth inhibition studies with Camellia sinensis (L.) Kuntze methanol and ethyl acetate/water extracts. The Panel considers that the evidence provided in the in vitro studies is not sufficient to predicting an effect of consumption of catechins from green tea on decreasing potentially pathogenic intestinal microorganisms in humans.
The Panel concludes that a cause and effect relationship has not been established between the consumption of catechins in green tea (Camellia sinensis (L.) Kuntze) and decreasing potentially pathogenic intestinal microorganisms.
3.5. Utrzymanie prawidłowego wzroku (ID 1280)
The references provided included four articles, one describing the possible mechanisms of action of potentially active ingredients in tea (Kaszkin et al., 2004) and three in vitro studies, two of which provided evidence for a reduction in oxidative damage to the retina in response to injection of epigallocatechin (EGCG) into the vitreous humour of animal eyes (Zhang and Osborne, 2006; Zhang et al., 2007). The remaining in vitro study found a reduction in UV related lens damage in a range of animal eyes following immersion in a solution of EGCG (Zigman et al., 1999). The Panel considers that the evidence provided in in vitro studies is not sufficient to predict an effect of consumption of catechins from green tea on maintenance of normal vision in humans.
The Panel concludes that a cause and effect relationship has not been established between the consumption of catechins in green tea (Camellia sinensis (L.) Kuntze) and maintenance of normal vision.
3.6. Utrzymanie prawidłowego ciśnienia tętniczego (ID 1546)
Among the references cited in relation to this claim, two referred to laboratory methods for the assessment of components in tea; three presented data from in vitro experiments, e.g. on the effects of tea on vascular smooth muscle cells; one referred to an animal study reporting on outcomes other than BP; eight reported on human epidemiological studies on the relationship between tea consumption and outcome variables other than blood pressure (e.g., markers of atherosclerosis, coronary artery disease (CAD), myocardial infarction, stroke, obesity, blood lipids, cancer); four reported on non- controlled human intervention studies and one on a randomised controlled trial investigating the effects on tea intake in relation to outcome variables other than BP (e.g. oxidative stress, blood lipids); and seven were (non-systematic) review papers that did not include original data on tea drinking and BP. The Panel considers that no scientific conclusions can be drawn from these references for the substantiation of the claim.
Four human intervention studies (Kim et al., 2006; Duffy et al., 2001; Vlachopoulos et al., 2006; Nagaya et al., 2004) and three human observational studies (Hodgson et al., 2003; Stensvold et al., 1992; Yang et al., 2004) investigating the effects of tea on measurements of BP were cited for the substantiation of the claimed effect.
The Panel notes that one of the intervention studies (Duffy et al., 2001), cited in one of the narrative reviews provided (Vita, 2003), did not address the effects of green tea (including EGCG) but rather of black tea, that a second study lacked a randomised-controlled design (Kim et al., 2006) and that the remaining two intervention studies assessed only the acute effects of green tea consumption on BP, that is green tea was administered on a single occasion (Vlachopoulos et al., 2006; Nagaya et al., 2004). In addition, none of the human intervention studies cited above report on daily intakes of the food constituent that is the subject of this health claim (i.e., EGCG in green tea). The Panel considers that no conclusions can be drawn from these studies for the substantiation of the claimed effect.
Hodgson et al. (2003) performed a cross-sectional epidemiological study in which tea intake and a biomarker of exposure (4-O-methylgallic acid in 24-h urine) were examined in relation to BP. The study included 218 women >70 years old with a mean BP of 138/74 mmHg and a mean daily tea intake of 525 mL. Tea intake comprised both black tea and green tea. A cohort study by Stensvold et al. (1992) examined the relationship between tea consumption and systolic BP. The study included ~20,000 Norwegian women aged 35-49 years with no history of cardiovascular disease or diabetes. The Panel notes that this study also focused on black tea consumption. The Panel considers that no conclusions can be drawn from these studies for the substantiation of the claim.
In a prospective epidemiological study by Yang et al. (2004), tea drinking in relation to the risk of hypertension was studied in 1,507 Taiwanese men and women aged >20 years with no history of hypertension. Detailed data on tea intake were obtained. Six hundred subjects (39.8%) were habitual tea drinkers, defined by tea consumption of 120 mL per day or more for more than one year. Of these, 96.3% were green or oolong tea drinkers and 4.8% added milk to their tea. The Panel notes that this study did not report on daily intakes of the food constituent that is the subject of the health claim (i.e., EGCG in green tea), and therefore considers that no conclusions can be drawn from this study for the substantiation of the claim.
Three animal studies on the relationship between tea consumption and blood pressure were cited (Negishi et al., 2004; Potenza et al., 2007; Ikeda et al., 2007). The Panel considers that the evidence provided in these animal studies is not sufficient to predict the occurrence of an effect of green tea (including EGCG) consumption on the maintenance of normal blood pressure in humans.
In weighing the evidence, the Panel took into account that none of the human studies presented reported on daily intakes of the food constituent that is the subject of the health claim (i.e., EGCG in green tea), and that the evidence provided in the animal studies is not sufficient to predict the occurrence of an effect of green tea (including EGCG) consumption on the maintenance of normal blood pressure in humans.
The Panel concludes that a cause and effect relationship has not been established between the consumption of EGCG in green tea (Camellia sinensis (L.) Kuntze) and the maintenance of a normal blood pressure.
3.7. Utrzymanie prawidłowego stężenia cholesterolu we krwi (ID 1113, 1114)
Two human intervention studies (Erba et al., 2005; Maron et al., 2003) on the effects of green tea catechins on blood cholesterol concentrations and three observational studies on the association between tea consumption and total/LDL-cholesterol concentrations (Tokunaga et al., 2002; Kono et al., 1996; Imai and Nakachi, 1995) were cited in relation to this claim. Three additional human
intervention studies were cited in the publication by Maron et al., (2003) and were considered by the Panel as pertinent to the claim (Princen et al., 1998; van het Hof et al., 1997; Duffy et al., 2001).
In a randomised, placebo-controlled intervention trial (RCT), daily consumption of two cups of green tea containing 250 mg per day total catechins during six weeks did not affect serum total, LDL-, or HDL-cholesterol concentrations in 12 healthy women compared with 12 control women not consuming green tea (Erba et al., 2005). In another parallel comparison RCT, 45 volunteers (aged 18-65 years) were randomised to consume 900 mL per day (6 cups per day) mineral water, 3 g green tea extract (21.4% by weight catechins) or 3 g black tea extract (7.2% by weight catechins) diluted in the same amount of water (900 mL) for four weeks. Consumption of either green or black tea did not change significantly blood lipid concentrations as compared to controls (van het Hof et al., 1997).
Similarly, in a RCT with parallel design, healthy male and female smokers (aged 34 12 years, 13 to 16 subjects per group) consumed 6 cups (900 mL) of either black, green tea or water per day, or received as a supplement 3.6 grams of green tea polyphenols per day (2.5 g per day green tea catechins equivalent to the consumption of 18 cups of green tea per day) for four weeks. Consumption of black tea, green tea or green tea polyphenols had no effect on plasma triglycerides, total-, HDL- or LDL-cholesterol concentrations (Princen et al., 1998). The effect of a theaflavin-enriched green tea extract, 375 mg per day including 75 mg theaflavin, 150 mg green tea catechins, and 150 mg other green tea polyphenols, was studied in 120 Chinese subjects with mild to moderate hypercholesterolaemia in parallel comparison with another 120 subjects who consumed placebo capsules (Maron et al., 2003). The Panel notes that theaflavins are oxidised catechins naturally present in black tea in significant amounts, whereas they are not a major component of green tea catechins. The Panel considers that no conclusions can be drawn from this study for the substantiation of the claim.
In some epidemiological studies, the relationship between green tea consumption and blood total- and LDL-cholesterol concentrations were investigated after adjustment for confounders (Tokunaga et al., 2002; Kono et al., 1996; Imai and Nakachi, 1995). None of these studies reported daily consumption of the food constituent (green tea catechins) that is the subject of the health claim. The Panel considers that no conclusions can be drawn from these studies for the substantiation of the claim.
In weighing the evidence, the Panel took into account that the three small-scale human RCTs presented failed to observe an effect of green tea catechin consumption on blood cholesterol concentrations.
The Panel concludes that a cause and effect relationship has not been established between the consumption of catechins in green tea (Camellia sinensis (L.) Kuntze) and maintenance of normal blood cholesterol concentrations.