![]() |
|
|
Department of Epidemiology, Nutrition, and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, 6200 MD, Maastricht, The Netherlands
* To whom correspondence should be addressed. E-mail: ilja.arts{at}epid.unimaas.nl.
| ABSTRACT |
|---|
|
|
|---|
| Introduction |
|---|
|
|
|---|
Tea, from a biological standpoint, is not a clearly defined substance. All tea is produced from the leaves of Camellia sinensis, but differences in processing result in several types of tea, of which green and black tea are the most consumed worldwide. Moreover, tea is a complex mixture of a large number of bioactive components, including catechins, flavonols, lignans, and phenolic acids. Theaflavins and thearubigins are present only in black tea as a result of oxidative processes (5). All types of tea and the major phenolic compounds present in tea have been the subject of epidemiological studies. The debate is still open as to which of these phenolic compounds might be of primary importance, whether the combination of compounds is essential, or if perhaps unknown components might be responsible for any health-modulating effects of tea.
An earlier review on flavonoids and chronic diseases (6) found evidence suggestive of a lower risk of lung cancer with a higher intake of flavonols/flavones. However, at the time, only 4 cohort studies were available. Data from studies on asthma incidence (7) and lung function (8) also suggested beneficial effects from flavonoids. In an animal study, where rats were given the major flavonol quercetin for 11 wk, the highest tissue concentrations were found in the lung (9). Taken together, these data suggested a beneficial effect of tea and/or flavonoids on lung health. This article provides an overview of observational epidemiological studies considering lung cancer incidence or mortality in relation to intake of green tea, black tea, flavonols/flavones, and catechins.
| Methods |
|---|
|
|
|---|
Case-control studies are vulnerable to recall bias, a phenomenon that leads to attenuation of associations and that occurs because diseased subjects may remember their diet differently from control subjects. Therefore, results from cohort studies and case-control studies were also discussed separately. A second major methodological issue in the analysis of observational studies is confounding. Confounding is particularly important when weak associations are studied in the presence of strong confounders. In the case of the tea/flavonoid-lung cancer association, smoking is one such strong confounder. Even after meticulous adjustment for smoking behavior, residual confounding may exist. To reduce the residual confounding presented by the strong smoking confounder, we also summarized studies that only considered never- or former smokers who had quit >20 y ago.
| Results |
|---|
|
|
|---|
|
|
|
|
| Discussion |
|---|
|
|
|---|
Accurate assessment of exposure to tea and/or flavonoids is not easy. In general, food frequency questionnaires were not designed to assess tea or flavonoid intake. In recent years, assessment of tea consumption has received more attention (45), but certainly baseline measurements of the older epidemiological studies have yielded imprecise exposure estimates. Even if the level of tea consumption is assessed accurately, differences in cultivars and production methods and in brewing methods at home also significantly influence the tea composition (46) and, consequently, the internal exposure to bioactive ingredients. Several databases have been used to estimate flavonoid intake from dietary data. The Dutch values (46–49) that were most frequently used in epidemiological studies are now part of the comprehensive USDA flavonoid database (50), which has rigorous quality control. It is my hope that more studies will use this database in the near future. Inaccurate assessment of exposure to tea/flavonoids has probably led to nondifferential misclassification and an underestimation of the true associations in the epidemiological studies presented here.
Although lung cancer is treated here as a single disease, etiologically and histologically clearly distinct types of lung cancer can be distinguished. Yet few authors of articles on this subject have stratified their data by type of lung cancer. Le Marchand et al. (23) found a stronger inverse trend with quercetin intake among cases with squamous cell carcinoma (OR in the highest quartile = 0.5; 95% CI = 0.2–1.9) compared with cases with adenocarcinoma (OR = 0.9; 95% CI = 0.4–2.0). Similarly, Zhong et al. (35) also reported a lower OR for nonsmoking women with nonadenocarcinomas compared with adenocarcinomas, but the numbers of cases were small, and trends were not significant. Baker et al. (39), on the other hand, found similar associations for black tea intake with different subtypes (adeno-, squamous cell, small cell, and large cell carcinoma) of lung cancer. More research is needed to determine whether lung cancer type is of importance.
Residual confounding occurs if confounders, extraneous factors that are associated with both the outcome and the exposure under study, are not or insufficiently accounted for in the statistical analysis. Studying associations in never-smokers is an effective way of ruling out residual confounding by smoking. Zhong et al. (35) have elegantly shown that the manner in which models are adjusted for confounding by smoking can greatly influence the results. The OR between green tea drinking and lung cancer among women was 1.69 (95% CI = 0.78–3.62) without adjustment for smoking. When 4 categories of pack-years were added to the model, the OR changed to 1.09, whereas adding the number of cigarettes per day (as 3 categories) instead gave an OR of 1.23. A smoothing technique, which allows more precise adjustment for confounding, changed the estimated OR to 1.23 and 0.94 for pack-years and number of cigarettes per day, respectively. So, with use of different techniques to adjust for smoking, the effect estimate changed significantly from 1.69 to 0.94, although none of the estimates was significant. In the same article, Zhong and co-workers (35) also reported the OR for never-smokers, which was 0.65 (95% CI = 0.45–0.93) and significant. Thus, residual confounding for strong confounders such as smoking can lead to higher risk estimates in populations where smoking is associated with tea drinking. Our overview of studies among nonsmokers suggests that, indeed, protective associations become more distinct in this group. On the other hand, when tea drinking is associated with a healthy lifestyle, associations may become more beneficial as a result of residual confounding. More research among never-smokers is needed to resolve this issue, taking into account exposure to environmental smoke and other determinants of lung cancer among never smokers.
In tea-drinking populations, the correlation between tea intake and flavonoid intake is high. For example, in the Zutphen Elderly Study in The Netherlands, the correlation between catechins and tea was 0.98, making the 2 variables essentially interchangeable (18). Which approach is preferred then, the food-based one or the component-based approach? Of course that depends on the hypothesized mechanism: if flavonoids are considered to be the active compounds in tea, then it makes more sense to look at flavonoids directly. In countries where tea intake is low, such as many Mediterranean countries, other sources of flavonoids will become important. However, if other compounds in tea, or combinations of compounds, are believed to be important, then tea would be the preferred exposure. In that case, calculating flavonoid intake will merely introduce additional error. The results presented in this overview show that a similar picture emerges, whether tea or flavonoids are used as exposure estimates. For catechins, too few studies have been published to draw any conclusions. Despite its drawbacks, observational epidemiology is the only type of research that is able to assess the effects of long-term exposure to physiological doses of bioactive compounds on real disease endpoints. It therefore has great value in the study of the association between intake of tea and flavonoids and lung cancer risk. Accumulating more data from well-designed studies, together with more mechanistic intervention studies, will bring us closer to firm conclusions about the health effects of tea and its bioactive ingredients.
Other articles in this supplement include references (51–60).
| FOOTNOTES |
|---|
2 I. C. W. Arts is supported by a VENI Innovational Research Grant from the Netherlands Organisation for Scientific Research—Earth and Life Sciences (NWO-ALW). ![]()
3 Author disclosure: I. C. W. Arts received compensation from the supplement sponsor for speaking at the Fourth International Scientific Symposium on Tea and Human Health. ![]()
| LITERATURE CITED |
|---|
|
|
|---|
1. Higginson J. Etiological factors in gastrointestinal cancer in man. J Natl Cancer Inst. 1966;37:527–45.[Medline]
2. Sun CL, Yuan JM, Koh WP, Yu MC. Green tea, black tea and colorectal cancer risk: a meta-analysis of epidemiologic studies. Carcinogenesis. 2006;27:1301–9.
3. Sun CL, Yuan JM, Koh WP, Yu MC. Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies. Carcinogenesis. 2006;27:1310–5.
4. Steevens J, Schouten LJ, Verhage BA, Goldbohm RA, van den Brandt PA. Tea and coffee drinking and ovarian cancer risk: results from the Netherlands Cohort Study and a meta-analysis. Br J Cancer. 2007;97:1291–4.[Medline]
5. Balentine DA, Wiseman SA, Bouwens LCM. The chemistry of tea flavonoids. Crit Rev Food Sci Nutr. 1997;37:693–704.[Medline]
6. Arts ICW, Hollman PCH. Polyphenols and disease risk in epidemiologic studies. Am J Clin Nutr. 2005;81:317S–25S.
7. Knekt P, Kumpulainen J, Jarvinen R, Rissanen H, Heliovaara M, Reunanen A, Hakulinen T, Aromaa A. Flavonoid intake and risk of chronic diseases. Am J Clin Nutr. 2002;76:560–8.
8. Tabak C, Arts ICW, Smit HA, Heederik D, Kromhout D. Chronic obstructive pulmonary disease and intake of catechins, flavonols, and flavones. The MORGEN Study. Am J Respir Crit Care Med. 2001;164:61–4.
9. de Boer VCJ, Dihal AA, van der Woude H, Arts ICW, Wolffram S, Alink GM, Rietjens IMCM, Keijer J, Hollman PCH. Tissue distribution of quercetin in rats and pigs. J Nutr. 2005;135:1718–25.
10. Heilbrun LK, Nomura A, Stemmermann GN. Black tea consumption and cancer risk: a prospective study. Br J Cancer. 1986;54:677–83.[Medline]
11. Huang C, Zhang X, Qiao Z, Guan L, Peng S, Liu J, Xie R, Zheng L. A case-control study of dietary factors in patients with lung cancer. Biomed Environ Sci. 1992;5:257–65.[Medline]
12. Kinlen LJ, Willows AN, Goldblatt P, Yudkin J. Tea consumption and cancer. Br J Cancer. 1988;58:397–401.[Medline]
13. Kuriyama S, Shimazu T, Ohmori K, Kikuchi N, Nakaya N, Nishino Y, Tsubono Y, Tsuji I. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006;296:1255–65.
14. Hertog MG, Feskens EJ, Hollman PC, Katan MB, Kromhout D. Dietary flavonoids and cancer risk in the Zutphen Elderly Study. Nutr Cancer. 1994;22:175–84.[Medline]
15. Knekt P, Jarvinen R, Seppanen R, Hellovaara M, Teppo L, Pukkala E, Aromaa A. Dietary flavonoids and the risk of lung cancer and other malignant neoplasms. Am J Epidemiol. 1997;146:223–30.
16. Goldbohm RA, Hertog MGL, Brants HAM, Van Poppel G, Van den Brandt PA. Intake of flavonoids and cancer risk: a prospective cohort study. In: Amadò R, Andersson H, Bardosz S, Serra F, editors. Polyphenols in Food. Office for Official Publications of the European Communities, Luxembourg 1998: Proceeding of the 1st workshop of the COST 916 Action; 1997 Apr 16–9, Aberdeen, Scotland. EUR 18169 EN. p. 159–66.
17. Hirvonen T, Virtamo J, Korhonen P, Albanes D, Pietinen P. Flavonol and flavone intake and the risk of cancer in male smokers (Finland). Cancer Causes Control. 2001;12:789–96.[Medline]
18. Arts ICW, Hollman PCH, Bueno de Mesquita HB, Feskens EJM, Kromhout D. Dietary catechins and epithelial cancer incidence: The Zutphen elderly study. Int J Cancer. 2001;92:298–302.[Medline]
19. Arts ICW, Jacobs DR, Jr., Gross M, Harnack LJ, Folsom AR. Dietary catechins and cancer incidence among postmenopausal women: the Iowa Women's Health Study (United States). Cancer Causes Control. 2002;13:373–82.[Medline]
20. Wright ME, Mayne ST, Stolzenberg-Solomon RZ, Li Z, Pietinen P, Taylor PR, Virtamo J, Albanes D. Development of a comprehensive dietary antioxidant index and application to lung cancer risk in a cohort of male smokers. Am J Epidemiol. 2004;160:68–76.
21. Garcia-Closas R, Agudo A, Gonzalez CA, Riboli E. Intake of specific carotenoids and flavonoids and the risk of lung cancer in women in Barcelona, Spain. Nutr Cancer. 1998;32:154–8.[Medline]
22. De Stefani E, Boffetta P, Deneo-Pellegrini H, Mendilaharsu M, Carzoglio JC, Ronco A, Olivera L. Dietary antioxidants and lung cancer risk: a case-control study in Uruguay. Nutr Cancer. 1999;34:100–10.[Medline]
23. Le Marchand L, Murphy SP, Hankin JH, Wilkens LR, Kolonel LN. Intake of flavonoids and lung cancer. J Natl Cancer Inst. 2000;92:154–60.
24. Lagiou P, Samoli E, Lagiou A, Katsouyanni K, Peterson J, Dwyer J, Trichopoulos D. Flavonoid intake in relation to lung cancer risk: case-control study among women in Greece. Nutr Cancer. 2004;49:139–43.[Medline]
25. Goldbohm RA, Hertog MG, Brants HA, van Poppel G, van den Brandt PA. Consumption of black tea and cancer risk: a prospective cohort study. J Natl Cancer Inst. 1996;88:93–100.
26. Zheng W, Doyle TJ, Kushi LH, Sellers TA, Hong CP, Folsom AR. Tea consumption and cancer incidence in a prospective cohort study of postmenopausal women. Am J Epidemiol. 1996;144:175–82.
27. Nakachi K, Matsuyama S, Miyake S, Suganuma M, Imai K. Preventive effects of drinking green tea on cancer and cardiovascular disease: epidemiological evidence for multiple targeting prevention. Biofactors. 2000;13:49–54.[Medline]
28. Nagano J, Kono S, Preston DL, Mabuchi K. A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan). Cancer Causes Control. 2001;12:501–8.[Medline]
29. Koo LC. Dietary habits and lung cancer risk among Chinese females in Hong Kong who never smoked. Nutr Cancer. 1988;11:155–72.[Medline]
30. Mettlin C. Milk drinking, other beverage habits, and lung cancer risk. Int J Cancer. 1989;43:608–12.[Medline]
31. Tewes FJ, Koo LC, Meisgen TJ, Rylander R. Lung cancer risk and mutagenicity of tea. Environ Res. 1990;52:23–33.[Medline]
32. Ohno Y, Wakai K, Genka K, Ohmine K, Kawamura T, Tamakoshi A, Aoki R, Senda M, Hayashi Y, et al. Tea consumption and lung cancer risk: a case-control study in Okinawa, Japan. Jpn J Cancer Res. 1995;86:1027–34.
33. Axelsson G, Liljeqvist T, Andersson L, Bergman B, Rylander R. Dietary factors and lung cancer among men in west Sweden. Int J Epidemiol. 1996;25:32–9.
34. Mendilaharsu M, De Stefani E, Deneo-Pellegrini H, Carzoglio JC, Ronco A. Consumption of tea and coffee and the risk of lung cancer in cigarette-smoking men: a case-control study in Uruguay. Lung Cancer. 1998;19:101–7.[Medline]
35. Zhong L, Goldberg MS, Gao YT, Hanley JA, Parent ME, Jin F. A population-based case-control study of lung cancer and green tea consumption among women living in Shanghai, China. Epidemiology. 2001;12:695–700.[Medline]
36. Hu J, Mao Y, Dryer D, White K. Risk factors for lung cancer among Canadian women who have never smoked. Cancer Detect Prev. 2002;26:129–38.[Medline]
37. Kubik AK, Zatloukal P, Tomasek L, Pauk N, Havel L, Krepela E, Petruzelka L. Dietary habits and lung cancer risk among non-smoking women. Eur J Cancer Prev. 2004;13:471–80.[Medline]
38. Bonner MR, Rothman N, Mumford JL, He X, Shen M, Welch R, Yeager M, Chanock S, Caporaso N, Lan Q. Green tea consumption, genetic susceptibility, PAH-rich smoky coal, and the risk of lung cancer. Mutat Res. 2005;582:53–60.[Medline]
39. Baker JA, McCann SE, Reid ME, Nowell S, Beehler GP, Moysich KB. Associations between black tea and coffee consumption and risk of lung cancer among current and former smokers. Nutr Cancer. 2005;52:15–21.[Medline]
40. Kubik A, Zatloukal P, Tomasek L, Pauk N, Havel L, Dolezal J, Plesko I. Interactions between smoking and other exposures associated with lung cancer risk in women: diet and physical activity. Neoplasma. 2007;54:83–8.[Medline]
41. Nagao M, Takahashi Y, Yamanaka H, Sugimura T. Mutagens in coffee and tea. Mutat Res. 1979;68:101–6.[Medline]
42. Peters U, Poole C, Arab L. Does tea affect cardiovascular disease? A meta-analysis. Am J Epidemiol. 2001;154:495–503.
43. Albanes D, Heinonen OP, Taylor PR, Virtamo J, Edwards BK, Rautalahti M, Hartman AM, Palmgren J, Freedman LS, et al. Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. J Natl Cancer Inst. 1996;88:1560–70.
44. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA. 2007;297:842–57.
45. Hakim IA, Hartz V, Harris RB, Balentine D, Weisgerber UM, Graver E, Whitacre R, Alberts D. Reproducibility and relative validity of a questionnaire to assess intake of black tea polyphenols in epidemiological studies. Cancer Epidemiol Biomarkers Prev. 2001;10:667–78.
46. Arts ICW, van de Putte B, Hollman PCH. Catechin contents of foods commonly consumed in The Netherlands. 2. Tea, wine, fruit juices, and chocolate milk. J Agric Food Chem. 2000;48:1752–7.[Medline]
47. Hertog MGL, Hollman PCH, Van de Putte B. Content of potentially anticarcinogenic flavonoids of tea infusions, wines, and fruit juices. J Agric Food Chem. 1993;41:1242–6.
48. Hertog MGL, Hollman PCH, Katan MB. Content of potentially anticarcinogenic flavonoids of 28 vegetables and 9 fruits commonly consumed in the Netherlands. J Agric Food Chem. 1992;40:2379–83.
49. Arts ICW, van de Putte B, Hollman PCH. Catechin contents of foods commonly consumed in The Netherlands. 1. Fruits, vegetables, staple foods, and processed foods. J Agric Food Chem. 2000;48:1746–51.[Medline]
50. USDA Database for the Flavonoid Content of Selected Foods. 2007. Release 2.1 [database on the Internet]. Beltsville, MD: U.S. Department of Agriculture. Available from: http://www.ars.usda.gov/Services/docs.htm?docid=6231.
51. Arab L, Blumberg JB. Introduction to the Proceedings of the Fourth International Scientific Symposium on Tea and Human Health. J Nutr. 2008;138:1526S–8S.
52. Henning SM, Choo JJ, Heber D. Nongallated compared with gallated flavan-3-ols in green and black tea are more bioavailable. J Nutr. 2008;138:1529S–34S.
53. Auger C, Mullen W, Hara Y, Crozier A. Bioavailability of polyphenon E flavan-3-ols in humans with an ileostomy. J Nutr. 2008;138:1535S–42S.
54. Song WO, Chun OK. Tea is the major source of flavan-3-ol and flavonol in the U.S. diet. J Nutr. 2008;138:1543S–7S.
55. Kuriyama S. The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies. J Nutr. 2008;138:1548S–53S.
56. Grassi D, Aggio A, Onori L, Croce G, Tiberti S, Ferri C, Ferri L, Desideri G. Tea, flavonoids, and NO-mediated vascular reactivity. J Nutr. 2008;138:1554S–60S.
57. Hakim IA, Chow HHS, Harris RB. Green tea consumption is associated with decreased DNA damage among GSTM1 positive smokers regardless of their hOGG1 genotype. J Nutr. 2008;138:1567S–71S.
58. Kelly SP, Gomez-Ramirez M, Montesi JL, Foxe JJ. L-Theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. J Nutr. 2008;138:1572S–7S.
59. Mandel SA, Amit T, Kalfon L, Reznichenko L, Youdim MBH. Targeting multiple neurodegenerative diseases etiologies with multimodal-acting green tea catechins. J Nutr. 2008;138:1578S–83S.
60. Stote KS, Baer DJ. Tea consumption may improve biomarkers of insulin sensitivity and risk factors for diabetes. J Nutr. 2008;138:1584S–8S.
This article has been cited by other articles:
![]() |
L. Arab and J. B. Blumberg Proceedings of the Fourth International Scientific Symposium on Tea and Human Health. September 18, 2007. Washington, DC, USA. J. Nutr., August 1, 2008; 138(8): 1526S - 1588S. [Full Text] [PDF] |
||||
![]() |
S. M. Henning, J. J. Choo, and D. Heber Nongallated Compared with Gallated Flavan-3-ols in Green and Black Tea Are More Bioavailable J. Nutr., August 1, 2008; 138(8): 1529S - 1534S. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Auger, W. Mullen, Y. Hara, and A. Crozier Bioavailability of Polyphenon E Flavan-3-ols in Humans with an Ileostomy J. Nutr., August 1, 2008; 138(8): 1535S - 1542S. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. O. Song and O. K. Chun Tea Is the Major Source of Flavan-3-ol and Flavonol in the U.S. Diet J. Nutr., August 1, 2008; 138(8): 1543S - 1547S. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Kuriyama The Relation between Green Tea Consumption and Cardiovascular Disease as Evidenced by Epidemiological Studies J. Nutr., August 1, 2008; 138(8): 1548S - 1553S. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Grassi, A. Aggio, L. Onori, G. Croce, S. Tiberti, C. Ferri, L. Ferri, and G. Desideri Tea, Flavonoids, and Nitric Oxide-Mediated Vascular Reactivity J. Nutr., August 1, 2008; 138(8): 1554S - 1560S. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. A. Hakim, H.-H. S. Chow, and R. B. Harris Green Tea Consumption Is Associated with Decreased DNA Damage among GSTM1-Positive Smokers Regardless of Their hOGG1 Genotype J. Nutr., August 1, 2008; 138(8): 1567S - 1571S. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. P. Kelly, M. Gomez-Ramirez, J. L. Montesi, and J. J. Foxe L-Theanine and Caffeine in Combination Affect Human Cognition as Evidenced by Oscillatory alpha-Band Activity and Attention Task Performance J. Nutr., August 1, 2008; 138(8): 1572S - 1577S. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. A. Mandel, T. Amit, L. Kalfon, L. Reznichenko, and M. B. H. Youdim Targeting Multiple Neurodegenerative Diseases Etiologies with Multimodal-Acting Green Tea Catechins J. Nutr., August 1, 2008; 138(8): 1578S - 1583S. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. S. Stote and D. J. Baer Tea Consumption May Improve Biomarkers of Insulin Sensitivity and Risk Factors for Diabetes J. Nutr., August 1, 2008; 138(8): 1584S - 1588S. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||