La consommation de thé est très élevée dans le monde. Le thé est une feuille souvent altérée par des transformations diverses pour en faire un produit. Le thé vert est aussi un produit transformé car il est chauffé à la vapeur puis séché; c'est celui des thés qui est le moins altéré. Il est établi que c'est un anti-oxydant puissant comme beaucoup d'extrémités foliaires des plantes. La consommation de thé vert peut augmenter les capacités anti-oxydantes du sérum. En conséquence les processus pathologiques comme l'oxydation des graisses (rancicité des graisses) ou bien les altérations de l'ADN des cellules(altération directe de la séquence des gènes ou bien altération de leur expression par méthylation ou bien modification des histones) peuvent être freinés.
Des études expérimentales et cliniques ont permis de mettre en évidence cet effet bénéfique. Il y a des enjeux économiques importants et ceci doit être particulièrement souligné pour comprendre les financements des recherches sur le thé.
Finalement le thé vert est un stimulant par son contenu en caféine, un anti-oxydant, un diurétique léger, une boisson très hydratante par son fort contenu en eau.
Il reste plusieurs incertitudes: combien de pesticides, de métaux lourds, de fluor (il semblerait qu'un excès de fluor soit délétère?) La culture étant hors de contrôle de l'UE et les origines souvent mal précisées, il est conseillé de consommer du thé vert issu de l'agriculture sans pesticides.
Les personnes ayant des facteurs de risque de cancer ou de maladies cardio-vasculaires peuvent bénéficier de la consommation de thé vert au lieu du café ou d'autres boissons. Pour autant l'arrêt du tabac est la mesure de loin la plus efficace en prévention. Ne nous méprenons pas! s'agissant des phénotypes les plus susceptibles de bénéficier de cette consommation il est établi qu'ils s'agit de personnes qui ont des modifications génétiques mineures (altérations génétiques alléliques d'un seul nucléotide) entrainant une diminution de l'activité enzymatique anti-oxydante. Les Glutathione-S-transférases sont des enzymes de ce type. Aujourd'hui la détermination de telle modifications génétiques n'est pas entrée en partique courante. Avec la possibilité de décoder l'intégralité du génome d'un individu pour une somme inférieure à 500 euro nous entrons dans l'ère de la médecine personnalisée. Cette évolution va bouleverser la médecine et la nutrition. Alors demain fumer du tabac ne sera plus un jeu de roulette russe? Probablement qu'une partie de cette assertion se vérifiera. Certains individus seront classés à très haut risque pour les cancers provoqués par la fumée comme le cancer du poumon, de la vessie, du sein etc. Pour autant il sera difficile d'effacer le message "fumer tue"! En revanche sur le plan nutritionnel il est sur que des modifications très importantes des conseils nutritionnels va intervenir. Le même régime prescrit à tout le monde pour ses bienfaits c'est terminé. Les recommandations vont devenir personnalisées en fonction des traits génétiques et épigénétiques. Le but c'est d'être plus efficace et ce but est facile à atteindre! Depuis que les recommendations nutritionnelles existent l'obésité n' a cessé de progresser. Cherchez l'erreur!
Références
1/Modification of urinary N7-methylguanine excretion in smokers by glutathione-S-transferase M1 polymorphism
I-Hsin Lin, Mu-Rong Chao, Chiung-Wen Hu, Ming-Lin Ho, Jo-Yun Huang, Hong-Shen Lee, Chun-Chieh Chen and Ruey-Hong Wong,
aDepartment of Public Health, College of Health Care and Management, Chung Shan Medical University, No. 110 Chien-Kuo N Rd., Sec. 1, Taichung 40242, Taiwan
bDepartment of Occupational Safety and Health, College of Health Care and Management, Chung Shan Medical University, Taichung, Taiwan
cDivision of Pulmonary Medicine, Department of Internal Medicine, Changhua Christian Hospital, Changhua, Taiwan
dDepartment of Family Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan
Received 14 January 2009;
Abstract
Tobacco smoke contains many carcinogens which can lead to DNA methylation. Glutathione-S-transferases (GSTs) are detoxifying enzymes, and the effects of the genes GSTM1, GSTT1, and GSTP1 on cigarette smoke-induced methylated adducts have not been elucidated. Therefore, we investigated the association of the GSTM1, GSTT1, and GSTP1 genes and N7-methylguanine (N7-MeG) adducts in smokers. Urinary N7-MeG concentrations were measured by using liquid chromatography–tandem mass spectrometry in 112 smokers and 89 non-smokers, and GSTM1, GSTT1, and GSTP1 genotypes were identified by polymerase chain reaction. Smokers had higher N7-MeG concentrations than did non-smokers (3238 ± 305 ng/mg creatinine [standard error] vs. 2386 ± 153 ng/mg creatinine; P = 0.01). Higher N7-MeG concentrations were observed with the GSTM1 null genotype than with the GSTM1 non-null genotype (3230 ± 292 ng/mg creatinine vs. 2336 ± 153 ng/mg creatinine; P = 0.007), particularly in smokers (3775 ± 483 ng/mg creatinine vs. 2468 ± 228 ng/mg creatinine; P = 0.02). However, the GSTT1 and GSTP1 genotypes were not associated with urinary N7-MeG concentrations. Therefore, the susceptible GSTM1 genotype may modulate the concentrations of N7-MeG adducts in the DNA of smokers.
Keywords: Smoking; GSTM1 gene; N7-Methylguanine
2/http://health.msn.com/health-topics/cancer/articlepage.aspx?cp-documentid=100252434
Green Tea May Lower Lung Cancer Risk
Benefits seen for smokers, nonsmokers, those with certain genetic makeup
TUESDAY, Jan. 12 (HealthDay News) -- Antioxidants in green tea appear to significantly lower the risk for developing lung cancer among smokers and nonsmokers alike, new research from Taiwan reveals.
The study suggests that smokers and nonsmokers who consume a minimum of one cup of green tea per day appear to have a nearly 13-fold and fivefold lower risk, respectively, for developing lung cancer than smokers and nonsmokers who don't drink any green tea.
"The health effect of green tea consumption could modify the risk of lung cancer, particularly among smokers," said study author I-Hsin Lin, of Chung Shan Medical University in Taichung.
Lin and her team are scheduled to present their findings at a lung cancer conference this week in Coronado, Calif. The conference is sponsored by the American Association for Cancer Research and the International Association for the Study of Lung Cancer.
The observed protective effect seems to result from the strong "antioxidative property" of polyphenols found in green tea preparations.
To determine just how strong this effect might be, the authors assessed the dietary intake and lifestyle habits of 170 lung cancer patients and 340 healthy patients.
The participants completed questionnaires outlining their smoking histories, green tea consumption habits, fruit and vegetable intake, and cooking practices. Patients were also asked to note any family history of lung cancer.
Genetic testing was also conducted to assess which particular insulin-like growth factor genotype -- among several -- each participant possessed.
This analysis was considered crucial, given the author's observation that, independent of green tea consumption, genetically determined hormonal differences can affect how quickly cancer cells spread, thereby predisposing people toward a greater or lesser general risk for developing lung cancer in the first place.
While emphasizing that both smoking and nonsmoking tea drinkers generally benefited from green tea consumption relative to non-tea drinkers, the team observed that tea drinkers with particular growth factor genotypes seemed to gain even more protection -- as much as 66 percent greater protection compared with tea drinkers bearing a different genetic background.
The findings reflect solely upon the potential interplay of green tea, genetics and lung cancer risk, the researchers noted, leaving aside potential questions regarding black tea consumption.
"Our results suggest the potential health benefits of green tea consumption," concluded Lin. "However, cigarette smoking can serve as an initiator and promoter of carcinogenesis, [so] cessation of smoking is the best way for cancer prevention."
Dr. Norman Edelman, chief medical officer of the American Lung Association, emphatically agreed.
"First of all, this is not a new concept," he observed. "The idea that various antioxidants are protective to the lung has been around for a while, and green tea is a powerful antioxidant. But for us to really know whether or not just one cup can have such an enormous effect, you really have to look at more data and all the other possibly confounding factors, such as whether patients are obese, whether they are leading otherwise healthy lives, that kind of thing."
"Meanwhile, what the American Lung Association is really afraid of," cautioned Edelman, "is that people will look at this and think, 'Oh, well, I can smoke as long as I have a few cups of green tea.' Nothing could be further from the truth. Smoking is extremely toxic, obviously, and extremely detrimental to your health. And nothing changes this fact. So the most important thing here is that we don't want anyone to get the message that it's OK to smoke so long as I drink green tea."
Meanwhile, another group reported that a diet high in leafy green vegetables, folate and some multivitamins might protect against smoking-related genetic changes that lead to lung cancer.
The researchers from Lovelace Respiratory Research Institute in Albuquerque, N.M., found those substances, including vitamins C, A and K, could influence a chemical modification called cellular gene methylation. Aberrant gene methylation is known to be a mechanism in the development of cancer in smokers.
Their findings were published online Jan. 12 in Cancer Research.
Exploring yet another front in lung cancer science, a second study scheduled for release at the lung cancer conference suggests that lung cancer patients who are smokers seem better able than nonsmoking patients to tolerate higher -- and presumably more effective -- dosages of a standard chemotherapy treatment known as erlotinib.
The research team, from the Wake Forest University in Winston-Salem, N.C., found that while nonsmokers ultimately developed dangerously toxic side effects -- such as rashes, diarrhea and/or dehydration -- when placed on an average daily dose regimen of just 225 milligrams of erlotinib, smokers didn't develop similarly problematic reactions until the daily average dosage reached 300 milligrams.
More information
For additional details on green tea and lung cancer prevention, visit the NCI
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