Entries tagged with “DNA”
Sep
3
2010
Drinking green tea every day for a month may protect against damage at a genetic levels, with benefits linked to the beverage’s antioxidant content, says a new study.
Combined results from a human supplementation trial and an in vitro study indicated a 20 percent reduction in levels of DNA damage, while measures of whole-body oxidative stress were unaffected, say findings published in the British Journal of Nutrition.
“The results indicate that green tea has significant genoprotective effects and provide evidence for green tea as a ‘functional food’,” wrote researchers from The Hong Kong Polytechnic University.
Tea break
The study adds to an ever-growing body of science supporting the potential benefits of green tea and the polyphenolic compounds it contains. Hundreds of studies report that the beverage may reduce the risk of certain cancers, aid weight management, and protection against Alzheimer’s.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
Study details
Led by Professor Iris Benzie, the researchers recruited 18 healthy volunteers to participate in a placebo-controlled, cross-over supplementation study. Subjects were randomly assigned to receive two cups of 1 percent green tea (‘Longjing’ green tea or ‘screw-shaped’ green tea) or water every day for 4 weeks. Six week washout periods separated each four-week intervention, and blood and urine samples were collected before and after each intervention.
Analysis of these bodily fluids showed a 20 percent reduction in DNA damage, measured using the formamidopyrimidine glycosylase (Fpg) enzyme-assisted comet assay.
For the in vitro study, the researchers pre-incubated human blood cells with green tea and then exposed these cells to the oxidising agent hydrogen peroxide (H2O2). “In vitro testing results of tea-treated cells showed increased resistance of DNA to the challenge,” they stated.
On the other hand, the human study showed no changes in urine levels of 7,8-dihydro-2-deoxyguanosine (8-oxodG), reported to be “a biomarker of whole-body oxidative stress”.
Biological aging
At the start of this year, scientists from the Chinese University of Hong Kong reported that the cells of regular tea drinkers may have a younger biological age than cells from non-drinkers.
By looking at the length of telomeres, DNA sequences at the end of chromosomes that shorten as cells replicate and age, the Chinese researchers reported that the telomeres of people who drank an average of three cups of tea per day were about 4.6 kilobases longer than people who drank an average of a quarter of a cup a day.
This average difference in the telomere length corresponds to “approximately a difference of 5 years of life”, wrote the Hong Kong-based researchers (British Journal of Nutrition, Vol. 103, pp 107-113).
Source: British Journal of Nutrition
Published online ahead of print, doi:
“Genoprotective effects of green tea (Camellia sinensis) in human subjects: results of a controlled supplementation trial”
K. C. Hana1, W. C. Wonga1 and Iris F. F. Benzie
Jul
15
2010
Higher blood levels of vitamin B6 may reduce the risk of lung cancer by about 50 per cent, says a new analysis of almost 400,000 people, including current and former smokers.
Researchers also report that the amino acid methionine, which is found in most protein, may also reduce the risk of lung cancer.
“Given their involvement in maintaining DNA integrity and gene expression, these nutrients have a potentially important role in inhibiting cancer development, and offer the possibility of modifying cancer risk through dietary changes,” wrote the authors in the Journal of the American Medical Association.
One in three Europeans are smokers, while the US figure is one in five. Tobacco smoke contains over 4,000 compounds, of which 60 are known carcinogens. The oxidative stress levels of smokers are significantly greater than non-smokers, and as such there is a bigger drain on the levels of antioxidants in the body.
Furthermore, the new study indicated that folate may also be beneficial, and that high folate levels combined with methionine and B6 were associated with a 66 per cent reduction in lung cancer risk.
Study details
Led by Paul Brennan from the International Agency for Research on Cancer in Lyon, France, the researchers used data from 385,747 people who donated blood while participating in the European Prospective Investigation into Cancer and Nutrition (EPIC). Out of this, 899 people with lung cancer were identified and matched with 1,770 cancer-free people.
The researchers noted that increasing blood levels of vitamin B6 were associated with lower risks of lung cancer. A similar risk reduction was observed for methionine, which extended to never, former, and current smokers. This indicated that smoking habits were not confounding the results.
“Our results suggest that above-median serum measures of both B6 and methionine, assessed on average 5 years prior to disease onset, are associated with a reduction of at least 50 percent on the risk of developing lung cancer,” wrote the researchers. “An additional association for serum levels of folate was present, that when combined with B6 and methionine, was associated with a two-thirds lower risk of lung cancer,” they added.
More research needed
Correlation does not prove causation, however, and more research is needed to clarify the role of B vitamins and methionine in lung cancer, said the researchers.
“It is essential that for lung cancer prevention, any additional evidence about causality does not detract from the importance of reducing the numbers of individuals who smoke tobacco,” wrote Brennan and his co-workers
“With this in mind, it is important to recognize that a large proportion of lung cancer cases occur among former smokers, making up the majority in countries where tobacco campaigns have been particularly successful, and a non-trivial number of lung cancer cases occur also among never smokers, particularly among women in parts of Asia.
“Clarifying the role of B vitamins and related metabolites in lung cancer risk is likely therefore to be particularly relevant for former smokers and never smokers,” they concluded.
Authors: JAMA
2010, Volume 303, Number 23, Pages 2377-2385
“Serum B Vitamin Levels and Risk of Lung Cancer”
Authors: M. Johansson, C. Relton, P.M. Ueland, et al.
Jun
29
2010
Higher blood levels of vitamin B6 may reduce the risk of lung cancer by about 50 per cent, says a new analysis of almost 400,000 people, including current and former smokers.
Researchers also report that the amino acid methionine, which is found in most protein, may also reduce the risk of lung cancer.
“Given their involvement in maintaining DNA integrity and gene expression, these nutrients have a potentially important role in inhibiting cancer development, and offer the possibility of modifying cancer risk through dietary changes,” wrote the authors in the Journal of the American Medical Association.
One in three Europeans are smokers, while the US figure is one in five. Tobacco smoke contains over 4,000 compounds, of which 60 are known carcinogens. The oxidative stress levels of smokers are significantly greater than non-smokers, and as such there is a bigger drain on the levels of antioxidants in the body.
Furthermore, the new study indicated that folate may also be beneficial, and that high folate levels combined with methionine and B6 were associated with a 66 per cent reduction in lung cancer risk.
Study details
Led by Paul Brennan from the International Agency for Research on Cancer in Lyon, France, the researchers used data from 385,747 people who donated blood while participating in the European Prospective Investigation into Cancer and Nutrition (EPIC). Out of this, 899 people with lung cancer were identified and matched with 1,770 cancer-free people.
The researchers noted that increasing blood levels of vitamin B6 were associated with lower risks of lung cancer. A similar risk reduction was observed for methionine, which extended to never, former, and current smokers. This indicated that smoking habits were not confounding the results.
“Our results suggest that above-median serum measures of both B6 and methionine, assessed on average 5 years prior to disease onset, are associated with a reduction of at least 50 percent on the risk of developing lung cancer,” wrote the researchers. “An additional association for serum levels of folate was present, that when combined with B6 and methionine, was associated with a two-thirds lower risk of lung cancer,” they added.
More research needed
Correlation does not prove causation, however, and more research is needed to clarify the role of B vitamins and methionine in lung cancer, said the researchers.
“It is essential that for lung cancer prevention, any additional evidence about causality does not detract from the importance of reducing the numbers of individuals who smoke tobacco,” wrote Brennan and his co-workers
“With this in mind, it is important to recognize that a large proportion of lung cancer cases occur among former smokers, making up the majority in countries where tobacco campaigns have been particularly successful, and a non-trivial number of lung cancer cases occur also among never smokers, particularly among women in parts of Asia.
“Clarifying the role of B vitamins and related metabolites in lung cancer risk is likely therefore to be particularly relevant for former smokers and never smokers,” they concluded.
Authors: JAMA
2010, Volume 303, Number 23, Pages 2377-2385
“Serum B Vitamin Levels and Risk of Lung Cancer”
Authors: M. Johansson, C. Relton, P.M. Ueland, et al.