Epigenetic changes are a regular and natural occurrence but can be affected by lifestyle factors, including smoking, food and exposure to chemicals.
Epigenetic changes can alter DNA accessibility and chromatin structure but they can also have damaging effects which lead to diseases.
The study found that epigenetic changes associated with tea consumption were found in genes involved in cancers and estrogen metabolism.
Tea and coffee: health benefits or detriments?
Tea and coffee, and their health benefits or detriments, have been studied extensively showing differing opinions from researchers.
Previous studies have found that tea and coffee could play important roles in suppressing tumours, decreasing inflammation and influencing estrogen metabolism.
It has also been found that coffee could lower the risk of Alzheimer’s disease, dementia, Parkinson’s disease and type 2 diabetes.
However, other studies have found that increased consumption could lead to heightened risk of high blood pressure and myocardial infarction.
Similar to coffee, tea also carries ambiguity on its health effects.
Polyphenols found in tea are linked to lower risk of heart disease, cancer and diabetes, yet tea has also been associated with increased risk of cardiovascular disease.
The study authors said that so far a systematic genome-wide analysis of the influence of coffee and tea on DNA methylation has not been performed.
Only women, not in men
A final set of 3,096 participants in four cohorts, with a mean age of 56 years, were used for meta-analysis.
Through measuring whole blood at 421,695 CpG sites – DNA regions where a cytosine nucleotide is followed by a guanine nucleotide and separated by one phosphate – researchers found that two CpG sites were differentially methylated in relation to tea consumption in women.
These two sites, DNAJC16 and TTC17, contained genes known to interact with estradiol metabolism and cancer.
No individual sites were associated with men.
However, it was also found that tea consumption was significantly higher in women across all cohorts apart from one, whereas men were found to drink more coffee.
This increase in consumption could explain the differing results for men and women, explained the researchers.
Researchers did not find an association between coffee consumption and DNA methylation in neither men nor women.
As the four cohorts mainly included adults and elderly people, the authors commented that the same conclusion cannot be given for young people.
However, in one cohort, females were split into two age groups – below 50 years and over 50 years – but no significant differences were found between the two groups.
The four cohorts analysed were the Northern Sweden Population Health Study ((NSPHS) n=723), the Dutch Hunger Winter Families Study ((HWFS) n=948), the EnviroGenomarkers Project in Italy ((EGM) n=621) and the Prospective Investigation of the Vasculature in Uppsala Seniors ((PIVUS) n=804).
Participants were given a self-reported food frequency questionnaire to measure the number of cups of coffee and tea they consumed each month.
Whole blood samples were collected from all participants and the Human Methylation450 BeadChip was used to assess DNA methylation.
Both statistical and stratified analyses were carried out due to the significant difference in consumption between sexes.
The authors concluded that more studies would need to be carried out to rule out any DNA methylation caused by smoking and/or age.
Source: Human Molecular Genetics
Title: “Tea and coffee consumption in relation to DNA methylation in four European cohorts”
Published online, https://doi.org/10.1093/hmg/ddx194
Authors: Weronica E. Ek, Elmar W. Tobi, Muhammed Ahsan, Erik Lampa, Erica Ponzi, Soterios A. Kyrtopoulos, Panagiotis Georgiadis, L.H. Lumey, Bastiaan T. Heijmans, Maria Botsivali, Ingvar A. Bergdahl, Torgny Karlsson, Mathias Rask-Andersen, Domenico Palli, Erik Ingelsson, Asa K. Hedman, Lena M. Nilsson, Paolo Vineis, Lars Lind, James M. Flanagan, and Asa Johansson