Researchers from the Chinese University of Hong Kong looked at the length of telomeres, DNA sequences at the end of chromosomes that shorten as cells replicate and age.
The ageing and lifespan of normal, healthy cells are linked to the so-called telomerase shortening mechanism, which limits cells to a fixed number of divisions. During cell replication, the telomeres function by ensuring the cell's chromosomes do not fuse with each other or rearrange, which can lead to cancer. Elizabeth Blackburn, a telomere pioneer at the University of California San Francisco, likened telomeres to the ends of shoelaces, without which the lace would unravel.
With each replication the telomeres shorten, and when the telomeres are totally consumed, the cells are destroyed (apoptosis). Previous studies have also reported that telomeres are highly susceptible to oxidative stress. Some experts have noted that telomere length may be a marker of biological ageing.
"The antioxidative properties of tea and its constituent nutrients may protect telomeres from oxidative damage in the normal ageing process," wrote the authors in the British Journal of Nutrition.
The Hong Kong-based researchers, led by Ruth Chan, noted that the telomeres of people who drank an average of three cups of tea per day were significantly 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 researchers, led by Ruth Chan.
Dr Chan told NutraIngredients that "Chinese tea" in their study refers to both black and green tea, but added: "Our data showed that the majority of Chinese tea consumed by our subjects was green tea".
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.
The study’s findings are based on the telomere lengths of 976 Chinese men and 1,030 Chinese women aged over 65. The participants’ dietary habits were evaluated using a food frequency questionnaire.
Overall, only tea consumption was associated with telomere length. The highest intakes, three cups or 750 millilitres per day, was associated with significantly longer telomere lengths, compared with people who drank 70 millilitres per day or less, said the researchers.
Recently, researchers from the US National Institute of Environmental Health Sciences reported that telomere length was longer in regular multivitamin users in their cohort of 586 women aged between 35 and 74.
Writing in the American Journal of Clinical Nutrition, the US-based researchers noted that theirs was the “first epidemiologic study of multivitamin use and telomere length.
“Regular multivitamin users tend to follow a healthy lifestyle and have a higher intake of micronutrients, which sometimes makes it difficult to interpret epidemiologic observations on multivitamin use,” they said.
Source: British Journal of Nutrition
2010, Volume 103, Issue 1, Pages 107-113, doi:10.1017/S0007114509991383
"Chinese tea consumption is associated with longer telomere length in elderly Chinese men"
Authors: R. Chan, J. Woo, E. Suen, J. Leung, N. Tang