The study – published in Nutrition and Cancer – tracked the health of more than 6,000 male volunteers over a period of 37 years, finding that those who drank more than seven cups of tea per day were 50% more likely to develop prostate cancer than those who sipped the least (0-3 cups a day).
Those drinking a moderate level of four to six cups of tea a day were not at any increased risk compared with those who drank the least, said the researchers.
“Most previous research has shown either no relationship with prostate cancer for black tea or some preventive effect of green tea,” said Dr Kashif Shafique from the University of Glasgow, UK – who worked on the study.
“We don’t know whether tea itself is a risk factor or if tea drinkers are generally healthier and live to an older age when prostate cancer is more common anyway.”
The UK NHS choices service noted that despite the large size and long duration of the research, the study had “many limitations that call into question the reliability of its results.”
For example, it notes that information on tea consumption and other lifestyle factors was only collected at the start of the study. “Given the average follow-up was 28 years, it is unlikely that tea drinking habits, and other behaviours such as alcohol and smoking levels, remained stable over this entire period. This could have affected the results.”
The collaborative study began in Scotland in 1970 and gathered data from more than 6,000 male volunteers, all between 21 and 75 years of age. Participants were asked to complete a questionnaire about their usual consumption of tea, coffee, alcohol, smoking habits and general health, and attended a screening examination.
Just under a quarter of the 6,016 men included in the study were heavy tea drinkers, said the researchers.
Of these, 6.4% developed prostate cancer during a follow-up of up to 37 years.
Data analysis revealed that the men who drank more than seven cups of tea per day had a significantly increased risk of prostate cancer compared to those who drank no tea or less than 4 cups per day.
“We found that heavy tea drinkers were more likely not to be overweight, be non alcohol-drinkers and have healthy cholesterol levels. However, we did adjust for these differences in our analysis and still found that men who drank the most tea were at greater risk of prostate cancer,” said Shafique.
Source: Nutrition and Cancer
Published online ahead of print doi: 10.1080/01635581.2012.690063
“Tea Consumption and the Risk of Overall and Grade Specific Prostate Cancer: A Large Prospective Cohort Study of Scottish Men”
Authors: Kashif Shafique, Philip McLoone, Khaver Qureshi, Hing Leung, Carole Hart, David S. Morrison