MEN who drink at least seven cups of tea a day increase their risk of developing prostate cancer by 50% compared to those who consume little or no tea, according to a study.
Research following 6016 men recruited from workplaces in Glasgow, Clydebank and Grangemouth between 1970 and 1973 found that 318 participants had gone on to develop prostate cancer by the end of 2007.
The study, published today in the journal Nutrition and Cancer, found that rates of the disease were significantly elevated among those men classed by the study as heavy tea drinkers – consuming seven or more cups of tea per day.
This was still apparent even when the researchers adjusted for other risk factors including age, BMI, cholesterol level, blood pressure, smoking, class, education, alcohol intake and coffee consumption.
Heavy tea drinkers were 50% more likely to have developed prostate cancer over the 37-year duration of the study compared to participants who drank zero to three cups per day, with the risk steadily rising in line with increases in tea intake.
Dr Kashif Shafique, of Glasgow University's Institute of Health and Wellbeing, said: "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."
About 2700 men in Scotland were diagnosed with the disease in 2010 and 849 died from the condition, according to figures.
Just under a quarter of the participants included in the study were heavy tea drinkers. Of these, 6.4% developed prostate cancer.
The data also indicated heavy tea drinkers were more likely to be a healthy weight, have safe cholesterol levels and be teetotal compared to participants drinking little or no tea, contradicting other evidence which points to excess weight and alcohol consumption as risk factors for the disease.
Researchers said this could be explained by a higher proportion of heavy tea drinkers reducing their risk of death from other factors due to their healthy weight, low alcohol intake and cholesterol levels, and therefore living long enough to develop prostate cancer. However, heavy tea drinkers were also more likely to be smokers.
Consumption levels were based on the answers given in a questionnaire filled out by participants when they first joined the study in the 1970s. They were also asked about their coffee and alcohol consumption, smoking habits and general health, and attended a screening examination. At the time of recruitment, the ages of the men ranged from 21 to 75.
The study classed tea as black tea as opposed to green tea but did not identify variations in how the beverage was prepared, such as whether participants were adding milk or sugar.
Green tea is prepared from the dried leaves of the plant whereas black tea involves crushing the leaves and a fermentation process which may increase the carcinogenic properties.
Black tea is the norm in Europe and the US, where prostate cancer has become the most frequently diagnosed form of the disease over the last two decades. It is the most common cancer among men in Scotland and between 2000 and 2010 incidence increased by 7.4%.
Dr Shafique said: "Most previous research has shown either no relationship with prostate cancer for black tea or some preventive effect of green tea.
"We found 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."
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