A new study from Scotland has found that men who are heavy tea drinkers may be at higher risk for prostate cancer. However, the researchers point out their study was not designed to find causes, so all they can say is that heavy tea drinking is linked to a higher risk for prostate cancer and not necessarily the cause of it.
Study leader Dr Kashif Shafique of the Institute of Health & Wellbeing at the University of Glasgow, told the media:
"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."
"Most previous research has shown either no relationship with prostate cancer for black tea or some preventive effect of green tea," said Shafique.
He and his colleagues write about the findings of their prospective study in a paper that was published online in the journal Nutrition and Cancer on 14 June.
The data they used covered 6,016 Scottish men aged from 21 to 75 years who were enrolled on the Midspan Collaborative study between 1970 and 1973 and were followed for up to 37 years.
The men had filled in questionnaires about their general health, smoking habits, and usual consumption of tea, coffee, and alcohol, and they also attended a screening examination.
When they analyzed the data the researchers found a statistically significant link (P=0.02, so unlikely to be due to pure chance) between tea drinking and overall risk of developing prostate cancer.
After water, tea is the most widely consumed drink in the world. They found the men who drank the most tea (more than seven cups a day, just under a quarter of all the men) had a 50% higher risk of developing prostate cancer than those who drank the least (0 to 3 cups a day).
Overall, 6.4% of the men who drank the most tea developed prostate cancer during the study period, compared with 4.6% of those who consumed the least.
The researchers found no significant link between tea drinking and low or high grade cancer incidence:
"Men with higher intake of tea are at greater risk of developing prostate cancer, but there is no association with more aggressive disease," write the authors, who conclude:
"Further research is needed to determine the underlying biological mechanisms for the association."
"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."
Dr Kate Holmes, Head of Research at The Prostate Cancer Charity, said in a statement released on Tuesday:
"Whilst it does appear that – of the 6,000 men who took part in this study – those who drank seven or more cups of tea each day had an increased risk of developing prostate cancer, this did not take into consideration family history or any other dietary elements other than tea, coffee and alcohol intake. It is therefore unclear as to whether there were other factors in play which may have had a greater impact on risk."
"We would therefore not wish any man to be concerned, as a result of this study, that drinking a moderate amount of tea as part of a healthy diet will put them at an increased risk of developing prostate cancer," she added.
Dr Carrie Ruxton is a dietician who sits on the Tea Advisory Panel, a health information group funded by the tea industry's UK Tea Council. On Tuesday, the Telegraph reported her saying:
"The study doesn't show a cause and effect relationship between tea drinking and cancer risk."
"Tea drinking is simply a marker for some other issue. That may be down to issues with stress, or perhaps diet," said Ruxton.
In the ten years leading up to 2010, the incidence of prostate cancer in Scotland went up by 7.4%. It is the most common cancer amongst Scottish men.