19 June 2012 Last updated at 00:00 GMT
Male tea drinkers 'may be at greater risk of prostate cancer'
Men who are heavy tea drinkers may be more likely to develop prostate cancer, according to new research.
A team from Glasgow University tracked the health of more than 6,000 male volunteers over a period of 37 years.
They found men who drank over seven cups of tea per day had a 50% higher risk of developing prostate cancer than moderate and non tea drinkers.
The team said it did not know if tea was a risk factor or if drinkers lived to ages where cancer was more common.
Prostate cancer is the most common cancer amongst men in Scotland and diagnosed cases increased by 7.4% between 2000 and 2010.
The Midspan Collaborative study began in Scotland in 1970 and gathered data from 6,016 male volunteers, all aged between 21 and 75.
Volunteers 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 men included in the study were heavy tea drinkers.
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We... found that men who drank the most tea were at greater risk of prostate cancer”
Dr Kashif Shafique
Of these, 6.4% developed prostate cancer during a follow-up of up to 37 years.
Researchers found that 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 four cups per day.
The study was led by Dr Kashif Shafique of Glasgow University's Institute of Health and Wellbeing.
He said: "Most previous research has shown either no relationship with prostate cancer for black tea or some preventive effect of green tea.
"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."
"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."
Chris Garner, a member of Edinburgh and Lothian Prostate Cancer Support Group, said the research would not stop him drinking tea.
He has adopted a healthier diet since being diagnosed with prostate cancer 10 years ago and drinks green tea.
Mr Garner said: "As usual you get evidence on one side and you get evidence on the other and you're left in the middle trying to decide who's right but I have to say, I don't think tea is very high on the agenda if you're looking at diet, lifestyle and so on.
"There are other things which come well above tea."
Dr Kate Holmes, head of research at the Prostate Cancer Charity, said: "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.
"We would therefore not wish any man to be concerned that drinking a moderate amount of tea as part of a healthy diet will put them at an increased risk of developing prostate cancer."
The findings of the study have been published in the journal Nutrition and Cancer.
Nutr Cancer. 2012 Jun 14. [Epub ahead of print]
Tea Consumption and the Risk of Overall and Grade Specific Prostate Cancer: A Large Prospective Cohort Study of Scottish Men.
Shafique K, McLoone P, Qureshi K, Leung H, Hart C, Morrison DS.
a Institute of Health and Wellbeing, Public Health , University of Glasgow , Glasgow , UK.
Tea may be a potentially modifiable and highly prevalent risk factor for the most common cancer in men, prostate cancer. However, associations between black tea consumption and prostate cancer in epidemiological studies have been inconsistent, limited to a small number of studies with small numbers of cases and short follow-up periods and without grade-specific information. We conducted a prospective cohort study of 6,016 men who were enrolled in the Collaborative Cohort Study between 1970 and 1973 and followed up to December 31, 2007. We used Cox proportional hazards models to investigate the association between tea consumption and overall as well as grade-specific risk of prostate cancer incidence. Three hundred and eighteen men developed prostate cancer in up to 37 years of follow-up. We found a positive association between consumption of tea and overall risk of prostate cancer incidence (P = 0.02). The association was greatest among men who drank ≥7 cups of tea per day (HR: 1.50, 95% CI: 1.06 to 2.12), compared with the baseline of 0-3 cups/day. However, we did not find any significant association between tea intake and low- (Gleason <7) or high-grade (Gleason 8-10) prostate 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. Further research is needed to determine the underlying biological mechanisms for the association.
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