regional medical center: Prostate Cancer Risk Higher For Heavy Tea Drinkers

Prostate Cancer Risk Higher For Heavy Tea Drinkers

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Main Category: Prostate / Prostate Cancer
Also Included In: Nutrition / Diet;Â Â Men's Health
Article Date: 20 Jun 2012 - 2:00 PDT

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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."

Shafique said:

"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.

Written by Catharine Paddock PhD
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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Visitor Opinions (latest shown first)

You'd better forget this study, it is seriously flawed.

posted by Mihai-Robert on 20 Jun 2012 at 3:32 am

My rating of one star is meant for the study, not for the MNT report.

The study is a very good example of "research" that shouldn't have passed any peer review without having its faulty design and conclusion rejected.

It's impossible to list up HERE all the reasons that make the study a piece of academic trash and a danger for public health.

However, let's try a summary.

Critical Conclusion:

"The strengths of this study are its size and long follow-up period, but it also has very significant limitations that should be considered when judging the reliability and relevance of these findings.

Lifestyle factors were recorded at a single time

Information on tea consumption and other lifestyle factors was only collected at the start of the study. Given the long average follow-up period of 28 years, tea habits and other behaviours such as alcohol and smoking levels are likely to have varied over this period. This could mean tea habits an d other lifestyle factors were incorrectly classified, which could significantly affect the conclusions drawn from this study.

Tea drinkers may live longer, allowing cancers to develop

The authors of the study highlight that many healthy behaviours, such as having a healthy weight, not drinking alcohol and having optimum cholesterol levels, were more common in those in the highest tea consumption group. They raised the possibility that these men, who were generally healthier, may have lived for longer, allowing more time for prostate cancer to develop. As prostate cancer risk is known to increase with age, those living longer are more likely to develop the condition, which could explain this result. The researchers did attempt to adjust for this age-related effect, but this may not have been completely successful with residual effects playing a part.

Only a small number of the men developed prostate cancer

Though this was a large study, only 318 men d eveloped prostate cancer during the follow-up period. If these men are further subdivided according to the amount of tea they drank, smaller sample sizes are created that can affect the reliability of risk estimates (only 92 men with prostate cancer drank seven or more cups a day).

The study measured cancer diagnoses not cancer deaths

This study looked at the risk of tea consumption on being diagnosed with prostate cancer rather than risk of dying from it. A large proportion of those diagnosed with prostate cancer will die with the disease but from other unrelated causes, rather than directly from prostate cancer itself.

The types of tea drunk are unclear

The study authors state that most of the study participants were drinking black tea (as opposed to green tea) in their discussion section. However, the results of the study by tea type are not reported. It is unclear whether tea type was measured at the start of the study or was assumed to be black t ea by the authors due to the trends in tea drinking at the time. This is important as different types of tea vary in their constituents and could potentially affect the body in different ways. It was also not clear whether tea was taken with or without milk which could further influence this potential link between tea and prostate cancer.

Family history is missing

The study did not collect data on family history of prostate cancer and other potential dietary factors that have been linked to prostate cancer in previous research. Not adjusting for these factors in the analysis may have biased the findings of this study.

Cancer grading difficulties

The amount of information on grade-specific prostate cancer was small and severely limited the power of the study to detect a potential link between the condition and tea consumption.

Cohort study design

The main limitation of cohort studies is that they show associations rather than prove causes. Hence, this study doesnâ€™t demonstrate that tea causes prostate cancer, only that those who drink the most tea generally develop prostate cancer more often. Other influencing factors are likely to be involved in explaining this potential causal link.

In summary, men who are tea drinkers should not be alarmed by the results of this study as it has many limitations that cast doubt on the reliability of the findings. However, men should remain alert to the signs and symptoms of prostate and other forms of cancer, regardless of their tea habits.

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Rabu, 20 Juni 2012

Prostate Cancer Risk Higher For Heavy Tea Drinkers

Visitor Opinions (latest shown first)

You'd better forget this study, it is seriously flawed.

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