So that we are clear, we really dislike studies like this that appear to suggest that one particular type of food or drink is “associated” with higher or lower risk for a specific disorder. While they may have some level of scientific interest, their clinical value is certainly limited and may be negligible … yet they get a lot of media coverage. Indeed, if this study hadn’t come from Dr. Janet Stanford’s research group in Seattle, we’d probably have ignored it entirely, but Dr. Stanford is a very highly regarded epidemiologist who has worked for years in prostate cancer research. We can at least be confident that she knows exactly what she is doing.
Both tea and coffee are well known to contain molecules that are biologically active in man, and data are available to suggest that regular drinking of tea and/or coffee is “associated” with a reduction in risk for a diagnosis of prostate cancer.
Geybels et al. wanted to to re-evaluate associations between tea and coffee consumption and risk for prostate cancer in King County, Washington (the county in which Seattle is located). To do this, they evaluated data from a group of men diagnosed with prostate cancer in King County between 2002 and 2005 and an age-matched group of “controls” (i.e., men of analogous ages who had not been diagnosed witrh prostate cancer).
Here is what the research team found:
- There were 892 men in the prostate cancer group (“cases”) and 863 “controls”.
- Among the control group
- 19 percent drank at least one cup of tea per day
- 58 percent drank at least one cup per day of coffee per day.
- Tea consumption was associated with a significant reduction in risk for prostate cancer diagnosis (adjusted OR = 0.63; P for trend = 0.02) for men in the highest compared to the lowest category of tea intake (≥2 cups/day vs. ≤ 1 cup/week).
- Risk estimates did not vary substantially by Gleason grade or disease stage.
- Coffee consumption was not associated with overall risk for diagnosis of prostate cancer or for risk of prostate cancer as defined by tumor grade or stage.
The authors’ conclusion is that their results “contribute further evidence that tea consumption may be a modifiable exposure” that potentially reduces risk for diagnosis of prostate cancer. This, of course, is a sound and very cautious conclusion.
The problem with a study like this, of course, is what we don’t know:
- For how long had the men in the “case” group and the “control” group been drinking tea or coffee on a regular basis (5 years or 40 years)?
- Did whether the individuals drank tea or coffee correlate with other dietary factors? For example, did the coffee drinkers eat more red meat?
- When did the participants start their regular tea or coffee regimen (at age 16 or at age 30)?
- How accurate were the participants reports on their actual tea/coffee consumption?
Obviously it would be really helpful to know, with a high level of certainty, whether drinking tea as opposed to coffee on a regular basis did in fact reduce risk for a diagnosis of clinically significant prostate cancer. From that perspective, research like this is important. The real problem is often that it is impossible (without a 60- or 70-year-long study) to correlate diet and specific aspects of lifestyle (e.g., more or less exercise) with a real change in risk for any specific disease. This is where the Framingham Heart Study — which started back in 1948 — has been so important in helping us to understand risk for cardiovascular disease. We could do with an equivalent to the Framingham Heart Study to look in detail at risk for prostate cancer (and other cancers too). My bet is that Dr. Stanford would love to have been doing this in Seattle … but it takes a lot of money, and a very real, long-term commitment (on the part of the research team and the participants).
Filed under: Diagnosis, Prevention, Risk | Tagged: coffee, Diagnosis, risk, tea |
THE "NEW" PROSTATE CANCER INFOLINK 
Something else we don’t know … why are prostate cancer-specific mortality rates higher in Great Britain than the US? Maybe the high consumption rate of peppers in the US? These are the studies that make me laugh. Another retrospective study. … Nuff said. …
I drank tea every day, all day, for my entire life; and I have prostate cancer. I agree with the Sitemaster on this one. FS
Dear Fred:
The study doesn’t come anywhere close to suggesting that if you drink tea on a daily basis it will stop you from getting prostate cancer. Reduction in risk and elimination of risk are by no means the same thing.
Dear Tony:
I am not sure why you think the prostate cancer-specific mortality (PCSM) rates are significantly different between the UK and the USA.
According to the SEER data the age-adjusted PCSM rate in the USA is 23.6 per 100,000 (click here). In the UK it is 23.8 per 100,000 (click here).
There may be slight differences in the statistical methodologies being used to generate these data, but these two numbers look about right to me. You do have to distinguish between the age-adjusted and the “raw” data, however.
Sitemaster,
There is a difference in the mortality rate. How to explain that 240,000 are diagnosed here and 30,000 die as compared to 40,000 and 10,700 dying in the UK? The stage at diagnosis is more advanced in the UK and other EU countries. The rate of PSA testing is much lower in several EU countries and mortality rates are among the highest in the World.
From the WHO database adjusted to the same population base the mortality rates are:
U.S.A.’s rate is 19.8 men per 100K population
Canada’s rate is 23.3
On the other hand, when PSA use is low, the trend is flat or even increasing and more men are dying.
Sweden’s rate is 54.8 men per 100K population
Norway’s rate is 45.4
Switzerland’s rate is 34.7
U.K.’s rate is 34.4
To clarify something … coffee drinking is associated with a lower risk of obtainig prostate cancer.
I never acquired a taste for coffee, thus I don’t drink it, and as for tea: one cup every 2 years.
Thus (according to this study) I am on the higher end of being “associated” with a risk of being diagnosed with prostate cancer.
Dear Ralph:
The WHO database is notoriously unreliable, which is why I gave the age-adjusted data for the UK and the USA developed by the agencies responsible for these data in each of the two nations. These are very clearly almost exactly the same. And age-adjiusted data of this type are now the standard method for presentation of cancer mortality rates.
There are many reasons why the data for the Scandanavian coutries tend to be higher. One is the high overall life expectancy of men in these countries; a second is because there appears to be a genetic predisposition to prostate cancer; a third may indeed be because of later diagnosis than is common in the USA today (although that has never been proven in any study I am aware of).
Dear Richard:
Some studies have reported that coffee-drinking is “associated” with an increased risk of diagnosis with prostate cancer. Others have shown no such association. And I think a few studies may even have shown that driking coffee actually increased risk for a diagnosis of prostate cancer.
As stated in the article, the clinical significance of most of these data is almost zero on ther basis of the studies carriued out to date.
If we are to discount the value of the WHO database, then why do we consider this study, which uses extremely unreliable methods. Prospective as it is, it does not have any control arms. I am with Ralph. I have seen quite a few renditions of studies that state prostate cancer mortality differences in GB to be never less than the US, and ranging from your stated 0.2% to percentages in the teens higher PCSM. I imagine it’s somewhere in between those numbers, and I imagine that it’s due in large part to limited screening methods. Still, we don’t have any data that we can rely on comparing tea consumption versus coffee consumption as it relates to prostate cancer. Certainly this study method is flawed.
SOME THOUGHTS ON GREEN TEA AS AN ANTI-CANCER TACTIC FROM A LONG-TIME CONSUMER
Those of us with challenging cases are likely much more willing to invest (time, attention, money), despite substantial uncertainty, in agents that appear to have some potential to help coupled with apparent low or nil side effect (in other words, an apparently favorable therapeutic index). That has been the case with me, and I quickly made green tea part of my daily routine after diagnosis. In fact, I have recorded how many bags I’ve used since May 2000, within six months of being diagnosed. Early on I averaged 12 bags per day, but I’m now down to “just” 8 (2 bags in two 12 ounce cups, twice a day, with only the first four caffeinated). I have a hunch that green tea consumption has played a significant role in the success I’ve had in controlling cancer, such as holding back metastases, in my particular biological and medical circumstances, but I have no solid evidence for that.
Here are my thoughts on tea as a long-time consumer motivated by the hope that it is helping me against my challenging case of prostate cancer. (That said, I have always regarded it as a supplementary tactic for main line tactics, especially intermittent triple androgen deprivation therapy, and, currently, TomoTherapy radiation.)
My impression is that various types of Camelia senensis-based tea (which I’ll call tea here) appear to have some good health effects, including some anticancer activity. Camelia senensis is the usual plant for “tea.” I’m basing my impression on a lot of published research.
It is clear, as Sitemaster observes, that the research on tea is far from conclusive. Much of it is based on animal and cell line/laboratory research, and there are few trials in humans.
It appears that tea that is less oxidized, such as green tea, is much more active than more oxidized tea, such as black tea. (That’s good for me as I can tolerate lots of green tea daily — up to 14 bags with no problems, but only a maximum of 3 bags of black tea.)
Existing research does demonstrate substantial favorable impacts against cancer in animal and laboratory studies. To me, the effects achieved in those research settings are impressive but are far from assurance that tea will be as effective or even at all effective in men with prostate cancer. However, I’m impressed with the trends and accumulation of research findings over the years, with substantial research interest in green tea continuing.
EGCG, epigallocatechin gallate, appears to be, by a substantial margin, the most important element in tea.
It is clear that preparation practices and internal biological processing influence the potency of green tea. Regarding preparation, the addition of a little acid, longer brewing, and stirring all enhance potency prior to drinking, as established by research. For many years I have always added a few drops of lemon juice. You can see that makes a difference by experimenting with teas juiced and unjuiced in clear glasses. The unjuiced tea turns browner fairly quickly, indicating oxidation.
I am surprised that studies using green tea intervention (the real tea, not extract) do not require addition of some lemon juice or other acid to protect potency.
An interesting and fairly recent study from UCLA’s well-known Center for Human Nutrition (with well-known researcher Dr. David Heber as a co-author) explores some of the biological transformation of consumed green tea in real prostate cancer patients.
At the moment I have reduced green tea consumption as I’m trying to assess whether its antioxidant effects might somewhat limit the desirable free radical generation effects of my radiation treatments. I suspect that the effects of the tea, even at 8 bags per day, do not degrade the radiation. Any thoughts?
Tony:
Huh? I never said that I thought this study had clinical significance. In fact I was very careful to point out that I doubted that it did! But that doesn’t make it a “bad” study from an epidemiological perspective. The reason I sometimes report on articles like this is because people are likely to see bad information based on such articles published in places like USA Today and The Daily Mail!
You brought up the UK data. All I did was refer you to the most recent data on mortality from both the UK and the USA. Please feel free to make whatever you like of this, but I think I’m going to believe those data since they have been developed by expert statisticians who have spent years working on this and who are trying to get epidemiologists to accept a similar methodology worldwide to assess national and international cancer incidence and mortality rates. The fact that you (and Ralph) have seen different figures over the years is because people have, until very recently, been using very different methods to create these statistics.
I really think we are confusing several utterly different issues here.
Dear Jim:
I’m not sure why your comments have any relationship to the study reported above, which was very much about whether drinking common or garden “black” tea or coffee had any effect on risk for prostate cancer diagnosis (even though I would argue that the results of the study were of dubious value). Are there some data suggesting that drinking “green tea” may lower risk for prostate cancer diagnosis or lower risk for prostate cancer progression? Sure there are. Are those data really compelling? Not exactly.
I would note that while the majority of teas are indeed developed from variants and subtypes of the plant Camellia sinensis, the actual chemicals and potential bioactive agents that are found in specific varieties of tea (and their concentrations) vary to an extraordinary extent based on the precise cultivar grown (there are probably now millions of different ones) and the method of processing the leaves to make the actual product used to brew the tea. Thus, there is even a vast range of bioactive molecules to be found in different forms of green tea. Trying to make rational sense of any of this from a clinical perspective is near to impossible (and it may well actually be impossible).
The only sensible way to look at this is to decide that, if you like drinking green tea, then it probably isn’t going to hurt you. Personally I find the taste rather off-putting!