Do dietary patterns really affect risk for prostate cancer?

Over the years a variety of factors have suggested an association between diet and risk for prostate cancer — with a particular emphasis on the “dangers” of larger quantities of things like red meat, meat fats, and milk-based products in the diet. This presumed association has also been supported by the well-known fact that, historically, Japanese men (whose domestic diet was low in meat and fats and high in soy, rice, and fish) had a relatively low risk for prostate cancer, but if they moved from Japan to America their risk appeared to increase rapidly to be similar to that of the average American male. It was assumed that this was very likely because of significant changes in diet associated with the change in place of residence. It is also notable that as the amount of meat and milk-based products in the diet of domestic Japanese has increased over the past 20 years, there has been an apparent increase in the risk of prostate cancer.

Muller et al. at the University of Melbourne have now conducted a prospective investigation of associations between dietary patterns and prostate cancer risk in 14,627 men of ages 34 to 75 years for an average of 13.6 years.

Over the follow-up period, the authors report 1,018 incident prostate cancers in these 14,627 men who were participating in the Melbourne Collaborative Cohort Study.

The bottom line to what is a complex epidemiological and statistical analysis is that Muller et al. were unable to identify any association between any dietary pattern and overall risk for prostate cancer. Specifically, the analysis also did not show any association between any dietary pattern and such factors as cancer aggressiveness, Gleason score, or age at diagnosis.

All that we can really conclude from this study was that in this specific population of men participating in the Melbourne Collaborative Cohort Study (recruited well over 10 years ago), it was not possible to demonstrate an association between diet and risk for prostate cancer.

The question that continues to stand out for The “New” Prostate Cancer InfoLink is whether there are environmental impacts (specifically including diet) that occur much earlier in life that have significant impact on our risks for prostate cancer as we age. We know that all sorts of things that we do or which are done to us in the first decade of life can have profound impact on us as we move into and through adulthood. It seems entirely reasonable to The “New” Prostate Cancer InfoLink that it may be things that happen very early in our lives that may predispose some proportion of every specific population to risk for prostate cancer — but then how do we explain the “Japanese immigration” effect?

7 Responses

  1. For all we know our brand of deodorant or car scent can trigger prostate cancer. These too would be differences in our lives versus those lives in the Pacific rim that never get mentioned in books like the China Study and others.

    A heart healthy diet is easily identifiable as a life-extending decision. I would recommend it for any prostate cancer patient before I would recommend a prostate healthy diet.

  2. What is the difference between a “heart healthy diet” and a “prostate healty diet”? I thought they were more or less the same. But I admit that I am somewhat ignorant about such things.

  3. They are (in fact) pretty much the same.

    I believe Tony was making a remark about some of the more extreme beliefs that diet can truly make a difference to one’s risk for prostate cancer.

  4. Ultimately something like two out of three men diagnosed with prostate cancer die of heart disease. So the advice of Dr. Mark Moyad of the University of Michigan Medical School is for men to live a heart-health-focused lifestyle (diet, exercise, weight, no smoking) in order to fend off that greater threat, which by happy coincidence likely increases one’s chances of avoiding or of surviving prostate cancer too! No magic wands, just moderate eating of things thought to be heart-healthy, moderate exercise, moderation in weight gain, and the only “absolute” is don’t smoke.

  5. I was commenting about some of the books published with diets for the prostate cancer patient. Clearly a heart healthy diet is what anyone should pay attention to. A cruciferous or vitamin E-rich diet, for example, is advertised in prostate cancer diets regularly, but if you can’t stand the broccoli, eat sufficient other greens to maintain a heart healthy diet and don’t worry about the missed selenium opportunity so much. I also regularly read about prostate cancer patients consuming large amounts of various supplements with the thought they can slow their disease progression. There is evidence that vitamin D3 is helpful, but very little evidence about the rest. Eating right is better than a medicine chest full of extracts.

  6. The question is asked “…how do we explain the “Japanese immigration” effect?”

    Has anyone ever looked at other nationalities other than the Japanese for an ‘immigration effect’ or merely taken one small study and quoted and re-quoted it?

    Would Englishmen, to take one nationality at random, have a higher incidence of prostate cancer if any were wise enough to move to the USA? Would this be because of a change in diet or because there is a greater emphasis — and a greater incidence — of prostate cancer in the US than in Britain?

    There is also, from what people who have lived in Japan say, a societal factor. They say there are still “macho-man” issues that make it difficult to admit to prostate cancer and the attendant problems with “loss of manhood.” They claim that some prostate cancer diagnoses are passed off as [cancers originating at] other sites and that the incidence of stomach cancer is higher in Japan because of this, which would also seem to undermine the “healthy Japanese diet” argument.

    I wonder how many people eat the same diet from go to whoa. Maybe I’m in a minority, but just from observation, none of my peers consistently eat what our parents ate — and our children have very different diets from ours.

    Given the estimated time scale for the development of prostate cancer, you’d have to wonder if any study could ever produce any kind of certainty because of the multiple variables in eating patterns.

    And, of course, food is not the only suspect in the development of prostate cancer. Does stress affect the issue? We simply don’t know. There are studies that demonstrate that stress is not a factor, but the same kind of problems apply, with another added — how on Earth can you measure stress accurately? Only by self-reporting — and my stress is simply not the same as anyone else’s. But if stress were a factor, then wouldn’t that have to be taken into account in any “immigration” study? Having moved around the world a fair bit, I can testify to some very high stress levels associated with that activity (and this is supported by studies).

    Anyhow, just my thoughts …. As usual, not entirely without controversy, I am sure. :-)

  7. And also as usual … some very sound thoughts too!

    I am not aware of what I would describe as any really well constructed immigration study that has ever replicated the original Japanese to US study. I would tend to agree with Terry that there are probably 1,001 confounding factors to all of this. The idea that moving from one country to another alone is a significant risk factor for prostate cancer doesn’t seem particularly realistic to me. For starters, many immigrants don’t actually change their dietary habits very much just because they have moved countries!

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