Can diet really prevent prostate cancer?


There seems to be little doubt that certain groups of men, who, for one or more reasons, have certain specific types of diet, living in certain places at certain times, are at lower risk for prostate cancer than those who consume what we might think of as the diet of the average American today.

In Japan, for example, there has been a historic reliance on a diet relatively high in rice, fish, and vegetables and low in red meat. There has also been a historically low risk for prostate cancer. However, as a more Westernized diet has become available in Japan, the risk for prostate cancer seems to have been rising.

In a recent publication from an Australian team, Itsiopoulous et al. have discussed the risk of prostate cancer among Greeks in Greece and the relatively high population of Greek ethnic origin now in Australia under the title, “Can the Mediterranean diet prevent prostate cancer?”

Itsiopoulous and colleagues clearly note some of the historic evidence for an association between environment and prostate cancer, including the (apparent) large worldwide variation in prostate cancer risk and the increased risk among migrants moving from low risk to high risk countries. They also rely heavily on the findings of an expert panel convened on behalf of the World Cancer Research Fund and the American Institute for Cancer Research, and new data published since that time linking identified foods and nutrients with prostate cancer. In their belief, “evidence indicates” that:

  • Foods containing lycopene probably protect against prostate cancer
  • Selenium and foods containing it probably protect against prostate cancer (which would recently seem to have been disproved recently, at least in American populations)
  • Excess consumption of foods or supplements containing calcium are a probable cause of prostate cancer
  • It is unlikely that β-carotene (whether from foods or supplements) has a substantial effect on the risk of this cancer
  • There may be protective effects of vitamin E, pulses, soy foods, and high plasma 1,25-dihydroxyvitamin D levels (again the protective effects of vitamin E in American populations can be questionned based on the results of the SELECT trial)

The point that they lead up to is that the so-called “Mediterranean diet” is abundant in foods containing products that are or have been believed to protect against prostate cancer and is associated with longevity and reduced cardiovascular and cancer mortality.

Itsiopoulous et al. go on to point out that, compared with many Western countries, Greece has a low prostate cancer mortality rate and that Greek migrant men in Australia appear to have have retained their low risk for prostate cancer. They conclude that “Consumption of a traditional Mediterranean diet, rich in bioactive nutrients, may confer protection to Greek migrant men, and this dietary pattern offers a palatable alternative for prevention of this disease.”

The “New” Prostate Cancer InfoLink has little doubt that certain types of diet, consumed over an entire lifetime, within a specific environment, have certain types of health benefit compared to the diet of the average American, which can generally be characterized as excessive, with an overabundance of fat, red meat, sugar, and all sorts of biochemicals used to “improve” agricultural productivity (from bovine growth hormone to preservatives). However, there are other common charactistics shared by those who traditionally consume Mediterranean-style diets that are less common among Americans:

  • They think working 14 hours a day is insane
  • They take vacations
  • They eat slowly; meals are a joy, not something to be crammed in between other obligations

We could go on.

Then there is another factor. Even if the Greek community in Australia continues to eat a Mediterranean diet, we can have little doubt that that Mediterranean diet is commonly based on products that were grown with the modern “benefits” of agribusiness. They aren’t importing their tomatoes from Greece or probably their olives either. It is unlikely that every Greek houswife in Australia is solemly buying only “certified organic” products. So it is questionable whether they are really eating the same diet as they would be eating in Greece at all in terms of the quantities of micronutrients and vitamins.

Let us look at an American subpopulation that (at least in some parts of the country) remains significantly “traditional” in its dietary habits — the Italian-American community. Italians have many of the same social and dietary habits as Greeks, and they proudly brought these habits with them to America (to the great pleasure of many of the rest of us!). However, to date we have neither heard nor seen any suggestion that Italian-Americans are at a specially lower risk for prostate cancer than most of the rest of Americans of European origin.

There is an enormous attraction to the idea that diet can prevent certain types of disease … and there is absolutely no doubt that diet is a key factor in risk for certain types of disease over time. (“You are” after all “what you eat”.) However, diet is only one in a vast number of factors that may affect prostate cancer risk. There are many, many excellent reasons for arguing that a Mediterranean-type diet is healthier than a regular diet of cheeseburgers and similar American convenience foods. But The “New” Prostate Cancer InfoLink continues to believe that diet is only one of the potential factors that affects prostate cancer risk.

So why is it that the male members of the Greek community in Australia still appear to have a lower risk for prostate cancer than the average Australian? We have no idea. We can think of several possibilities, however:

  • Time since migration (has it been long enough?)
  • Continuing ethnic intermarriage (do Greeks in Australia still tend to intermarry with other Greeks, thereby maintaining a specific gene pool with selective benefits associated with risk for prostate cancer?)
  • Better adaptation than average Australians to high levels of sunlight (Greek genes have thousands of years of adaptation to high levels of sunlight on their skin; does this make them better at maintaining certain vitamin and hormone levels?)

Again, we could go on.

The point of this commentary is in no way to disparage the article by Itsiopoulous et al. These authors have proposed a hypothesis that needs to be tested. The point of this article is to thoroughly emphasize the word “may” in their above-mentioned conclusion, and to make it clear that actually testing the hypothesis that they have put forward could be extremely difficult (if not impossible) unless they can identify highly controllable comparator populations (which is becoming increasingly unlikely in our highly connected world).

2 Responses

  1. Your article exploring whether diet is a risk factor for prostate cancer is well-crafted and extremely balanced.

    Its key argument is that many factors apart from nutrition can explain why Greek migrants in Australia tend to have fewer incidents of prostate cancer than Australia’s general population and those who live in the U.S. or other Western countries. In my mind this excellent presentation raises a larger issue than whether the right diet can lower the incidence of prostate cancer in a given country.

    The bigger issue is whether prostate cancer can be prevented or avoided all together, through any known means, be it diet or other factors, given the many variables that lead to this disease. My assumption, as underscored in my book Conquer Prostate Cancer: How Medicine, Faith, Love and Sex Can Renew Your Life (www.ConquerProstateCancer.com), is that we neither know what causes prostate cancer nor what can stop it or prevent it altogether, even if we eat “right” — meaning even if we ingest only doctor-recommended food.

    This does not mean that as a society, Americans may as well eat, drink and be merry, avoiding fish rich with omega oil and substances like lycopene, in favor of red meat and shmaltz! Surely eating food that will help avoid other complications like blockage of the arteries is best. And if that happens to coincide with a lower risk of getting prostate cancer, so much the better!

    Rabbi Ed Weinsberg (Sarasota, Florida)

  2. Dear Rabbi Ed:

    We wouldn’t disagree with your premise that (at present) we have no idea how to prevent prostate cancer at all. We also wouldn’t degree with your postulate that prevention of heart disease in men is probably more important than preventing prostate cancer anyway (see “What is prostate cancer?” elsewhere on this site).

    Please understand that our focus in this commentary was entirely on what appeared to us to be “magical thinking” — a well-defined scientific phenomenon in which the hypothesis the investigators would like to be able to demonstrate is argued to be near to true based on its supposed self-evidence.

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