Diet and prostate cancer risk: a case-control study analysis

The idea that one’s diet may affect one’s risk for prostate cancer in general — or perhaps for one’s risk of more aggressive forms of prostate cancer — is not exactly new. There have been all sorts of hypotheses and concepts tested over the years, but to date there are no definitive data from large, randomized trials that have ever established that a specific diet of any type reduced risk for clinically significant prostate cancer.

In a newly published report, Hardin et al. have now looked at the impact of diets high in leafy vegetables (spinach, broccoli, collard greens), high carotenoid fruits and vegetables (carrots, squash, tomatoes), and high glycemic index foods (white bread, donuts, Corn Flakes) on risk for more aggressive forms of prostate cancer.

The authors conducted a case-control study among 982 men, comparing the highest 25 percent (quartile) of men in each group to the lowest quartile based on their diet.

Here is what they report:

  • 470 study participants (the “cases”) had aggressive forms of prostate cancer cases.
  • 512 study participants acted as the “controls”.
  • High intakes of leafy vegetables were inversely associated with risk of aggressive prostate cancer (adjusted odds ratio [OR] = 0.66).
  • Higher intakes of high carotenoid vegetables were inversely associated with risk of aggressive prostate cancer (adjusted OR = 0.71).
  • High intakes of foods with a high glycemic indexwere positively associated with risk of aggressive cancer (adjusted OR = 1.64).
  • These results were driven by a number of specific foods within the food groups.

We have asked the authors for a copy of the full test of this paper so that we can review it in more detail. However, we have not yet received such a full text. As a consequence, it is hard to know what to make of this paper. The abstract of the paper does not indentify the “specific foods” mentioned above. Also, it is not clear from the abstract whether the “controls” had to have no diagnosis of prostate cancer or were diagnosed only with low-risk prostate cancer.

The authors claim that their findings “support the hypothesis that diets high in vegetables and low in high glycemic index foods decrease risk of aggressive prostate cancer.” However, case-control studies like this should always be interpreted with caution. It is true that the stdy findings appear to “support” this hypothesis, but that is a long way from proving that the hypothesis is actually correct.

3 Responses

  1. Even if the study is bogus, it’s still good to eat well, i.e., high content of vegetables and fruits and less meat and carbo.

  2. Reuven’s comment is absolutely correct. A “heart healthy” diet is a prostate healthy diet.

  3. I suggest one look at the published results of research done by Maria Traka et al “Broccoli consumption interacts with GSTM1 to perturb oncogenic signalling pathways in the prostate.” This paper is available on the PlosOne website. This may not be a clinical trial but then the question needs to be raised, Why not?

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