Is eating meat frequently really a risk factor for prostate cancer?

We regularly tell our readers that a well-balanced, “Mediterranean”-style diet is generally good for our health — whether you are trying to prevent disease in general or because you are trying to manage a diagnosis of prostate cancer.

In making that statement, we should note that the long-term benefits of such a diet have never been proven, specifically, to prevent diagnosis or death from any type of cancer. What has been shown, however, is that such diets, which tend to be lower than most in red meats, dairy fats, and carbohydrates, and higher in products like olive oil, fish, vegetables, fruits, and nuts, appear to be associated with a lower risk for cancer in general as well as a lower risk for all sorts of other common disorders like heart disease and diabetes and obesity. We are all going to die from something, sooner or later. The trick is to live as well as one can for as long as one can manage.

With that background, a new paper by Gilsing et al. in the European Journal of Clinical Nutrition has reported finding that

… individuals consuming meat 1 day per week were at a 75 percent increased risk of advanced prostate cancer compared with 6–7 days per week meat consumers.

In other words, Gilsing et al. say that in their study eating low quantities of meat appeared to raise men’s risk for clinically significant prostate cancer by 75 percent compared to frequent meat eaters. However, they are careful to note that:

… our observations are not supported by previous studies examining prostate cancer risk in relation to meat consumption, meat carcinogens and other variables that are characteristic for a low meat diet. In addition, our findings for a reduced risk of advanced prostate cancer with increasing intake of chicken and processed meat are not supported by previous research …. As a consequence, our observation may be due to chance and warrants replication in other studies.

Gilsing et al.’s study is based on data from a subset of men and women enrolled in The Netherlands Cohort Study — Meat Investigation Cohort (NLCS-MIC), which started to enroll men and women back in 1986. All the 11,082 patients enrolled were between 55 and 69 years of age; all completed a detailed questionnaire on dietary habits and other cancer-related risk factors; and they were then classified into one of groups:

  • Vegetarians, including vegans, i.e., those who ate no meat at all (n = 691)
  • Pescetarians, i.e., those who ate fish but no other form of meat (n = 389)
  • Meat eaters, in three subgroups
    • Those who ate meat on 1 day per week (n = 1,388)
    • Those who ate meat on 2 to 5 days per week (n = 2,965)
    • Those who ate meat on 6 or 7 days a week (n = 5,649)

After 20.3 years of follow-up, the authors report that they found the following:

  • Their study group identified 279 cases of lung cancer, 312 cases of postmenopausal breast cancer, and 399 cases of prostate cancer.
  • 136/399 cases of prostate cancer (34 percent) were “advanced” (by which we assume the authors mean metastatic, but the study report does noit state this explicitly)
  • After taking confounding risks (such as smoking) into account, there was no association between any of the food consumption groups and risk for
    • Lung cancer
    • Postmenopausal breast cancer
    • Prostate cancer (overall)
  • But, men who ate meat 1 day per week and men who ate no meat at all were both at a significantly increased risk of advanced prostate cancer compared with men who ate meat 6 to 7 days per week.
  • Also, after taking confounding risks (such as smoking) in to account,
    • There was no association between low consumption of any individual category of meat item and risk for any of the three type of cancer overall.
    • There was a significantly increased risk for advanced prostate cancer among men who did not eat chicken and who did not eat processed meats.

Interestingly, however, there was almost no difference at all between the risk for advanced prostate cancer between the men who ate meat 2 to 5 days a week and the men who ate meat 6 to 7 days a week. It is also important to note that we are talking about comparing very small numbers of patients out of a relatively large study overall. Of the 136 men with advanced prostate cancer after a median follow-up of 20.3 years,

  • 7 men were vegetarians.
  • 7 men were pescetarians.
  • 19 ate meat on 1 day a week.
  • 31 ate meat on 2 to 5 days a week.
  • 72 ate meat on 6 or 7 days a week.

Quite frankly we don’t know what to make of this study other than to confirm the previously quoted statement by the authors that their results do not conform with data from prior studies. However, for those who believe (or at least want to believe) that eating steak or processed meat on a daily basis is a good thing, this study may offer some degree of comfort! The “New” Prostate Cancer InfoLink would suggest, politely, that if one is going to eat significant quantities of red meat on a daily basis, you’d be wise to make sure that your exercise level or other energy output level justifies that sort of calorie intake!

In a prior paper, the same research group has reported that, based on the same study group of 11,082 men and women, the vegetarians and those with low meat diets were at a non-significantly lower risk for colorectal and (especially) rectal cancers.

2 Responses

  1. The study appears to conclude that a small number of men (136 or 1.2%) got advanced prostate cancer but of that small number, 103 (76%) ate meat from 2-7 times per week. This clearly shows that eating meat frequently, to the extent it causes prostate cancer it causes advanced prostate cancer, no?

  2. Bob:

    I don’t think you can necessarily make that argument because these patients were being enrolled in the study back in 1986. No one in The Netherlands was getting PSA tests on a regular basis until well into the 1990s, so many of the men in this study would never have had the chance to be diagnosed until they had at least progressive disease.

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