Background

The goal of this systematic review was to determine whether dietary patterns are associated with risk of prostate cancer. Dietary patterns were defined as the quantities, proportions, variety or combination of different foods, drinks and nutrients in diets and the frequency with which they are habitually consumed.

Conclusion statement

No conclusion can be drawn regarding the relationship between dietary patterns and the risk of prostate cancer. This is due to limited evidence from a small number of studies with wide variation in study design, dietary assessment methodology and prostate cancer outcome ascertainment.

2015 DGAC Grade: Not assignable

Methods

Literature searches were conducted using PubMed, Embase, Navigator (BIOSIS, CAB Abstracts and Food Science and Technology Abstracts) and Cochrane databases to identify studies that evaluated the association between dietary patterns and risk of prostate cancer. Studies that met the following criteria were included in the review: randomized controlled trials (RCTs), non-randomized controlled trials, prospective cohort studies, or nested case control studies; human subjects aged two years and older who were healthy or at elevated chronic disease risk; subjects from countries with high or very high human development (2012 Human Development Index); and published in English in peer-reviewed journals. The date range was from January 2000 to January 2014. The intervention or exposure was adherence to a dietary pattern (e.g., a priori patterns, data-driven patterns, reduced rank regression (RRR) or patterns derived from other methods, and a description of the dietary pattern(s) (i.e., foods and beverages) consumed by subjects was provided. The outcome was incidence of prostate cancer.

Data from each included article were extracted, and risk of bias was assessed. The evidence was qualitatively synthesized, a conclusion statement was developed and the strength of the evidence (grade) was assessed using pre-established criteria including evaluation of the quality and risk of bias, quantity, consistency, magnitude of effect and generalizability of available evidence.

Findings

• This systematic review included seven prospective cohort studies (from six different cohorts) published since 2000 that examined the relationship between dietary patterns and risk of prostate cancer
• The studies used different methods to assess dietary patterns. Three studies used index scores to assess dietary patterns, two studies used factor analysis, one study used principle components analysis and one made comparisons on the basis of animal product consumption
• Most of the seven studies included in this systematic review did not detect clear or consistent relationships between dietary patterns and risk of prostate cancer, although one found that adherence to the Dietary Guidelines (assessed using the HEI-2005 and AHEI-2010) was associated with a lower risk of prostate cancer, particularly among men who had a prostate-specific antigen (PSA) screening in the past three years.

Limitations

The ability to draw strong conclusions was limited by the following issues:

• These studies used a range of different approaches for assessing dietary patterns in populations with variable cancer screening patterns
• Had heterogeneous prostate cancer outcome ascertainment
• Were typically limited to dietary exposure late in life
• Results were inconclusive regarding risk for clinically significant prostate cancer.