ETHNIC DIFFERENCES IN DIET AND ASSOCIATIONS WITH SURROGATE MARKERS OF PROSTATE DISEASE IN NEW ZEALAND: ISEE-120


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Abstract

IntroductionOf cancer deaths in New Zealand men prostate cancer is one of the major causes after lung and large bowel. While the majority of NZers are Caucasians of European descent, there are two large populations of Pacific origin-Mäori and Pacific Island people. More Mäori and Pacific Island men die from prostate cancer than NZ European. Ethnicity and diet are linked factors that have been suggested to influence prostate cancer risk. For example, the incidence of prostate cancer in Asian men is significantly lower than in American men. Features of the Asian diet include soy, vegetables, fish and tea, which have all been investigated for possible protective effects. The Western diet is high in meat and saturated fats, and low in fibre, factors that have been associated with increased risk of cancer. Several aspects of red meat have been studied for possible carcinogenic mechanisms, including the fat content and cooking technique used. In our study we aimed to characterise differences in dietary intake between three ethnic groups of New Zealand men- Mäori, NZ European, and Pacific Island; and to examine associations between levels of total Prostate Specific Antigen (PSA) and it's derivatives [complex PSA, free PSA (fPSA), and the ratio of free to total PSA (%fPSA)].Methods1031 men with no history of clinical prostate cancer in the Wellington region of New Zealand completed a food frequency questionnaire. The data was analysed in two separate parts. Firstly we examined the ethnic-specific levels of the selected dietary items. We also looked at cooking technique used for lamb, pork and fish. Secondly, we investigated the relationship between dietary items, PSA levels and urinary symptom scores.ResultsOf the 1031 respondents, there were 616 NZ European, 230 Mäori, and 185 Pacific Island men. The three ethnic groups differed significantly in diet and cooking technique employed. Pacific Island men were found to eat more raw and cooked tomatoes, tomato soup and fish. NZ Europeans were found to eat more tomato paste and drink more alcohol. The Pacific groups were found to eat significantly more lamb, pork and shellfish than NZ Europeans. NZ Europeans were found to fry their meat significantly more so than Mäori or Pacific Island men. Combined tomato intake had a significant positive correlation with fPSA and %fPSA (p=0.021, r=0.197 and p = 0.011, r = 0.096 respectively). Intake of tomato sauce (in NZ, called tomato paste or puree) was positively correlated with %fPSA (p=0.015, r=0.098). Beer intake was significantly negatively correlated with total PSA (p=0.028, r= −0.071) and fPSA (p = 0.004, r= −0.094). The likelihood of having elevated PSA decreased with increasing beer intake (p=0.023). Conclusions:Ethnic variation in diet exists within the population of NZ. It is not clear whether this difference impacts the incidence of prostate disease, although a high intake of tomatoes has been found to be beneficial in terms of lowering prostate cancer risk. It could be important in clinical practice to take features of diet such as high daily beer intake into account when interpreting PSA results.

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