Phytochemicals, polyunsaturated fatty acids and selenium in prostate cancer : - a randomized controlled trial

Abstract

Background: Prostate cancer (PC) is the most commonly diagnosed type of cancer in the Norwegian population. Several dietary factors are proposed to affect PC development. The aim of this study was to evaluate whether a dietary intervention have effects on prostate specific antigen (PSA)-development, biomarkers of inflammation and insulin-like growth factor-1 (IGF-1) in the period between diagnosis and elective therapy in PC patients.

Methods: A randomized controlled trial was conducted, patients (n = 78) were allocated to control or one of two interventions; 1) tomato product containing 30 mg/day of lycopene, or 2) a “multi-diet” approach with the same tomato products plus daily supplementation of 200 µg selenium, 200 mg soy isoflavones, 5 g fish oil, 1 cup black and green tea as well as 0.33 L of pomegranate- and grape juice. The trial lasted a median of 21 days. Statistical analysis was stratified by baseline values as well as developments in biochemical markers of compliance. Primary endpoints were changes in PSA levels, secondary endpoints were IGF-1 and biomarkers of inflammation.

Results: Increase of total PSA values was lower in patients with intermediate tumor risk in both tomato and multi-diet intervention (p=0.015 and p=0.037 respectively). Patients with high increases in plasma lycopene, selenium and eicosapentaenoic acid combined during the intervention had lowered total and free PSA values (p=0.003 and p=0.004 respectively) compared to those with low increases. Similarly, when stratifying by plasma lycopene changes, different changes in both total PSA and free PSA levels were found (p=0.009 and p=0.039 respectively). No significant differences were seen in biomarkers of inflammation.

Conclusion: Tomato and multi-diet supplementation decreased PSA development in patients with intermediate tumor risk. Tomato supplementation decreased PSA development most efficiently in patients with high increase in plasma lycopene. There was an added effect on PSA in patients with corresponding increases also in selenium and omega-3 fatty acids. The results add substantially to the evidence from clinical human trials of diet as a modulating component of PSA-development on established PC, and warrant further studies.