The study is a randomised double-blinded dietary intervention study. The study population will consist of smoking and non-smoking men aged between 18 and 80 years old. Participants recruited into this study will be randomly placed into one of three dietary groups in which they will be required to consume one portion of broccoli soup per week, delivering a different level of glucoraphanin (sulforaphane precursor), as part of their normal diet for one year. The three types of soup will contain (i)standard broccoli, (ii)glucoraphanin-enriched broccoli (Beneforte®), or (iii)Beneforte extra. Beneforte and Beneforte extra broccoli are especially cultivated to deliver high sulforaphane levels after consumption. All the three broccoli varieties have the same appearance and flavour thus enabling a blinded human intervention study to be undertaken. Broccoli soups will be manufactured by a food company that supplies soups to the leading supermarket retailers in the United Kingdom. In order to assess the habitual diet of the participants, they will be asked to keep three 7-day diet diaries, one pre-intervention, after 6-months and another one week before the end of their intervention. Considering the effect of exercise on whole body metabolism we will also obtain information on the physical activity of study participants. They will be asked to complete a validated physical activity questionnaire together with the diet diary (i.e before starting the study diet then at 6 and 12 months). Twenty six participants will be recruited to each of the broccoli groups. The participants will be characterised as having a low or intermediate risk of developing prostate cancer and will be undergoing active surveillance. A number of physiological tests will be performed on the participants before they start the dietary intervention (baseline) and after their 12 months on the intervention. The study will involve collection of prostate biopsies, blood and urine samples at baseline and after a 12 month dietary intervention. Prostate biopsies will be obtained through transperineal template biopsy (TPB) where possible or standard transrectal ultrasound scan guided biopsy (TRUS biopsy). TPB is a clinical procedure carried out under a general or regional anaesthetic which gives more detailed information about the position, amount and aggressiveness of the cancer within the prostate than other standard techniques. However, patients who do not wish to undergo TPB can alternatively choose the standard TRUS biopsy.

At the end of the trial participants will be asked to give written consent if they wish to continue the diet for a further 12 months. Consenting patients will thereafter be required to eat one portion of broccoli soup per week for 12-months. We will not ask participants to attend extra hospital visits for the purpose of the study or give additional biological samples; instead we will capture clinical data related to their follow up of prostate cancer.

It is anticipated that the dropout rate for this study will be approximately 25% due to the clinical progression of prostate cancer within the 12-month study period. In the event of clinical progression the volunteer will discontinue the intervention, receive advice from the urologist in charge and in case of prostatectomy will be asked to donate part of their prostate gland for research purposes.