The study is a randomised double-blinded dietary intervention study. The study population will consist of men (n=20) aged 18-80 years with a BMI between 19.5 and 35 kg/m2 with low risk prostate cancer (prostate specific antigen [PSA] < 10ng/ml; Gleason grade 6; T category T1 or T2) or intermediate risk prostate cancer patients (PSA 10-20ng/ml; Gleason 7 (including selected 4+3 cases that will not be advised for radical prostatectomy; T category T1 or T2) who have visible lesions on MRI and have already decided to take up active surveillance/monitoring. The investigators chose these inclusion criteria because they reflect the population of men on active surveillance that the investigators are currently recruiting in the ESCAPE study (Effect of Sulforaphane on Prostate CAncer PrEvention; ClinicalTrials.gov Identifier: NCT01950143) via the Norfolk and Norwich University Hospital. Volunteers recruited onto this study will be randomly allocated to one of two arms in which they will be required to consume one portion of broccoli soup per week, delivering different levels of glucoraphanin (SF precursor) in each study arm. This will be part of their normal diet for 6 months. The two soups will contain standard broccoli (i), or glucoraphanin-enriched broccoli named for the study 'Beneforte extra' (ii). The study will involve MRI monitoring at baseline and after 6 months. In addition the investigators will collect blood and urine samples at baseline and after 6 months. The volunteers' habitual diet and physical activity will also be assessed during the intervention period.