Prostate cancer is a major public health problem and there is a strong need of new preventive strategies based on drug and lifestyle interventions. It is now well-established that healthy eating patterns and increasing physical activity can prevent or delay prostate cancer progression. Intake of cruciferous vegetables (e.g. broccoli, cabbage, cauliflower, Brussels sprouts, kale) has been associated with decreased risk of prostate cancer progression; however the underlying biological mechanisms remain unknown. The investigators propose to undertake a pilot study on a group of men with early prostate cancer on active surveillance to determine whether a diet rich in broccoli will induce changes in tumor size and blood flow measured by conventional Magnetic Resonance Imaging (MRI) techniques. Men with early prostate cancer on active surveillance who have visible cancer lesions on MRI will be recruited onto this double-blinded randomized intervention and they will be asked to eat one portion of broccoli soup per week for 6 months. The investigators will test two varieties of broccoli (standard and 'Beneforte extra' broccoli) that are able to deliver two different levels of sulforaphane (SF), an active compound extensively studied for its potential anticancer properties. This study will involve MRI scans, blood and urine collection before and after a 6 month intervention period. This study design will not only allow us to observe diet-induced changes within the prostate but also at the systemic level. In addition, participant's lifestyle (habitual diet and physical activity) will be assessed by food diaries and exercise questionnaires.