A diet high in vegetable intake can reduce the risk of prostate cancer (CaP), says a new study.
In the online edition of Molecular Nutrition and Food Research, Ruth Chan and collaborators suggested that the primary mechanism of the protective vegetable effect is antioxidant protection against DNA and cell damage.
Literature, which was already available, was identified for the study. Of the available studies, 29 were cohort studies, 69 case-control studies, and 4 randomised clinical trials.
Tomatoes and their byproducts contain the carotenoid antioxidant lycopene. Two cohort studies reported tomatoes decreased CaP risk and 3 cohort studies reported a non-significant association. For case-control studies, 2 showed significant decreased risk and 5 showed a non-significant association.
One study suggested that the potential benefit was greater in advanced as compared to localized CaP. Overall, studies for tomatoes and lycopenes show inconsistent results on decreasing CaP risk, but lycopene based foods are probably protective.
Yellow orange vegetables contain the antioxidant ▀-carotene. Data on ▀-carotene and CaP risk from cohort and case-control studies were inconclusive for a protective effect.
Supplemental use of ▀-carotene was not shown to be protective. Flavonoids are a carbon structure compound ubiquitously present in plant foods and have anti-oxidative and anti-inflammatory properties.
They may suppress angiogenesis, induction of apoptosis and down-regulation of hormone receptors expression. Overall there is some evidence suggesting that consumption of legumes, including soy and soy products, is protective against CaP.
Regarding vitamins, vitamin C has had limited study, but with the data available there is no evidence of a protective effect.