Packed with catechin and epicatechin, these two compounds neutralize free radicals that damage cells genetic material and provoke cancer. Catechins also help to lower cholesterol levels which in turn reduces the risk of heart disease. The quercetin in blackberries attacks production of free radicals and help in preventing bad cholesterol from causing damage to blood vessels. Another benefit of quercetin is that it halts the production of substance called histamine that makes allergy sufferers sneeze and wheeze. Fibers in blackberries prevent constipation and colon cancer.