Fresh cranberries are low in calories and are an excellent source of vitamin C, soluble fiber, and insoluble fiber. They also provide a good source of manganese and copper. Cranberries are a rich source of anthocyanidins, which are antioxidant pigments that give fruits and vegetables their blue, purple, and red pigments.
For centuries, Native Americans have used cranberry preparations to treat urinary tract infections (UTIs) and other illnesses. Studies have shown that the chemical and physiological effects of cranberries provide benefits to the urinary tract, and drinking cranberry juice may help to prevent urinary tract infections. Cranberries contain proanthocyanidins (PACs). PACs are effective in inhibiting the fimbrial adhesion of bacteria, including Escherichia coli, to the urinary tract epithelium.
Studies have also shown that cranberries are effective in the prevention of kidney stones. In the United States, about 75 to 85 percent of kidney stones are made up of calcium salts. Several studies have shown that cranberries are beneficial in decreasing the amount of ionized calcium by greater than 50 percent in patients with recurrent kidney stones.
The deeper the red color of the cranberries, the higher the concentration of the healthy anthocyanin pigments. Fresh cranberries, compared to the dried, have the highest amount of the antioxidants. Processing, storage, and heating reduces the antioxidant levels.