The taste qualities of blueberry jam are combined with incredible benefits for the body. So blueberries are rich in various useful substances. It contains large amounts of B vitamins, ascorbic acid (vitamin C). It is endowed with such minerals as potassium, phosphorus, manganese and magnesium. These berries contain melatonin (a substance that helps fight cancer cells and normalizes sleep), various acids (for example, oxalic, succinic, quinic), as well as tannins.