Black currant is the king of currants in terms of nutritional value. It's a vitamin C bomb and is commonly known as a "cold medicine". When you have a cold, you are advised to drink warm blackcurrant juice, but by juicing blackcurrant, the amount of vitamin C is halved.
In addition to vitamin C, black currants also contain vitamin E and flavonoids. These are antioxidants and are believed to slow down the aging of the body and prevent the development of arterial diseases and some cancers. Flavonoids, on the other hand, seem to protect against cardiovascular diseases.
Blackcurrants can help with weight management, as they contain only a small amount of energy and the water and dietary fiber contained in the berries together maintain a feeling of satiety.
Blackcurrants also contain potassium, which promotes salt secretion and thus lowers blood pressure. As well as organic acids, which in turn enhance the absorption of iron.
Source: https://www.hyvaterveys.fi/artikkeli/ruoka/mustaherukasta_apua_silmille_ja_aivoille