The kidneys are the main organs of the urinary system. They function chiefly to filter blood in order to remove wastes and excess water. The waste and water are excreted as urine. The kidneys also reabsorb and return to the blood needed substances, including amino acids, sugar, sodium, potassium, and other nutrients.
But many popular brands actually contain considerably less than an old-fashioned cup of black coffee. An 8.4-ounce serving of Red Bull, for instance, has a relatively modest 76 to 80 mg of caffeine, compared to the 95 to 200 mg in a typical cup of coffee, the Mayo Clinic reports.
According to one study published in Mayo Clinic Proceedings, a typical energy drink can have as much as a quarter cup of sugar, and upwards of 200 mg of caffeineâmore than youâll find in two very strong cups of coffee (a tall cup has about 71 mg)! Itâs not all doom and gloom.