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.
The Coffee Beanery. Their website states that an 8 oz cup of their brewed coffee would have between 100-150 mg of caffeine. Since the other coffees have been calculated for a 14 ozâ16 oz cup, we can double this and estimate around 200-300 mg of caffeine for a 16 oz cup of coffee. 4. Peetâs Brewed Coffee