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.
Eight ounces of brewed coffee may contain as little as 80 to as much as 200 mg of caffeine per cup (an âaverageâ cup probably contains about 100 mg). Your best bet: Skip the fat-filled, sugar-laden coffeehouse beverages and order a basic black coffee. Alternatively, switch to skim milk or unsweetened soy or nut milk.