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.
Larger sizes, which are made with two, or even three, espresso shots (16 oz), likewise contain 150 or 225 mg of caffeine. Decaf coffee from Starbucks contains 15â30 mg of caffeine, depending on cup size. Bottom Line: An 8-oz, brewed coffee from Starbucks contains 180 mg of caffeine. A single espresso and espresso-based drinks contain 75 mg, while an 8-oz cup of decaf coffee contains about 15 mg of caffeine. McDonaldâs