Lois is a 65-year-old female who participates in an exercise class at least three times a week. In addition, she drinks six glasses of water each day and consumes a lot of fresh fruits and vegetables and whole-grain breads and cereals. Lois has high blood pressure, takes medication for hypertension and experiences constipation frequently. Which of the following is the most likely cause of her constipation.
A) Lack of exercise
B) Dehydration
C) High-fiber diet
D) Medication side effects