Final answer:
Most Americans do not meet the recommended intake levels of dietary fiber, consuming less than needed due to a diet rich in refined grains and lacking in fruits, vegetables, and whole grains.
Step-by-step explanation:
The intake of dietary fiber in the current American diet is generally lower than the recommended levels. According to the Institute of Medicine and various health guidelines, including those from the Mayo Clinic, an adequate intake of fiber is essential for good health, offering benefits such as improved bowel regularity, blood glucose regulation, cholesterol removal, and potentially reduced risks of diseases like coronary heart disease, type 2 diabetes, and colon cancer. The recommended daily fiber intake for adults varies by age and gender, but dietitians often suggest a ratio of about 3 parts insoluble fiber to 1 part soluble fiber.
Fiber is found in whole grains, legumes, vegetables, and fruits; however, the Standard American Diet (SAD) is heavy in processed and artificially sweetened foods, which contain lower amounts of fiber. To increase fiber intake, one should incorporate more of these whole, plant-based foods into their diet. Despite the availability of fiber-rich foods, most Americans consume too little fiber, often due to a lack of fruits and vegetables and an overreliance on refined grains.
In summary, the final answer to the student's question is B, which states that Americans consume too little fiber because of too few fruits and vegetables and too many refined grains. Increasing intake of whole foods can help bridge this dietary gap.