What is the primary source of dietary fiber in the human diet?

Dietary fiber is primarily made up of non-starch polysaccharides (NSPs), which are a significant component found in plant foods. NSPs are complex carbohydrates that are not digested by the human digestive system, and they play a crucial role in promoting digestive health. They help to add bulk to the stool, facilitate regular bowel movements, and can aid in the prevention of certain diseases such as constipation, diverticulitis, and potentially colorectal cancer.

Eating a diet rich in NSPs—found in foods like fruits, vegetables, legumes, whole grains, and nuts—contributes significantly to overall health. Unlike the other options listed, which include sugars, fats, and proteins (all of which serve different nutritional purposes), NSPs are specifically recognized for their fiber content and benefits in supporting digestive health. Thus, the identification of NSPs as the primary source of dietary fiber accurately reflects their unique and vital role in the diet.