Nutrition Science and Everyday Application - beta v 0.1

218 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
sure why. One hypothesis is that dietary fiber decreases transit time (the time it
takes for food to move through the digestive tract), thereby exposing the cells of
the gastrointestinal tract to carcinogens from food for a shorter time.
• Helps maintain a healthy body weight. Research has shown a relationship
between higher dietary fiber intake and lower body weight. The mechanisms for
this are unclear, but perhaps high-fiber foods are more filling and therefore keep
people satisfied longer with fewer calories. High-fiber foods also tend to be more
nutrient-dense compared to many processed foods, which are more energy-dense.
WHOLE VS. REFINED GRAINS
Before they are harvested, all grains are whole grains. They contain the entire seed (or
kernel) of the plant. This seed is made up of three edible parts: the bran, the germ, and the
endosperm. The seed is also covered by an inedible husk that protects the seed.
Figure 4.24. Wheat growing in a field.