RELATED: What’s the Difference Between Whole Wheat, Whole Grain, and Multigrain Bread? Fiber is a key component of gut health, including elimination and detoxification of the colon, which helps to regulate digestion and can reduce the risk of colon cancer, says Joy McCarthy, CNP, a holistic nutritionist and founder of Joyous Health. Fiber also feeds your gut microbiome, which is made of trillions of good bacteria essential to a healthy immune system. RELATED: We Know Whole Grains Are Good for You, but These 11 Are the Healthiest