Middle-school students will be recruited and randomized to receive >/=80 g of whole grains (>/=5 servings) or similar foods made with refined grains each day for six weeks. Based on treatment group, subjects will be provided either whole grain or refined grain foods and snacks. They will be instructed on how to use these foods to replace other foods already contained in the diet. Stool, blood, and saliva samples will be obtained at baseline and at study end to examine the microbiota and markers of digestive and immune health. Daily records will be maintained by the students to assess bowel habits and compliance. It is anticipated that whole grains will increase stool bulk resulting in increased stool frequency and softer stools. Additionally, fermentation of the fiber within the colon will alter the microbiota profile. Because the majority of the immune system resides within the gastrointestinal tract, improved balance of the intestinal microbiota may prime the immune system thus contributing to improved immune defense.