The purpose of this study is to investigate the effects of 3 different corn flours: (1) whole grain corn flour, (2) 50% refined corn flour + 50% corn bran derived from whole corn meal, and (3) refined corn flour, on cardio-metabolic outcomes and changes in the gut microbiome.

Dietary fibers are extremely complex and foster health in a variety of ways that are not fully understood. The Adequate Intake of fiber (14 g per 1000 kcal consumed) is based on data that strongly support a relationship with cardiovascular disease prevention (Slavin, 2013). While cereal fibers have been shown to be most effective at reducing cardiovascular disease risk (IOM, 2002), the components of dietary fiber (e.g. germ, bran) that exert this effect remain inadequately studied in cardiometabolic outcomes. Further, specific types of dietary fiber (natural and synthetic) have been shown to increase beneficial microbial species in the gastrointestinal tract, which are accompanied by improvements in inflammatory and metabolic disease markers. Very little is known about how isolated or intact fiber in whole grains solicit beneficial health effects via microbial mechanisms. Our goal is to study both changes in cardiometabolic outcomes and the gut microbiome after consuming different types of corn-based meals.

Aim 1: To evaluate cardio-metabolic outcomes (primary outcome: LDL cholesterol) after consuming 48 g/d of whole grain corn flour, 50% refined corn flour + 50% corn bran derived from whole corn meal, and refined corn flour for 4 weeks in adult males and females with elevated LDL cholesterol in a crossover design.

Aim 2: To evaluate changes in the gut microbiome after consuming 48 g/d of whole grain corn flour, 50% refined corn flour + 50% corn bran derived from whole corn meal, and refined corn flour for 4 weeks in adult males and females with elevated LDL cholesterol in a crossover design.

Inclusion Criteria:

• Healthy English and Spanish speaking males and females with elevated circulating cholesterol levels (LDL-c ≥ 120 mg/dL).
• Individuals with LDL-c > 190 mg/dL will be permitted to participate but must provide a letter from their doctor stating that they are comfortable with their participation in the study.

Exclusion Criteria:

• recent weight fluctuations (> 5 lb in past 3 months), following specialized or restrictive diets (e.g. carbohydrate restriction, veganism)
• use of supplements (antioxidants, fiber, botanicals)
• allergies to dairy, egg, wheat, corn or gluten
• use of antibiotics in the past 2-3 months
• use of lipid lowering medications
• regular physical activity ≥ 30 min/d for ≥ 5 days/wk
• history of thyroid disorders, diabetes, heart disease, cancer, hepatitis, inflammatory conditions and/or gastrointestinal disorders which may impact gut function and metabolism
• anyone with a fear of needles or blood draws
• If female, women may not be pregnant or lactating during the study.
• Unwillingness to comply with study protocols will also result in exclusion from the study.
• Participants in this study will not be eligible if they are participating in other research studies at the same time.