The Effects of Corn Flour on Heart Health and the Gut Microbiome on Hyperlipidemic Adults

Grains are a major dietary staple in many cultures and countries. Corn can be consumed as either a fruit, vegetable, or grain. In the case of the Corn and Heart Health Study (CHS), the effect of corn flour was examined. The study used three varieties of corn flour (whole grain, refined, and a refined plus bran blend), provided by the North American Millers Association (NAMA), to examine the effectiveness of corn flour on lowering low-density lipoprotein (LDL) cholesterol as well as its effects on the diversity of the gut microbiome. The objective of this analysis was to determine the magnitude of change between pre- and post- intervention serum blood samples and the changes in alpha (within-sample) diversity in the gut microbiome. The study utilized a randomized-single blinded, crossover model. The study was 16 weeks long, with three 4-week long treatment periods with two-week washout periods in between. During each treatment period blood samples, stool samples, a diet record, and questionnaires were collected from participants. Two blood samples were collected at the beginning and end of each treatment period to account for potential day to day changes on LDL cholesterol. For the purpose of this study, the results of blood and fecal analysis were used to determine the effectiveness of the intervention. Fecal analysis using the Shannon Index showed that there was no significant difference in the within-sample microbiome diversity by corn flour type (H=2.86, p=0.72). Pre-treatment plasma LDL levels were subtracted from post-treatment levels and analyzed using a general linear model that controlled for sequence, period and a nested (ID[sequence]) variable to account for the within-person crossover design. This showed that the bran-enriched flour had the highest mean reduction in LDL cholesterol while the refined and whole grain flour resulted in increases in LDL cholesterol. The change in LDL cholesterol for bran-enriched flour was significantly different from the refined flour (Mean Difference of -14.97 mg/dL; P=.041). The results of this study indicate that refined corn flour enriched with bran could be a recommended addition to the diet to prevent cardiovascular disease and reduce LDL cholesterol in individuals who are at low risk.