The findings of the randomized crossover clinical trial, available online now and slated to appear in an upcoming issue of the Journal of Nutrition, reveal simply swapping in foods made from refined corn flour + corn bran can lower LDL cholesterol concentrations by anywhere from 5% - 13.3% in just four weeks.
The trial compared the impact of whole-grain corn meal, refined corn meal, and a blend (refined corn meal plus corn bran) and found that 70% of the participants saw significant reductions in LDL cholesterol concentrations when consuming the blend. For the other corn flours, participants did not see a decrease in their LDL or total cholesterol levels, nor did they see an increase.
"People often think that dietary changes must be robust and significant to have a real impact on cardiovascular health and metabolic regulation," said Corrie Whisner, PhD, lead researcher and Associate Professor in the College of Health Solutions at Arizona State University. "The bottom-line is this: corn is unique and underappreciated. The art and science of refining grains and making full use of corn bran can result in delicious foods that, in this case, also happen to produce real results for heart health."
Dr. Whisner noted that the team intentionally centered the study around avoiding dramatic dietary changes to create a realistic intervention that could be easily folded into a regular diet. Researchers provided study participants with baked goods in order to control type and quantity of corn flour, and study participants did not increase or decrease their grain food intake during the study. These baked goods were developed by a master baker familiar with food formulation techniques and specialty ingredients used in foods commonly found in the grocery store. Their goal in this design was to ensure the study findings would illustrate how practical it can be to regularly incorporate foods made with corn bran-enriched flour as part of a heart-healthy diet pattern.
Surprisingly, the findings did not reveal significant or consistent changes to gut microbiota diversity, which aligns with the fact that study participants reported no digestive discomforts or changes during the interventions. Two genera, unclassified Lachnospiraceae and Agathobaculum, differed significantly by treatment, and while an increase was seen in Agathobaculum (a common bacterium in the gut microbiota) during the whole-grain corn meal phase, that change was not seen in the other two phases.
"The increase in Agathobaculum could be due to the greater diversity of polyphenols found in whole grain corn, which has the highest antioxidant capacity (compared to wheat, oats, and rice), but the study did not analyze this possibility," said Whisner. "Nevertheless, while the influence of whole grains on the microbiota varies from person-to-person, some universals are generally known fibers in whole grains can be fermented by microbes into butyrate, and both fiber and butyrate are frequently associated with a healthy gut. These findings support that understanding.
The 36 study participants were all located in Phoenix, AZ, and spanned in age from 18-67. They included a mix of women (~58%) and men, all entered the study with mild-to-moderately elevated LDL cholesterol levels, and none were taking cholesterol-lowering medications during the study. Over the course of the study, the participants individually cycled through each food intervention for four weeks (with a minimum of a two-week washout period in between interventions to return to baseline) to more evenly assess the impacts of each intervention.
The newly released study in the Journal of Nutrition can be found online here. It was led by a team of researchers at Arizona State University, with funding from the Corn Division of the North American Millers' Association (NAMA). NAMA did not provide any oversight over the study design, collection, analysis, and interpretation of data, nor writing and revising the manuscript for publication.
