Two Days of Oatmeal May Lower Bad Cholesterol by 10 Percent, Study Finds

Eating mostly oatmeal for just two days may significantly lower "bad" LDL cholesterol and trigger beneficial changes in gut bacteria, according to a randomized clinical trial from the University of Bonn published in Nature Communications. The study involved people with metabolic syndrome, a cluster of risk factors that includes excess body weight, high blood pressure, elevated blood sugar, and abnormal cholesterol levels.

During the 48-hour intervention, participants consumed 300 grams of oatmeal per day—served as three meals—while reducing their overall calorie intake by about half. They were allowed only small portions of fruit and vegetables. A control group also followed a calorie-restricted diet but did not consume oats. In total, 32 individuals completed the short-term oat-based phase.

Although both groups experienced some benefits from eating fewer calories, the improvements were more pronounced in the oat group. LDL cholesterol levels dropped by approximately 10%, a substantial reduction linked to lower cardiovascular risk. Participants in the oat group also lost an average of two kilograms and experienced slight reductions in blood pressure. Notably, the cholesterol-lowering effect remained measurable six weeks after the two-day intervention.

Further analysis suggested that changes in the gut microbiome may explain part of the benefit. Oat consumption increased specific bacteria that produce phenolic compounds such as ferulic acid, which has been associated with improved cholesterol metabolism. Researchers also observed microbial shifts related to histidine metabolism, potentially influencing insulin sensitivity.

In a separate six-week phase where participants consumed 80 grams of oats daily without calorie restriction, only modest improvements were seen. The findings suggest that short, intensive oat-based interventions may offer a practical strategy to improve heart and metabolic health.

REFERENCE: Linda Klümpen, Aakash Mantri, Maren Philipps, Waldemar Seel, Laura Schlautmann, Mohamed H. Yaghmour, Verena Wiemann, Birgit Stoffel-Wagner, Martin Coenen, Leonie Weinhold, Jan Hasenauer, Thomas Fließwasser, Sven Burgdorf, Christoph Thiele, Peter Stehle, Marie-Christine Simon. Cholesterol-lowering effects of oats induced by microbially produced phenolic metabolites in metabolic syndrome: a randomized controlled trial. Nature Communications, 2026; 17 (1) DOI: 10.1038/s41467-026-68303-9