Oatmeal has long been a breakfast staple, but a new study suggests that eating it beyond your usual morning bowl may offer a distinct benefit: helping to lower cholesterol in just a couple of days. Here’s what to know.
Oats have been widely studied for their cholesterol-lowering effects. But researchers at the University of Bonn in Germany wanted to investigate how an oat-rich diet affects cholesterol short-term and the role that gut microbes—the bacteria that help break down food—may play in that process.
The new study, published in the journal Nature Communications, included 34 people with metabolic syndrome, a group of health conditions—such as high blood pressure, elevated blood sugar, and abnormal cholesterol levels—that increase the risk of type 2 diabetes or cardiovascular disease.
In two small trials, researchers instructed participants to consume either a diet that included oats or no oats. For the shorter-term study, 17 participants ate three meals of 100 grams (about 3.5 ounces) of rolled oats boiled in water for two consecutive days, while a control group consumed three standardized control meals with no oats. In the other trial, 17 people consumed 80 grams (about 2.8 ounces) of oats per day, with no other restrictions, for six weeks.
Blood tests showed that participants in both groups experienced reductions in LDL cholesterol (the “bad” type). But the two-day group saw a more pronounced drop, with levels falling by an average of 10%. The numbers remained below baseline during a six-week follow-up period, suggesting the oat-rich diet had lasting effects.
“The most striking finding is the persistence of the effect,” said Jason V. Tso, MD, a cardiologist with the Sports Cardiology Program and the Center for Inherited Cardiovascular Disease at the Stanford University School of Medicine.
The staying power suggests oatmeal may actually be “reprogramming” the metabolic environment in a way that leads to lasting change, he said. Indeed, researchers also found that both groups showed increased levels of cholesterol-lowering compounds produced by gut microbes, with a stronger effect in the two-day group.
Although the study was small, it provides insight into the short-term benefits of a high-dose oat diet, said Keith C. Ferdinand, MD, a cardiologist and professor of medicine at the Tulane University School of Medicine.
Still, it’s important to note that all of the participants had metabolic syndrome, meaning the findings may not apply to people without the condition, Marisa Moore, RDN, a culinary and integrative dietitian based in Atlanta, pointed out. “We don’t know that the average healthy person would see the same effects,” she said.
While experts acknowledge the potential of oats as a cholesterol-lowering strategy, they don’t recommend that everyone start eating oatmeal around the clock.
Instead, an oatmeal-heavy diet may serve as a targeted tool for certain people, Tso said. “If other studies confirm the beneficial effects of very short oatmeal-only days, periodic oatmeal loading may even become a therapy for those with metabolic syndrome,” he said.
Still, oats can be a component of a heart-healthy diet, experts said, provided they’re prepared thoughtfully. In the study, for example, the oatmeal was topped with fruits like apples, pears, and berries, as well as vegetables like spinach and leeks. Ingredients like butter or cream contain saturated fat that, when consumed regularly, can have the opposite effect and raise cholesterol levels.
“For most people, adding oats to your diet is a good move for overall heart health, blood sugar control, and digestive health,” Moore said. However, “simply adding oats doesn’t replace the need for overall heart-healthy eating. It’s important to still eat a variety of foods for balanced nutrition.”
