Scientists have revealed a simple yet effective diet that keeps cholesterol levels in check.
According to researchers at the University of Bonn, just two days of eating an almost exclusively oatmeal-based diet significantly lowered harmful cholesterol levels, with benefits still visible six weeks later.
The findings, published in the journal Nature Communications, come from a controlled trial involving people with metabolic syndrome—a common cluster of risk factors that includes excess weight, high blood pressure, elevated blood sugar and unhealthy cholesterol levels.
While none of the participants had diabetes, all were considered at increased risk for developing it.
For two days, one group followed a strict but straightforward plan: oatmeal, three times a day. The oats were boiled in water, with the addition of small amounts of fruit or vegetables allowed.
Participants ate about 300 grams of oatmeal per day and consumed roughly half their usual calories. A control group also reduced calories but did not eat oats.
Both groups saw some health improvements, but the oatmeal group stood out. Their levels of LDL cholesterol—the type most strongly linked to heart disease—dropped by around 10 percent in just 48 hours.
On average, they also lost about two kilograms (roughly four and a half pounds), and their blood pressure dipped slightly. Crucially, the cholesterol improvement didn’t vanish once normal eating resumed. Six weeks later, the lower LDL levels largely held steady.
“That is a substantial reduction,” said paper author and nutrition and microbiota professor Marie-Christine Simon of the University of Bonn, Germany, in a statement. While the effect is not as strong as what modern cholesterol-lowering drugs can achieve, she noted that it is still impressive given the simplicity and short duration of the oat-based intervention.
High LDL cholesterol is dangerous because it can build up in blood vessel walls, forming plaques that narrow arteries. If those plaques rupture, they can trigger blood clots, heart attacks or strokes. Even modest reductions in LDL can lower long-term cardiovascular risk.
The benefits of the two-day oat-rich diet were demonstrated specifically in people with metabolic syndrome, meaning the effect is yet be demonstated in healthy individuals.
However, Simon said the cholesterol-lowering mechanism itself is likely not unique to this population. The drop in LDL cholesterol was closely linked to compounds produced when gut microbes break down oats—particularly ferulic acid-related metabolites—a process that occurs in most people, though with varying efficiency, she explained.
“This indicates that the observed effects are mechanistically general, but their magnitude may differ across populations,” Simon told Newsweek.
“Individuals with metabolic syndrome may experience more pronounced improvements because they typically have elevated baseline cholesterol levels and altered metabolic regulation, leaving greater room for measurable improvement.”
Further studies in healthy people and other metabolic conditions are needed to determine how widely the benefits apply and who stands to gain the most, she added.
So how can two days of oatmeal have such a lasting impact? The answer appears to lie in the gut. The researchers found that the oat-heavy diet changed the makeup of participants’ gut bacteria.
“We were able to identify that the consumption of oatmeal increased the number of certain bacteria in the gut,” explained paper author Linda Klümpen, also of the University of Bonn, in a statement.
These bacteria, the researchers explain, release metabolic by-products into their environment, providing energy to gut cells and supporting their function.
One of these substances, formed when bacteria break down components of oats, has previously been linked to healthier cholesterol metabolism. At the same time, other gut bacteria helped reduce compounds associated with insulin resistance, a key driver of type 2 diabetes.
Interestingly, the researchers also tested a gentler approach: eating a smaller amount of oats—about 80 grams per day—over six weeks, without cutting calories.
That strategy led to only minor improvements. The results suggest that a short, intensive oat “reset,” paired with temporary calorie reduction, may be more effective than sprinkling small amounts of oats into an otherwise unchanged diet.
The researchers warned that oatmeal is not a replacement for medication or medical advice.
“As a next step, it can now be clarified whether an intensive oat-based diet repeated every six weeks actually has a permanently preventative effect,” Dr. Simon said.
Do you have a tip on a health story that Newsweek should be covering? Do you have a question about cholesterol? Let us know via health@newsweek.com.
Reference
Klümpen, L., Mantri, A., Philipps, M., Seel, W., Schlautmann, L., Yaghmour, M. H., Wiemann, V., Stoffel-Wagner, B., Coenen, M., Weinhold, L., Hasenauer, J., Fließwasser, T., Burgdorf, S., Thiele, C., Stehle, P., & Simon, M.-C. (2026). Cholesterol-lowering effects of oats induced by microbially produced phenolic metabolites in metabolic syndrome: A randomized controlled trial. Nature Communications, 17(1), 598. https://doi.org/10.1038/s41467-026-68303-9