By changing the composition of the human gut microbiome, a short-term oat-based diet may effectively lower cholesterol levels, according to two recent trials. The findings build on cereal’s long-standing status as a dietary intervention for diabetes.

“Today, effective drugs are available to treat patients with diabetes,” says Marie-Christine Simon, an associate professor at the Institute of Nutrition and Food Science at the University of Bonn in Germany.

“As a result, this method has been almost completely ignored in recent decades. We wanted to find out how a special oat-based diet affects patients.”

The 32 participants in the study did not have diabetes but were diagnosed with metabolic syndrome, which is associated with an increased risk of diabetes. This condition is characterized by high body weight, blood pressure, blood sugar, and blood lipid levels.

Get meaningful results in 2 days

Trial published in nature communications The study consisted of a single 2-day high-dose oat intervention study followed by a longer-term, lower-dose 6-week intervention study.

In the short-term study, participants assigned to the oat group received three meals consisting of only 100 g of boiled oats in water each day for two days. This completely replaced their customary Western diet.

This short-term intervention was followed by a 6-week follow-up period to determine potential long-term effects. During this period, participants in the oat group replaced only one of their daily Western habitual meals with 80 g of oatmeal. Those in the control group followed a completely Western diet.

Oatmeal increased the number of certain beneficial bacteria in the gut.After six weeks, the participants’ cholesterol levels improved significantly compared to the control group, whose levels remained stable. The researchers note that microbial phenolic metabolites produced by the gut microbiome appear to contribute to oats’ positive effects.

“Levels of LDL cholesterol, which is particularly harmful, were reduced by 10% for them. Although it doesn’t quite match the effects of modern drugs, this is a significant reduction,” Simon says.

The positive effects of the oat-based diet were still evident at the end of the 6-week follow-up. “Regularly following a short-term oatmeal-based diet may be a well-tolerated way to keep cholesterol levels within normal limits and prevent diabetes,” Simon emphasizes.

Nourishes healthy intestinal flora

Researchers took blood and stool samples from participants before they changed their diets. We also measured blood pressure, weight, height, waist size, and body fat.

The second test was conducted immediately after the 2-day oat-based diet, followed by three more tests at 2, 4, and 6 weeks.

Based on the findings, study lead author Linda Klümpen from the University of Bonn explains how oatmeal exerts its beneficial effects: “We were able to confirm that oatmeal consumption increases the number of certain bacteria in the intestine.”

“In recent decades, the microbiome has increasingly become the focus of research. After all, it is now known that gut bacteria play a decisive role in the metabolism of food. Bacteria also release into the environment metabolic byproducts that they produce. Bacteria, among other things, provide energy to the cells of the intestine, allowing them to perform their jobs better.”

Furthermore, microorganisms influence the body through various intestinal organ axes. “For example, we were able to show that gut bacteria produce phenolic compounds by breaking down oats,” says Krumpen.

“Animal studies have already shown that one of them, ferulic acid, has a positive effect on cholesterol metabolism. This also appears to be the case for some other bacterial metabolites.”

Meanwhile, other microbes in the gut process the amino acid histidine. Without this process, the body converts histidine into a molecule that researchers suspect helps promote insulin resistance, a key feature of diabetes.

“As a next step, we can now determine whether an intensive oat-based diet repeated every six weeks actually has a lasting protective effect,” concludes Simon.