Just two days of mostly oatmeal cut low-density lipoprotein (LDL) cholesterol (often referred to as "bad" cholesterol) by 10% and triggered beneficial changes in gut bacteria linked to better heart and metabolic health.

The study focused on people with metabolic syndrome, a cluster of conditions that includes excess body weight, high blood pressure, elevated blood sugar, and abnormal blood lipid levels. Participants followed a calorie-restricted plan made up almost entirely of oatmeal for 48 hours.

Compared with a control group that also reduced calories but did not eat oats, those on the oat- based plan saw a markedly greater improvement in their cholesterol levels. The reduction remained noticeable even six weeks later.

During the intensive phase of the study, participants ate boiled oatmeal three times daily and could only add small amounts of fruit or vegetables. In total, 32 women and men (mean age, 58) completed the two-day oat-based intervention. Each person consumed 300 grams of oatmeal per day and cut their usual calorie intake roughly in half. The control group also reduced calories but did not consume oats.

Both groups experienced some benefits from eating fewer calories. However, the improvements were stronger among those who ate oats.

To understand why oats had this impact, researchers examined the gut microbiome. and found that intestinal bacteria produce phenolic compounds by breaking down the oats. One of these compounds, ferulic acid, was shown in animal studies to have a positive effect on cholesterol metabolism. This also seems to be the case for some of the other bacterial metabolic products.

At the same time, certain microbes help eliminate the amino acid histidine. Without this process, the body can convert histidine into a compound believed to promote insulin resistance, a hallmark of type 2 diabetes.

In a separate six-week phase of the study, participants ate 80 grams of oatmeal per day without additional dietary limits. That approach produced only modest changes.

As a next step, the researchers will investigate whether an intensive oat-based diet repeated every six weeks actually has a permanently preventive effect on heart and gut health.

To download the full study, published in Nature Communications, click here