Researchers have conducted a small trial with human volunteers showing that a short-term diet that includes oats can reduce cholesterol levels. In this trial, people with metabolic disease, defined as some combination of high levels of blood lipids, blood pressure, body weight, and blood glucose were given a diet that consisted almost entirely of oatmeal and contained fewer calories than normal. This investigators found that cholesterol levels went down significantly in these individuals compared to people who had metabolic disease and consumed a more typical diet. The cholesterol-reducing effect of the diet also lasted as long as six weeks. The study authors suggested that this lasting impact was due to changes in the gut microbiome. The findings have been reported in Nature Communications.
Metabolic syndrome and diabetes are not the same but they are related. A group of 64 patients with metabolic syndrome were divided into two groups; one group consumed a diet that was almost exclusively oatmeal and about 50% lower in calories than their normal diet; another group consumed a diet that only had fewer calories than usual. Blood and stool samples were collected before the diet began and after it was concluded.
"We wanted to know how a special oat-based diet affects patients. Today, effective medications are available to treat patients with diabetes," said corresponding study author Marie-Christine Simon, a junior professor at the University of Bonn, among other appointments. "As a result, this method has been almost completely overlooked in recent decades.”
There was a metabolic benefit in both groups, but this effect was much more significant in the people who ate the oat-based diet.
"The level of particularly harmful LDL cholesterol fell by 10% for them; that is a substantial reduction, although not entirely comparable to the effect of modern medications," noted Simon. "They also lost 2 kilos [4.4 pounds] in weight on average and their blood pressure fell slightly."
Since LDL cholesterol, can build up in blood vessels, forming plaques that causes blood vessels to narrow, these findings could be very beneficial by helping people to easily reduce their risk of heart disease.
The positive impact of oatmeal appears to work through the gut microbiome, by increasing the levels of some bacterial species. Some gut microbes can generate phenolic compounds when exposed to oats; one is called ferulic acid and it can boost cholesterol metabolism, for example.
Other microbes can lower the levels of an amino acid called histidine, which can be converted into another molecule that may promote insulin resistance, raising diabetes risk.
"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," added Simon.
Sources: University of Bonn, Nature Communications