Two day oat-based diet significantly lowers bad cholesterol, study finds

A new study led by Mary Christine Simon at the Institute for Nutrition and Food Science at Bonn University has shown that consuming a very low calorie and concentrated oat diet over a short period of time can significantly lower the amount of LDL cholesterol, which is known as bad cholesterol, in individuals who have metabolic syndrome.

Metabolic syndrome includes excess body weight, high blood pressure, high blood glucose, and abnormal cholesterol levels. In addition to providing a source of soluble fiber, the study showed that oats also changed gut bacteria and their metabolic by-products.

The participants were placed on a strict diet that was predominantly made up of oatmeal for two days. This resulted in a significant decrease in their LDL cholesterol levels, approximately 10 percent, during the diet and six weeks after the diet intervention.

Historically, oats were famously used for many years in the treatment of diabetes. In the early 1900s, a German doctor named Karl von Norden used oat-based diets to successfully treat diabetics. Dr. Simon states, “Now with advancements in the knowledge of how best to manage diabetes and also the many medications available, oat diets are seldom utilized by physicians as treatment for diabetes.”

The diet trial included 68 adults with metabolic syndrome. Most were around 60 years of age and had obesity, hypertension, or unhealthy blood fats. None had been diagnosed with diabetes; nevertheless, all were at high risk of developing diabetes in the future.

The short-term study found that 32 participants completed the two-day intervention. The oatmeal group was directed to have three meals per day of oatmeal cooked in water. Each daily meal consisted of 300 grams of oats, with the addition of limited fruit and vegetable consumption. The diet decreased the calories consumed per day to about 50 percent of the normal caloric intake. The control group followed a calorie-restricted diet that did not contain oatmeal.

Individuals in both groups demonstrated some benefit from a reduction in calorie intake, but the benefits of the oatmeal group were far more substantial. “They had a 10 percent decrease in their level of the bad cholesterol, or LDL. That is a significant decrease, even though it is not a direct comparison to the effect of modern medications,” said Simon. “The individuals in this group also experienced an average weight loss of 2 kilograms and a slight decline in their blood pressure as well.”

The researchers also conducted another, longer study that lasted six weeks. In this study, the participants consumed 80 grams of oats per day and were not restricted from eating anything else in their diet. The effects of this study were much less than the first study indicated. Therefore, the researchers concluded that the dose and timing of oat consumption play an essential role in establishing oat health benefits.

"The presence of high amounts of LDL cholesterol can damage blood vessel linings. Cholesterol builds up in the vessel wall and creates plaques that can cause narrowing of the arteries. A plaque can rupture during times of stress or physical activity, which may result in blood clotting that can block blood flow. Heart attacks and strokes can occur during this process," Simon told The Brighter Side of News.

"The potential for significant health benefits from even small decreases in LDL cholesterol, due to the risk of developing various health problems, has prompted researchers to investigate the rapid improvement experienced by subjects who consumed oats for only two days. However, we wondered how oat consumption could improve LDL cholesterol levels so significantly and so quickly," she added.

Initially, researchers speculated that changes in the bacteria residing in the gut may be responsible for the rapid change in LDL cholesterol levels in the study’s participants.

Researchers were able to identify the presence of additional gut bacteria in the samples collected from the study participants after they began eating oats. These bacteria are responsible for breaking down some of the components of the oats used in the study and sending their by-products into the bloodstream.

Phenolic metabolites are one of the types of by-products produced by gut bacteria when they metabolize food. “We demonstrated that the bacteria in the intestines were producing phenolic compounds from their breakdown of oats,” Klümpen stated. Recent animal studies have shown that these compounds, particularly ferulic acid, are known to positively affect cholesterol metabolism.

Researchers found that the amount of dihydroferulic acid, which is formed when gut bacteria metabolize ferulic acid, increased following the two-day oat diet. Higher concentrations corresponded closely with larger reductions in LDL cholesterol concentrations than lower amounts.

Additionally, some of the gut bacteria that were activated from the consumption of oats also produced histidine. This compound is converted by the body into a substance believed to contribute to the development of insulin resistance. Type 2 diabetes is characterized by an impaired response to insulin.

Both the short-term and long-term studies were randomized controlled trials, and participants were randomly allocated to the oat or the control diet. Although it was not possible to blind the participants to the intervention, researchers assessing blood, stool, weight, and blood pressure data were not aware of assignment groups.

Samples for blood and stool were collected at the start of the study, right after the two-day intervention, and two, four, and six weeks after the diet began. The investigators measured different markers in the blood and stool samples, including LDL cholesterol and dihydroferulic acid. Stool samples were analyzed using 16S RNA sequencing, which is a method that identifies bacterial species using genetic information.

The data confirmed that oat consumption altered the profile of the gut microbiome. Specific groups of bacteria increased during the oat phase and decreased afterward, corresponding to changes in phenolic metabolite levels and cholesterol levels.

Among the most significant findings was that a short-duration, high-volume consumption of oats was more effective than a low-volume consumption of oats over the longer term. This comparison refers to the six-week study in which participants consumed 80 grams of oats daily.

Simon stated that “a short-term oat eating strategy at regular intervals may be another approach to achieving a normal cholesterol level and preventing diabetes.” She suggested more research on whether repeating an intensive oat regimen every few weeks provides effective protection over the long term.

Additionally, the reduction in caloric intake during the two-day study may have contributed to a greater response to the intervention. In the long-term study, oats were added to a normal Western diet. As a result, more variation in the foods consumed and the gut microbiomes is expected.

Metabolic syndrome is expected to affect nearly one in three people globally. Because it arises through several biological pathways, no single drug is effective for treating it. Diet is one of the best ways to reduce the risk.

Oats are an excellent source of dietary fibre, particularly beta-glucans. They contain vitamins, minerals, and phytochemicals, are readily accessible, and are inexpensive.

This research contributes to the knowledge of what oats do. They slow digestion but also interact with the gut bacteria and produce products that influence how cholesterol is metabolised.

The findings of this study may indicate that a simple, low-cost, measured approach using a short-term intervention based on oat consumption could be effective in improving cholesterol levels quickly for those at elevated cardiovascular risk. This option may be especially beneficial for people with metabolic syndrome who are not currently receiving medical treatment, or for those who wish to supplement what they are already receiving.

This study emphasises to the scientific community that gut microbiomes play important roles in determining how dietary effects are produced. In addition, it points to the potential for phenolic metabolites as viable targets for the future development of therapies.

By better defining how food, microbes, and metabolism impact one another, progress can be made toward personalising nutrition strategies and reducing the chances of heart disease and diabetes.

Research findings are available online in the journal Nature Communications.

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