Bitter polyphenols in plant-based foods may help lower obesity and diabetes risk

• Polyphenols are a type of chemical naturally occurring in plant-based foods that are antioxidants.
• Because polyphenols taste bitter, they interact with the bitter taste receptors on the tongue, known as the Type 2 taste receptors (TR2).
• Past studies show that TR2 taste receptors are not only on the tongue, but can also be found in other body organs, including those that make up the gastrointestinal system.
• Researchers from Shibaura Institute of Technology in Japan have found that polyphenol-caused activation of T2R in the GI tract causes the secretion of hormones that may help lower a person’s risk of developing type 2 diabetes and obesity.

Polyphenols are a type of chemical naturally occurring in plant-based foods like fruits, vegetables, whole grains, and nuts and seeds.

There are more than 8,000 types of polyphenols, all of which are antioxidants that have the potential to protect the body’s cells from aging and damage from outside factors like injuries, environmental pollution, smoking, and eating processed foods .

Because polyphenols are generally considered to taste bitter , they interact with the bitter taste receptors on the tongue, known as the Type 2 taste receptors (TR2) .

Past studies show that TR2 taste receptors are not only on the tongue, but can also be found in other organs and tissues of the body, including those that make up the gastrointestinal system.

“Recently, it has been reported that bitter taste receptors are widely expressed in the digestive tract and are involved in the secretion of incretin , a digestive hormone, and appetite suppression,” Naomi Osakabe, Ph.D., professor in the Department of Bioscience and Engineering at the Shibaura Institute of Technology in Japan told Medical News Today .

To help clarify how this works, Osakabe took the lead on a new study focused on the relationship between the bitterness of polyphenols and glucose tolerance .

Researchers found that polyphenol-caused activation of T2R in the gastrointestinal tract causes the secretion of hormones that help regulate appetite and blood sugar, including glucagon-like peptide-1 (GLP-1) .

Together, scientists believe the gastrointestinal hormones triggered by polyphenols could help reduce a person’s risk for both obesity and type 2 diabetes.

Polyphenols and diabetes risk

Through their study, Osakabe and her team wished to better understand the connection between polyphenols, T2R in the gastrointestinal tract, and potential health benefits.

Previous studies show that polyphenols may help lower a person’s risk for type 2 diabetes and obesity, as well as other health conditions including high cholesterol , high blood pressure , osteoporosis , Alzheimer’s disease , and certain cancers such as colorectal cancer .

“Despite their poor absorption, there are reports that polyphenols improve glucose tolerance,” Osakabe said in a press release . “We are investigating the relationship between polyphenol intake and the risk of type 2 diabetes, as the mechanism of this beneficial effect is still unknown.”

Through their research, the scientists discovered that polyphenol-caused activation of T2R in the gastrointestinal tract causes the secretion of gastrointestinal hormones including cholecystokinin (CCK) and incretins like GLP-1.

Both CCK and GLP-1 are known to help decrease appetite and regulate blood sugar levels.

Potential to replace current GLP-1 drugs

Osakabe said that it is important for researchers to continue to find new ways to regulate blood sugar levels and appetite to help combat conditions like type 2 diabetes and obesity because medications currently used to treat diabetes many times have side effects, and there are no drugs that can be used preventively by the general population.

“Type 2 diabetes results in impaired glucose tolerance, but the receptor agonists for the gastrointestinal hormone GLP-1, currently used in clinical practice, markedly improve this,” she explained.

“They are also abused because of their effect in preventing obesity by suppressing appetite. These drugs always have side effects and are, therefore, a risky choice for use by the general population for the prevention of obesity and diabetes,” she continued.

“GLP-1 receptor agonists are absorbed and act on GLP-1 receptors in target organs and cause unintended gastrointestinal disturbances and adverse effects on blood glucose. Similarly, an essential characteristic of polyphenols that stimulate GLP-1 secretion is that they are virtually absent in the blood and have been shown to cause few side effects. We believe that the intake of polyphenols, which are safer and show similar effects, is preferable. Given the above, there is potential to replace current GLP-1-targeted drugs.”
— Naomi Osakabe, Ph.D.

More potential for body regulation through food than we realize

After reviewing this study, Mir Ali, MD , a board certified bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, told MNT he found the research to be very interesting.

“There’s a lot more potential to help regulate our bodies from food than we realize, so this study is demonstrating that if we perhaps add certain foods and things to our diet, we can improve our health,” Ali explained.

“Both diabetes and obesity are on the rise, so anything we can do to find ways to combat this is going to be helpful. There [are] medications and surgeries and things out now, but anything we can to improve upon that is going to be beneficial,” he said.

“I’d like to some kind of quantification, like how much of these type of foods need to be eaten to make a noticeable difference in diabetes and weight regulation, and is it possible to maybe get these type of naturally-found chemicals in a concentrated form so that it may be a supplement people can pay to help them,” he added.

How can I increase my polyphenol intake?

MNT also spoke with Monique Richard, MS, RDN, LDN , a registered dietitian nutritionist and owner of Nutrition-In-Sight, about this study.

“My initial reaction was not necessarily surprising, but it was also married with a healthy dose of skepticism as there are a multitude of variables and responses that happen as a result in the metabolic cascade from ingestion of polyphenols, receptors, and signals depending on the individual, genetics, environment and so much more,” Richard said.

“I do see this in practice when analyzing results of functional labs, microbiota , and organic acid tests which look at metabolites, or end-products, of the metabolic cascade. Those individuals that have higher fiber intake, a variety of fruits and vegetables rich in color and species, and cook more tend to have better blood glucose regulation, weight management, satiety with meals and bowel movement regularity,” she explained.

For readers looking to expand their intake of polyphenols in their diet, Richard advised adding those plants can help increase polyphenol levels including servings of:

• all vegetables
• apples
• beans
• black tea
• blueberries
• cherries
• cocoa powder and/or dark chocolate
• elderberries
• herbs
• nuts and seeds

“Studies vary in levels of polyphenols used but some studies have seen benefits result in consumption of 650 mg of polyphenols a day. A half-cup of blueberries may contain 535 mg. Also aiming for a minimum of 35-40 gm of fiber a day from these foods will be beneficial as most are naturally high in polyphenols as well. Try getting three to four different servings of plants a day — fruits, vegetables, legumes, pulses, seeds, whole grains— to reach close to 30 in a week, as varied as possible from fresh, frozen or canned sources.”
— Monique Richard, MS, RDN, LDN

“Help your body help itself by naturally increasing hormones such as GLP-1 and systemic function with all the goodness that mother nature produces in its own harvests. Let’s prioritize getting produce at the ‘farm’acy with food first versus pills and drugs at the pharmacy,” she added.