Tokyo Researchers Connect Poor Oral Hygiene to Metabolic Diseases 

Tokyo Researchers Connect Poor Oral Hygiene to Metabolic Diseases 

oral hygieneBlood Sugar


What does oral hygiene have to do with your odds of diabetes? As it turns out–quite a lot.

In a recent study, Tokyo researchers have identified poor oral hygiene as a risk factor for metabolic diseases. This group of conditions increases the risk for ailments such as heart disease, stroke, and diabetes. Researchers from Tokyo Medical and Dental University (TMDU) discovered the bacterium which causes periodontal disease: Porphyromonas gingivalis.

Furthermore, they found that this bacteria causes skeletal muscle metabolic dysfunction, leading to metabolic syndrome. This occurs by altering the composition of the gut microbiome. Scientists have known for some time that periodontal bacteria can cause inflammation in the mouth. However, they have recently found that the bacteria can result in inflammation throughout the whole body.


Chronic inflammation as a result of sustained infection due to periodontal bacteria can therefore cause other problems. Common issues that arise include increases in body weight, insulin resistance, and type 2 diabetes. Of course, insulin helps to carry glucose from the blood into tissues throughout the body – most importantly, skeletal muscle. Muscles store 25% of the body’s glucose.

Insulin resistance occurs when the cells in your muscles, fat, and liver can’t process insulin correctly. When the cells can’t utilize glucose in your blood for energy, the pancreas responds by creating more insulin. As a result, your blood sugar goes up, which can lead to type 2 diabetes over time.


The impact of insulin

oral hygiene
Insulin resistance correlates strongly with the development of metabolic syndrome, which includes conditions such as:

  • obesity
  • high blood pressure
  • high blood glucose levels
  • chronic inflammation
  • inhibited lipid metabolism
  • type 2 diabetes
  • heart disease
  • stroke

According to WebMD, insulin resistance could affect as many as 1 in 3 Americans.

Some signs of insulin resistance include:

  • A waistline over 40 inches in men and 35 inches in women
  • Blood pressure readings of 130/80 or higher
  • A fasting glucose level over 100 mg/dL
  • A fasting triglyceride level over 150 mg/dL
  • A HDL cholesterol level under 40 mg/dL in men and 50 mg/dL in women
  • Skin tags
  • Patches of dark, velvety skin called acanthosis nigricans

Risk Factors and Causes of Insulin Resistance

  • Obesity, especially belly fat
  • Sedentary lifestyle
  • Diet high in carbohydrates
  • Gestational diabetes
  • Health conditions like nonalcoholic fatty liver disease and polycystic ovary syndrome
  • A family history of diabetes
  • Smoking
  • Being of African, Latino, or Native American ethnicity
  • Being older than 45
  • Hormonal disorders like Cushing’s syndrome and acromegaly
  • Medications like steroids, antipsychotics, and HIV medications
  • Sleep problems like sleep apnea

More recently, researchers have added poor oral hygiene to the list of risk factors. It’s been well-established in the scientific community that more muscle people usually have lower blood glucose levels. However, they have just begun to establish the connection between periodontal disease and skeletal muscle’s metabolic function.

“Metabolic syndrome has become a widespread health problem in the developed world,” says the first author of the study Kazuki Watanabe. “The goal of our study was to investigate how periodontal bacterial infection might lead to metabolic alterations in skeletal muscle and thus to the development of metabolic syndrome.”


How researchers found the connection between poor oral hygiene and metabolic disease

Researchers first analyzed antibody levels against Porphyromonas gingivalis in the blood of patients with metabolic syndrome to perform the study. Researchers found a positive correlation between these antibody levels and higher insulin resistance. Thus, the results revealed that patients with metabolic syndrome likely had a past infection with Porphyromonas gingivalis. Therefore, their immune system had antibodies against the invading bacteria.

To understand how poor oral hygiene can cause metabolic disease, the team performed a study on mice. They gave mice on a high-fat diet the bacterium Porphyromonas gingivalis by mouth. (A high-fat diet is a precursor to developing metabolic syndrome). Not surprisingly, the mice developed higher insulin resistance. They also had lower glucose uptake and increased fat in their muscles than mice in the control group.

However, they still didn’t know how the bacteria led to chronic inflammation and eventually metabolic syndrome. To understand the mechanism behind it, the team turned their attention to the gut microbiome. This refers to the total of the bacteria in the gut, where much of the immune system exists. Interestingly, mice given the Porphyromonas gingivalis bacteria had a drastically altered gut microbiome, which may decrease insulin sensitivity.


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“These are striking results that provide a mechanism underlying the relationship between infection with the periodontal bacterium Porphyromonas gingivalis and the development of metabolic syndrome and metabolic dysfunction in skeletal muscle,” says corresponding author of the study Professor Sayaka Katagiri.

Science now proves the importance of maintaining good oral hygiene. Having a healthy mouth and gums will improve your overall wellness and reduce the risk of chronic disease.

oral hygiene
How to maintain a healthy oral microbiome

Here are a few tips on how to heal your oral microbiome:


  • Eat a mostly unprocessed diet. This includes a diet high in fresh fruits and veggies, lean proteins, nuts, grains, and seeds. Severely limit or cut out processed carbs since these lead to cavities and other oral health issues.
  • Practice good oral hygiene. This includes flossing and brushing your teeth each day and also using a tongue scraper to remove toxins. You’ll want to go to a dentist for regular cleanings as well. Avoid toothpaste and mouthwashes with harsh ingredients like unnatural dyes, triclosan, propylene glycol, and sodium laurel sulfate. That’s because these cause an imbalance in the mouth’s bacteria.
  • Consume probiotics. This will populate the oral microbiome with good bacteria, just as they do for the gut microbiome.

Final thoughts: Scientists report finding a connection between poor oral hygiene and insulin resistance

A new study by Tokyo researchers found that an unhealthy mouth microbiome could lead to metabolic disease. Previously, scientists have focused on other conditions like obesity and type 2 diabetes in relation to metabolic syndrome. However, just as gut dysbiosis can lead to disease, so can having poor oral hygiene. In particular, they found that a bacteria called Porphyromonas gingivalis led to higher insulin resistance.

So insulin resistance plays a key role in developing metabolic disease, an umbrella term for many conditions. To maintain overall health, eat a healthy diet, practice good oral hygiene, and take probiotics regularly.



Kristen Lawrence is a Staff Writer at Power of Positivity since 2014. Kristen describes herself as an "average coffee-drinking girl who gets to put words together for a living." She enjoys sharing positive news and stories with the Power of Positivity audience. Kristen was also featured on the popular travel website, Only In Your State. When she's not writing or editing, she enjoys hiking in the great outdoors, making smoothies, eating out at yummy vegan restaurants, and relaxing with a nice big cup of coffee. She just wants to share a slice of happiness with as many people as possible. Kristen hopes that her articles bring a little bit of hope, happiness, and inspiration into the lives of her readers. She hopes to help people find their purpose and inspire them never to give up.

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