The research team has patented one prebiotic compound and several probiotics with the identified molecules and bacteria. The results, published in the journals "Scientific Reports" and "Frontiers in Microbiology," confirm that nitrate is a factor that stimulates oral and cardiovascular health
València (03.11.2020). The Oral Microbiome Research Group of the Foundation for the Promotion of Health and Biomedical Research of Valencia Region (Fisabio), led by Alejandro Mira, has patented one prebiotic compound and several probiotics to prevent the main oral diseases: tooth decay (caries), periodontitis and halitosis.
A prebiotic is a substance that contributes to the growth of healthy bacteria or their beneficial functions, while a probiotic is a bacterium that can improve health if it is taken in suitable doses.
The combination of nitrate, which is a bioactive molecule naturally present in vegetables, together with oral bacteria identified by the team has proved to be effective against oral diseases.
In addition, it is beneficial in preventing cardiovascular diseases and could even have a positive effect on diabetes. This is the first time a treatment simultaneously beneficial for all these pathologies has been described.
The development has been made possible after the research team observed that different beneficial bacteria in the mouth use nitrate (coming mainly from vegetables) and turn it into nitrite and nitric oxide (a well-known vasodilator with anti-microbial properties).
The new results of their study, recently published in the prestigious journal "Scientific Reports" from the Nature group, prove how nitrate both reduces blood pressure and improves oral health, neutralizing acids that cause cavities and eliminating pathogenic bacteria that cause gums to bleed and produce bad breath.
For example, after eating a salad, beneficial bacteria in the mouth turn the nitrate from vegetables into beneficial compounds for oral health. The researchers have proved that this is a quick process and it starts while we are chewing vegetables. However, a large part of the nitrate is lost after swallowing.
But here is where the process becomes fascinating because a significant part of this nitrate passes to the blood and is captured by the salivary glands, which concentrate it in the mouth for several hours. That's how our body uses these bacteria like a factory to turn nitrate into nitrite, which the human body is not able to produce."
Dr. Alex Mira, Principal Researcher, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO)
"This nitrite," explains Dr. Mira, "improves oral health and also produces nitric oxide, which reduces blood pressure. Nitric oxide is also used by immune cells to destroy tumor cells and improves sports performance, among other functions. The bacterial conversion of nitrate to nitrite has an important role because if a person eliminates all their oral microbiota due to the excessive use of mouthwash, the blood pressure rises and physical performance gets worse," explains the Fisabio scientist.
The research team gathered saliva from 12 healthy donors, and it was tested in vitro with a sole low nitrate dose. The samples were analyzed after 5 hours (when most of the nitrate had been reduced and part of the nitrite had been produced); and after 9 hours (when all the nitrate and most of the nitrite had been metabolized).
The researchers observed that the nitrate decreased the production of lactic acid, increased the levels of ammonium (an acid neutralizer), and increased the pH in the mouth. The increased pH in the mouth limits enamel damage and prevents the development of cavities - the most common infectious disease in the world.
Moreover, they detected the growth of nitrate-reducing bacteria, Neisseria and Rothia, which are associated with oral health; and a reduction of the bacteria associated with the development of cavities (Streptococcus, Veillonella, and Oribacterium), halitosis, and periodontitis (Porphyromonas, Fusobacterium, Leptotrichia, Prevotella, and Alloprevotella).
"We concluded that nitrate can be a stimulating factor for oral health, with the power to reduce cavities, periodontitis, and halitosis. We have seen that nitrate provides resilience against the acidification that results from sugar consumption because it decreases the production of lactate and increases the production of an acid neutralizer," says Bob Rosier, a Ph.D. researcher at Fisabio, who did the experimental part of this work.
"Nitrate is clearly," adds Bob Rosier, "a molecule associated with health in the oral cavity. That's the reason for us to recommend it to be used as a prebiotic, as well as strains of nitrate-reducing bacteria as probiotics, to stimulate the benefits of nitrate metabolism."
The identification and selection of the beneficial probiotic bacteria have been made using a culture on which researchers have added a substance that changes color in the presence of nitrate, according to the researchers' recent publication in the journal "Frontiers in Microbiology." Some of these bacteria are especially good at producing acid neutralizers, and others are especially good at producing nitric oxide.
"Preventive personalized treatments could be planned for each person in order to improve their oral or systemic health by modifying the patient's oral microbiota in a directed way," says Bob Rosier.
"We obtain over 80% of nitrate," explains Rosier, "from fruit and vegetable consumption, which are considered anti-carcinogenic and promote health and longevity. However, sometimes, the link between nitrate and health is misunderstood, because it is used as a preservative in processed meat, which can lead to the proliferation of N-nitroso compounds considered to be carcinogenic. The antioxidants in fruits and vegetables prevent this, allowing us to obtain the beneficial effects of nitrate without undesired side effects."
From these observations, the research team has developed a diagnostic test capable of determining whether or not a person has these beneficial bacteria and a sufficient quantity to turn nitrate into nitrite.
This test consists of taking a saliva sample where different compounds are measured. With the result, the risk of developing cavities, periodontitis or bad breath is assessed, as well as the risk of stroke and other diseases resulting from the lack of nitric oxide. If necessary, prebiotic and probiotic treatment could help to reduce the risk, for example by including them in toothpaste.
The researchers are now looking for companies from the oral health, clinical diagnosis, and functional food industries interested in developing and marketing the diagnostic kit and products containing prebiotics and probiotics.
The most common oral pathologies
Cavities is considered to be the most widespread infectious disease in the world, as it affects 80-90% of the population.
Periodontal diseases are characterized by inflammation and destruction of the tooth support tissues, which sometimes produces halitosis and, in advanced cases, tooth loss.
Oral diseases not only cause tooth loss and pain; poor oral health is also involved in systemic diseases, like esophagus and stomach cancer, and has even been related to cardiovascular diseases, diabetes, and Alzheimer's.
In Spain, one out of four adults has periodontitis and/or halitosis, whose main cause is the activity of bacteria on the gums and tongue.
"Trying to eliminate these bacteria has been the traditional strategy for decades, but it has not been successful; the present trend is to try to modulate those microorganisms in order to contribute to a healthy ecosystem, but until now there has not been a prebiotic capable of performing this function. Our prediction is that this study will open up a new wave of nitrate-based oral health products, for example, vegetable extracts or low amounts of nitrate salts in combination with anti-oxidants, to complement the role of fluoride," conclude the researchers.
Rosier, B. T., et al. (2020) Nitrate as a potential prebiotic for the oral microbiome. Scientific Reports. doi.org/10.1038/s41598-020-69931-x.