How Your Spit Talks To Your Microbes

I’ve long thought of saliva as a digestive aid, helping us chew, swallow, and break down fats and carbohydrates.

But it’s so much more.

Saliva serves as our primary system for delivering digestive enzymes, buffering acids, and regulating immune responses.

It contains:

• Electrolytes (like sodium, potassium, calcium, and bicarbonate)

• Digestive enzymes:

  • Salivary amylase (for starches)

  • Lingual lipase (starts fat digestion, especially in infants)

  • Other hydrolases

• Proteins and immune factors:

  • Mucin (for lubrication and microbial binding)

  • Lysozyme, defensins, and secretory IgA (antimicrobial and immune support)

• Metabolic waste products: including urea and uric acid

One fascinating aspect of saliva is that it transfers our oral microbiome down the digestive tract. We swallow an estimated 1–2 liters of saliva daily, carrying millions of microbes and molecular messages.

One of the most intriguing messages we now know about?

microRNA's

Saliva transfers microRNAs (miRNAs) — tiny, non-coding strands of RNA that can regulate gene expression. But here’s what’s wild: these miRNAs may also serve as messages between the oral microbiome and the gut.

The 1–2 liters of saliva we swallow daily aren’t just transporting bacteria; they may also be carrying signals that shape our microbial ecosystems for the better or for the worse.

What Are MicroRNAs?

Think of miRNAs as Post-it notes on your genes. They don’t create proteins but decide which proteins get made, often by turning off specific gene messages.

They’re small (around 22 nucleotides) but regulate critical functions in inflammation, immunity, metabolism, and even cancer.

Until recently, we mostly thought of them as regulating human biology. Now we’re learning they also interact with microbes, shaping the ecosystems of both the mouth and the gut.

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The Language of Saliva

Saliva contains hundreds of miRNAs—most tucked inside exosomes, which are microscopic bubbles that protect and deliver molecular messages. Your oral cells, immune cells, and even the food you eat influence the miRNAs that get packaged into saliva. But here’s what I find out of this world: these miRNAs can influence bacterial gene expression. MiRNAs are being read by the bacteria that live in and on you. This is molecular cross-talk between human and microbe, happening in your mouth all day, every day. Exosomes, which are microscopic bubbles that protect and deliver molecular messages.

Your oral cells, immune cells, and even the food you eat influence which miRNAs get packaged into saliva.

But here’s what I find just out of this world:

These miRNAs can actually influence bacterial gene expression

MiRNAs are being read by the bacteria that live in and on you. This is molecular cross-talk between human and microbe, happening in your mouth all day, every day.

picture: courtesy of Azari H, George M, Albracht-Schulte K. Gut Microbiota–microRNA Interactions and Obesity Pathophysiology: A Systematic Review of Integrated Studies. International Journal of Molecular Sciences. 2024; 25(23):12836. https://doi.org/10.3390/ijms252312836

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Here are some microbes that may be tuning in:

• Akkermansia muciniphila – A gut microbe that supports metabolism and immune balance. miR-30d, found in saliva and feces, helps Akkermansia thrive by activating genes involved in mucin utilization

• Porphyromonas gingivalis – A key player in gum disease. It may be influenced by inflammatory miRNAs like miR-155 or miR-21, which increase during chronic oral inflammation.

• Bifidobacteria and Lactobacilli – These beneficial microbes may respond to dietary and host-derived miRNAs, potentially enhancing colonization in the mouth and gut. – A gut microbe that supports metabolism and immune balance. miR-30d, found in saliva and feces, helps Akkermansia thrive by flipping on genes involved in mucin use.

Why does this matter?

We may have the ability to influence our microbiome not just through diet, probiotics, or supplements — but also through its own genetic signaling system.

And that opens doors to:

• New ways to promote beneficial microbes, such as Akkermansia and bifidobacterium, naturally by enhancing our oral microbiome and saliva.

• We may need to treat dysbiosis in the gut by also addressing mouth dysbiosis.

• We can use salivary miRNAs as early biomarkers of oral and systemic disease. I am unaware of Direct To Consumer companies offering this currently.

• Potential therapies may include miRNA lozenges or oral sprays that encourage the microbiome toward better health, along with oral probiotics.Akkermansia and Bifidobacterium) by improving our oral microbiome and saliva.

• We may also need to treat dysbiosis in the gut by addressing mouth dysbiosis.

• We can use Salivary miRNAs as early biomarkers of oral and systemic disease. I am unaware of Direct-to-Consumer Companies offering this now.

• Potential therapies include miRNA lozenges or oral sprays that nudge the microbiome toward health and oral probiotics.

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What Can You Do Now?:

• Mind your inflammation –Oral inflammation (from gum disease, stress, poor diet) alters miRNA levels.

• Eat colorful plants – Polyphenols can influence miRNA expression and microbial diversity.

• Hydrate and protect saliva—A dry mouth limits miRNA communication. If saliva is not transferred adequately, the messages may not be robust.

• Consider oral probiotics – These may enhance microbial receptivity to beneficial signals.

• Consider testing your oral microbiome with oral microbiome testing methods, such as oral DNA.
  
  I have been using Mouthflora recently to improve my mouth microbiome. I don’t have any affiliation with it or dispense it. I buy it on Amazon.

  My new routine is brushing, flossing, and massaging my gums Living Libations - Organic Ozonated Happy Gum Gel (no affiliation). After this is done, I empty the Mouth flora in 4 oz. of water, then swish the Mouth flora in my mouth for 1 minute and then swallow. I like how I feel in the morning when I wake up. No morning breath! I am hoping it reduces flares of IBS and Celiac Gluten flares down the road.

What are your favorite practices for oral health? Comment below and let me know how you feel your best in the oral health department.