9+ fascinating facts about saliva

You probably don’t think about saliva all that much. You know it’s there, and you might know that it helps kick off the digestive process. But is that it? Spoiler alert: It’s not.

Saliva is a complex fluid with a wide range of jobs. We’ll cover just some of these jobs today.

Although it might seem like an unsavory subject, we’re confident you’ll view drool in a new light after reading this.

So, let’s leap headlong into a vat of saliva science.

1. Saliva contains more than 1,000 compounds

Mostly, saliva is water — about 99.5%. The rest is a complicated mix of proteins, salts, and other compounds.

Among them are immune system components, enzymes, bacteria-fighting proteins, and factors that support growth and repair.

And aside from proteins, saliva also contains:

• electrolytes, including potassium, magnesium, calcium, and phosphate

• mucus, which contains water, proteins, salts, and sugars

• short chains of amino acids, like opiorphin, a painkiller

• bacteria — around 1 billion bacteria per milliliter, though the numbers vary greatly throughout the day

• human cells — about 500,000 per ml of saliva

2. You have more than 1,000 salivary glands 

Saliva is created in your aptly named salivary glands. About 90% of it is produced by the three "major" salivary glands:

• parotid: just in front of your ears

• submandibular: beneath your lower jaw

• sublingual: below your tongue

An incredible 1,000 minor salivary glands produce the remaining 10% of your saliva.

And it comes in different forms: Serous saliva is watery, mucous saliva is thicker, and mixed saliva is somewhere in between.

3. You produce up to 2.5 pints of saliva each day

When the secretion of saliva is stimulated, for instance, when you’re chewing food, you produce up to 7 ml per minute.

Even when your mouth is unstimulated, you produce around 0.3–0.4 ml per minute. However, this figure varies a great deal between individuals.

Interestingly, a range of surprising factors can influence how much saliva you produce when you’re unstimulated. These include:

• Body position: When you’re standing, you produce more saliva than when you’re sitting.

• Daily rhythms: You produce the most saliva during the afternoon and hardly any during sleep.

• Seasonal changes: There’s some evidence that you produce the most saliva in winter and the least in summer. This may be due to dehydration in the hotter months.

4. Sour flavors stimulate the most saliva

A small study of eight participants investigated which flavor triggers the greatest release of saliva. 

It found that a sour flavor stimulated the most. This is how the flavors ranked from highest to lowest:

1. sour: citric acid

2. savory or umami: monosodium glutamate, better known as MSG

3. salt

4. table sugar

5. bitter: magnesium sulfate

5. Saliva protects your mouth

Saliva helps protect the inside of your mouth as you eat, chew, and talk. People with xerostomia — a condition in which you don’t produce enough saliva — often have sore mouths.

These folks also find that without the lubrication of saliva, dry foods, in particular, stick to the insides of their mouths. And they can find swallowing difficult for the same reason.

Saliva may also offer some protection against burns from hot foods and drinks, simply by diluting the contents of your mouth.

And saliva can protect against acid, too.

You may have noticed that your mouth fills with saliva just before you vomit. Because your stomach contents are notoriously acidic, this influx of saliva might help protect your teeth and the inside of your mouth. 

6. Saliva starts the digestive process

Saliva gets the work of digestion started as soon as food enters your mouth. Among its various enzymes is amylase, which breaks down starch into simpler sugars.

Saliva also contains salivary lipase, which starts the breakdown of fats. However, according to experts, salivary lipase doesn’t play a particularly important part in digestion. 

It seems more important for flavor perception, as we’ll discover next.

7. Without saliva, food wouldn’t be as tasty

People with xerostomia, a lack of saliva, often experience distorted taste, which is called dysgeusia. For instance, they sometimes report that things taste metallic.

It turns out that saliva plays a big part in how you perceive flavor. First, because it’s fluid, it helps ferry chemicals from food to your taste receptors.

Saliva’s enzymes play a role, too. As amylase breaks starch into simple sugars, it allows you to taste the sweetness of starchy foods. Without amylase, many foods that contain carbs might taste quite different.

Similarly, salivary lipase breaks down fat and helps unlock its flavor. Scientists have shown that if they block lipase activity, study participants find it harder to tell whether they're eating fats.

Researchers are still investigating the role of saliva in taste, but it seems that a range of proteins in saliva might play a part, including leptin, ghrelin, and insulin. 

We might be tempted to overlook the importance — why would saliva make such an effort just to ensure you can enjoy the complex flavors of your morning coffee?

But in the wild, where food safety laws don’t exist, flavor can be a matter of life and death: Before you swallow, it’s vital to discern whether something will provide you with life-giving nutrients or life-threatening food poisoning. 

8. Saliva protects you from invading microbes

Because your mouth is warm, damp, and open to the outside world, it faces an almost constant battle with microbial invaders. Your saliva, however, has your back. 

Some authors have called saliva the “gatekeeper of the oral cavity.” And it approaches its microbial foes with a multipronged attack.

For instance, saliva contains proteins called agglutinins that clump bacteria together, making them easier to clear as you swallow. And proteins called mucins stop bacteria from sticking to surfaces like your teeth.

Some other enzymes in saliva lead to the production of compounds that are toxic to bacteria. And others can puncture microbes’ cell walls, killing them by emptying their contents. 

Although we’ve not covered it all, that’s already an impressive array of defenses. 

But what’s perhaps even more impressive is that, while it's killing some microbes, saliva can also help support “good” bacteria.

Like your gut, your mouth hosts bacteria that benefit health. Although we know very little about how the oral microbiome functions, scientists think that compounds in saliva help feed “good” microbes.

9. Saliva helps you heal wounds

An animal with a mouth wound that keeps it from eating might not survive very long. 

So, if injuries do happen, your body must heal them quickly. And saliva has, once again, got your back.

And laboratory research suggests that other compounds, called histatins, might also help close wounds and rebuild the lining of your mouth.

Because scientists have noted that wounds in the mouth heal quickly and often without scarring, some are investigating ways to use human saliva to help wounds on your skin heal quicker. 

Rounding up

Thanks for joining us on this journey; you’re now within spitting distance of the finish line. 

We hope you’ll leave this article with a newfound appreciation for saliva. Without it, life would be much less flavorful — and perhaps shorter.

Saliva enhances our enjoyment of food, protects against microbes and poisons, helps you swallow, looks after your teeth, and heals wounds. You certainly wouldn’t want to be without it.