Saliva is more than just a way to keep your mouth lubricated; scientists are discovering that their cocktail of substances is the determining factor in the flavors we taste. At first glance, saliva seems like a pretty boring thing; however, it is just a convenient way to moisten our food. But the real thing is quite different, as scientists are beginning to understand.
This fluid interacts with everything that enters the mouth and, although it is made up of 99% water, it influences the flavors -and our enjoyment- of what we eat and drink. “It’s a liquid, but it’s not just a liquid”, says oral biologist Guy Carpenter of King’s College London.
Scientists have long known about some of the functions of saliva: it protects teeth, facilitates speech, and creates a welcoming environment for food to enter the mouth. Now researchers are discovering that saliva is also a mediator and translator, influencing how food moves through the mouth and how it arouses our senses. The new evidence suggests that interactions between saliva and food may even help determine what foods we like to eat.
Here we share 5 facts that you may not have known about saliva, and how it can lead us to have a healthier diet:
1. Saliva allows us to detect the chemical information of food
Through saliva, says Jianshe Chen, a food scientist at Zhejiang Gongshang University in Hangzhou (China), “we detect the chemical information of food: flavor, taste”. When people eat, he explains, they don’t taste the food itself, but a mixture of food and saliva. For example, an eater can only perceive a sweet or sour flavor molecule in a bite if that molecule reaches the taste buds. To do this, it must pass through the layer of saliva that covers the tongue.
2. Saliva can affect our perception of aromas
Saliva can also affect the aromas -responsible for most of our perception of taste- that are released from food in the mouth. When chewing, some food aroma molecules dissolve in the saliva, but those that do not can pass into the nasal cavity and be perceived by the innumerable receptors in it. As a result, people with different salivary flow rates or different composition of their saliva—especially of proteins called mucins—can have very different taste experiences of the same food or drink.
3. Saliva affects our perception of texture
For example, astringency is that sensation of dryness that occurs in the mouth when drinking red wine or eating green fruit. Actually, wine does not dry out the mouth. Instead, molecules called tannins in wine can cause proteins to precipitate out of saliva, so that saliva no longer lubricates as effectively.
4. Saliva helps us tell the difference between high-fat and low-fat foods
Even if 2 yogurts look the same, and serve the same, the low-fat version feels drier in the mouth, says Anwesha Sarkar, a food scientist at the University of Leeds in the UK. “What you are trying to understand is not the property of the food, but how it interacts with the surface [of the mouth]”, explains Sarkar. Milk fat can combine with saliva to create a layer of droplets that mask astringency and add a rich feeling to yogurt, she adds.
5. Saliva and perception vary throughout the day and from person to person
Saliva usually flows slowly in the morning and faster in the early afternoon. The components of each person’s saliva -the amounts of certain proteins, for example- vary throughout the day and in the presence or absence of stimuli such as tempting aromas.
According to Ann-Marie Torregrossa, a behavioral neuroscientist at the University at Buffalo, the composition of saliva varies from person to person and depends in part on previous food choices. When Torregrossa fed rats diets containing bitter-tasting additives, she observed remarkable increases in multiple categories of saliva proteins. As those changes occurred, the rats were more likely to accept the bitter taste of the food. “If you eat broccoli all the time, broccoli does not taste bad to you”, says Torregrossa.
What’s exciting about fully understanding these interactions between saliva, food, and the mouth—and how the information is transferred to the brain—is that it could lead to the design of healthier foods. Sarkar envisions developing a “grade food” that includes enough sugar on the outside of the food to dissolve in saliva to create a sweet sensation, but with a lower concentration and caloric level in the food as a whole. According to her, a similar conceptual approach could help reduce fat in food.
But if these patterns can be decoded and understood, the potential is enormous, says oral biochemist Elsa Lamy of the University of Évora (Portugal). If you could somehow provide children with an additive that would cause changes in their saliva and thus make their experience with a bitter vegetable more enjoyable, it could encourage healthier eating. If their first experience with a new food is not accompanied by a high level of bitterness, she says; “they will probably associate a good experience with that vegetable”.
More generally, a better understanding of how saliva influences taste -and how diet, in turn, affects the composition of saliva- could open up a host of new ways to skew dietary preferences towards healthy foods that are often they are scorned. “How can we turn haters of these foods into people who love them? Thatiswhatobsesses me”, addsTorregrossa.