Why are tears salty?

2024-02-11 06:30:00

You may have already noticed that the tears streaming down your face had a slightly salty taste. But have you ever wondered why? As Dr Jean du Breuillac, general practitioner and deputy secretary general of the College of General Medicine (CMG), explains to us, our tears contain sodium, just like our table salt! Where does this sodium come from? And what is it for? We take stock.

What are tears for? Where do they come from?

Our tears are secreted by our lacrimal glands, located in the upper outer corner of each eye. Often associated with strong emotions, they play a crucial role in protecting and lubricating the eyes. “Their function is to moisturize, clean and protect the surface of the eye, the conjunctiva,” explains Dr Du Breuillac. They also play an important role in communication and emotional regulation.

At the risk of breaking down an open door, there are several types of tears:

basal tearsproduced continuously in small quantities to keep the cornea moist and supply the cells on the surface of the eye with oxygen and nutrients.reflex tearsproduced in response to eye irritation or injury to quickly remove foreign substances (such as dust, smoke, or propanethial oxide from cut onions) and protect the eye.and emotional tearsproduced in response to strong emotions such as sadness, joy or laughter.

When they are secreted, all spread to the surface of the cornea and flow through the tear ducts located in the inner corners of the eye.

Why are our tears hot?

The tear temperature is influenced by our body temperature. The tear glands are located inside the eye socket and are surrounded by body tissues maintained at normal body temperature (around 37°C). Therefore, freshly produced tears have almost the same temperature as our body and may appear “hot”.

Composition of tears: why do they taste salty?

Tears simply taste salty due to their chemical composition, replies Dr Du Breuillac. In fact, they are composed of water, proteins, iron, potassium, calcium and the sodium, an essential electrolyte that is also found in table salt, he explains. But where does this sodium come from?

Since the work of Claude Bernard, the father of modern physiological science, we have known that all our biological fluids contain sodium, particularly blood. However, our tear glands filter our blood to produce our tears. Dr Du Breuillac, general practitioner.

In other words, our tears are salty because they are made from salty blood. Ultimately, however, our tears are slightly saltier than our blood.

Good to know: some tears may be less salty than others depending on different factors such as emotion, eye irritation, or other physiological conditions (more information below).

What is the sodium in our tears used for?

” To be in good health, all our cells need to evolve in a slightly salty environment. They cannot survive in an environment composed of pure water,” Dr Du Breuillac tells us. Concretely, the sodium present in our tears therefore participates in good health of the conjunctiva. Tears made from pure water could damage the cells (lysis phenomenon)!

So pay attention to the composition of your physiological serum or your artificial tears: these two medical devices contain sodium in small amounts to reproduce the exact composition of natural tears and avoid damaging the eye walls.

Does diet impact sodium levels in tears?

The level of sodium present in our tears is constant and similar in most people, assures Dr Du Breuillac. It does not depend on our diet, nor even on our blood sodium level., he notes. On the other hand, it can depend on the emotional context and climatic conditions!

“When it is very hot, for example, our tears evaporate more or less quickly and our tear glands are in great demand: they must make tears faster… Therefore, the latter may contain less sodium, and therefore be a little less salty. »

Our tears are less salty when we are sad!

Other surprising information, emotional tears are generally less salty as basal or reflex tears. “Emotional tears come unexpectedly and have no physiological benefit. Fact, they are made in a hurry by the tear glands and generally contain less sodium,” confirms Dr Du Breuillac.