Salt turns out to have a very surprising effect on our brains

Interestingly, it slows blood flow in the brain, which can lead to low oxygen levels and damage brain tissues.

It is known that too much salt is harmful to your health. For example, it leads to high blood pressure, which increases the risk of cardiovascular disease. But what exactly happens in the brain if you often eat too much salt? In a new study researchers took a closer look – literally.

Functional hyperemia

When neurons (the body’s information and signal processors that receive and transmit nerve impulses) are activated, it usually produces a rapid increase in blood flow to the affected area. Also referred to as ‘functional hyperemia’, this occurs through removal of blood vessels in the brain. However, the study of functional hyperemia is still in its infancy. For example, in previous studies only superficial parts of the brain – such as the cerebral cortex – have been studied. Scientists then examined how blood flow changes in response to sensory stimuli from the environment (think visual or auditory stimuli).

Salty

In a new study, the researchers wanted to know how functional hyperemia occurs in deeper parts of the brain. The team focused on the hypothalamus; a region of the brain involved in critical brain functions, including eating, drinking, regulating body temperature, and reproduction. The researchers then decided to study how blood flow to the hypothalamus changes in response to salty food. “We chose salt because the body has to control sodium very carefully,” explains researcher Javier Stern. “We even have specific cells that detect how much salt is in your blood. When you ingest salty food, the brain senses it and activates a series of compensatory mechanisms to lower sodium levels again.”

Decrease in blood flow

The body lowers sodium levels, among other things, by activating neurons that release vasopressin; a hormone that plays a key role in maintaining the correct salt concentration in the body. The researchers make a surprising discovery. Because unlike previous studies that found a positive association between neuron activation and increased blood flow (functional hyperemia), the research team found a decrease in blood flow as neurons in the hypothalamus were activated. “This finding surprised us,” Stern says. “It is the opposite of what is usually seen in response to a sensory stimulus. In addition, slowed blood flow in the brain is normally seen in a variety of diseases, such as Alzheimer’s disease or after a stroke.”

Oxygen content

It means that if you eat too much salt, blood flow in your brain slows down. And that can have far-reaching consequences. A reduced blood flow can lead to a low oxygen level, whereby tissues in the body are not supplied with sufficient oxygen (hypoxia). “When you chronically ingest a lot of salt, the vasopressin neurons go crazy,” Stern explains. “This mechanism can then cause hypoxia, which can lead to tissue damage in the brain.”

The findings raise interesting questions about how high blood pressure affects the brain. It is known that in many cases too high a salt intake is the culprit of high blood pressure. The researchers hope to learn more about how hypoxia can be prevented in follow-up studies. “We may be able to find ways to stop the hypoxia-dependent activation,” Stern suggests. In addition, the researchers plan to study other brain regions and diseases, including depression, obesity and neurodegenerative disorders (such as Alzheimer’s, Parkinson’s and Huntington’s disease).