Unlocking salty secrets

The negative health impact of excessive salt intake has led food scientists to seek salt replacers or enhancers that will enable a reduction in the sodium content of food, while still retaining the taste profile enjoyed by consumers.

However, these efforts have been hindered by a lack of understanding of the complex processes by which humans taste salt.

Now, a team from the Monell Senses Center in the US has further characterised the identity and functionality of salt-responding taste cells on the tongue.

“Understanding more about the mechanisms involved in detecting salt taste moves us closer to developing strategies to reduce the amount of salt in our food while still retaining the salty taste that people enjoy,” said the study’s lead author, Brian Lewandowski, PhD, a neurophysiologist at Monell.

‘Salt’ is a chemical term that describes a compound made of positively and negatively charged ions; the most well-known example is sodium chloride (NaCl). The primary process by which mammals detect NaCl, common table salt, is well understood, and occurs via a sodium receptor known as ENaC (epithelial sodium channel). The ENaC receptor responds almost exclusively to sodium (Na+) salts and is not influenced by the salt’s negative ion (eg, Cl-).

However, scientists know that a second salt-sensing receptor also exists, but much about this receptor, including its identity, remains unknown. Like ENaC, the second receptor detects sodium salts, but it is also sensitive to non-sodium salts such as potassium chloride (KCl), which is frequently used to replace sodium in foods.

In the current study, published in the Journal of Neuroscience, Monell researchers identified the taste cells involved in this second salt taste mechanism and increased understanding of how they function.

The Monell scientists used a rodent model and applied sophisticated neurophysiological techniques to isolate single living taste cells. They then measured the isolated taste cells’ responses to different salts to classify the cells and identify those involved in the second salt pathway.

The isolated second pathway cells were found to be a subset of what are known as Type III taste cells, which are also thought to be involved in detecting sour taste.

By knowing which cells to study and more about how they interact with salts, the team can now focus on determining the identity of the second salt receptor.

The new findings provide an important step towards a more complete understanding of salty taste and how it is detected, with the ultimate goal of identifying alternative approaches to activate salty taste and alleviate the negative health consequences of sodium overconsumption.