An increase in products with lower salt content, coupled with salt substitutes, highlights this heath initiative as a major focus for food manufacturers. Salt is often added to food because it extends the shelf life of fresh food and, in some cases, makes cheap ingredients taste better.
Whilst many UK food manufacturers initially made a concerted effort to reduce the salt in their products, others are now failing to do so and in turn are putting the health of populations at risk. A recent study looking into the link between salt and obesity believed this action to be unacceptable.
The study's co-author and Consensus Action on Salt and Health (CASH) chairman, Graham MacGregor, said the findings demanded decisive action from government and industry to achieve a 30% reduction in population salt intake. “The government and the food industry now need to take much stronger action. Unfortunately the previous government handed power back to the food industry with the Responsibility Deal which has completely failed to tackle these issues in the way that it needs to be,” he said.
Overconsumption of salt has been strongly linked with high blood pressure, strokes and heart disease. According to the World Health Organisation (WHO), an estimated 2.5 million deaths could be prevented each year if global salt consumption were reduced to the recommended level.
Ion size determines saltiness
The study, featured in the Journal of Neuroscience took a look at the amiloride-insensitive (AI) pathway, one of two main biological pathways that mediate the salty taste in humans.
This pathway is also able to detect salts such as common sodium-derived table salt (NaCl), but is also sensitive to non-sodium salts such as potassium chloride (KCl), which is frequently used to replace sodium in foods.
Crucially, this pathway is affected by the size of the salt’s negative ion. In other words, salts with smaller negative ions taste more salty. For this reason, sodium chloride, a salt with a small negative ion, tastes saltier than sodium gluconate (Na(C6H11O7)), which has a very large negative ion.
The researchers from the Monell Centre in Philadelphia used a mouse model and applied a number of techniques to isolate single living taste cells.
They then measured the isolated taste cells’ responses to different salts to categorise the cells and identify those involved in the second salt pathway.
The isolated second pathway cells were found to be a subcategory of Type III taste cells, which are thought to be involved in detecting sour taste.
Additional experiments with these isolated second pathway cells revealed that negative ions still influenced the cells’ response to a given salt, with the effect of the negative ion remaining dependent on the ion’s size.
The researchers concluded that this result was not an indirect effect of the ion’s size as previous studies had believed, but pointed towards a direct interaction between the taste cell and the negative ion.
Therefore both positive and negative ions directly interacted with cells involved in the second salt pathway to influence how these cells responded to salts.
By knowing which cells to study and more about how they interact with salts, the team are now able to focus on discovering the identity of the second salt receptor.
The taste of success
“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 Dr Brian Lewandowski.
Lewandowski and his colleagues’ findings have additional support in a similar study that recognised the amiloride-sensitive taste transduction mechanism and its associated neural pathway in the recognition of the sodium ion.
“Now that we have isolated and better understand the cells involved in the second salt taste pathway, we can begin to study them in more detail,” said study author Dr Alexander Bachmanov, a behavioral geneticist at Monell.
“We now will analyse these cells to determine which genes and proteins are expressed and which are important for sensing salty taste. This should help us pinpoint the specific receptor mechanism.”
Source: The Journal of Neuroscience
Published online ahead of print, doi: 10.1523/JNEUROSCI.2947-15.2016
“Amiloride-Insensitive Salt Taste Is Mediated by Two Populations of Type III Taste Cells with Distinct Transduction Mechanisms.”
Authors: Brian Lewandowski, Sunil Sukumaran, Robert Margolskee, and Alexander A. Bachmanov