12 January - 20 June 2016

A very high salt diet found to effect the brain and cause cognitive impairment

A mouse study published in Nature Neuroscience by scientists from Weill Cornell Medicine has found that an extremely high salt diet reduced blood flow to the brain and caused signs of declining mental performance and cognitive impairment. Ladecola et al. state that this occurred even when blood pressure did not increase.

A mouse study published in Nature Neuroscience by scientists from Weill Cornell Medicine has found that an extremely high salt diet reduced blood flow to the brain and caused signs of declining mental performance and cognitive impairment. Ladecola et al. state that this occurred even when blood pressure did not increase.

The scientists fed mice a high salt diet (4 or 8% NaCl) which they state was an 8-fold to 16-fold increase over the normal mouse diet.  Ladecola et al. report that this amount is “comparable to the high end of the spectrum of human salt consumption”.  Blood and urine samples were analysed over the period of the experiment (8-24 weeks).  Whilst there was an increase in NaCl in the urine, and reduction in creatinine due to the high NaCl increase, there were no metabolic alterations.  The team analysed the cerebrovascular effect of the high diet by examined resting cerebral blood flow and found that the diet reduced blood flow to both the cortex and hippocampus regions of the brain that are associated with memory and learning.  They note that alterations in blood flow are known “to produce neuronal dysfunction and cognitive impairment”.  Endothelial dysfunction was seen in the mice fed the 4% NaCl diet for 12 weeks but vascular inflammation was not seen, and “the blood-brain barrier permeability, which is highly susceptible to cerebrovascular inflammation was not altered in cortex or hippocampus of mice fed HSD.” The team discovered that production of nitric oxide was reduced in cells lining blood vessels, called endothelial cells.  Nitric oxide is used to relax blood vessels and increase blood flow. The team wanted to investigate whether the effect of the HSD could be reversed so fed the mice the HSD mice normal chow for 4 weeks.  This was found to reverse the effect of the HSD on the brain.

Ladecola et al. then investigated the effect of blood flow on cognitive function.  Using nonspatial memory tests involving an object recognition task, the team found that whilst the HSD had no effect on the time spent on exploring the objects used in this test, the HSD mice failed to identify a familiar object from an unfamiliar object.  When they were given the normal diet, the mice obtained normal performance results.  Using middle-aged mice, the team found that HSD did not “enhance the magnitude of the HSD-induced endothelial dysfunction but it led to a significant attenuation of CBF response to whisker stimulation suggesting a worsening of the harmful cerebrovascular effect of HSD.” 

The team investigated cognitive function further using the Barnes Maze test and found differences in the HSD and the normal fed chow mice, with the HSD mice showing “a deficit in spatial memory”.  When they investigated nesting behaviour the HSD mice would use less material compared to the normal fed mice, however this was reversed when the HSD mice were fed a normal salt intake.

Using several experiments the scientists investigated the mechanisms involved and report that the HSD diet mice developed an adaptive immune response in their gut which increased the activity of white blood cells TH17 in the intestine.  These cells increase the circulating protein interleukin (IL-17) which “promotes endothelial dysfunction and cognitive impairment” and therefore lead to a reduction in the production of nitric oxide in endothelial cells. 

RSSL's Product and Ingredient Innovation Team, has considerable experience in re-formulating products to provide more healthy options including low salt, low sugar versions and using pre- and probiotics.  To find out more please contact Customer Services telephone 0118 918 4076 or e-mail enquiries@rssl.com 

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