Dietary sodium is an element the body needs to work properly. The body uses sodium to control blood pressure and blood volume as well as ensuring muscles and nerves work properly. Table salt is 40% sodium.
Healthy adults should limit sodium intake to around 2,300 mg per day, which would equate to one teaspoon of salt.
Healthy adults should limit sodium intake to around 2,300 mg per day, those with high blood pressure should have no more than 1,500 mg per day and adults with congestive heart failure, liver cirrhosis and kidney disease should have far less. One teaspoon of table salt contains 2,300 mg of sodium - an adult's intake for the entire day.
Previous studies have found a potential relationship between salt and asthma, salt and mortality in type 1 diabetes, salt and risk of accelerated cellular aging in teens, salt and heart disease, and salt and cardiovascular disease.
Salt has also been linked to playing a role in autoimmune diseases such as psoriasis, rheumatoid arthritis and ankylosing spondylitis by manipulating salt levels and causing more TH17 cells to be produced - the overproduction of which is tied to the above diseases.
Multiple sclerosis is currently considered an autoimmune disease where damage to the myelin in the central nervous system (CNS) - and to the nerve fibers themselves - interferes with the transmission of nerve signals between the brain and spinal cord and other parts of the body.
The average person in the US has about a 1 in 750 (0.1%) chance of developing MS, with it affecting more than 2.3 million people worldwide.
With previous research indicating that salt may alter the autoimmune response - which is also connected with MS development - the researchers aimed to observe if salt has a direct effect on the course of the disease.
An observational study was conducted including two groups of participants with relapsing-remitting MS.
The first group involved 70 patients. Clinical, radiological and sodium intake data was collected over the follow-up period of 2 years. Blood and urine samples were taken 12 months after enrolment. Levels of salt and a marker of inflammatory activity called creatinine were measured in urine, together with measurements of serum sodium (the concentration of sodium in the blood) and vitamin D levels - low levels of which have been linked to MS.
The second group consisted of 52 patients. Casual urine samples were collected and analyzed by following the same procedures as those used for the first group.
Those on high salt intake were four times as likely to have exacerbating MS symptoms
Both groups averaged an intake of just over 4 g of salt a day, ranging from under 2 g (low), 2-4.8 g (moderate) to 4.8 g or more a day (high). Group one had a higher proportion of males with higher levels of sodium intake, whereas the results of the second replication group did not differ between sexes.
Influential factors including age, gender, disease duration, smoking status, vitamin D levels, body mass index and treatment were taken into consideration, and the analysis shows a link between dietary salt and MS symptoms becoming severe.
When compared with the individuals in the group who consumed the least salt per day, people consuming moderate or high intakes of salt had around three more episodes of symptoms progressing and were 4 times as likely to have exacerbating symptoms.
X-rays and scans were observed to look for signs of disease progression. This radiological evidence showed further signs of deterioration with higher dietary salt intake levels. People with high salt intake were 3.5 times as likely to have radiological signs of further progression.
The researchers say:
"High salt intake is implicated in various aspects of poor health. Findings suggest further research into whether dietary salt reduction could ease MS symptoms or slow the progression of the disease might now be warranted."
As a point of discussion in the research paper, the investigators note that although there is an association between increased salt intake and increased disease activity, there is a possibility that individuals who had more relapses received more steroids, and as a result, their salt intake and excretion increased because they have higher disease activity and not the other way around.
Last month, Medical News Today reported that a survey of ready-to-eat salads exposed high salt content. The survey found that 77% of these salads (a total of 511 products) contained more salt than a packet of potato chips.