Cystic Fibrosis & Salt

August 15 ~ Written By Aabha Vadapalli

“The child will soon die whose forehead tastes salty when kissed,” is a lyric from a 17th century European folk song. When the song was written, people didn’t understand why their babies were dying and what it had to do with salty sweat. However, we now know that high amounts of salt indicates that a disease called cystic fibrosis (CF) is present. CF is a genetic disease which causes thick mucus to form in the lungs and prevents breathing. Every year, by measuring the salt quantity in sweat, around 2,500 infants are diagnosed with CF. To further understand the connection between salt and CF, let’s look into why CF patients lose salt in their sweat, how they can combat salt deficiency, and how salty sweat helps diagnose infants (History).

In a non-CF patient, one pound of sweat typically contains 500 mg of salt, however, in a CF patient, one pound of sweat can have up to five times that amount. To understand why, we first need to understand the cause of CF. CF is caused by a mutation which prevents the CFTR protein from functioning. CFTR is found in many parts of the body, including the lungs and sweat glands. One of the functions of the protein is to help cells move chloride, one of the two elements that make up salt. When the protein isn’t functioning, salt molecules (sodium chloride) cannot move normally through the cells that line the sweat duct, as a result, they are released with sweat. Therefore, CF patients have an incredibly high salt content in their sweat (Nemo Paediatrics).

A deficiency in salt can lead to vomiting, muscle cramps and can mess up the body’s fluid balance. However, there is a surprisingly simple way to combat deficiency, simply consume more salt. Many processed, canned and frozen foods have large amounts of salt in them. Consuming these foods help CF patients fight the deficiency (Minerals).

The excess salt in a CF patient’s sweat, however, can be useful. In the United States, it is mandatory for infants to take the sweat test, which measures the amount of salt in their sweat. Sweat is collected on a piece of filter paper or in a plastic coil and the amount of chloride is measured. If the amount is between 30 and 59mmol, further testing takes place, if the amount is over 60mmol the child almost definitely has CF, which means they require treatment. According to the Cystic Fibrosis Foundation, the sweat test is the most efficient and accurate method of diagnosing CF to date (Sweat Test).

The loss of salt is another inconvenience in the life of a CF patient. It causes pain and creates imbalance in the patient’s fluid levels. However, there are positives. It can easily be treated by consuming saltier foods, and the high salt content in sweat has helped diagnose thousands of people. So next time you kiss a baby and their sweat is too salty, get them tested for CF and ensure that they eat lots of salt.

References

“History of CF and Diagnostic Testing.” History of CF and Diagnostic Testing - LabCE.Com, Laboratory Continuing Education, www.labce.com/spg793917_history_of_cf_and_diagnostic_testing.aspx#:~:text=In%201 959%2C%20Dr.,for%20the%20diagnosis%20of%20CF.

“Minerals.” Cystic Fibrosis Foundation, www.cff.org/managing-cf/minerals#:~:text=Not%20getting%20enough%20salt%20can,e specially%20during%20hot%2C%20humid%20weather.

Nemo Paediatrics Salt Replacement in Cystic Fibrosis - Queensland Health, www.health.qld.gov.au/__data/assets/pdf_file/0027/154917/paeds_saltrplcment.pdf.

“Sweat Test.” Cystic Fibrosis Foundation, www.cff.org/intro-cf/sweat-test.