We have long heard that too much salt can be bad for our health. But now, researchers have found that low levels of chloride, a component found in salt, could actually increase the risk of mortality and heart disease in those suffering from hypertension.
Researchers from the University of Glasgow in Scotland analyzed data of almost 13,000 patients with high blood pressure over a 35-year follow-up period, from the early 1970s until 2011.
The study, published in the journal Hypertension, revealed that the group with the lowest level of chloride present in their blood had a 20% increased risk of mortality, compared with those who had higher chloride levels.
Dr. Sandosh Padmanabhan, of the Institute of Cardiovascular and Medical Sciences, says that sodium - a chemical found in salt - is "cast as the villain" for the central role it plays in increasing the risk of high blood pressure (hypertension), with "chloride little more than a silent extra in the background."
Chloride may play role in 'physiology of the body'
Salt certainly has a bad reputation. Not only can its high levels of sodium increase the risk of hypertension, it also increases the risk of stroke, heart failure, osteoporosis, stomach cancer and kidney disease.
Just one single teaspoon of salt contains 2,325 mg of sodium, higher than the recommended daily intake of 2,300 mg for those aged under 50, and significantly higher than the 1,500 mg a day recommended for those aged 51 and over.
However, salt also contains chloride - an electrolyte that works with potassium, sodium and carbon dioxide in order to maintain the correct balance of body fluids, as well as maintaining the body's acid-based balance.
Dr. Padmanabhan says:
"Our study has put the spotlight on this under-studied chemical to reveal an association between low levels of chloride serum in the blood and a higher mortality rate, and surprisingly this is in the opposite direction to the risks associated with high sodium.
It is likely that chloride plays an important part in the physiology of the body and we need to investigate this further."
Since chloride levels are already monitored as part of routine clinical screening, the researchers say that checking chloride levels could be easily incorporated into clinical practice in order to determine who is at higher mortality risk.
Salt intake 'now a grey area'
The study authors note that these findings may present confusion among individuals, particularly as people are widely familiar with the fact that high salt intake can increase the risk of numerous health problems.
"The results we see from this study are confounding against the knowledge that excess salt is a bad thing, yet higher levels of chloride in the blood seems to be an independent factor that is associated with lower mortality and cardiovascular risk," adds Dr. Padmanabhan.
"We seem to have entered a grey area here that requires further investigation."
He adds that It is too early to draw any conclusions about relating this finding to salt intake and diet, and that further research is needed to establish exactly what the relationship between chloride and health risk is.