Most people know to limit their sodium intake for the sake of their health, but few know exactly how salt affects the body’s ability to fight off infection. Understanding the link can help you to build your immunity this winter.
It’s well established that eating too much salt – or sodium chloride, by its chemical name – can harm your health. An extensive body of scientific research shows that excess sodium increases your risk of high blood pressure, heart attack, stroke and kidney disease.
And while awareness of these risks is fairly widespread, not many people know that a high-salt diet can also damage the workings of your immune system, making it more difficult to fight off infections.
How does salt harm your immune system?
A study from the University of Bonn, published in March 2020, showed that people who ate just six additional grams of salt daily – more or less what you’d get from two fast food meals – displayed “pronounced immune deficiencies”.
“Excess salt can impair immune function at several levels, as well as increasing inflammation in the body,” explains Johannesburg-based registered dietitian Lila Bruk. “It appears that the immune cells of those who consume a high-salt diet are poorer-equipped to deal with pathogenic bacteria than those on a lower salt diet.”
As it’s important for the salt concentration in your blood and organs to remain relatively constant, your kidneys must work hard to expel excess salt via your urine. So that they know exactly how much salt to dump, the kidneys have a little ‘salt sensor’.
An oversupply of salt overworks this sensor. And when this happens, it causes a build-up of hormones called glucocorticoids. When your glucocorticoids are high, certain ‘scavanger’ cells in your immune system are much less effective at killing bacteria. And it’s this that makes you more vulnerable to infection.
But your immune system also needs salt
At the same time, explains Bruk, we do need salt to activate certain immune cells, so the goal should not be to eliminate all salt.
On a cellular level, certain immune cells (namely neutrophils and macrophages) make hypochlorite (the chemical name for bleach) in order to kill microbes. To produce enough hypochlorite – which works as a very effective ‘microbicide’ to kill off a wide range of bacteria, fungi and viruses – these cells need chloride. Your body gets chloride from salt.
There are a number of reasons the body might become deficient in salt. Vomiting and diarrhoea lower your levels, as does eating a low-carb (or ketogenic) diet, adrenal burn out from high stress, drinking too much water or doing a lot of endurance exercise.
So how do you get the right amount of salt?
“The risks of excess salt are much higher than the potential benefits,” says Bruk, who says that, in her professional experience, South Africans tend to be consume far too much. “Try to limit added salt and be conscious of the use of ready-made sauces, convenience meals, stock cubes, breakfast cereals and tinned foods,” she advises.
The World Health Organization recommends adults consume no more than five grams of salt per day, which is the equivalent of one level teaspoon. But, don’t make the mistake of thinking that this limit doesn’t apply to ‘health salts’, such as Himalayan pink salt – sodium is sodium, no matter its source and, according to Bruk, there are no proven benefits to pink salt. “Normal table salt is perfectly adequate and is usually iodated, so it provides a source of iodine - an essential mineral,” she says.
Buying fresh raw ingredients and preparing your meals from scratch at home is an excellent way to cut back on salt. Not only will controlled salt intake help your bacteria-busting immune cells to run at peak form, but you’ll also get more micronutrients and fewer nasties like refined sugar, processed carbs and unhealthy fats, which is a sure win for your overall health.
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