Excess Dietary Salt Can Weaken Your Immune System

Updated on November 3rd, 2020
salt and immune system

According to the AHA (American Heart Association), 9 out of 10 people in the US take too much sodium chloride (salt). The DGA (Dietary Guidelines for Americans), which the Department of HHS (Health and Human Services) publish, recommend that individuals consume no more than 2.3 grams (g) of sodium per day.

This amount is approximately equivalent to 5.8 g of salt, which would fit into a level teaspoon [1].

The reason for the advice is that there is strong evidence that too much dietary salt raises blood pressure, which is a risk factor for stroke and heart disease.

However, new research featuring in Science Translational Medicine indicates for the first time that such a diet could also make it more challenging for the immune system to kill bacteria in some human organs [2].

Salt and Immune system

A rich-salt diet is not only detrimental to one’s blood pressure but also for the immune system [3]. This is the conclusion of the latest study under the mentorship of the University Hospital Bonn. Mice fed a rich-salt diet were found to suffer from much more extreme bacterial infections.

Human volunteers who took an extra 6 grams of salt per day also showed significant immune deficiencies. This quantity corresponds to the salt content of 2 fast-food meals. The results are published in the journal STM (Science Translational Medicine).

5 grams a day, no more: This is the maximum amount of salt that one should consume according to the recommendations of the WHO (World Health Organization). It corresponds roughly to one level teaspoon.

In reality, however, many Germans exceed this threshold remarkably: Figures from the RKI Robert Koch Institute indicate that, on average, men consume 10, women more than 8 grams a day.

This infers that we reach for the salt shaker much more than is beneficial for us. After all, sodium chloride, which is its scientific term, increases the risk of stroke or heart attack and raises blood pressure.

But not just that: We have now been able to prove for the first time that too much salt intake also significantly weakens a critical arm of the immune system.

This finding is unexpected, as some clinical trials point in the opposite direction. For instance, infections with certain skin parasites in laboratory animals heal significantly quicker if these eat a rich-salt diet: The macrophages, which are immune cells that eat, attack, and digest parasites, are specifically active in the presence of salt.

Several doctors concluded from this observation that sodium chloride has a typically immune-improving effect.

The skin serves as a salt reservoir

The results show that this generalization is not accurate. There are 2 reasons for this: Initially, our body keeps the salt concentration in the blood and largely constant in several organs. Otherwise, critical biological processes would be impaired.

The only significant exception is our skin: It functions as a salt reservoir of our body. This is why the extra intake of sodium chloride works so well for few skin conditions [4].

However, other parts of our body are not exposed to the extra salt consumed with food. Rather, it is filtered out by our kidneys and flushed out urine. And this is where the next mechanism comes into force: The kidneys have a sodium chloride sensor that activates the salt excretion function.

However, this sensor also leads to so-called glucocorticoids to pile up in the body as an undesirable side effect. In turn, these inhibit the function of granulocytes, the most common kind of immune cell in our blood.

The Research

Granulocytes, similar to macrophages, are scavenger cells. However, they do not attack parasites, but particularly bacteria. If they do not do this to an adequate degree, infections proceed much more severely. Researchers were able to show this in mice with a listeria infection.

The researchers had earlier put some of them on a rich-salt diet. In the liver and spleen of these animals, they counted 100 to 1,000 times the number of disease-causing pathogens. Listeria is bacteria that are present, for example, in contaminated food and can cause vomiting, fever, and sepsis.

Urinary tract infections also healed much more gradually in laboratory mice fed a high-salt diet.

Sodium chloride also appears to harm the human immune system. The scientists examined volunteers who consumed 6 grams of salt in addition to their daily intake. This is approximately the amount contained in two fast-food meals, i.e., two burgers and two portions of French fries.

After a week, the scientists took blood from their subjects and evaluated the granulocytes. The immune cells coped much worse with bacteria after the test subjects had started to consume a high-salt diet.

In human volunteers, too much salt intake also resulted in increased glucocorticoid levels. That inhibits the immune system is not astonishing: The well-known glucocorticoid cortisone is conventionally used to suppress inflammation.

Only through investigations in an entire organism, they discovered the complex control circuits that lead from salt intake to this immunodeficiency. Their work, therefore, also confirms the limitations of experiments purely with cell cultures.

Simple Salt Swaps

  • Use an array of fresh vegetables. The tastier the vegetable, the less seasoning it will require.  Organic veggies taste more flavorsome than non-organic, and homegrown veggies are even tastier. If you have enough time to start a small veg patch or little container garden or your taste buds will love it.
  • A pack of crisps while watching a movie is one of life’s little pleasures, but wow, are they filled with salt. For a low salt variant, try homemade unsalted popcorn. Try making homemade veggie crisps for a real treat. Use root vegetables like parsnips and carrots, so you get an added sweet flavor.
  • Consider making homemade sauces and stocks and freezing them instead of using store-bought variants that are packed with salt.

Bottom Line

It takes time for your taste buds to adapt to this new low salt world. Gradually you will become used to it, and other flavors you hadn’t noticed before will start to disappear.

Minimize the amount of salt you use slowly, and try to be patient. It can take up to six weeks for your taste buds to adapt. Our immune system (amongst other body systems) will thank you for it.

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