It has long been known that a high salt intake increases the risk of developing certain health conditions — especially hypertension (high blood pressure) — and is linked to a higher risk of death. It’s also known that sodium levels in the blood increase following meals containing salt, and that areas of the body where there is a high level of inflammation can accumulate sodium from the blood. To help understand how salt intake may be related to inflammation, researchers designed a study in which sodium levels outside cells were manipulated to mimic the effects of eating salt in the body. They then looked at the effects this had on cells called mononuclear phagocytes (MNP), which are integral to the immune system.
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Immune cell metabolism changes found in response to high salt concentrations
As noted in a press release from the Max Delbrück Center for Molecular Medicine in Berlin, where the research took place, previous research has shown that small increases in sodium in the blood reduce the amount of energy produced in mitochondria, sometimes known as the “power plants” of cells in our body. The latest study shed some light on why this happens in the context of immune cells. When these immune cells were exposed to high salt concentrations, their metabolism (use of energy) changed within three hours. Salt was found to disrupt the respiratory chain that’s essential to cellular function, causing the cells to consume less oxygen. The cells produced less ATP (adenosine triphosphate), which is the universal fuel for cells in the body.
Having less ATP means that cells can’t do as much “chemical work,” such as synthesizing proteins and other molecules. In response to this lower level of ATP, immune cells mature differently in a way that makes them more effective at fighting off infections. But these adaptations may also promote inflammation, which could increase the risk of cardiovascular problems.
In addition to studying these specific immune cells, a team of researchers also conducted a pair of studies involving humans as part of a collaboration with Charité – Universitätsmedizin Berlin, a leading research hospital. In one study, healthy men took a 6-gram salt supplement in addition to their normal diet each day for 14 days, and in another, the researchers looked at immune cells after participants ate a delivered pizza. They found that the dampening effect of salt intake on immune cell mitochondria was seen not just in participants who took the salt supplements, but also in the other participants after eating a single pizza containing 10 grams of salt. Blood samples taken three and eigt hours after eating the pizza showed that while this effect was pronounced after three hours, it was barely noticeable after eight hours. This results suggest that cellular changes are unlikely to last if people eat high-salt meals now and then, but that a steady high-salt diet could lead to persistent inflammation.
The next step, the researchers noted, is to investigate the effects of high salt intake on other cells in the body — and since mitochondria exist in almost every type of cell, they have their work cut out for them. But since mitochondria are especially prevalent in muscle cells, neurons (nerve cells), and egg cells, these cell types are all strong candidates for future research on salt intake.
Want to learn more about the immune system? Read “Ways to Support Your Immune System: Fact or Fiction,” “Type 1 Diabetes: Meet Your Immune System,” and “Strengthening Your Immune System for a Healthy Winter.”