A high-fat and high-calorie diet makes the immune system more aggressive
The diet in modern industrialized nations is often too high in fat and calories. The spread of health problems such as obesity and diabetes is increasing accordingly. So far, the effects of unhealthy nutrition on the immune system have remained largely unclear. According to a recent study, the high-fat and high-calorie diet triggers an immune system response that is similar to that of a bacterial infection and causes increased inflammatory reactions in the long term.
The international research team led by scientists from the University of Bonn has shown that unhealthy eating not only activates the immune system in the short term, but also makes the body's defenses more aggressive in the long term. So long after switching to healthy food, inflammation occurs faster. This directly promotes the development of arteriosclerosis and diabetes. The study results were published in the specialist magazine "Cell".
Unexpected increase in immune cells
As part of the study, the researchers gave mice a so-called “western diet” for a month that was high in fat, high in sugar and low in fiber. As a result, the animals developed "a massive inflammation across the body, almost like after infection by dangerous bacteria," according to the Rheinische Friedrich-Wilhelms-Universität Bonn.
According to Anette Christ, postdoctoral researcher at the Institute for Innate Immunity at the University of Bonn, "the unhealthy diet led to an unexpected increase in some immune cells in the blood." This is an indication of the involvement of precursor cells in the bone marrow in the inflammatory process.
Large number of genes activated
In further investigations, the researchers isolated and analyzed the precursor cells of immune cells from the bone marrow of the mice in order to better understand the changes. Genomic studies actually showed that a large number of genes were activated in the progenitor cells by the Western diet, reports Prof. Dr. Joachim Schultze from the Life & Medical Sciences Institute (LIMES) of the University of Bonn and the German Center for Neurodegenerative Diseases (DZNE).
Long-term genetic reprogramming
Among the activated genes were, among other things, hereditary predispositions for their multiplication and maturation and the “fast food leads to the body quickly recruiting a huge, powerful fighting force,” says Prof. Schultze. If the mice were then offered the typical cereal diet for a further four weeks, the acute inflammation disappeared, but the genetic reprogramming of the immune cells remained.
"Even after these four weeks, many of the genes that had been switched on during the fast-food phase were still active," said the researchers at the University of Bonn.
Immune system has a memory
Only recently, according to Professor Dr. Eicke Latz, head of the Institute for Congenital Immunity at the University of Bonn and scientist at the DZNE, known that “the innate immune system has a memory.” After an infection, the body's defenses remain in a kind of alarm state, so that they can react more quickly to a new attack can. This process, known as “innate immune training”, was not triggered in the mice by a bacterium, but by an unhealthy diet.
"Fast food sensor" identified
In their study, the scientists were even able to identify the "fast food sensor" in the immune cells that is responsible for the effect, according to the University of Bonn. On the basis of an examination of the blood cells in 120 test subjects, it could be shown that the innate immune system shows a particularly strong training effect in some test subjects. Genetic studies have shown that a so-called inflammasome is involved.
Inflammasome activated by certain food ingredients
As sensors of the innate immune system, inflammasomes recognize harmful substances and subsequently release highly inflammatory messenger substances, the scientists explain. The identified inflammasome is activated by certain food ingredients, which has long-term consequences in addition to the acute inflammatory reaction. According to the researchers, the way in which the genetic information is packaged is changed.
Epigenetic changes through diet
The DNA threads with the genetic information are wrapped around proteins and heavily tangled, which is why many genes cannot be read on the DNA - they are simply too difficult to access, the scientists explain. The unhealthy diet leads to the fact that some of these normally hidden DNA parts unroll and make the areas of the genetic material easier to read in the long term. These so-called epigenetic changes are triggered by the inflammasome, explains Professor Latz. As a result, the immune system already responds to small stimuli with stronger inflammatory responses.
Increased risk of diabetes, arteriosclerosis, strokes and heart attacks
The changed inflammatory response dramatically accelerates the development of vascular diseases or type 2 diabetes, according to the scientists. For example, in arteriosclerosis, the growth of typical vascular deposits (so-called plaques) is promoted by the inflammatory reaction. If the plaques become too large, they burst open, are carried away by the blood stream and can block other vessels, which in the worst case can result in a stroke or heart attack, the scientists explain.
Dramatic consequences of unhealthy eating
According to the researchers' results, malnutrition shows dramatic long-term consequences. According to Prof. Latz, this finding has enormous social relevance. Average life expectancy in western countries has risen steadily in recent centuries, but this trend is only being broken for the first time. Those who are born today will probably live on average shorter than their parents, although poor nutrition and too little exercise play a decisive role in this, according to the experts.
According to Professor Latz, the basics of a healthy diet must become even more of a school subject than today, since children can only be immunized against the temptations of the food industry at an early stage before long-term consequences unfold. Today, children have a choice of what they eat every day and "we should enable them to make a conscious decision about their diet," the expert concluded. (fp)