How likely is it that food can give you an autoimmune disease like diabetes, celiac disease or arthritis?
One popular explanation as to why there’s been a sharp increase in autoimmune diseases is changes in our diet. But diet is only one of many factors that can be important, according to a Norwegian researcher.
Type 1 diabetes. Multiple sclerosis. Psoriasis. Arthritis. Celiac disease. Inflammatory bowel disease (IBD).
These are just some of the 80 diseases that researchers know of where the immune system attacks its own body.
The immune defence that is supposed to protect us from invading microorganisms is no longer able to distinguish the difference between healthy cells and invaders.
Problem in the Middle East and East Asia
The number of cases of autoimmune diseases worldwide has increased sharply.
Although some of the increase may be due to more attention and more diagnoses of the diseases, researchers also believe that there is a real increase.
It started about 40 years ago here in the West. But now some of these diseases are most prevalent in countries in the Middle East and East Asia. These are countries where previously almost no autoimmune diseases had been recorded, according to James Lee, who was recently interviewed by the newspaper The Guardian.
Is diet the cause?
Many researchers today believe that environmental factors must be playing a key role in the increase.
Humans probably haven’t changed much genetically in recent decades. Researchers in London consequently believe that there must be something in the environment that has changed.
Researcher Carola Vinuesa says in the same article from The Guardian that one theory is that changes in our diet can be important.
As more people in the world have started eating much more fast food, there have also been more and more reports of autoimmune diseases. Vinuesa points out that fast food lacks important ingredients, such as fibre, which has a positive effect on our intestinal bacteria.
Must have a genetic susceptibility
But no matter how many Big Macs you eat, you won’t get an autoimmune disease — as long as you don’t have any genetic susceptibility.
Instead of taking up a hopeless battle against companies that sell fast food, we would be better off understanding how our genes work, Vinuesa said to The Guardian.
Why do some people get sick from the foods they eat, while others don’t?
Anette Susanne Bøe Wolff is a professor at the University of Bergen (UiB). She works in the research group for endocrine autoimmunity, formerly the KG Jebsen Center for Autoimmune Disorders. Researchers here are studying the disease on a number of levels to determine what causes autoimmune reactions, the course of the disease and better treatment.
Understanding how our own bacterial flora affects our immune system and relating it to diet is a very "hot" topic right now, Wolff tells sciencenorway.no.
“But which comes first, the chicken or the egg? Will getting a disease affect your bacterial flora or will changes in the bacterial flora make you sick? Both are probably true,” she said.
Diet is just one part of a complex picture, Wolff believes.
Hormones also matter
Wolff says that even if you have a genetic risk of getting an autoimmune disease, you can go through life without getting the condition.
“You may have a high genetic risk, but still not get the disease. And vice versa,” she said. “This is where the environmental factors come in. Different environmental factors, such as diet, can probably directly change how genes are expressed, but it can also work in other ways.”
The reasons for autoimmune diseases are probably a complex mix of genes and environment. Researchers are pursuing different directions to find out why these diseases are on the increase, she said.
Environmental impacts, such as diet, probably have something to say here. But other things may matter much more than just diet, she says.
“It can be hormones, for example. More women than men get autoimmune diseases,” she said.
“There can also be infections, various environmental toxins, changes in the bacterial environment in the body, and so on. The combination of many small risks can turn into one big risk.”
Much is not known
Wolff is clear that there are many things we still don’t know about autoimmune diseases.
The hygiene hypothesis has often been put forward to explain the increase in both allergies and autoimmune diseases. This hypothesis suggests we have become so hygienic that our immune system is not triggered and trained during childhood to understand the difference between friend and foe.
Wolff believes that the answer to this is complex.
“We know little about what the answer is, so research in this area is also important,” she says.
Need a lot of data over a long period
What makes the research challenging, Wolff believes, is that researchers often have to study patients after they have been diagnosed.
“This makes it possible to look at genetic factors. But a diagnosis at this time is too late to map out exact environmental factors,” she said.
Instead, what’s needed are large studies with many people, and the studies must go over an entire life cycle. And researchers need to ask the right questions and take the right samples at the right time.
“I don’t think we have all the right questions yet to be able to study this whole complex picture,” she said.
Many common features
Type 1 diabetes, lupus, multiple sclerosis and arthritis can all be characterized as the immune system attacking a person's own tissues.
There are also commonalities in the way this attack takes place. But different tissues are attacked depending upon the disease.
Researchers in the United States have shown remarkable similarities in the way tissues respond to immune attacks in each disease, according to an article in Nature in 2020.
Although many of these diseases have something in common, each disease probably also has its specific causal relationship in terms of genes — and probably environmental factors that come into play.
But if researchers find molecular mechanisms for one of the diseases, it will probably be able to give them a hint about how to proceed with the others, the University of Bergen’s Wolff said.
“Some conditions are more similar to each other than others. For example, organ-specific diseases such as diabetes and adrenal insufficiency have several common features,” she said.
One disease is better understood
In the late 1980s, two Norwegian researchers, Ludvig M. Sollid and Knut E. A. Lundin at the University of Oslo (UiO), determined which genes are involved in celiac disease.
This is a disease in which the body responds negatively to gluten. The two Oslo researchers later discovered how the disease works in the body. Sciencenorway.no has written about this research before.
Today, celiac disease is the only one of the autoimmune diseases where scientists know exactly why the soldiers of the immune system resort to armed combat. It is because the immune system perceives gluten as dangerous.
This knowledge means that many pharmaceutical companies are now working to be first on the market with a celiac pill. In 2021, sciencenorway.no wrote that the pill is being tested on patients and that there have been good results.
The knowledge the researchers at UiO have gained about celiac disease can help many others with autoimmune diseases.
Central immune cells in celiac disease have also been found in patients with lupus, systemic sclerosis and arthritis, by researchers at the University of Oslo researchers.
Searching for tiny differences in DNA
At the Francis Crick Institute in London, researchers James Lee and Carola Vinuesa will also intensify their efforts to find out more about the cause of autoimmune disease, according to The Guardian.
The British researchers have started two research groups that will use advanced DNA technology to find tiny differences in the genetic material of a large number of people.
In this way, they believe it is possible to identify genetic patterns in those who suffer from these diseases.
Lee tells the newspaper that when he started his research career, scientists only knew of a few DNA variants involved in one of the diseases, inflammatory bowel disease (IBD). Now they know of more than 250.
Today, researchers have the tools they need to sequence large amounts of genes, including those that can be important in causing autoimmune diseases.
Translated by Nancy Bazilchuk
Read the Norwegian version of this article at forskning.no