A research team from the University of Bonn discovered that cow milk protein may trigger more severe multiple sclerosis symptoms.
Multiple sclerosis is an autoimmune condition that can affect the brain and spinal cord. This is a common cause of disability in younger adults. Multiple sclerosis symptoms include problems with vision, fatigue, and muscle stiffness.
Patients with multiple sclerosis often see more severe symptoms following the consumption of dairy products and researchers at the Universities of Bonn and Erlangen-Nuremberg set out to discover the reason for this. In their research, they found that a protein in cow’s milk can trigger inflammation that targets the ‘insulating layer’ around nerve cells.
The prompt for the study came from MS patients: “We hear again and again from sufferers that they feel worse when they consume milk, cottage cheese or yoghurt,” explained Stefanie Kürten from the Institute of Anatomy at University Hospital Bonn. “We are interested in the cause of this correlation.”
The study has now been published in the journal PNAS.
The link between dairy and severe multiple sclerosis symptoms
The research team administered a cow’s milk constituent casein with an effect enhancer to mice and found that they went on to develop neurological disorders. Electron microscopy showed damage to the insulating layer around the nerve fibres (the myelin). The fat-like substance prevents short circuits and significantly accelerates stimulus conduction.
With multiple sclerosis, the body’s immune system essentially destroys the myelin sheath, which results in life-changing consequences such as vision problems and movement disorders. The insulating sheath was also massively perforated in the mice, apparently triggered by the casein administration.
“We suspected that the reason was a misdirected immune response, similar to that seen in MS patients,” observed Rittika Chunder, who is a postdoctoral fellow in Professor Kürten’s research group. “The body’s defences actually attack the casein, but in the process, they also destroy proteins involved in the formation of myelin.”
Such cross-reactivity can occur when two molecules are very similar in part of their build-up. In essence, the immune system mistakes them for each other.
“We compared casein to different molecules that are important for myelin production,” Chunder said. “In the process, we came across a protein called MAG. It looks markedly similar to casein in some respects – so much so that antibodies to casein were also active against MAG in the lab animals.”
This illuminated that in the casein-treated mice, the body’s defences were also directed against MAG, destabilising the myelin. To understand how these results could be transferred to people with multiple sclerosis, they added casein antibodies from mice to human brain tissue. Similarly, they accumulated in the cells responsible for myelin production in the brain, therefore, exacerbating multiple sclerosis symptoms.
Casein antibodies
Scientists have observed that certain white blood cells known as the B cells are responsible for antibody production. The researchers found that B cells found in people with multiple sclerosis respond strongly to casein.
Thus, it is presumed that the affected individuals developed an allergy to casein because of milk consumption, leading to worsening multiple sclerosis symptoms. As a result, when dairy products are consumed, the immune system produces casein antibodies and cross-reacts with MAG, damaging the myelin sheath around the nerve fibres. This subsequently results in more severe multiple sclerosis symptoms.
However, this only affects multiple sclerosis patients who are allergic to cow’s milk casein. “We are currently developing a self-test with which affected individuals can check whether they carry corresponding antibodies,” commented Kürten, who is also a member of the Cluster of Excellence ImmunoSensation2. “At least this subgroup should refrain from consuming milk, yoghurt, or cottage cheese.”
