Fish has long been considered a healthy food, linked to improved long-term cognitive health, but the reasons for this have been unclear. Omega-3 and -6, fatty acids commonly found in fish, are often assumed to be responsible, and are commonly marketed in this fashion. However, the scientific research regarding this topic has drawn mixed conclusions. Now, new research has shown that the protein parvalbumin, which is very common in many fish species, may be contributing to this effect.

One of the hallmarks of Parkinson's disease is amyloid formation of a particular human protein, called alpha-synuclein. Alpha-synuclein is even sometimes referred to as the 'Parkinson's protein'.

What the researchers have now discovered, is that parvalbumin can form amyloid structures that bind together with the alpha-synuclein protein. Parvalbumin effectively 'scavenges' the alpha-synuclein proteins, using them for its own purposes, thus preventing them from forming their own potentially harmful amyloids later on.

"Parvalbumin collects up the 'Parkinson's protein' and actually prevents it from aggregating, simply by aggregating itself first," explains lead author on the study.

With the parvalbumin protein so highly abundant in certain fish species, increasing the amount of fish in our diet might be a simple way to fight off Parkinson's disease. Herring, cod, carp, and redfish, including sockeye salmon and red snapper, have particularly high levels of parvalbumin, but it is common in many other fish species too. The levels of parvalbumin can also vary greatly throughout the year.

"Fish is normally a lot more nutritious at the end of the summer, because of increased metabolic activity. Levels of parvalbumin are much higher in fish after they have had a lot of sun, so it could be worthwhile increasing consumption during autumn," says researcher on the study.

Other neurodegenerative diseases, including Alzheimer's, ALS and Huntington's disease, are also caused by certain amyloid structures interfering in the brain. The team is therefore keen to research this topic further, to see if the discovery relating to Parkinson's disease could have implications for other neurodegenerative disorders as well.

The link between higher consumption of fish and better long-term health for the brain has been long established. There is correlation between certain diets and decreased rates of Parkinson's disease - as well as other neurodegenerative conditions.

"Among those who follow a Mediterranean diet, with more fish, one sees lower rates of Parkinson's and Alzheimer's," says lead researcher on the study. This has also been observed in Japan, where seafood forms a central part of the diet. The team is careful to note that no definite links can be established at this point, however.

https://www.chalmers.se/en/departments/bio/news/Pages/Eating-fish-could-prevent-Parkinsons-disease.aspx

https://www.nature.com/articles/s41598-018-23850-0