Well, we all know that junk food is bad for us, don’t we!?
Yes, I hope so. But Western societies still consume vast quantities of junk food.
And what happens to the brain?
That is precisely the question that Anna Hayes and colleagues of the University of Southern California wanted to answer. There are piles and piles of research into how so-called Western diets (highly processed, high fat, and high sugar) are harmful for us and the correlations with all sorts of diseases including Alzheimer’s. But there is little knowledge of the precise mechanism that are at play in the brain.
I thought it was inflammation?
Yes, that is one mechanism in that this diet causes low level inflammation - basically stress in the brain. There are others such as the change in the gut microbiome. Suffice to say it is really not good for you.
But the question here is can we measure this over time and the impacts in the brain? This is precisely what the researchers did. They fed baby rats an unhealthy Western diet and then monitored the changes in the brain compared to a control group.
Oh, and did they find anything interesting or useful?
Yes, indeed they did. They specifically tracked a brain transmitter called acetylcholine because this is known to be lower in those with Alzheimer’s, and this brain transmitter is known to be involved in learning, attention, arousal, and involuntary muscle movement.
The rats went through various learning exercises at various times and also had their brains analysed after death.
What did they find?
They saw that those who were raised on the “junk food” had impaired memory and brain analysis showed that there was disrupted acetylcholine processing and production.
But can this be improved by changing the diet?
Well, this is the bad news. It seems that changing to a healthier diet - with these rats at least - does not improve the already impaired memory! The rats that had grown up on a junk food diet had permanently impaired memory functions.
However, in human beings maybe take that with a pinch of salt - we do know that various healthy habits can have very positive effects. But in this case the rats had grown up with this diet and obviously developmental phases are critical to healthy development of brain systems - here the acetylcholine system. This applies to rats as well as humans.
Wow - so there was no way to improve their memory?
Well, actually yes, there was. But this involved injecting acetylcholine directly into the hippocampus, a brain region critical for memory formation. Doing that improved cognitive function of these rats. But that will not happen in humans any time in the near future.
OK so, feed your kids healthy food!
Yup, or feed all kids in a society healthy food!
And avoid junk food as an adult as well!
Well, yes, healthy nutrition is critical to optimal brain functioning - something we all want!
Reference
Anna M.R. Hayes, Logan Tierno Lauer, Alicia E. Kao, et al.
Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling.
Brain, Behavior, and Immunity, 2024; 118: 408
DOI: 10.1016/j.bbi.2024.03.015