Professor Kaeberlein, you list some fictions of anti-aging diets in your review in science? What are those?
I mean, I think we've touched on some of them. Right. So, you know, the idea that anti-aging diets are all the same, I think, is clear, you know, that remains to be determined. Dr. Matt Kaeberlein, PhD. Dr. Anton Titov, MD.
I think, you know, the idea that something like caloric restriction always works is a common misperception. I would say, in the field, right, that every experiment where somebody has tried to calorically restrict a mouse, you've seen lifespan extension. And, you know, we dive into this a little bit in the review, in the context of the importance of genetic background on the efficacy of caloric restriction and potentially some of these other dietary interventions. Dr. Matt Kaeberlein, PhD. Dr. Anton Titov, MD. And I think that's important to appreciate this gets back to the idea that, you know, when we study something like caloric restriction in a laboratory animal, usually that's done in an inbred mouse or rat strain.
So genetically homogeneous individuals, and as we've already talked about in a well-controlled environment, so, the fact that you know, these experiments are done in a specific inbred strain background is useful from the perspective of controlling variation. Still, what you might miss is that a different genetic background may not show the same effect. Dr. Matt Kaeberlein, PhD. Dr. Anton Titov, MD. And, in the studies that have been done in yeast in fruit flies, and In mice, where people tried to look across, you know, dozens of different genetic backgrounds.
The results are pretty striking that in about a third of the genetic backgrounds tested in all three organisms, the effects of caloric restriction ranged from zero to actually negative effects on lifespan. Dr. Matt Kaeberlein, PhD. Dr. Anton Titov, MD. So, again, when we think about taking caloric restriction, intermittent fasting, time-restricted feeding out of the laboratory and into the real world, people are genetically heterogeneous, right?
We're all genetically different from each other to some extent, or epigenetically, different from each other. And so it's important to understand, you know, in which genetic backgrounds will caloric restriction be beneficial, in which genetic backgrounds might it have no effect and in which genetic backgrounds might be harmful?
So I think that's a really important misperception about caloric restriction and dietary strategies to affect aging that a lot of people have. Dr. Matt Kaeberlein, PhD. Dr. Anton Titov, MD. They don't always work. And there are going to be individuals, even if they can have a positive effect on biological aging in humans, there are going to be individuals where those effects will be modified. And it may go the other direction. And at this point, I would say the field really has almost no mechanistic understanding of that interaction between genotype and response to caloric restriction. So I think that's a really important fiction for people to understand. So those are, those are some of the big ones. That's probably a good place to start.