How Aerobic Exercise Supports Hippocampal Growth and Memory

Rich Roll: Let's like start with brain health and go a little bit deeper on what you were talking about with respect to like brain-derived neurotrophic factor and like what this is doing. So like when we're building up lactate as a result of vigorous exercise, it's passing through the brain-blood, the blood-brain barrier, it's going into our brains, and it's doing all sorts of beneficial things like something called neurogenesis, right? Like, so talk a little bit more in depth about the importance of lactate or the relationship between it and, and the healthy brain that we all are trying to, you know, kind of foster? Yeah, um, I would love to.

Dr. Rhonda Patrick: It's, it's one of the reasons why I, I really try to engage in, uh, a lot of vigorous-intensity exercise, that I've got neurodegenerative disease on both sides of my family. So for me, I'm very brain-focused when it comes to exercise. It's, it's, it's one of the main reasons I do exercise. I feel better, but I also know that I'm delaying the aging of my brain and helping prevent neurodegenerative disorders. So lactate, it depends on how, there's a lot of factors at play in terms of how much lactate you're going to make, right? So how intense you're going in terms of your exercise, your mitochondrial function, a lot of individual variability here at play.

But generally speaking, when you start to go into that vigorous-intensity zone, you can start, typically, our steady-state lactate levels are less than 1 millimolar. When you start to go into 80%, 85%, 90% max heart rate, you can get anywhere between 7 to 14 millimolar of lactate in your bloodstream. And this can be measured. You can go out and get tests. I've measured it before for myself. The lactate levels don't last long in your blood system, and that is because it is being transported and going and taken up by other tissues. So, really, as far as I've measured repeatedly, it's about a 20-minute, about 20, 25 minutes, and then it goes back to your baseline.

So, there have been a variety of studies that have shown, by the way, Dr. George Brooks from UC Berkeley was the first to really propose at the time this lactate shuttle theory, as he called it, and it's not really a theory anymore, it's been proven time and time again, but he was really the first to propose that lactate was being transported into circulation, it was being taken up by a variety of other tissues, notably the brain, and that it was having beneficial effects in these other organs. In the brain, there is a transporter lactate goes through, this— it's called a monocarboxylate transporter, and it gets into the brain. And there's been a variety of human studies showing that actually during physical activity, lactate is fueling the brain. Because, you know, your brain is working hard too.

Your heart is working hard during exercise, your lungs are working hard, your brain is also working hard, right? I mean, you know this as you're— as an endurance athlete, your brain is also working hard during exercise, and lactate's fueling that. fueling the brain activity. That's been shown. And some of that also has to do with the fact that lactate, it's increasing brain-derived neurotrophic factor. So, you mentioned that, BDNF for short, and that is doing a lot of things. It is helping grow new neurons, particularly in a part of the brain called the hippocampus, which is involved in learning and memory. It's also a part of the brain that atrophies with Alzheimer's disease.

So, there have been a variety of studies that have shown even older adults that are engaging in moderate-intensity activity for about a year, can increase the size of their hippocampus by like 2%.

Rich Roll: Wow.

Dr. Rhonda Patrick: Which is amazing, 'cause typically older adults lose, their hippocampus atrophies with time. So, not only were they fighting and staving off the atrophying, but they were also increasing it. So, that was pretty, I think, one of the big eye-opening studies, and this was over 10 years ago. This was like a 2012 study that was published showing this. The brain-derived neurotrophic factor is growing new neurons, can increase the size of the hippocampus, but also it's really important for something called neuroplasticity.

And that is, it, it, it's kind of like you can think about keeping our brains more pliable and, and malleable and, um, adaptable. So really, neuroplasticity allows our brains to adapt to a changing environment. And this is important for aging. But it's also important for mental health. So, so people with major depressive disorder, for example, they have dysfunction in neuroplasticity. So, and then that kind of makes sense, right? If you can't adapt to a changing environment, it's very stressful and can cause anxiety. It can be depressing.

Rich Roll: Hmm.

Dr. Rhonda Patrick: So, um, there've been a variety of different researchers that are trying to target neuroplasticity as a treatment for depression.

Dr. Rhonda Patrick: So neuroplasticity not only plays a role in brain aging, but it also plays a role in mental health, and I think that's important to point out, because, I mean, I think almost everyone by now knows that exercise is one of the best things you can do for mental health, right? I mean, it's like, it's just, you can't deny it, right? I mean, you go out, even just, even doing like a 10-minute high-intensity workout, you feel better, you know, you feel better.

Rich Roll: Sure, but that's downstream of all kinds of other things that are happening, right? The hormonal regulation aspect of it. I mean, how important is the plasticity piece in the mental health conversation? And what is the significance of that plasticity increase as a result of vigorous exercise?

Dr. Rhonda Patrick: Yeah, it's a good thing you point out. I think there are a lot of things that are changing with exercise. I mean, endorphins that make you feel good, you know, endocannabinoids that make you feel good. I mean, there's serotonin gets increased, right? So there's a lot of different I would say, short-term effects that are potentially responsible for the beneficial, like, elevation in mood that you experience after exercise. With neuroplasticity, I would argue there's more of a long-term effect, right? It's your brain is now able to adapt better to a changing environment, and that's going to have more of a long-term consequence.

So, neuroplasticity is another really important thing that brain-derived neurotrophic factor regulates, and again, coming back to the lactate, which is what we were talking about, you know, lactate is also, when I say it's a signaling molecule, it is communicating and activating a lot of different things in the brain. So, norepinephrine is another one that's been shown to increase, and norepinephrine is a neurotransmitter that is responsible for focus, attention, but also mood.

Rich Roll: Mm-hmm.

Dr. Rhonda Patrick: You know, people are often treated with norepinephrine reuptake inhibitors for anxiety and also depression. So lactate plays a role in increasing that as well.

Dr. Rhonda Patrick: But again, we're just getting down into the nitty-gritty of one aspect of exercise, and as you pointed out, there's a whole plethora of changes that occur with exercise that are beneficial, not limited to lactate. I just, I think the lactate story is so important because it really is a proven mechanism, both human and animal studies. It's something that's measurable, you know, and again, it's something also that we've known is it links the more high-intensity exercise, the more vigorous exercise with a lot of these beneficial effects on the brain.