Dr. Rhonda Patrick

to 116 nanograms per milliliter.

And to reach this IGF-1 sweet spot, researchers estimated a daily protein intake of around 50 to 80 grams, which is not very much protein.

Not to mention this study did not specifically look at healthy, physically active people.

And that's a critical piece to the puzzle because a strong response to exercise requires IGF-1.

So it raises a philosophical question.

Are these recommendations aimed at healthy, physically active individuals, or are they tailored to people maintaining a largely sedentary lifestyle?

Physical activity fundamentally changes how IGF-1 behaves in the body.

Exercise lowers IGF-1 in the bloodstream, redirecting it to where it can be beneficial, like the muscle, and notably the brain.

Here's why that's important.

When you exercise, whether it's cardiovascular exercise or strength training or high-intensity interval training, it stimulates muscle fibers and increases IGF-1 receptor density

in the muscle cells.

This makes muscle tissue more sensitive to IGF-1, potentially enhancing its uptake.

While this precise mechanism is still being explored in research, what's clear is that exercise increases the ability of IGF-1 to cross the blood brain barrier.

Once in the brain, IGF-1 plays a crucial role in promoting neurogenesis.

That's the growth of new brain cells, especially in regions of the brain

like the hippocampus, which is important for learning and memory.

Exercise doesn't stop there.

Exercise, particularly intensive exercise, also raises levels of proteins that bind to IGF-1 and reduce its bioavailability to damaged cells that could potentially form cancer cells.

Exercise alone causes more amino acids to be taken up into skeletal muscle, which also has the effect of reducing circulating IGF-1.

In fact, when protein is consumed after exercise, IGF-1 levels do not increase in the ensuing 24 hours like they do when protein is eaten without exercising beforehand.