Your brain makes up about 2% of your body weight, yet it uses roughly 20% of the oxygen you breathe. That single fact explains a lot about why circulation matters so much for how clearly you think.
Neurons are extremely energy-hungry and have almost no capacity to store fuel locally. They depend on a constant, well-regulated supply of oxygen and glucose delivered through blood vessels.
When cerebral blood flow is reduced, even temporarily, the effects tend to show up first in the systems that need the most continuous fuel — attention, working memory and recall are often the earliest to feel foggy.
Rather than trying to force alertness with a stimulant, ingredients like L-Arginine and L-Citrulline are aimed at the vessels themselves — supporting the pathway oxygen travels through to reach neurons in the first place.
Circulation isn't the only factor in cognitive wellness, but it's a foundational one — which is why it's worth understanding before looking at any other piece of the puzzle.