How does caffeine make you more alert and work as a cognitive enhancer if it reduces blood flow to the brain?

Question

I’ve just read that a 250mg dose of caffeine can reduce blood flow to the brain by 22%-30%.

It seems counter intuitive to me that a chemical that restricts blood flow to the organ responsible for all mental operations actually improves our mental functioning.

There’s probably a simple answer but 22-30% seems like it would significantly impair the brain’s functioning

In: 129

Answer 1

There are two studies that have found this effect in an experiment with a relatively small samplesize of health young adults. While 17 and 45 is a small sample the measured magnitude seems consistent in both experiments. The first study from 1990 suggests that there is a minimum CBF of approximately 30ml/min/100g of tissue which acts as a tolerable minimum that avoids cognitive impairment and suggests that a regulatory mechanism preserves this minimum CBF even under the influence of caffeine. In the other hand caffeine acts antagonistic on adenosine receptors and can thereby delays physiological responses to fatigue and increase periods of alertness.