# Caffeine does more harm than good Plants evolved to produce caffeine because it confuses predators that eat them and attracts pollinators. For instance, bees have been shown to prefer caffeinated water over sweet water. However, pollinators tend to become addicted to the substance, coming back to the plant even when there is no more pollen. Caffeine raises our levels of serotonin, adrenaline and dopamine, but it also blocks our adenosine receptors ; adenosine is a hormone which reduces neuron activity and makes us sleepy. Caffeine has a quarter life of 12 hours: after 12 hours, 25% of the caffeine you ingested is still in your body. Such an amount may be enough to disrupt deep sleep (contra [[Sleep is critical to your body]]).