Conventional wisdom suggests that eating carrots, or other vegetables rich in vitamin A, can improve your night vision. While it's true that vitamin A is important for healthy eyesight, the idea that devouring carrots can actually improve your vision is an unsubstantiated myth.
But researchers have discovered another plant that might actually improve your night vision: cannabis. That's right, your bloodshot eyes might not look very healthy, but there's now evidence that getting stoned might enhance your sight in the dark, according to a new study published in the journal eLife.
The principal psychoactive constituent in marijuana, THC, produces the sensation of being stoned by binding to receptors in the brain. One of these receptors is known as CB1, and it just so happens that the human retina contains a high concentration of CB1 receptors. Scientists have therefore suspected that cannabis has an effect on the eyes, but this connection has not been well researched.
To study it, a team of researchers applied synthetic cannabinoids to the eye tissue of tadpoles of the African clawed toad. Tadpoles might seem like an unusual choice for this research, but like humans, their eyes also contain CB1 receptors. Readings of the tadpoles' light-sensitive retinal ganglion cells — captured thanks to attached electrodes — revealed heightened activity in the presence of the cannabinoids.
Researchers then placed the tadpoles in a petri dish that was dotted with black marks on the outside that were shaped to look like the shadows of predators. When the lights were turned down, tadpoles that were given the cannabinoids were far more effective at avoiding the fearsome marks.
The study's authors guessed that the improved vision had something to do with the fact that the preoccupied CB1 receptors caused a decrease in the number of negatively charged chloride ions that traveled inside the neurons. This should cause the membranes to become hyperpolarized, which means more electrical activity.
Of course, before you toke up expecting to reap the potential night vision benefits, it might be best to wait until this research can be duplicated in animals closer related to humans than tadpoles. Certainly, as the medicinal properties of cannabis continue to be researched, those studies will come.