By Grace Paget, science writer.
It’s long been said that carrots help you to see in the dark, but it has become synonymous with encouraging children to eat their vegetables in the hope that they will gain the power that is night vision! Like all ‘old wives’ tales’ and myths, there’s often some truth in the phrase, so I thought perhaps I should do some myth-busting and explore how light helps us to see and whether eating the humble orange-coloured food can help us out in the absence of light.
Light is critical for our 
visual senses and even very simple organisms are sensitive to it, but humans have a far more complex relationship with light and we rely on it for seeing the world in great colour with clear and focused vision. In order for us to see, we have over a hundred million photoreceptor cells in the retina of the eye, which are sensitive to light and they help us to see in black and white (rods) and in colour (cones).
These photoreceptors located in the retina of the eye act as detectors that respond to the presence of light by chemically changing. When light hits the rods in the eye for example, there are two main pigments concerned with ensuring that the light absorbed through the lens and onto the photoreceptors is sent along the optic nerve to the brain for us to see what is in front of us. These two pigments are retinal, a form of vitamin A, and opsin, and together they are commonly referred to as rhodopsin.
Rhodopsin is what chemically changes when in contact with light and sends an electrical impulse to the brain. So if you think of it in terms of a digital camera; the lens is what enables the camera to take the photo and the better the quality of the lens (zoom and definition etc.) the higher the quality of the photo. Once the photo has been taken then you are able to view it on the screen (unless your camera looks like it should belong to a museum!), so a message has to be sent to link the optical (lens), chemical (if you have a film) and mechanical elements (the camera itself) together. In the dark, you have to use a flash so that the image can be taken so you could think of rhodopsin as the chemical element that must have light for it to do its job.
In the same way that better lenses take sharper images, the healthier our eyes are, the better we can see, including in the dark. Retinol is made in the eye to use the light around us, but the more vitamin A we have in our bodies that can be used to aid this function, the better.
It’s not really true that you will develop some sort of visual power by eating carrots, but they can help to improve your night vision by aiding the process which enables the eye to use light. Carrots are rich in beta-carotene, which is used to make vitamin A in the liver, a vital component for this message to be transmitted in low light. That’s not to say that the effects will be immediate, neither will a small amount be enough to improve your vision, but eating foods that are rich in beta-carotene is likely to maintain a good level of eye health.
Light plays a vital role in our daily lives and is an imperative cross-cutting discipline of science in the 21st century. The International Year of Light is focusing on the topic of light science and its applications. They are aiming to raise global awareness about how light-based technologies promote sustainable development and provide solutions to global challenges in energy, education, agriculture and health.
Get involved with life science events and activities all over the UK and beyond this Biology Week.