Still waiting for your carrot-induced night vision to kick in? You might have a long wait.
The myth that carrots help you see in the dark began during World War II to try and hide the rapid improvement of British radar. We needed an explanation for why our pilots could suddenly take down enemy planes in the dead of night, so propaganda posters were produced spreading the line that carrots could help you to see during the blackouts.
Unfortunately carrots can’t improve a healthy person’s night vision, but you can see why the enemy might have been fooled. Carrots are rich in the orange-red coloured pigment beta-carotene, which our bodies convert into vitamin A to use in vision.
Plants use chlorophyll to harvest light energy for photosynthesis, the process by which they convert carbon dioxide and water into sugars (and oxygen). Chlorophyll isn’t brilliant at soaking up the blue wavelengths of light, so beta-carotene steps in alongside it to mop up the blue and indigo rays. When we eat it, beta-carotene is broken down into retinal, one of the vitamin A compounds. It lets us see blue light at pretty similar wavelengths to those it absorbs in plants.
Photosynthesis is performed by reaction centres in plant cells called photosystems. As well as light harvesting, beta-carotene can be added to these complexes for its antioxidant properties. If too much light reaches photosystems, they can produce highly reactive singlet oxygen molecules. Singlet oxygen can cause a lot of damage to cells, but beta-carotene is able to quench its effects before DNA, proteins and lipids are adversely affected. Whilst we don’t photosynthesise, our cells can be the victims of chemically reactive damaging compounds produced by our metabolism. Luckily beta-carotene from our diet retains its antioxidant effects, helping to prevent cell damage and cancer. That’s a better reason than “night vision” to eat your veg!
Plants use beta-carotene to produce beautifully colourful flowers to entice pollinators and fruits for other hungry animals to distribute their seeds. To that end, apricots, sweet peppers and tomatoes are all very high in beta-carotene.
It’s not altogether clear why root vegetables like carrots and sweet potatoes are so rich in beta-carotene, since none of the above benefits seem to apply.
Use in GM
Many people living in the developing world do not have access to foods containing enough beta-carotene. They become deficient in vitamin A, which can lead to blindness and death in extreme cases.
Now, genetic modification (GM) of food is a complicated topic that I don’t want to get into in this post, but there is a fairly famous crop specifically designed to target vitamin A deficiency. Golden Rice has been engineered to produce beta-carotene in the rice grains by adding one gene from maize (corn) and another from Erwinia, a type of bacterium. The proteins encoded by these two genes work together to produce beta-carotene.
Maybe it can’t help you see in the dark, but beta-carotene is vital for healthy vision and cancer-preventing antioxidant effects. Keep munching those carrots.