Why Are Carrots Orange? Scientists Reveal the Answer

Carrots may be closely associated with the color orange, but it turns out that these brightly-hued veg get their color due to only three specific genes.

Research into the genetics of 630 types of carrot has found that these three genes are specific to the orange color of the vegetable, with all three needing to be "switched off" for orange to result, according to a new study in the journal Nature Plants.

"In the paper, we identified three genes responsible for the accumulation of alpha and beta carotene, which make carrots orange," Massimo Iorizzo, an associate professor of horticultural science with North Carolina State University's Plants for Human Health Institute and co-corresponding author of the paper, told Newsweek.

"Based on multiple analyses that helped us to understand their function, we hypothesized that two of these genes regulate the chromoplast development (chromoplast are the organelle in the plant cell where alpha and beta carotenoids accumulate), and one gene regulates the communication with the photosystem where beta carotene is used for this cell system to function. Future work will validate this hypothesis."

In their research, which was a collaborative project with scientists at USDA-ARS, UW-Madison, UC-Davis, Bayer, and other collaborators from Poland, the authors also found that areas of the carrot genome under strongest selection by humans were genes involved in flowering. This is because the flowering process of a carrot plant causes the taproot that we know as the edible part of the carrot to turn woody and inedible.

This finding backs up the chronology of the history of carrots, which are thought to have first been domesticated in western and central Asia in the 9th or 10th century. They were initially purple in color before coming to Europe later, being selectively bred to be a number of different colors. It is also thought that orange carrots, which first appeared in Western Europe in the 15th or 16th century, may have resulted from crossing white and yellow carrots.

"Based on historical documents we know that at the time the orange carrot was selected (around the 15th century) there was no scientific knowledge about its health benefits. But we know that in general orange carrots can be sweeter and tastier, so the selection of orange carrots may have occurred by chance and later became more popular because of his taste and maybe also for his attractive color," Iorizzo said.

"Our data suggests that the orange carrot was selected from a group of white and yellow carrots that have their origin in Northern Europe including the Netherlands. Now that we know the genes responsible for the orange color, we can look at a larger set of carrot samples from Europe and try to narrow the geographic region where the orange carrot was selected from."

Carrots' orange color comes from the presence of carotenoids, pigments that are precursors to the production of vitamin A in the human body.

"Carrot is one of the highest single sources of alpha and beta carotene which in our body represent the precursors of Vitamin A, that is an essential nutrient (our body does not produce Vitamin A, we need to take from our food)," Iorizzo said. "One of the functions of Vitamin A is indeed to improve eyesight. If you consider some of the most important sources of provitamin A (Beef liver, sweet potato, frozen spinach, pumpkin and carrot), carrot does not need to be cooked, has a good taste, is appreciated by consumers and kids like it—what an ideal source of this essential nutrient."

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