Will eating carrots often make you black? Answer: You don’t eat enough to turn black!

Produced by: Science Popularization China

Author: Denovo Team

Producer: China Science Expo

Do you eat carrots often? There is a saying that eating too many carrots will make you black, is this true?

The answer is: It is possible! You just have to eat a lot.

The mystery of carrot color: from genetics to nutrition?

Carrots can be roughly divided into three categories based on how they were domesticated: Oriental carrots, Western carrots, and wild carrots. Oriental carrots were originally purple or yellow and originated in Asia and Central Asia. Western carrots, which are mainly orange, originated in Europe in the 17th century and quickly became the main type of carrot in the world.

Carrots of different colors

(Image source: Wikipedia)

Although we are more familiar with orange carrots in China, the earliest carrots cultivated by humans were actually purple and yellow .

Purple carrots get their color primarily from their high content of anthocyanins, powerful antioxidants that are also found in a variety of other purple, blue, and red fruits and vegetables.

Early studies showed that purple carrots tasted better than white carrots, but purple carrots fell out of favor because they tended to leach their pigment into other foods during cooking , affecting the appearance of the food.

I can't imagine what pork cutlets with purple carrots would look like

(Photo credit: Photo taken by the author)

So why do different types of carrots have different colors? This is mainly related to carotenoids .

Carotenoids are natural pigments that are responsible for giving fruits and vegetables their various colors, such as red, orange and yellow. Of course, there are many different types of carotenoids, including lutein, lycopene, alpha-carotene and beta-carotene. Of these, beta-carotene is responsible for giving carrots their bright orange color.

In September 2023, a research team from North Carolina State University and the University of Wisconsin-Madison published a study on carrots in the journal Nature Plants. The study used advanced genome sequencing technology to conduct a comprehensive analysis of 630 different carrots.

Genomic characteristics of carrot

(Image source: Reference [7])

Generally speaking, for an organism to perform certain functions, it needs to "turn on" the relevant genes. To give carrots their orange color, three specific genes are needed.

The researchers found that these three genes are located in three specific genetic regions, REC, Or and Y2, and must be recessive, which is essential for selecting the orange phenotype with high α-carotene and β-carotene.

Three genes control the accumulation of high α-carotene and β-carotene by regulating the interaction between the carotenoid biosynthetic pathway, the photosynthetic system, and chloroplast biogenesis.

The study also found that the accumulation of high α-carotene and β-carotene content was regulated through a light-responsive feedback mechanism and chloroplast biogenesis.

Will eating too many carrots change your skin color?

When we eat carrots, beta-carotene is digested in the intestines and broken down into two vitamin A molecules, which are involved in many important physiological functions such as vision, reproduction, immunity and growth.

Carrots are rich in beta-carotene

(Photo credit: Photo taken by the author)

Of course, our body will control the process of converting beta-carotene into vitamin A according to needs. When the body's vitamin A reaches a certain level, the conversion of beta-carotene will slow down or stop.

So where does the excess beta-carotene go?

Some of it is stored in the liver and fat tissue and excreted through defecation, while the other part is deposited on the surface of the skin, causing the orange skin "tanning" phenomenon.

Typically, this hyperpigmentation is most noticeable on the palms of the hands and soles of the feet , and may also appear in other skin folds. Medically, this is also known as carotenoidemia.

Of course, carrots are not the only foods that contain beta-carotene. Dark green leafy vegetables, some other yellow and orange vegetables and fruits also contain high amounts of beta-carotene. In addition, cilantro, basil, leeks, paprika, and sun-dried tomatoes also contain a lot of beta-carotene.

How many carrots do you need to eat to turn black?

Since eating more carrots can really make people darker, what counts as “too much”?

In fact, eating a lot of carrots for several days in a row is unlikely to cause skin color changes. Of course, there is no high-quality scientific research to clearly indicate how many carrots you need to eat every day to cause skin color changes. However, there is evidence that carotenoidemia occurs when the carotenoid level in the blood is higher than 250-500µg/dL.

A case report published in 2012 pointed out that a patient ate about six pounds of carrots a week for several months, which not only caused constipation but also caused changes in skin color. This amount is completely not what we eat on a daily basis.

The amount of carrots needed to change your skin color also depends on the variety, size, maturity, how the carrots are cooked (raw or cooked), and whether they are eaten with a fat source. An individual's weight and gastrointestinal health also affect the amount of beta-carotene absorbed.

So, if you just eat some carrots on a daily basis, you don’t have to worry about the problem of blackening.

Beta-carotene

(Photo source: veer photo gallery)

Conclusion

Carrots are one of the most common and familiar vegetables in our daily lives. However, this "regular guest" on the table can actually produce such a wonderful reaction with the human body. What other unknown surprises can the colorful biological world bring? Let's wait and see...

References:

[1]Alasalvar, Cesarettin, et al. "Comparison of volatiles, phenolics, sugars, antioxidant vitamins, and sensory quality of different colored carrot varieties." Journal of agricultural and food chemistry 49.3 (2001): 1410-1416.

[2]Maharshak, Nitsan, Johnatan Shapiro, and Henri Trau. "Carotenoderma–a review of the current literature." International journal of dermatology 42.3 (2003): 178-181.

[3]Nakagami, Futoshi, et al. "Carotenemia induced by iron deficiency." BMJ Case Reports 14.1 (2021).

[4]Sansone, Randy A., and Lori A. Sansone. "Carrot man: A case of excessive beta-carotene ingestion." International Journal of Eating Disorders 45.6 (2012): 816-818.

[5]Haskell, Marjorie J. "The challenge to reach nutritional adequacy for vitamin A: β-carotene bioavailability and conversion—evidence in humans." The American journal of clinical nutrition 96.5 (2012): 1193S-1203S.

[6]Alpha-Tocopherol Beta Carotene Cancer Prevention Study Group. "The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers." New England Journal of Medicine 330.15 (1994): 1029-1035.

[7]Coe, Kevin, et al. "Population genomics identifies genetic signatures of carrot domestication and improvement and uncovers the origin of high-carotenoid orange carrots." Nature Plants (2023): 1-16.

[8]Iorizzo, Massimo, et al. "A high-quality carrot genome assembly provides new insights into carotenoid accumulation and asterid genome evolution." Nature genetics 48.6 (2016): 657-666.

[9] Al Nasser Y, Jamal Z, Albugeaey M. Carotenemia. [Updated 2023 Jun 12].