Do Too Many Mandarins Turn Your Palms Yellow, and Is It a Sign of Illness?
― The Color Isn't on Your Hands. It Seeps Out From Inside.
One winter, after eating mandarin after mandarin at the kotatsu, you suddenly notice your palms are yellow. You might assume the juice from peeling stained them, but that's not it. The yellow is the mandarins' pigment, carried through your blood around the whole body and collected at the surface of your skin. And in most cases, there is nothing to worry about. The key to telling the difference is the whites of your eyes.
It's winter vacation. A box of mandarins has arrived, and your family eats five or six a day.
One day you hold your hands next to a friend's, and only yours have yellowish palms. Look closer, and even the soles of your feet are a little yellow.
You don't remember peeling any mandarins with your feet. So where did this color come from? And is it a dangerous warning from your body?
Let's check two things people often say
The color did not come from outside. The pigment you ate was carried by your blood to your skin. That is why even the soles of your feet, which never touch the peel, turn yellow.
The yellow from liver disease (jaundice) reaches the whites of the eyes. With mandarins, the whites stay white. If you cut back on how much you eat, the color is said to fade on its own within weeks to months.
This condition has a name: "carotenoderma" (kanpishō in Japanese). We'll first look at what the color is, then at why it shows up on the palms.
The mandarin's color is one that dissolves in fat
The orange of a mandarin comes from a pigment called β-cryptoxanthin. It belongs to the same family as the color in carrots and pumpkins (β-carotene), and the whole family is called carotenoids. The color that shows up when autumn leaves turn yellow is a relative too.
This pigment barely dissolves in water, but it dissolves well in fat. When you eat it, your gut absorbs it together with the fat in your food. Then, in the blood, it rides on tiny particles that carry fat and is delivered all over the body.
The satsuma mandarin is a fruit very rich in this pigment. The Japanese food composition tables give about 1.7 milligrams per 100 grams, which is known to be far higher than other fruits. If you eat several every day, the level of pigment in your blood keeps rising. In Figure 1 below, try changing the number you eat per day.
Why do only the palms and soles stand out?
The pigment reaches the skin all over the body. Even so, the palms and soles show it first, for two reasons.
The first is that the outermost layer of skin, the "stratum corneum," is thick there. It is a film of spent cells stacked in many layers. The fat-soluble pigment soaks into this layer along with sweat and skin oil and collects there. The thicker the layer, the more pigment it holds, and the deeper the color looks (Figure 2).
The second is that the palms and soles have little suntan pigment (melanin). Their base color is light, so the yellow is not hidden and shows as it is. The pigment is also said to sometimes turn oily areas yellow, such as the sides of the nose and the forehead.
Jaundice, caused by liver or bile-duct disease, comes from a different yellow substance called bilirubin building up, and the whites of the eyes turn yellow first. If you notice yellow eye whites, dark brown urine, or lasting tiredness, don't just blame the mandarins. See a doctor.
Babies who eat a lot of carrots or pumpkin in their baby food can also get a yellow nose tip or yellow palms. That comes from β-carotene, and the mechanism is the same.
Summary
Palms turn yellow from mandarins not because juice soaked in. A fat-soluble pigment is carried by the blood and collects in the thick outer layer of the palms and soles, where it shows through. If the whites of your eyes stay white, it is usually nothing to worry about, and the color fades on its own when you eat less.
The yellow is not on your hands, but "inside your body."
To tell the difference, look at your eye whites, not your palms.
The same family of pigments also appears in the color of dried persimmons and in autumn yellow leaves. For more on food and the body, try the story of vitamin C and scurvy too.
- Next to a window in bright daylight, put your palm on a sheet of white paper. Compare its color with the back of your hand.
- Put your family's palms side by side, and see whether people who eat lots of mandarins look different from those who don't.
- Check the color of your eye whites in a mirror. If your palms are yellow but the whites are white, that fits the typical pattern of carotenoderma.
Fluorescent and bulb lighting change how colors look, so if you can, compare them in natural daylight.
For those who want to know more ― terms, formulas, and links to textbooksShows clearly which level each part is, from middle-school science to university courses
- Middle schoolCovered in middle-school science
- High schoolCovered in high-school basic biology and chemistry
- High school+Advanced high-school material, or textbook sidebar content
- UniversityNot taught in high school; university specialist courses (nutrition, dermatology)
- ResearchNot yet settled textbook knowledge; what researchers are investigating now
Middle schoolTerms: this phenomenon has a name
- Carotenoderma (kanpishō): A state where the skin looks yellow after taking in a lot of carotenoids. It is regarded as pigment buildup in the body rather than a disease.
- Carotenoids: A family of yellow, orange, and red pigments made by plants and others. It includes β-carotene and β-cryptoxanthin.
- Stratum corneum: The outermost layer of skin, made of stacked spent cells. It is especially thick on the palms and soles.
- Jaundice (ōdan): A state where bilirubin rises in the blood and turns the skin and the whites of the eyes yellow. It occurs with liver or bile-duct disease, among other causes.
Middle schoolHigh schoolChecking with a formula: how many milligrams of pigment do you take in per day?
The amount that builds up is set by the balance between what comes in each day and what leaves each day. First, calculate the amount coming in from the number of mandarins.
| In symbols | M ＝ c × w × N 、 S ＝ M × T |
| In words | Daily pigment intake ＝ pigment per gram × weight of one fruit × number eaten. Amount stored ＝ daily intake × number of days it stays |
| Where it comes from | A balance of inflow and outflow. If the same amount comes in every day and is replaced over a roughly fixed number of days, the stored amount settles at "inflow rate × time it stays" |
| Symbol | Meaning and unit |
| c | Pigment per gram of flesh (milligrams per gram) |
| w | Weight of the edible part of one mandarin (grams) |
| N | Number eaten per day |
| M | Pigment taken in per day (milligrams) |
| T | Rough number of days the pigment stays in the stratum corneum (days) |
| S | Rough amount stored in the stratum corneum (milligrams) |
| β-cryptoxanthin per 100 grams of satsuma mandarin | About 1.7 milligrams (listed as 1600–1700 micrograms in the food composition tables) |
| Edible part of one medium mandarin | About 80 grams (a rough figure that varies with size) |
| Number eaten per day (a common winter example) | 4 |
| Days for the skin surface to be replaced | Said to be about 28 days (about 4 weeks) |
| Per gram | 1.7 ÷ 100 ＝ 0.017 milligrams |
| Per mandarin | 0.017 × 80 ≒ 1.36 milligrams |
| Eating 4 a day (M) | 1.36 × 4 ≒ 5.44 milligrams |
| Intake over 4 weeks (a guide for S) | 5.44 × 28 ≒ 152 milligrams |
| With just 1 a day, over 4 weeks | 1.36 × 28 ≒ 38 milligrams |
| Difference between 4 and 1 | 152 ÷ 38 ＝ 4 times |
At 4 a day, about 150 milligrams of pigment come in over a month. Picture an amount like one scoop of an ear pick, spread thinly across all your skin. In this formula, the amount stored is directly proportional to the number you eat. And it does not vanish the moment you stop. The color is thought to remain for the weeks it takes the stratum corneum to turn over, and until the pigment stored in body fat has drained away. That is why people say it takes "weeks to months to return."
High schoolHigh school+Why does it look yellow? ― Light absorption and color
High schoolThe color of an object is the color of the light that reaches your eye without being absorbed. Carotenoids absorb blue to blue-green light well. The remaining light reaches the eye, so they look yellow to orange, the opposite side of the color wheel.
High school+Carotenoid molecules have "conjugated double bonds," a long run of alternating carbon double and single bonds. The longer this run, the more the absorbed light shifts toward red. β-carotene and β-cryptoxanthin have about 11 such bonds, which is just the right length to absorb blue light. Also, because most of the molecule is made of only carbon and hydrogen, it does not mix with water and dissolves easily in fat (fat-solubility).
UniversityHow it travels in the body ― lipoproteins and deposition in the skin
The fat-soluble pigment is taken up into "micelles" together with fat in the small intestine and absorbed, then enters the blood from the lymph on chylomicrons. After passing through the liver, it is carried around the body mainly on low-density lipoprotein (LDL) and similar particles. In the skin, it is thought to be secreted from sebaceous and sweat glands and deposited in the stratum corneum. Like β-carotene, β-cryptoxanthin is a provitamin A, and part of it is converted to vitamin A in the body. But this conversion is adjusted to the body's needs, so eating too many mandarins is said to rarely cause vitamin A excess.
📖 Derivations and further reading: Carotenoderma (Wikipedia, Japanese) ／ Carotenoids (Wikipedia, Japanese)
ResearchWhat is still not clear
- Individual differences in who turns yellow. Some people turn yellow and others don't, even on the same intake. Absorption efficiency, amount of body fat, and genetic differences in the enzymes that break down the pigment are thought to play a part, but which matters how much has not yet been sorted out.
- The pigment and health. A long-term follow-up of residents in Mikkabi, Shizuoka Prefecture, reported that people with more β-cryptoxanthin in their blood tended to have a lower risk of several lifestyle-related diseases. But the lifestyles of people who eat mandarins are mixed in, so whether the pigment itself is responsible is still being studied.
- Using skin color to gauge vegetable intake. Researchers are studying methods that measure skin carotenoids with light as a rough guide to how many vegetables and fruits someone eats. How accurately this reflects diet is still being tested.
In other words, this article too is "an explanation within what is known today." In particular, please keep in mind that how many days it takes for the color to go away differs greatly from person to person.
Links to textbooks (by level)
| Level | Subject / unit | Where in this article |
|---|---|---|
| Middle school | Grade 8 science, "Digestion and absorption" | The pigment is absorbed in the gut and carried by the blood |
| High school | Basic biology, "The internal environment"; chemistry, "Light and color" | Telling apart by the eye whites; why it looks yellow |
| High school+ | Chemistry, "Organic compounds" (conjugated double bonds) | Why the pigment absorbs blue light; fat-solubility |
| University | Nutrition, dermatology | Transport by lipoproteins and deposition in the stratum corneum |
| Research | Nutritional epidemiology | Individual differences, links to health, judging diet by skin color |
| ― | Link to daily life | When you notice yellow palms, check the eye whites and judge calmly |
- Food Composition Database (食品成分データベース), Ministry of Education, Culture, Sports, Science and Technology
- β-Cryptoxanthin (β-クリプトキサンチン), Wikipedia, Japanese
- Carotenoderma (柑皮症), Wikipedia, Japanese
- Maharshak N, Shapiro J, Trau H. Carotenoderma — a review of the current literature. International Journal of Dermatology, 2003.
- National Agriculture and Food Research Organization, Institute of Fruit Tree and Tea Science (農研機構 果樹茶業研究部門), report on the "Mikkabi study" (nutritional epidemiology survey of satsuma mandarins and β-cryptoxanthin)
*This article is a general science explainer. The figures given are rough guides and estimates meant to help you understand the mechanism. If you are worried about a change in body color, especially if the whites of your eyes are yellow or you feel unwell, do not decide on your own. Please consult a doctor.