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Pigments in the Human Body - Functions and Health Effects

Updated on December 26, 2015
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Linda Crampton is a teacher with an honours degree in biology. She enjoys writing about human biology and the science of health and disease.

Brown eyes contain a lot of eumelanin.
Brown eyes contain a lot of eumelanin. | Source

The Functions of Pigments in the Body

A pigment is a chemical that has a specific color. Biological pigments color our bodies and body products, but this isn't their primary function. The pigments often play vital roles in the daily operation of the body. For example, melanin is a yellow to black pigment in our skin that helps to protect the skin from sun damage. Rhodopsin is a purple pigment in our eyes that enables us to see in dim light. Hemoglobin is a red pigment that carries oxygen from our lungs to our cells.

Some pigments in our bodies are waste products and appear to have no function. Others are very important to our wellbeing and even to our survival. In some cases, health problems can develop if too much pigment collects in the body or if too little is made.

A Melanocyte in the Skin

A melanocyte is a star-shaped cell that makes melanin.
A melanocyte is a star-shaped cell that makes melanin. | Source

Melanin in the Skin

Melanin is the main pigment in skin, where it’s made by cells called melanocytes. There are two forms of skin melanin – eumelanin, which appears brown or brown-black, and pheomelanin, whose color ranges from yellow to red. These molecules are present in various proportions in the skin of different people to produce the range of human skin colors. Blood vessels in the skin also contribute to skin color due to the presence of hemoglobin, a red pigment in blood.

Melanin is deposited near the surface of the skin. It absorbs dangerous ultraviolet rays from the sun, preventing the UV light from traveling deeper into the skin. Ultraviolet light can cause DNA damage in cells and skin cancer, so melanin is an extremely important molecule.

Sunscreen or protective clothing is necessary for everyone, even for people with lots of melanin in their skin.
Sunscreen or protective clothing is necessary for everyone, even for people with lots of melanin in their skin. | Source

Melanin Concentration

When light-colored skin is exposed to intense sunlight, it responds by making more melanin than usual. The extra melanin provides additional (but not complete) protection from UV damage and gives the skin a tanned appearance. Although a tan is often considered to be desirable, it's an indication that the skin has been under stress from sunlight exposure.

Since dark-colored skin already contains a lot of melanin before being exposed to sunlight, it provides more protection from sun damage than light-colored skin. However, this protection still isn't complete. Dermatologists say that people of all skin colors should wear sunscreen.

Like skin, hair contains melanin.
Like skin, hair contains melanin. | Source

Melanin in the Hair and the Iris of the Eye

Melanin is found in other areas of the body besides the skin. Both eumelanin and pheomelanin contribute to the color of hair. Eumelanin exists in two varieties - brown eumelanin and black eumelanin. Pheomelanin colors the hair yellow or orange. The proportions of these pigments determine actual hair color.

Melanin is also present in the inner ear, where its function is unknown. A dark form of melanin called neuromelanin is found in parts of the brain. In addition, melanin contributes to the color of the iris in the eye.

The thickest layer of the iris is called the stroma. The stroma contains fibers, melanocytes and other cells in a loose arrangement. Iris color is determined by a combination of factors, including the density of the stroma cells, the amount of eumelanin in the melanocytes and the ability of stroma cells to scatter blue light.

Carrots are rich in a pigment called beta-carotene. This is converted to vitamin A in our bodies. Vitamin A is essential for producing a pigment called rhodopsin, which enables us to see in dim light. It's also necessary for color vision.
Carrots are rich in a pigment called beta-carotene. This is converted to vitamin A in our bodies. Vitamin A is essential for producing a pigment called rhodopsin, which enables us to see in dim light. It's also necessary for color vision. | Source

Rhodopsin in the Rods of the Retina

Several pigments are present in the eye and are essential to its function. Rhodopsin is located in the rod cells of the retina. The retina is the light-sensitive layer at the back of the eyeball. Rhodopsin is also known as visual purple due to its color. It functions in dim light and enables us to see shades of grey. In bright light, rhodospin is bleached and breaks up into retinal and a protein called opsin. In darkness the process is reversed and rhodopsin is regenerated.

Since retinal is made from vitamin A, this vitamin is an essential nutrient for night vision. Beta-carotene is a yellow or orange plant pigment which our bodies can convert into vitamin A. This pigment is especially abundant in carrots, so the old “myth” that carrots are good for night vision is actually true! Pumpkin purée and orange sweet potatoes (yams) are also great sources of beta-carotene.

It’s not safe to eat large amounts of pre-formed vitamin A, which is toxic at high levels, but eating a large amount of beta-carotene doesn’t seem to be dangerous. However, research does suggest that while smokers can eat foods containing beta-carotene, they shouldn’t ingest beta-carotene supplements, which may increase the risk of lung cancer. The same is true for people who have had a long-term exposure to asbestos fibers.

Eating large amounts of beta-carotene in food or supplements can result in some of the pigment being deposited in the skin, giving it a yellow color. This condition is called carotenemia and is harmless.

Pumpkins are another great source of beta-carotene.
Pumpkins are another great source of beta-carotene. | Source

Cone Pigments in the Retina of the Eye

The cone cells in the retina respond to bright light and enable us to see color and detail. Humans have three types of cone cells, which are known as the S, M and L cones. Each type of cone responds best to a specific range of light wavelengths, although there is some overlap in cone sensitivity.

  • S cones are most sensitive to the shorter wavelengths of light, which produce a blue color, and are sometimes called blue cones. This alternate name is bit confusing, because S cones respond to blue light but are not blue in color.
  • M cones, or green cones, are more sensitive to medium wavelengths, which produce green light.
  • The L cones, or red cones, respond best to long wavelengths, which produce red light.

The cone pigment molecules are called iodopsins and are chemically similar to rhodopsin. Vitamin A is required for the manufacture of the iodopsins, so this vitamin is important for color vision as well as for night vision. Each of the three types of cones contains its own version of iodopsin.

Parts of the Eye

Structure of the human eye
Structure of the human eye | Source

Zeaxanthin and Lutein in the Eye

The central part of the retina provides very detailed vision and is known as the macula. When we look directly at something, the reflected light rays from the object strike the macula. The central portion of the macula has the best vision in the retina and is called the fovea centralis (or sometimes just the fovea). The fovea contains cones but no rods. This is why at nighttime when there is little illumination it's useful to look at objects from the side of our visual field rather than looking directly at the objects. This allows reflected light rays from the objects to fall on the outer portion of the retina, which has rods.

Zeaxanthin and lutein are yellow pigments in the macula. These two pigments belong to the carotenoid family, just as beta-carotene does, and give the macula a yellow appearance. They are thought to help maintain the health of the macula by protecting it from light damage and possibly by reducing oxidative stress. It's known that when people ingest zeaxanthin and lutein the levels of these pigments in the macula increases. Eggs are good sources of zeaxanthin and lutein, and so are corn and green leafy vegetables.

Egg yolk is a great source of lutein, which may boost eye health.
Egg yolk is a great source of lutein, which may boost eye health. | Source

Age-Related Macular Degeneration (AMD or ARMD)

Age-related macular degeneration is the leading cause of vision loss in older people. As theIr macular degenerates, it becomes harder for a person to see a clear image. In people with AMD, the macula has a lower level of zeaxanthin and lutein than in people without AMD. Scientists suspect - but don't know for certain - that ingesting more zeaxanthin and lutein will decrease the chance of AMD development and may help to prevent the disorder from getting worse once it has started.

Hemoglobin

Hemoglobin is a red protein and pigment inside red blood cells that transports oxygen around the body. The hemoglobin is responsible for the blood’s color. One hemoglobin molecule joins to four oxygen molecules.

A normal red blood cell contains 250 million to 300 million hemoglobin molecules. Since there are 4 million to 6 million red blood cells per microliter of blood in a healthy person (one microliter = one millionth of a liter), a lot of oxygen travels through the blood. This oxygen is an essential nutrient for the estimated 50 to 100 trillion cells in the human body. These cells need oxygen to produce energy from digested food.

Red blood cells get their color from a pigment called hemoglobin. (The white cell at the bottom of this illustration is a type of white blood cell.)
Red blood cells get their color from a pigment called hemoglobin. (The white cell at the bottom of this illustration is a type of white blood cell.) | Source

Bile Pigments

Red blood cells live for about 120 days and are then broken down by the liver and spleen. Their hemoglobin is changed into a green pigment called biliverdin. Biliverdin is then changed into yet another pigment known as bilirubin, which is yellow. Bilirubin enters a liquid called bile, which is made in the liver.

The liver sends bile to the gall bladder. The gall bladder stores the bile and releases it into the small intestine (or small bowel) when fat is present in the intestine. Bile contains salts whose function is to emulsify ingested fats. This emulsification prepares the fats for digestion by enzymes.

Bile and food that is not digested pass from the small intestine into the large intestine. Here bacteria and chemical reactions change the bilirubin from bile into a brown pigment called stercobilin. Stercobilin leaves the body in the feces and is responsible for giving feces its color.

Some bilirubin is converted into urobilin, a yellow pigment that is absorbed through the intestinal lining into the bloodstream. The kidneys excrete the urobilin in urine, giving urine its typical yellow color.

Bile is made in the liver and stored in the gall bladder. The hepatic ducts transport bile from the liver. The liver is a large organ which covers the gall bladder.
Bile is made in the liver and stored in the gall bladder. The hepatic ducts transport bile from the liver. The liver is a large organ which covers the gall bladder. | Source

Pigment Disorders

There are many disorders that are caused by an insufficient or excessive amount of a pigment. Three of these disorders are vitiligo, jaundice and iron-deficiency anemia. In vitiligo, melanin is lost from the skin. In jaundice, bilirubin collects in the skin. In iron-deficiency anemia, the blood lacks hemoglobin or the red blood cells that contain the hemoglobin.

Melanin Loss and Vitiligo

Vitiligo is a condition in which melanocytes in the skin are destroyed, resulting in white patches that contain no melanin. The cause of vitiligo is unknown, but it may develop due to the inheritance of specific genes that make a person susceptible to melanin loss. Another theory is that vitiligo is an autoimmune disease. In an autoimmune disease, the immune system mistakenly attacks the body's own cells - in this case, the melanocytes.

An example of vitiligo in the hands
An example of vitiligo in the hands | Source

Bilirubin and Jaundice

Hyperbilirubinemia is a condition in which bilirubin becomes too concentrated in the body. As a result, bilirubin collects in the skin and the sclera (the white part of the eye), producing a yellow color known as jaundice.

Hyperbilirubinemia may develop if too many red blood cells are destroyed, which results in too much hemoglobin breakdown and excess production of bilirubin. It may also develop due to liver damage that prevents release of bilirubin into the small intestine or due to an obstruction in the passageways that transport bile.

Carotenemia and jaundice both involve yellowing of the skin. In carotenemia the sclera of the eye remains white while in jaundice it develops a yellow color.

A Doctor Discusses Jaundice

Hemoglobin and Iron-Deficiency Anemia

Red blood cell and hemoglobin destruction, an insufficient amount of hemoglobin in the red blood cells or the production of abnormal hemoglobin can cause a number of disorders, including several types of anemia. The anemia may be mild or severe.

The most common type of anemia is called iron-deficiency anemia. Hemoglobin contains iron and can't be made without this element. If the body lacks hemoglobin, an insufficient number of red blood cells will be produced and an inadequate amount of oxygen will be delivered to the body’s tissues. Iron-deficiency anemia can arise due to a diet that is low in iron, inadequate absorption of iron or blood loss.

The main symptom of iron-deficiency anemia is fatigue, but other symptoms may be present as well. These include the craving to eat non-food substances, such as ice. This condition is known as pica.

Red Blood Cells and Anemia

The Importance of Pigments in the Body

Melanin, zeaxanthin, lutein, hemoglobin and the other pigments in our body are important molecules. Investigating their functions, mechanisms of action and interactions with other components of the body is a very worthwhile activity. Discoveries made by scientists may lead to better treatments for health problems involving pigments. They may also give us a better understanding of how the body works.

© 2011 Linda Crampton

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    • thougtforce profile image

      Christina Lornemark 5 years ago from Sweden

      A very informative and interesting article about pigments in the human body. We do need to be more observing about our skin in the sometimes fanatic chase for a beautiful tan. As soon as the sun begins to shine in spring the young girls starts to work on a quick tan! They have so many years ahead of them and run the risk of so many sunburns.

      I guess it is no use to ingest more green leafy vegetables and such once the sight already has decreased?

      Up/useful! Tina

    • Simone Smith profile image

      Simone Haruko Smith 5 years ago from San Francisco

      This is so interesting, AliciaC! I had not known that it was the mixed proportions of different types of melanin that contributed to varying skin color. Voted up!

    • AliciaC profile image
      Author

      Linda Crampton 5 years ago from British Columbia, Canada

      Hi, Tina. It is a shame that so many young people try to get a tan, injuring their skin at the same time. Green leafy vegetables are so good for our health that I think we should always eat a lot of them, even if they can't repair damage that has already been done! Thank you for your comment and rating.

      Hi, Simone. Thank you for your comments. I appreciate them very much! Thanks for the vote too.

    • Chatkath profile image

      Kathy 5 years ago from California

      Very interesting stuff Alicia! Easy to understand and well written, thanks for sharing!!!!

    • tonymac04 profile image

      Tony McGregor 5 years ago from South Africa

      Great information and very useful. I think some of my fellow melanin-challenged (i.e. so-called "white") writers here on HubPages could learn from reading this.

      Love and peace

      Tony

    • AliciaC profile image
      Author

      Linda Crampton 5 years ago from British Columbia, Canada

      Thank you very much for your comment, Chatkath.

      Thanks for the visit and comment, Tony.

    • kashmir56 profile image

      Thomas Silvia 5 years ago from Massachusetts

      Hi AliciaC, thank you for this very interesting hub, not only was it a fascinating read i learned a few things has well .

      Awesome hub !!!

    • AliciaC profile image
      Author

      Linda Crampton 5 years ago from British Columbia, Canada

      Thank you very much for your kind comment, kashmir56. This was an interesting hub to create!

    • prasetio30 profile image

      prasetio30 5 years ago from malang-indonesia

      We need this pigment. Everybody has different pigment. Thanks for writing this. You have valuable information here. Rated up! Take care..

      prasetio:)

    • AliciaC profile image
      Author

      Linda Crampton 5 years ago from British Columbia, Canada

      Hi, prasetio. Thanks for the visit and thanks for the rating too! Yes, pigments have very important functions in humans. It's interesting to learn about them.

    • souleru profile image

      souleru 5 years ago

      Wish I learned high school bio from you ;)

    • AliciaC profile image
      Author

      Linda Crampton 5 years ago from British Columbia, Canada

      Thank you very much, souleru!

    • sarmin898 profile image

      Sarmin Sultana 4 years ago from Bangladesh

      Great article.very helpful

    • AliciaC profile image
      Author

      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you for the visit and the comment, sarmin898.

    • Maurice 4 years ago

      Worth reading. Thanks for the research efforts!

    • AliciaC profile image
      Author

      Linda Crampton 4 years ago from British Columbia, Canada

      Thanks for the comment, Maurice!

    • Dr.Ibrahim 4 years ago

      Nice information about some pigments and food related to their metabolism. It is not true to say foods containing caretonoids are of no use once macular degeneration is developing. In fact the progress of the degeneration will certainlty be retarded though not stoped completely. More over there are a lot of benefits in eating vegetables like fibre, minerals and vitamins besides their nutrient values.

      Dr.Ibrahim

    • AliciaC profile image
      Author

      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you for the comment and the information, Dr. Ibrahim (although in the article I didn't refer to the intake of carotenoids once macular degeneration has already begun). The scientific evidence for the benefits of lutein and zeaxanthin is growing. They seem to be very useful nutrients!

    • B K Karan profile image

      B K Karan 3 years ago

      its great!!!! I had not known that it was the mixed proportions of different types of melanin that contributed to varying skin color. its realy great

    • AliciaC profile image
      Author

      Linda Crampton 3 years ago from British Columbia, Canada

      Thank you very much for the comment, B K Karan!

    • Ishrael 2 years ago

      O thank God you provide the right information I need :)

    • AliciaC profile image
      Author

      Linda Crampton 2 years ago from British Columbia, Canada

      I'm glad the hub was helpful for you, Ishrael.

    • Qurat ul Ain Majeed Khan 8 months ago

      Thank you so much! This hub helped me alot..

      Thanks once again..!

      :)

    • AliciaC profile image
      Author

      Linda Crampton 8 months ago from British Columbia, Canada

      Thank you very much, Qurat ul Ain Majeed Khan. I'm glad the article helped you.

    • Jean C 5 months ago

      I do not sat in the sun never did but to-day had a lower top at the back and in the middle of my back got three big marks never had before come up just like that I am trying to find why.

    • AliciaC profile image
      Author

      Linda Crampton 5 months ago from British Columbia, Canada

      Hi, Jean. I suggest that you watch the marks to see if they fade or disappear. I can't say what they are because I'm not a doctor. If the marks don't disappear or if you have any other concerns about them, you might want to visit a physician.

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