Do You Like Green Eggs And Ham?

Do You Like Green Eggs And Ham?

Yes, I like them, Sam-I-Am

White eggs, Brown eggs,  Pink ones too

But Tell me, how Do they turn Blue?

(With apologies to Dr. Seuss) 

Egg color in birds evolved for obvious reasons of camouflage and recognition, and for less obvious reasons such as thermal regulation, protection against UV light, and even antimicrobial defense. Chicken eggs are commonly white (no pigment), or brown (protoporphyrin). Rare breeds from China and Chile lay blue eggs, colored by the bile pigment biliverdin, a breakdown product of the hemoglobin in red blood cells.  Biliverdin is normally excreted by liver cells into the bile. So how does it end up in the egg shell? 

Organic anion transporters are proteins that move a large number of compounds- drugs, toxins, hormones and bile pigments, across cell membranes, as part of the liver’s detoxifying day job. Genetic sleuthing mapped the blue color trait to a region of a chicken chromosome. Here was a gene for a transporter protein, SLCO1B3, that could provide blue-green biliverdin to color the shell. But why was the gene inexplicably turned on only in the shell gland of the blue egg laying chicken?

Endogenous retroviruses (ERV) are ancient viruses that inserted randomly into the genomes of prehistoric birds. One such viral fragment inserted right next to the SLCO1B3 gene in blue egg laying chickens, where it behaved like an accidental transcription enhancer, or “on switch”. Because of its sequence, scientists speculate that it mediates estrogen specific regulation, accounting for the high levels of the biliverdin transport protein in the shell gland. Although this story nicely explains our Seussian curiosity about green eggs and ham, it also shows how viruses shape diversity in the living world. For example, an insertion of the avian leukosis virus inside a gene for the enzyme tyrosinase results in white plumage in chickens. Viral insertions can also be incredibly harmful, triggering cancer when they accidentally turn on oncogenes.

REFS (open access papers): and

Fun Fact: Green Eggs and Ham, published in 1960, is one of the best selling and most beloved children’s books of all time. It has just 50 words, and was written by Dr. Seuss in response to a bet by his publisher. 

Photo: Tammy Riojas, Elgin, TX;

H/T to Lorna Salgado for posting the news story that led to this   #ScienceSunday  post. 

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99 Responses to Do You Like Green Eggs And Ham?

  1. One of the first non chicken eggs I ever came across was blue with brown speckles, it was a Eurasian Blackbird quite common in these parts.

  2. Rajini Rao says:

    Julie Dongray , that’s egg color is also found in ducks and many other wild birds. It’s thought that similar viral integrations could account for their egg colors. 

  3. I like green eggs… on the inside. What are usually called “millennial eggs” or similar names. They are to normal eggs something similar as what blue and green cheese are to normal cheese.

  4. Satyr Icon says:

    In Turkey I came across white chicken eggs. I wondered if they were a different breed of chooks, or whether they bleached the eggs somehow?

    Of course, not real bleach, but some kind of whitewashing perhaps?

  5. Rajini Rao says:

    I’ve not heard of the term “millenial eggs”..I’m guessing they are celebratory? 

  6. Rajini Rao says:

    Satyr Icon , white chicken eggs are common..they don’t have significant amounts of pigment, that’s all. Actually, bird eggs are thought to have started out as white and “immaculate”, which I believe is the term for not speckled. 

  7. Satyr Icon says:

    They’re mostly brown here in Australia. I hadn’t seen that many white eggs until I was over seas.

  8. Eye candy vs. good nutrition! Lol

  9. Rajini Rao says:

    Charles Dickens DVM , eye candy and nutrition are not mutually exclusive. In this case, it is “and” instead of “versus” 🙂

  10. Rajini Rao says:

    Satyr Icon , thanks for the link. It suggests that feather color is linked to egg color, in genetic terms. I doubt that it is as simple as that, but I will dig around and report back. Interesting observation that brown eggs are common where you are. Growing up in India, I mostly saw white ones. I suspect it was the same here in the US, although now one can find both brown and white. I could be wrong..someone will correct me if I am 🙂

  11. Rajini Rao says:

    Yikes, Víktor Bautista i Roca ! I’ll pass on them 🙂

    P.S. Víktor Bautista i Roca  edit your wiki link to remove the extra l at the end. 

  12. You are right Rajini! Good nutrition is great if it looks good! Great picture!

  13. Satyr Icon says:

    If eggs weren’t so high in cholesterol I’d probably eat more per day.

    Often it’s the easiest meal to cook. Nearly as easy as making a sandwich. And if heating is an issue one can even eat them raw.

  14. I saw Lorna’s post earlier this week, and I wondered about the related science. Wonderful post!

    As an aside, I make my husband and son eggs on Sunday morning as my son looks at some of his favorite books. Currently, Green Eggs and Ham is the coffee table book of choice… I wonder if my boys will appreciate the science behind it all.

  15. Rajini Rao says:

    Chryle Elieff , Lorna’s post “egged” me on to find the science behind the color 🙂 I love the Seuss collection of books..I had not realized that Green Eggs and Ham used only 50 words! 

  16. it’s not just the outside colours but the yolk colour as well. Nothing like a deep, almost orange yolk from a still warm egg to make your day.

  17. I have the chickens that lay those eggs. mostly green and blue.

  18. Rajini Rao says:

    I did a quick search and found that supplements in chicken feed could effect yolk color, Suzanne Catty . For example, with omega-3 rich microalgae “yolk colour shifted from yellow to a more intense red colour”.

  19. Satyr Icon says:

    And I guess you all know how to make brown (or white eggs) red. Or any other colour. Just boil them for a few minutes in food die.

    If you boil them together with dry red onion leaves they turn out red too.

  20. Rajini Rao says:

    Michael Fisher , do you know the name of your breed? The Chinese ones are Dongxiang or Lushi and the South American ones are called Araucana or Mapuche (after the tribe of native people who bred them).

  21. Rajini Rao says:

    Matthew Sherertz , thanks! 🙂

    Satyr Icon , indeed that is a fun Easter activity for many kids. 

  22. Chad Haney says:

    Egg-cellent post. Today is going to be quite rainy. Sunny side up would be nice. Omelette William McGarvey take care of some puns while I fetch my tea.

  23. Rajini Rao says:

    I can never have un oeuf of egg puns, Chad Haney . Enjoy punday! 

  24. Rajini Rao  have kept chickens, guinea fowl, ducks and geese for eggs. They all were true free-run (no cages) and lived on what they found and our kitchen compost. Yolk colours changed slightly through the year as different plants were in season.

  25. noor dixit says:

    Cool never saw pink and green eggs

  26. Srija says:

    Wow. That’s truly amazing.

  27. This makes me wonder about what appears to be a number of pigments somewhat randomly appearing on quail eggs – although given where quail nest, I wonder if this wasn’t selected by virtue of its camouflage benefit – the eggs are pretty irregular looking.

  28. Rajini Rao says:

    David Archer , it is believed that speckled eggs are for camouflage and recognition against brood parasitism. Apparently, nests set deep in the ground have immaculate white eggs so they can be easily seen by parents in dim light, while the speckled ones are hidden in ground cover. I found a lot of publications on speckled/maculate eggs on Pubmed alone! I’ll have to check it out 🙂

  29. Lol! Rajini Rao You had me at “Great Tits”!

  30. Rajini Rao says:

    Hehe, I got a chuckle out of that too! 

  31. So how do researchers explain this, huh?

    Pretty interesting speculation in that article – even if it hedges towards a vestigial phenomenon.

  32. Rajini Rao says:

    LOLOL! I’ll take that as a challenge to find a genetic explanation for that, David Archer . There has to be a Martha Stewart gene or something. 

  33. Gaythia Weis says:

    Is Satyr Icon ‘s question related to white shells or white yolks?  White yolks are possible:

    Here in the US, it is now common for some egg producers to deliberately feed their chickens carotenoids (like beta carotene as in carrots) to make them yellower and thus seem healthier overall.

    See this article from a farm journal:

    And here is the commercial product line:

    “BASF offers a variety of carotenoids (beta-carotene, canthaxanthin, astaxanthin, citranaxanthin and beta-apo-8 ester) for poultry products (egg yolks and broiler skins) and aquaculture products (salmon and shrimp).”

    “How do the Lucantin® and Lucarotin® carotenoids work?”

    “We also eat with our eyes. With our Lucantin® and Lucarotin® brands, we offer a highly effective and efficient option for pigmenting your breakfast eggs or salmon filet for dinner. When these carotenoids are mixed with feed, they are absorbed by the animals’ metabolism and give the final product an attractive color.. Animals cannot usually synthesize carotenoids themselves, so they need to receive them in their diet. “

    Ready  for breakfast now?

  34. Rajini Rao says:

    Excellent info, thanks Gaythia Weis !

  35. Good grief, pigments for salmon. I remember an acquaintance who found himself sharing a ferry ride with a guy from a Dept of Oceans and Fisheries research station; he asked him “So, what are you excited about? What’s the big thing you’re working on?” His answer: “Finding a red dye that was miscible in both water and oil” so they could make cheap pink salmon look like much more expensive coho/chinook, etc.

  36. Rajini Rao says:

    What a waste of research time, sheesh. Did you know that arsenic is fed to chicken to give their flesh a “healthy pink color” that customers like? 

  37. And this was our tax dollars at work.

    Brown-shelled eggs are no more nutritious than white-shelled eggs, but they’re more popular (in our markets, at least), because, well, sugar, flour, etc. – white is bad, right? 

  38. Rajini Rao says:

    At least with the brown shelled eggs, and the blue ones, it is a harmless preference. Adding arsenic based drugs for a “healthy” pink color is not! I read somewhere that the white eggs were preferred by farmers because the Leghorn breed were more prolific layers and ate less. That may be why they are cheaper too. 

  39. Adding arsenic belongs right next to adding melamine to milk products to boost the apparent protein content. As in, resulting in very long prison sentences. 

  40. I’ve been photographing the “Easter Egg Chicken’s” contribution to our Easter every year for many years now.  Our friend raises the kind of chickens who produce a great variety of colors, Araucana.

  41. Rajini Rao says:

    Beautiful blue eggs, BJ Bolender ! 

  42. If the eggs are prehistoric how do you insert something into them?

  43. Rajini Rao says:

    Hehe, the eggs are not prehistoric, Todd Haarstick .Unless you refer to Viktor’s so-called “millenial” eggs that he describes above 🙂 I said that viruses inserted into the genomes of prehistoric birds and have been passed down through generations. 

  44. It was a time in Romania, David Archer , when the eggs bought from a supermarket were exclusively white, and the eggs bought directly from peasants were brownish. The yellow part of the eggs from commercial distribution networks is more lighter than the others, this being a direct result of a different style in the chicken’s feeding, so the housewives are still convinced that “white is no good”.

    Rajini Rao What a post, so rich 🙂

  45. Mary T says:

    Egg-cellent post Rajini Rao ~ and beautiful photo.  Time for an omelete!

  46. Mart Bay says:

    #eggs .. use hashtags !

  47. Great post, I love eggs! 🙂

  48. Marta Rauch says:

    Rajini Rao love it! Thanks:)

  49. Rajini Rao says:

    Thanks for your original post, Lorna Salgado . I had fun looking this up. Marta Rauch , I’m going to have to look for blue eggs now 🙂

  50. Interesting info Rajini..thank U for sharing it with us..:)

  51. Marta Rauch says:

    Rajini Rao our auraucana chicken lays blue-ish eggs, and I was just wondering about this question this week. So glad to see your post!

  52. Cher Darling says:

    Nice paraphrase of The Doc

  53. Rajini Rao says:

    Cher Darling , what is “The Doc” and how is this post a paraphrase? 

  54. Cher Darling says:

    Dr. Seuss is the author of a whimsical children’s book called “Green Eggs and Ham”. The main character, Sam, tells of the many ways he likes to eat green eggs and ham. “On a train, in the rain, with a book…” The eggs (and ham), however, are always green.

  55. Rajini Rao says:

    Yes, that poem was a fun inspiration for this post (and my poor attempt at verse), thanks Cher Darling 🙂

  56. Cher Darling says:

    Not a “poor attempt” at all. It took me right back to a warm, sleepy child on my my lap listening to the cadence of the rhyme as I read the story. You’re welcome,  Rajini Rao.

  57. œufs de différentes couleurs!

  58. Hi rajini how or to day? I do hope u or ok u or a verry niceo looking lady ido hope we can be friends god bless hope to hear from u soon glen bye

  59. Rajini Rao says:

    Rashid Moore , Do You Like Green Eggs and Yam? 😀

  60. Rajini Rao says:

    Rashid Moore , love the Seussian genius! 

  61. Kathryn Kure says:

    Rajini Rao as a miniscule – scale chicken farmer, I’m not fussed with the colour of the egg – shell, but definitely with the colour of the yolk, simply because it tells me how well the chickens have eaten (not only of leafy greens but also bugs and worms and so on). In other words, the Romanian cooks that Daniel Mihai Popescu mentions were correct, the light yolks are not as good for you as the golden yellow or even bright orange ones:

    “Our preference for golden yellow egg yolks is rooted in history. Pale yolks were always a sign of sick hens, worm infestation, or poor feed. Only healthy, well-nourished hens store carotenoids (preliminary forms of vitamin A) in their yolks. Bright golden-yellow yolks show that the hens are well supplied with essential carotenoids such as lutein or canthaxanthin. These protective substances are widely found in nature; they not only give the yolk its yellow color, but also prevent the oxidation and destruction of fragile, vital substances such as vitamins in the egg.” ( 

    I can see why white eggs have become dominant in many countries, the Leghorn is an amazingly prolific layer, definitely the ‘gold standard’ when it comes to egg production:

    “Leghorns are good layers of white eggs, laying an average of 280 per year and sometimes reaching 300–320.[1] They have a good feed-to-egg conversion ratio, needing around 125 grams per day of feed. Leghorns rarely exhibit broodiness and are thus well suited for uninterrupted egg laying. The Leghorn is a light breed that matures quickly; it is not considered a viable meat producer. Leghorns are active and efficient foragers.” (

    Interestingly enough, they appear not to be a particularly suitable breed for South Africa, so here brown eggs are dominant.

    As a sometime decorator of pysanky eggs, I have had to adapt techniques to account for the brown egg – shell base (the white produces your more traditional forms):

  62. Mike Sweet says:

    Looks like you’ve got all your eggs in a basket lol

  63. Rajini Rao says:

    Don’t be a rotten egg, Mike Sweet 😀

  64. Mike Sweet says:

    Beautiful, smart, and funny 🙂

  65. Rajini Rao says:

    Aww, how Sweet 🙂

  66. Chad Haney says:

    Hamming it up again, Rajini Rao ?

  67. Rajini Rao says:

    I diseggree, Chad Haney . Just yolking around. 

  68. 楊朱 says:

    too good to be eaten. haha !

  69. just to watch more than to eat would really be great

  70. Nick James says:

    I really enjoy these blue eggs in UK (from Morrisons if you need!) Somehow they just taste better.

  71. Rajini Rao says:

    They do look good, Nick James 🙂

    According to the official website, “The first Cotswold Legbars were bred near Broadway in the late 1980’s, using descendants from blue egg laying stock brought to England from Patagonia in 1940 by Clarence Elliott, a well known botanist, and grandfather of Martin, an estate agent in Stow-on-the Wold.”

  72. Nick James says:

    Rajini Rao You do great research!  I just know that these things cost about twice as much as ordinary eggs and taste far better:-)

    My father-in-law lives just outside Stow-on-the-Wold. I’ll ask him if he knows the Elliotts. Small place, not a lot goes on:-)

  73. Rajini Rao says:

    I remember driving around the Cotswalds. Stow-on-the-Wold sounds familiar, but then they all sound the same, so quaint! The flowers were so beautiful..the blues more intense, the hollyhocks huge. 

  74. Nick James says:

    Rajini Rao Obviously not there in November, then! But the stone still glows its gentle yellow, even in the darkest weather.

  75. Yaprak Tatas says:

    Çok güzel yumurta türipü💋😍🍺😇😀🍒yazan sıla yaprak tatas

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