Quality of the egg: does the colour matter?

By Dagmar
In Complementing
May 28th, 2014

Before reading the following article please answer this question for yourself: Why do you eat eggs (if you do)?

The reasons are numerous: because they taste good, they contain proteins, or just fill the stomach and help to survive until the next meal. Some say that eggs are healthy, but others have expressed quite an effort to convince the audience that eggs are harmful, or even deadly, such as Dr Greger in his video. Vegans seem to keep buying the story about dietary cholesterol rising the blood cholesterol and causing arterial plaque formation, although this has been disproved several years ago.

What made me writing this article was a video of Dr Mercola on which I randomly clicked today. It is about eggs, but he has critically looked at the misleading claims that eggs are harmful, in contrast with the biased vegan anti-egg propaganda which does not seem to look closer into the outdated health claims of eggs consumption and cardiovascular diseases. In this second video you will not only learn why we need cholesterol and therefore eggs are healthy in this respect, but you will also get an insight into the questionable quality of the particular study and the conflict of interests, which is often present in such studies. These and other factors have led to misconceptions about the diet, having the power to advise wrongly the whole population, resulting in health consequences on such a massive scale.

However, I did not want to discuss the war between the industries regarding the nutrition advice. The main reason for writing this article was the confusion about the colour of the egg yolks and the nutrition and health claims associated with it, which were also briefly discussed by Dr Mercola in his video.


Which eggs are healthier?

Most of people will know the basic answer: organic eggs. True, partly. Organic is definitely healthier than from caged hens as it is (should be) free of GMO, herbicides, pesticides, fungicides and antibiotics. However, Dr Mercola praises the hens that have been pasture raised, which is typical for small farms, where you can go and see how the chicks are raised, what they eat, where they are kept, whether they can freely enjoy the typical activities such as dust bathing, i.e. whether they are happy. Happy hens lay happy eggs, right? It is good so far.

How about the colour of the yolk? Dr Mercola mentioned that chicken having green pasture consume compounds called carotenoids, which add a lovely yellow or even orange colour to the egg yolk. Based on this Dr Mercola suggests that egg yolks that are pale are suspicious and likely to lack the usual nutrients, right? Not quite.

I remember watching a short documentary how the yellow colouring agents are added to the chicken feed so that they not only have lovely golden colour of the skin, but the yolks are also orange coloured, trying to convince the customers that these are of a higher quality eggs than those with paler yolks. Since I did not remember the name of the compound, I have turned to Google to help me with that. Although I am not sure whether I found the name of that compound, I have found more information as I have read around. What I have found may sound confusing, but it is not when you realize what Dr Mercola said: go for pasture raised eggs!


What I have found

The Poultry Site website contains an article which says that one cannot rely on the colour of the egg yolk regarding the nutritional value. They say that the content of the carotenoids in the poultry feed is not constant and the egg yolk colour can vary. Wikipedia also states that the colour of the egg yolk does not directly reflect the nutritional value of the egg. So, did Dr Mercola say good-bye for no reason to the farmer selling eggs with paler yolks?

The carotenoids is a broad name for about 600 compounds mainly of plant origin, belonging to the same family, but they can have different properties in terms of nutritional value or the pigmenting properties. These compounds can be split in two main groups: the xanthophylls (containing oxygen atom) and these include lutein and zeaxanthin in chicken feed, according to the The Poultry Site website. The other groups of carotenoids are carotenes, having no oxygen atom and only three of these have a vitamin A activity in humans, according to another Wikipedia article.

Because the content of these compounds in the chicken feed was reported as inconsistent, the farmers add other pigmenting compounds of natural origin (apoester and canthaxanthin) to the chicken feed and these add to the deep yellow colour that we seek when using eggs in cooking. However, these compounds do not have the same nutritional value so the customers can be deceived, especially when they judge the overall quality of the egg from the yolk colour without checking the actual class of the egg which are used to distinguish the conditions in which the hens were raised and kept. Moreover, Wikipedia says that even the xanthophylls do not have a high nutritional value, in contrast to the carotenes. Nonetheless, lutein and zeaxanthin are still valuable compounds which are important for healthy retina, the back of our eyes.

Interestingly, The Poultry Site further states that even when the chicken does not have a high intake of these colouring compounds, it still can have a high vitamin A levels, which deposits in the egg yolk. However, it was not specified where the active vitamin A would come from, since these pigmenting beta-carotenes have to be metabolically altered in animal bodies for having a vitamin A activity and when there is not enough of these primary compounds, the vitamin A clearly cannot be made. My suggestion is that this may be the case of caged hens, the feed of which contains also the animal materials from slaughter houses, but I cannot say this for sure. Can someone confirm this?

The main point of this detail is that if we wanted to obtain vitamin A as an active compound, we can get it from pale yolks and we do not have to stress about the deeply coloured, sometimes artificially died, egg yolks in this respect. 

In fact, yolks, particularly from free-range eggs, can be of a wide range of colors, ranging from nearly white, through yellow and orange to practically red, but even olive green, depending on the pigments in their food. (Wikipedia)

Except the free range is not the same as pasture raised, according the page 6 of another article. Hence we come again to the highlighted point: go for the eggs of pastured hens! If you can afford them as they cost quite a lot in the supermarket, I do not know how much they cost directly from the farmer as I do not have access to any. The yolk colour is likely to vary in these eggs as well, since they peck on different plants throughout the year, but the quality of these eggs is not only about the yellow colour. Here is another great article discussing the opposing pressures of the egg industry vs. pasture raised eggs practice, with some references about the proven higher nutritional content of the latter, which the egg industry tries to dismiss.


Organic lacking the nasties, but is it really different from caged?

Saying all what I have said above, I did not mean that eggs are precious only for the carotenoids or vitamin A found in the yolk. There is a whole spectrum of beneficial compounds in healthy eggs produced by healthy and pastured hens which consume grass, herbs and insects in addition to grains, whereas the grains, soy and other less pleasant ingredients form the usual feed of caged hens. However, the overall quality, the organic eggs seem to be somewhere between the caged and pasture eggs. Organic are free of pesticides, herbicides, fungicides and antibiotics, and they also should be free of GMO, although this can be difficult to achieve due to the cross-polination across the fields. Organically raised hens do not receive the remains of other animals from the slaughter house in their feed as the caged chicken do (page 3). However, the organic eggs have not been found too different from the eggs of caged hens in terms of nutritional value. The superior eggs are truly the ones from pasture raised hens, such as those described on page 4. The study, which was not specified closer, is claimed to report better nutritional content of eggs from the pastured hens in terms of a higher content of vitamins, unsaturated fatty acids, including the naturally occurring omega-3, which are secondarily added into the conventional or organic eggs. More reference about the nutritional values of such eggs can be found in the article introduced in the previous paragraph (here).


How about the free range?

The article in Time suggests that the caged hens might produce healthier eggs than freely ranging ones in terms of environmental polutants. The free range (and also organically grown) animals were found to contain up to 100 times more PCB than caged hens just because there was a factory nearby that used this chemical and the free range raised birds were allowed to peck anywhere they wanted. Also some pesticides and other pollutants have quite a long time of degradation and even after nine years the residues can be found in open land and hence in the bodies of the birds and the eggs they produce. The organic farming regulations have the limit only of 3 years. Therefore it is not enough to know the current feeding and keeping conditions of the hens as Dr Mercola suggests. It is also good to know the history of the land and adjusted fields, unless you have an opportunity to test the land for pollutants in the present time and learn whether there is a risk of pollution or not. However, the conventionally kept hens are also fed with cheap grains and similar staple, which is most likely grown with the use of large amounts of pesticides, herbicides and anything that increases the yield of the produce and when taking this into account it truly appears that the organically and free range raised birds and eggs are better, except of the occassional unfortunate incidences as with the PCB. In addition, the organic and free ranged birds are not intentionally exposed to the other pollutants already discussed earlier (antibiotics, hormones).

Therefore, the conclusion so far is: anything than caged is generally better, but the pasture raised are the top quality you can get if the source is trustworthy.


Does the colour of the shell matter?

Obviously not, most of us have known already. However, only when reading the Times article I have learned why the brown coloured eggs can cost more: because the breed that produces these dark coloured eggs needs to be fed more to lay eggs, which adds on the cost of egg production. Simple as that. Another article mentioned here already confirmed it: the hens laying white eggs are lighter, hence they need less food than the other laying eggs with darker shell. This does not answer my question though, what is the purpose of having more expensive breed? Are there any more benefits? I am open to your comments on this.

About "" Has 48 Posts

Graduated at London Metropolitan University: BSc (Hons) Human Nutrition in 2014. Working as a research assistant at the MRC, The University of Cambridge.

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