Are unfertilized chicken eggs really that paleo? No doubt humans have been eating them for millenia, but...
I love eggs. But sometimes I think that they make me feel bad. Other times I think I'm unfairly blaming them. Here's my preliminary thoughts:
- From what I can tell, wild birds lay mostly fertilized eggs. Modern man suddenly having a huge and steady supply of unfertilized eggs throughout all seasons seems a bit unnatural.
- Hunting animals is the hard part. Once you get them, eat away. But with eggs, I'd imagine that there's some protective mechanisms to keep predators from eating what may or may not become a baby.
- "even cooked egg protein, which has generally been considered to be easily digestible, is malabsorbed to some extent after ingestion of a physiologic load. Incomplete assimilation of dietary protein may have important consequences not only from a nutritional point of view, but also from a gastrointestinal point of view. Indeed, some metabolites resulting from bacterial fermentation of malabsorbed proteins in the colon have been implicated in the ethiopathogenesis of diseases such as colonic cancer and ulcerative colitis"
- Avidin as an antinutrient (counteracted by cooking the egg?)
I'm wondering if eating eggs everyday is a bit like eating lots of nuts. Nuts aren't terrible per se, but they were not really available in modern amounts back in paleo times. And while people have been finding and eating eggs for eons, I somehow doubt that they'd routinely start their days with a four egg omelet. If a bird kept getting its eggs stolen, I would think it would move somewhere else. And there probably weren't billions of ground birds (chickens) roaming around either.
Do you have any arguments for or against eggs, both for health reasons and just-for-fun paleo re-enactment reasons?
asked byKamal (24543)
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on December 08, 2010
at 12:06 AM
Here's Loren Cordain's take:
Lysozyme from Egg Whites by Loren Cordain
In all three of my books, I have advocated egg consumption, particularly eggs that are produced with high omega 3 fatty acid contents. Chicken eggs are generally a nutritious food and are a good source of selenium, vitamin A, vitamin D and the B vitamins, some minerals and lutein as Barbara indicated. Additionally, numerous recent experimental and epidemiological studies (reviewed in references 1, 2) indicate that regular egg consumption (7 per week) does not increase the risk for coronary heart disease (CHD). As I have previously noted, although eggs are one of the most concentrated sources of dietary cholesterol (212 mg per egg), dietary cholesterol has a minimal effect upon blood cholesterol concentrations in most people1, 3. Further, high cholesterol egg diets cause an increase in blood HDL particles1 and reduce the highly atherogenic small dense LDL particles while simultaneously increasing the less atherogenic large, "fluffy" LDL particles4, 5.
So, should everybody include eggs in their diet on a daily basis? Not necessarily, particularly if we examine the evolutionary template. Without question our preagricultural ancestors would have collected and consumed eggs from birds??? nests whenever possible. However, in the wild, bird eggs only appear seasonally. Hence, pre-agricultural humans could have never consumed two eggs for breakfast every morning of the year similar to some westernized people, but rather only occasionally for a few brief weeks or months.
If we follow up on the clue from the evolutionary template and examine eggs more closely, they maintain certain nutritional shortcomings that may be problematic, particularly for people suffering from autoimmune diseases and allergies. Although eggs are classified as animal food sources and are lumped together with meats in the USDA My Pyramid, eggs are uniquely different from meats in that they represent the reproductive endpoints of adult birds which exist outside their mother???s body in a semipermeable, warm compartment. As such, all eggs are particularly vulnerable to invasion, attack and destruction by microorganisms such as fungi, bacteria and viruses present in their nesting environment.
The innermost yolk of a chicken egg represents the growing embryo which is anchored to the albumen or egg white by structures called chalazae. Outward from the egg white are the inner and outer membranes and then the shell, all of which provide physical barriers to infection from pathogens and microorganisms. The egg white makes up about 58% of the total egg volume and contains about 50% of the total egg protein and is composed of 88.5% water, 10.5% protein and 0.5% carbohydrate6. The function of the egg white is threefold: 1) storage of nutrients for the growing embryo (yolk), 2) protection of the egg from microbial attack, and 3) transport of nutrients into the growing embryo.
As I have previously mentioned, a chicken egg is the reproductive endpoint for adult birds and survives by living outside its mother???s body in a semi permeable compartment that is essentially immovable. Accordingly, it has no means of protecting itself from microorganisms or predation by physical escape or avoidance. For this reason, the evolutionary strategy eggs have taken to protect themselves from microbial invaders is to select for toxic substances in the egg white; mainly in the form of antimicrobial proteins. Table 1 lists the major proteins in egg whites and their likely functions.
Table 1. Major proteins and their properties found in egg whites (adapted from references 6-10). Protein % total proteins Functions Ovalbumen 54 Storage protein Ovotransferrin 12 Iron binding with antimicrobial activity Ovomucoid 11 Protease inhibitor/antimicrobial activity? Ovomucin 3.5 Potent antiviral activity Lysozyme 3.4 Antibacterial activity G2 globulin 4.0? Antibacterial activity G3 globulin 4.0? Antibacterial activity Ovoinhibitor 1.5 Protease inhibitor/antimicrobial activity? Ovoglycoprotein 1.0 ? Thiamin binding protein 1.0 Thiamin transport Ovoflavoprotein/Riboflavin binding protein 0.8 Riboflavin transport Ovomacroglobulin (Ovostatin) 0.5 Protease inhibitor/antimicrobial activity? Cystatin 0.05 Protease inhibitor/antimicrobial activity? Avidin 0.05 Antimicrobial activity Total 88.8
Note that except for ovalbumen, which comprises 54% of the total protein in egg white, virtually all the other major proteins (~33% of the total) maintain one form or another of antimicrobial activity.
Egg white allergy in the general population varies between 1.6 ??? 3.2% and is the second most common cause of food allergy in children next to milk8. For both adults and children one or more of the following symptoms may occur: hives, atopic dermatitis (red, flaky itchy skin), asthma, runny nose, diarrhea, abdominal pain, rapid swelling of the skin and mucosa, and anaphylactic shock which may be life threatening. The major allergens in egg white are ovomucoid, ovalbumen, ovotransferrin and lysozyme8 (Table 1). So for the vast majority of children and adults (98.4 ??? 96.8% of the population), egg white allergy is not a problem, and except for anaphylactic shock is not a debilitating or life threatening condition.
The same conclusion may not be true for people suffering from an autoimmune disease (e.g. multiple sclerosis, rheumatoid arthritis, ankylosing spondylitis, lupus erythematosus and others), since egg white consumption may contribute to the origin and progression of these diseases via a process of molecular mimicry that I have previously outlined for dietary lectins found in wheat, peanuts and other grains and legumes11.
You can see from Table 1 that egg white protein is no simple protein, but rather a conglomeration of multiple proteins which have been designed by natural selection to cause toxic and lethal effects in bacteria and microorganisms reminiscent of food lectins found in grains and legumes11. In order for any food proteins to potentially cause or promote an autoimmune disease, it must:
Survive the human digestive processes intact Cross the gut barrier intact either alone or with other attached proteins Interact with the immune system in a manner suspected of causing an autoimmune disease. A number of egg white proteins fulfill these necessary steps. Most problematic is the egg white protein, lysozyme which is actually an enzyme known as Nacetylhexosaminodase that is also found in many human tissues, including tears12. The function of lysozyme in both egg whites and in human tears is to act as a potent bacterialcidal agent by binding and dissolving bacterial cell walls12.
Bacterial cell walls are called the murein or peptidoglycan layer which is a gigantic polymer of (N-acetylglucosamine and N-acetylmuyramic acid) polysaccharide strands cross linked through short peptide bridges at the lactyl groups of the muramic acid residues. Lysozyme degrades bacterial cell walls by catalyzing hydrolysis of the beta (-1,4-) linkage between N-acetylglucosamine and N-acetylmuramic acid. Human cells do not maintain a murein (peptidoglycan) exterior lining. Consequently, dietary lysozyme from egg whites do no increase intestinal permeability by breakdown of intestinal cell membranes but rather lysozyme increases intestinal permeability by other means that I will explain. It is this increase in intestinal permeability or "leaky gut" that makes egg white consumption problematic for people with egg allergies or autoimmune disease.
Lysozyme is unusual among the major egg white proteins in that it has an alkaline isoelectric point, which means that it can form strong complexes with other egg white proteins including ovomucin, ovalbumen and ovotransferrin6, 12. Hence, even though lysozyme is a benign enzyme produced in our own bodies, when we eat egg white lysozyme, it comes as a compound attached to other egg white proteins or to gut borne bacterial proteins foreign to our bodies.
In the human digestive tract, enzymes called proteases normally break down proteins into their constituent amino acids so that the amino acids can be absorbed across the intestines. Because egg white protein contains high concentrations of protease inhibitors (ovomucoid, ovoinhibitor, ovostatin, cystatin - see Table 1), the human gut proteases (trypsin and chymotrypsin primarily) are less effective in degrading egg white proteins, and lysozyme/egg white protein complexes. Additionally lysozyme is stable in the acidic gut environment12 and therefore arrives intact in the lower gastrointestinal tract. It should also be mentioned that Lysozyme is heat stable, having been reported to withstand 100 degrees C with little loss of activity13. Matsuoka et al14 reported lysozyme to be stable in acidic solution (pH 4.5, 100 degree C for 3 min; pH 5.29, 100 degree C, 30 min. So lysozyme would survive any normal cooking procedures used for eggs.
So what???s wrong if lysozyme/egg white protein/bacterial complexes aren???t dissolved by normal digestive processes? Normally, large multifaceted proteins such as these complexes don???t have a prayer of getting across the intestinal barrier and into the bloodstream where they can interact with the immune system. Once again, lysozyme is an unusual protein because it rapidly breeches the gut barrier and enters human circulation15, due to its unusual chemical properties (a positively charged isoelectric point)16. Because lysozyme maintains a positive charge, it results in an electrostatic attraction to the negatively charged proteoglycans (the glycocalyx) of intestinal epithelial cells which in turn allows lysozyme to be absorbed rapidly into circulation16.
Absorption of pure egg white lysozyme by itself into circulation is likely not problematic because lysozyme is an enzyme that the body naturally produces. Rather it is the complexes that lysozyme forms with other egg white proteins, gut borne bacterial peptides and food peptides that may adversely stimulate the immune system. When these chimeric (monster) molecules breech the gut barrier via their net positive charge and enter circulation, they have the capacity to promote allergy and autoimmune disease.
Just how autoimmune diseases are triggered by gut borne antigens from egg white lysozyme and other common foods (cereal grains, legumes, dairy and certain saponin containing foods) is another good story that our research group has been working on for the past decade. We hope to publish this seminal paper in 2010.
Fernandez ML. Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations. Curr Opin Clin Nutr Metab Care. 2006 Jan;9(1):8-12. Kritchevsky SB. A review of scientific research and recommendations regarding eggs. J Am Coll Nutr. 2004 Dec;23(6 Suppl):596S-600S. Howell WH, McNamara DJ, Tosca MA, Smith BT, Gaines JA. Plasma lipid and lipoprotein responses to dietary fat and cholesterol: a meta-analysis. Am J Clin Nutr. 1997 Jun;65(6):1747-64. Herron KL, Lofgren IE, Sharman M, Volek JS, Fernandez ML.High intake of cholesterol results in less atherogenic low-density lipoprotein particles in men and women independent of response classification. Metabolism. 2004 Jun;53(6):823-30. Maki KC, Van Elswyk ME, McCarthy D, Seeley MA, Veith PE, Hess SP, Ingram KA, Halvorson JJ, Calaguas EM, Davidson MH.Lipid responses in mildly hypertriglyceridemic men and women to consumption of docosahexaenoic acidenriched eggs. Int J Vitam Nutr Res. 2003 Oct;73(5):357-68. Stevens L. Egg white proteins. Comp Biochem Physiol B 1991;100:1-9. Szxena I, Tayyab S. Protein proteinases inhibitors from avian egg whites. Cell Mol Life Sci 1997;53:13-23. Mine Y, Yang M. Recent advances in the understanding of egg allergens: basic, industrial and clinical perspectives. J Agric Food Chem 2008;56:4874-4900. Wellman-Labadie O, Picman J, Hincke MT. Comparative antibacterial activity of avian egg white protein extracts. Br Poult Sci. 2008 Mar;49(2):125-32. Takahashi K.G., Nakamura A., Mori K. Inhibitory effects of ovoglobulins on bacillary necrosis in larvae of the pacific oyster, Crassostrea gigas. J Invert Pathol 2000;75:212-217. Cordain L, Toohey L, Smith MJ, Hickey MS. Modulation of immune function by dietary lectins in rheumatoid arthritis. Br J Nutr. 2000 Mar;83(3):207-17. Proctor VA, Cunningham FE. The chemistry of lysozyme and its use as a food preservative and a pharmaceutical. Crit Rev Food Sci Nutr 1988;26:359-395. Proctor VA, Cunningham FE. The chemistry of lysozyme and its use as a food preservative and a pharmaceutical. CRC Crit Rev Food Sci Nutr 1988;26:359-395. Matsuoka Y, Hidaka Y, Yashima M. Japanese Patent 41-150, 1966. Hashida S, Ishikawa E, Nakamichi N, Sekino H. Concentration of egg white lysozyme in the serum of healthy subjects after oral administration. Clin Exp Pharmacol Physiol. 2002 Jan-Feb;29(1-2):79-83. Nishikawa M, Hasegawa S, Yamashita F, Takakura Y, Hashida M. Electrical charge on protein regulates its absorption from the rat small intestine. Am J Physiol Gastrointest Liver Physiol. 2002 Apr;282(4):G711-9.
on December 08, 2010
at 12:01 AM
And we have Chris Masterjohn's blog about getting Choline from Eggs and Liver. http://blog.cholesterol-and-health.com/2010/12/meeting-choline-requirement-eggs-organs.html
Paleo for me is not about recreationism of our ancesters. For me it is eating foods that provide the nutrients we think our long lost ancestors got...but we know our ancestors did not eat beef as we know it.....they did not eat coconuts/oil if our ancestors lived in Europe...they did not make hard cheese from mastadon milk......etc So don't fret. Just eat lots of real food. And eggs are real food...even though the chicken was fed a carb diet. Relax and enjoy paleo and its benefits to your health. You will be around a lot longer than your SAD friends.
on December 07, 2010
at 11:03 PM
Fertilized eggs from a store, like WholePaycheck or Trader Joe's, are indistinguishable from unfertilized eggs, unless you put them under a broody hen for a few weeks and the embryo develops. By the way, my wife has done this twice and sold the resulting chickens.
I agree with you some, Kamal, that eating large amounts of eggs all the time should give us pause. Eggs might have been available only intermittently, and in relatively small amounts. (I saw a show where hunter gatherers cooked an ostrich egg and shared it among a few people). Mark Sisson's mass gaining protocol is (was?) to eat 12 eggs a day. I think that falls in the realm of "err, maybe that's not paleo." Otherwise, if you are talking maybe a few/several eggs a week, rotating with other proteins, I don't how that would be a major departure from "paleo".
on February 14, 2011
at 10:45 PM
I'm kind of leaning in the direction of Kurt Harris when it comes to a lot of these "is it paleo" questions. If the nutrient profile is similar to what we'd have had in our forager days, it's probably all right to eat even if we wouldn't have had access to the food year-round back then. Or maybe I should say "if the nutrient profile is similar to the overall profile of foods we'd have had for most of the year back then." I think for that reason it is more important to be skeptical of plant foods than animal, since animals would have been available year round, but plants might not have been, depending on the part of the world you lived in.
That's why I don't stress about dairy--most of what's in dairy, we would have gotten from other sources, especially the low-lactose stuff. Not everyone has a casein allergy.
I don't fuss about oxidized cholesterol because I eat eggs over easy most of the time that I eat them. I never was much able to get into scrambled eggs. When I do make them I use dairy cream rather than scramble them by themselves. I don't know if the fat in the cream has a protective effect on the cholesterol in the yolk, all I know is I like the taste, but you never know, I might be on to something. :D
on February 13, 2011
at 09:44 PM
I think Kamal raises a very important point: although eggs were consumed for millions of years they may have been available only seasonally. Something similar to the critique to fruit or nut consumption. I feel comfortable with my "rule of thumb" of having one egg a day, some fruit, two or three walnuts...I do not have any science to back it though, just that I like the stuff and its moderate consumption should not be any problem...
on February 13, 2011
at 09:32 PM
I hope they are paleo because I am eating a ton of them.
What do you think about oxidized cholesterol from cooking/scrambling eggs. I know dietary cholesterol does not equal serum cholesterol, but...I am reading conflicting views of this even within the paleo community.
on December 08, 2010
at 05:23 AM
This is so ironic. For many years, they have been telling us to only eat the egg whites. The thing is, I love the yoke, so if I can't eat the yoke, I'm skipping the egg altogether! Of course, now that I eat paleo, I feel free to eat as many eggs as I please, but typically what I find is that I cook up a bunch of eggs, eat mostly only yoke, and give the whites to the dog. Interesting to think this might be potentially the healthiest route!
I do think that eggs are paleo. There were probably times when many eggs were available. Bird species tend to nest all at one once and sometimes all in one general area. Our ancestors probably knew all the seasonal nesting sites and made trips to harvest when the time was right. The same also goes for reptile eggs. Larger reptiles lay a lot of eggs! My bet would be that during certain times of the year, many human populations were able to totally pig out on eggs. Plus eggs keep for a long time and some traditional cultures even found ways to ferment or treat the eggs to keep even longer. Eggs are definitely a great storage food and we would probably have eaten a lot of them, but probably not such that we ate mutliple of them every single day like some people do now. But I think eggs are a lot more healthy for most people than most other SAD options.
on December 07, 2010
at 11:13 PM
Well, if dairy products like milk, cheese and butter are eaten by a lot of paleo dieters even though they are definitely not paleo, makes sense that eggs would be accepted as well. I guess Neolithic animal products are more accepted than Neolithic plant foods like grains and beans. You're right about the quantity of eggs that were probably eaten is much smaller than a lot of people are eating.
Eggs are definitely more paleo than dairy because they can be more easily scavenged. I can't imagine hunter-gatherers going out and milking wild cows.
on December 07, 2010
at 10:54 PM
My chickens lay fertilized eggs when there is a rooster in the flock and have also laid unfertilized eggs when there has been no rooster around (darn fox). There is no difference in taste, consistency, color, etc. They sell fertilized eggs in the stores around here in southern PA so if the idea of unfertilized eggs bothers you, I would say go ahead and buy them. I, personally, will enjoy my pastured hens' eggs whichever way they want to lay them.
on December 07, 2010
at 10:44 PM
Whether or not paleoman ate them every day or not is probably irrelevant. If eggs do a body good, eat away. I'm sticking to pastured eggs only.
on December 07, 2010
at 10:22 PM
I see unfertilized eggs like any other convenient domesticated food, so they're as paleo as the chicken itself I guess.
The protective mechanisms for eggs in nature can be the shell and parents, plus having a nest hidden or in an awkward place.