Hey Everyone. I follow this site with interest.
I think it would be great to start informational discussion- and experience sharing threads related to consumption of various types of nutrient rich foods. I noticed some questions raised about eggs – cholesterol, cooked vs raw, etc So, I post here some information I had from earlier research, which could be discussed here, questioned and revised.
Why Eggs Don’t Contribute Much Cholesterol To Diet
Nutrition researchers at Kansas State University have published the first evidence that the absorption of cholesterol is reduced by another compound in the egg, a lecithin.
The research by Sung I. Koo, Yonghzhi Jiang and Sang K. Noh has resulted in the issue of U.S. Patent No. 6,248,728, ”Compositions and methods for lowering intestinal absorption and plasma levels of cholesterol.” The patent was issued June 19 to the KSU Foundation.
A peer-reviewed research paper by the three researchers, ”Egg phosphatidylcholine decreases the lymphatic absorption of cholesterol in rats,” appears in the September issue of Journal of Nutrition.
Many people believe that dietary cholesterol directly contributes to raising blood cholesterol. Because eggs provide about half the dietary cholesterol in a typical Western diet, the public has been advised to limit its egg consumption.
Under the experimental conditions using an animal model that closely mimics human physiology, Koo and his associates found that a particular egg phospholipid interferes with the absorption of egg cholesterol and markedly lowers its uptake by the intestine. When the phospholipid is saturated, its inhibitory effect is further enhanced.
The researchers controlled experimental conditions to specifically look at egg phospholipid and its effect on cholesterol absorption. Even though a good amount of cholesterol is consumed when an egg is eaten, much of the cholesterol becomes ”unavailable for absorption” in the presence of the phospholipid, Koo said.
“This may be a reason why so many studies found no association between egg intake and blood cholesterol,” he said. The phospholipid, or lecithin, found in egg markedly inhibits the cholesterol absorption. The inhibition is not 100 percent, he said. Some cholesterol is absorbed but the amount is significantly reduced in the presence of this phospholipid.
“Less absorption means less cholesterol introduced into the blood,” Koo said. ”We were able to determine experimentally that a substantial amount of the egg cholesterol is not going into the blood stream.”
Koo says people with normal cholesterol levels and no family history of cardiovascular disease should not worry about eating one to two eggs a day. There’s more overall nutritional benefit than harm to be gained from eating ”nutrient-dense” eggs – in moderation, he said.
Egg contains a higher quality protein than protein found in meat, milk or fish.
Furthermore, egg is a significant source of vitamins A and E, and B vitamins B-6, B-12 and folate, which are known to lower blood levels of homocysteine, an independent risk factor for heart disease.
Koo’s research has received support from the Kansas Agricultural Experiment Station and the USDA National Research Initiative Competitive Grants Program.
Koo is a professor of human nutrition at K-State; Jiang received a master’s degree in nutrition from K-State; and Noh is a postdoctoral researcher at K-State who is continuing research with Koo. - By Kay Garrett
Egg-Irony: High Cholesterol Food May Reduce Blood Pressure
Main Category: Hypertension
Also Included In: Cholesterol; Nutrition / Diet
Article Date: 19 Feb 2009 - 2:00 PST
Researchers in Canada are reporting evidence that eggs - often frowned upon for their high cholesterol content - may reduce another heart disease risk factor - high blood pressure.
They describe identification of egg proteins that act like a popular group of prescription medications in lowering blood pressure. The report appeared in the Feb. 11 issue of ACS’ Journal of Agricultural and Food Chemistry, a bi-weekly publication.
In the new study, Jianping Wu and Kaustav Majumder note that eggs are an inexpensive source of high-quality protein and other nutrients. Egg consumption, however, has decreased during the last 40 years amid concerns about cholesterol. Recent studies do suggest that healthy people can eat eggs without increasing their heart disease risk. Other research hinted that certain egg proteins might have effects similar to ACE inhibitors, prescription drugs used to treat high blood pressure.
Pursuing that lead in laboratory studies, the scientists identified several different peptides in boiled and fried eggs that act as potent ACE inhibitors. The scientists showed that enzymes in the stomach and small intestine produce these peptides from eggs. Fried eggs had the highest ACE inhibitory activity. It will take studies in humans to determine if the egg proteins do lower blood pressure in people, the scientists emphasized. Funding for the research came from livestock and poultry industry groups.
“Angiotensin I Converting Enzyme Inhibitory Peptides from Simulated in Vitro Gastrointestinal Digestion of Cooked Eggs”
Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations.
Department of Nutritional Sciences, University of Connecticut, Storrs, Connecticut 06269, USA.
PURPOSE OF REVIEW: Extensive research has not clearly established a link between egg consumption and risk for coronary heart disease. The effects of egg intake on plasma lipids and low-density lipoprotein (LDL) atherogenicity in healthy populations need to be addressed. RECENT FINDINGS: The lack of connection between heart disease and egg intake could partially be explained by the fact that dietary cholesterol increases the concentrations of both circulating LDL and high-density lipoprotein (HDL) cholesterol in those individuals who experience an increase in plasma cholesterol following egg consumption (hyperresponders). It is also important to note that 70% of the population experiences a mild increase or no alterations in plasma cholesterol concentrations when challenged with high amounts of dietary cholesterol (hyporesponders). Egg intake has been shown to promote the formation of large LDL, in addition to shifting individuals from the LDL pattern B to pattern A, which is less atherogenic. Eggs are also good sources of antioxidants known to protect the eye; therefore, increased plasma concentrations of lutein and zeaxanthin in individuals consuming eggs are also of interest, especially in those populations susceptible to developing macular degeneration and eye cataracts.
SUMMARY: For these reasons, dietary recommendations aimed at restricting egg consumption should not be generalized to include all individuals. We need to acknowledge that diverse healthy populations experience no risk in developing coronary heart disease by increasing their intake of cholesterol but, in contrast, they may have multiple beneficial effects by the inclusion of eggs in their regular diet.
PMID: 16340654 [PubMed - indexed for MEDLINE]
Egg White Protein
The ”Egg, White - Raw, Fresh” has a Nutritional Grade of C+ even though it has 0% fat, while a whole hard boiled egg gets a B-, even though it has well over half its calories from FAT. Nutritionally, eggs are considered a good source of protein.
Egg White protein is the purest form of protein known to man in the entire world. Each 8-ounce cup gives you 26 grams of pure protein, only 2 grams of carbohydrates, NO fat and NO cholesterol. They are 100% bio-available, which means NONE of it’s amino acids are wasted. No artificial protein powder can make that claim. Other high protein sourced foods and supplements need to be broken down before the body absorbs the protein. All natural products have always been the recommended way to get the nutrients your body needs. I’d want them cooked though to be sure no salmonella
What is better as a protein source – hard boiled egg whites or raw egg whites?
Proteins do denature with heat. However, most proteins are denatured by your stomach acid or broken down by enzymes. Truly it is the amino acid content that matters, as most of the time that is what your body is using anyway. Even if there’s a different in protein the amino acid content is the same.
If you were concerned about enzyme or vitamin count, then there could be a difference.
Egg raw versus cooked
If you cook egg-white the digestability is ~90%.
1. Digestibility of Cooked and Raw Egg Protein in Humans as Assessed by Stable Isotope Techniques:
2. Amount and fate of egg protein escaping assimilation in the small intestine of humans:
Cooked Vs. Raw? Safe Egg Preparation
Because eggs are well-known as a high-quality protein source, many physically active individuals choose to incorporate them into their training diets.
While the chance of eating an egg contaminated with Salmonella Enteritidis (SE) is small (1 in 20,000 eggs might contain the bacteria), properly cooking eggs eliminates the potential for illness from SE
The cooking process does not decrease the quality or bio-availability of egg protein, nor does it significantly change the nutrient content.
In fact, research shows that the cooking process actually increases the digestibility of egg protein.
What is the protein difference between raw eggs and cooked eggs?
The protein content does not change when cooked, like some answers stated. They simply become ’denatured’.
The food value of proteins lie in their amino acid content, and heating does not change this. So the food value remains the same.
Cooking eggs gets rid of all the bacteria in it. So it’s healthier. In fact, it’s not a good idea to eat any animal food uncooked.
It’s raw eggs which produce allergies, not cooked eggs.
Raw egg advocates argue that raw eggs are healthier than cooked eggs because cooking somehow reduces the nutritional value of the egg and protein. However, the science doesn’t really support this.
There is no clinical evidence or peer-reviewed research to indicate that cooking eggs reduces the availability of protein or significantly degrades vitamin or nutrient content. While the modern raw food movement would like to paint all foods with a broad brush that says they are healthier and more “natural” when not cooked, there really is little scientific evidence to back this up.
A 1997 study published in The Journal of Nutrition found that the protein in cooked eggs was actually 40% more bio-available to the body than when uncooked. In practical terms, this means that you’d have to eat seven raw eggs to absorb the amount of protein available in five cooked eggs. So cooking actually ehances the biological value (BV) of eggs, versus degrading it.
Egg Protein assimilation, cooked vs raw
The Journal of Nutrition Vol. 128 No. 10 October 1998, pp. 1716-1722
Egg proteins contribute substantially to the daily nitrogen allowances in Western countries and are generally considered to be highly digestible. However, information is lacking on the true ileal digestibility of either raw or cooked egg protein. The recent availability of stable isotope-labeled egg protein allowed determination of the true ileal digestibility of egg protein by means of noninvasive tracer techniques. Five ileostomy patients were studied, once after ingestion of a test meal consisting of 25 g of cooked 13C- and 15N-labeled egg protein, and once after ingestion of the same test meal in raw form. Ileal effluents and breath samples were collected at regular intervals after consumption of the test meal and analyzed for 15N- and 13C-content, respectively. The true ileal digestibility of cooked and raw egg protein amounted to 90.9% (cooked) and 51.3% (raw) respectively. A significant negative correlation (r = 0.92, P < 0.001) was found between the 13C-recovery in breath and the recovery of exogenous N in the ileal effluents. In summary, using the 15N-dilution technique we demonstrated that the assimilation of cooked egg protein is efficient, albeit incomplete, and that the true ileal digestibility of egg protein is significantly enhanced by heat-pretreatment. A simple 13C-breath test technique furthermore proved to be a suitable alternative for the evaluation of the true ileal digestibility of egg protein……..
Raw egg white protein is generally considered to be less digestible than heat-pretreated egg white protein. In this study, it was shown that after ingestion of 25 g of raw egg protein, almost 50% is malabsorbed over 24 h. The higher digestibility of cooked egg protein presumably results from structural changes in the protein molecule induced by heating, thereby enabling the digestive enzymes to gain broader access to the peptide bonds. It has been suggested that the reduced digestibility of raw egg white is at least partially related to the presence of trypsin inhibitors in raw egg white.
Biotin and egg whites….
Biotin’s name comes from the Greek word for life, bios. Although biotin has been known to be essential for half a century, research has not yet fully revealed all of its roles. We know it is essential for the syntheses of protein and fatty acids, and to the metabolism of carbohydrates. In addition, biotin is an essential coenzyme in many enzyme reactions. We know that the thyroid and adrenal glands, the reproductive tract, the nervous system, and the skin depend on an adequate supply of the vitamin.
Some nutritionists maintain that a biotin deficiency can occur only when the biotin in the body is destroyed by an antagonist, such as raw egg white. On the other hand, there is also research which demonstrates that large numbers of people do indeed have low levels of biotin in their blood. These include the elderly, athletes, pregnant women, alcoholics, and people with achlorhydria (absence of hydrochloric acid in the stomach). In pregnant women, for example, the biotin level in the blood starts out lower than in other adults and decreases as pregnancy progresses. Biotin in mother’s milk after birth, and for at least four days, is too low to be measured. After that, it varies from individual to individual. People with liver disease also have lower than normal levels of biotin. Blood plasma levels of biotin have been shown to drop below normal in children with burns and scalds, too.
The principal biotin antagonist is avidin, a component of raw egg white. Avidin combines with biotin (or binds it) and renders the vitamin unavailable for utilization.
A biotin deficiency may also be produced by antibiotics. Researchers believe that bacteria normally found in the intestines can synthesize biotin, which is absorbed into the bloodstream. Antibiotics can kill these bacteria and shut off a potentially important supply of biotin.
Biotin is available in supplement form in doses ranging from a few micrograms up to several hundred micrograms.
Where is it found?
Good dietary sources of biotin are liver and other organ meats, egg yolk, peanuts, filberts, mushrooms, bananas, soy, peanuts, and cauliflower. Whole grains are also good sources. Processed cereals and grains, such as white rice and flour, have had most of the biotin removed and none returned through fortification.
Who is likely to be deficient?
Certain rare inborn diseases can leave people with depletion of biotin due to the inability to metabolize the vitamin normally. A dietary deficiency of biotin, however, is quite uncommon, even in those consuming a diet low in this B vitamin. Nonetheless, if someone eats large quantities of raw egg whites, a biotin deficiency can develop, because a protein in the raw egg white inhibits the absorption of biotin. Cooked eggs do not present this problem. Long-term antibiotic use can interfere with biotin production in the intestine and increase the risk of deficiency symptoms, such as dermatitis, depression, hair loss, anemia, and nausea. Long-term use of anti-seizure medications may also lead to biotin deficiency. Alcoholics, people with inflammatory bowel disease, and those with diseases of the stomach have been reported to show evidence of poor biotin status; however, the usefulness of biotin supplementation for these individuals remains unclear. In animals, biotin deficiency can cause birth defects.
How much to take?
The ideal intake of biotin is unknown; however, the amount of biotin found in most diets, combined with intestinal production, appears to be adequate for preventing deficiency symptoms. Researchers have estimated that 30 mcg per day appears to be an adequate intake for adults. Typically, consumption from a Western diet has been estimated to be 30-70 mcg per day. Larger amounts of biotin (8-16 mg per day) may be supportive for diabetics by lowering blood glucose levels and preventing diabetic neuropathy. Biotin in the amount of 2.5 mg per day strengthened the fingernails of two-thirds of the individuals with brittle nails, according to one clinical trial.
Excess intake of biotin is excreted in the urine; no toxicity symptoms have been reported.
Biotin works with some other B vitamins, such as folic acid, pantothenic acid (also known as vitamin B5) and vitamin B12; however, no solid evidence indicates that people supplementing with biotin need to also take these other vitamins. Symptoms of pantothenic acid or zinc deficiency have been reported to be lessened with biotin, though people with these deficiencies should supplement with the nutrients they are deficient in. Researchers have speculated that biotin and alpha lipoic acid may compete with each other for absorption or uptake into cells; but little is known about the importance of these interactions in humans.
Article on biotin deficiency, here:
Also, from an e-medicine article (online reference for medical professionals) which is here:
- There is the following information: ”Eating raw egg whites: Eating raw egg whites is commonly believed to be the only way to develop biotin deficiency. Although this is not true, consuming raw egg whites is a relatively certain (and quick) way to develop biotin deficiency.”
Eggs are an excellent source of carotenoids.
These are primarily highly absorbable forms of lutein and its partner zeaxanthin. These carotenoids accumulate in the back of the eye and appear to protect against age-related macular degeneration. There is no RDA for them, as researchers are still trying to understand their importance. All of the lutein and zeaxanthin in an egg is contained in the yolk.
Egg Yolks Contain Essential Fatty Acids DHA and Arachidonic Acid
One important set of nutrients that should not be overlooked is the long-chain essential fatty acids. Egg yolks contain the long-chain omega-3 fatty acid DHA, which is necessary for the brain and proper retinal function in the eye, and the long-chain omega-6 fatty acid arachidonic acid, which is required for the healthy skin, hair, libido, reproduction, growth and response to injury. These fatty acids are primarily needed by young children, pregnant and lactating women, and people with degenerative diseases involving oxidative stress, especially those of the nervous system such as Alzheimer’s. While fatty fish and cod liver oil supply DHA in larger amounts, egg yolks have an advantage over these foods because they also contain arachidonic acid and because they do not contain EPA, which interferes with arachidonic acid metabolism.
According to NutritionData.Com, one egg yolk contains 75 mg of arachidonic acid (AA), 20 mg of DHA, but no EPA. As I describe in my Special Report, How Essential Are the Essential Fatty Acids?, DHA and AA are the two fatty acids essential to humans and other mammals, while EPA interferes with the body’s use of AA and probably does not belong in the mammalian body at all.
Animal foods from animals raised on pasture are likely much richer in DHA. In all eggs, both the DHA and AA are contained in the yolk.
Vitamins and Minerals
Egg yolk is ’the fruit of the egg’, containing all the vitamin A, -D, -K and -E and cholesterol, and most iron, zinc, calcium, magnesium and iodide.
Of all proteinous foods, egg yolk contains most vitamins and minerals;
Vitamin- and mineral contents of different proteinous foods are compared below. Contents have been indexed to the highest level ( = 100 ). Original contents have been taken from : Souci, S.W. et al, Food Composition and Nutrition Tabels, Medpharm Scientific Publishers Stuttgart 1994.
Cheese calcium contents have been disregarded for being far too high.
vit.B2 vit.B5 vit.B8 vit.B9 iron calcium
100 100 100 100 100 100 egg yolk
9 6 24 47 94 Brazil nut
43 27 14 2 14 9 salmon
40 18 9 14 29 tuna
90 12 8 1 14 9 mackerel
65 16 6 2 30 4 beef, muscles
58 19 9 2 15 2 pork, muscles
38 17 7 16 28 45 wheat whole meal bread
88 8 571 Edam cheese, 30%
vit.E vit.B1 selen. magnesium
75 29 18 10 egg yolk
100 100 100 100 Brazil nut
29 17 25 18 salmon
16 80 tuna
16 13 38 19 mackerel
6 23 5 beef, muscles
5 90 8 17 pork, muscles
11 86 8 58 wheat whole meal bread
5 21 37 Edam cheese, 30%
Zinc vit.B3 vit.B6 vit.B12
89 1 31 22 egg yolk
93 2 11 0 Brazil nut
19 89 100 32 salmon
100 47 47 tuna
89 64 100 mackerel
100 89 19 56 beef, muscles
47 59 58 23 pork, muscles
49 41 8 0 wheat whole meal bread
0 1 0 Edam cheese, 30%
Raw Egg Whites Contain Digestive Enzyme Inhibitors and Anti-Nutrients
Raw egg whites should not be consumed. They contain inhibitors of the digestive enzyme trypsin, which are destroyed by heat.
Raw egg whites also contain an anti-nutrient called avidin. Avidin is a glycoprotein that binds to the B vitamin biotin, preventing its absorption. Biotin is necessary for fatty acid synthesis and the maintenance of blood sugar, and is especially important during pregnancy when biotin status declines.
Egg white is comparable to the womb, ovaries and oviduct, containing the same substances as are produced in the human oviduct (which is enhanced by progesterone (avidine), respectively estrogen (ovomucoid));
- Avidine in raw egg-white de-activates vitamin B8 (biotine).
- Ovomucoid in raw egg-white inhibits trypsin, an enzyme that decomposes absorbed nutrients.
Residual Egg White Avidin — Cooking Does Not Fully Destroy the Anti-Nutrients
It is a myth that light cooking completely destroys the avidin.
According to this study, poaching eggs only destroys one third of the avidin while even frying leaves 30 percent of it behind.
This raises the question of whether there is a net nutritional advantage to eating any egg whites at all. Most likely, it depends on the individual person. There is controversy over whether biotin produced in the intestinal tract is absorbed — if intestinal biotin production is indeed nutritionally important, then people whose intestinal flora are less avid producers of biotin probably need to be more concerned about the potential adverse effects of consuming egg white.
Finding The Right Kind of Eggs
Pastured eggs, meaning eggs from chickens that are free to forage for grass and insects, are of much higher nutritional quality than eggs from confinement chickens. The marginal increase in value, of course, is found mostly in the yolk
Insects provide a higher DHA content, found exclusive in the yolk, and grass provides a higher vitamin E and carotene content, also found exclusively in the yolk. Egg yolks from pastured chickens are thus a powerful supplement to a healthy diet — a super-food — providing necessary nutrients in which the Standard American Diet is deficient.
The value of pasture eggs vs conventional
The numbers don’t lie. I readily admit it can be hard to find genuine, free range/pasture organic eggs; even if you can, manufacturers are becoming savy, and slapping labels on by meeting minimum standards.
Eggs are an exceptionally nutritious food. It’s not surprising, considering they contain everything necessary to build a chick! But all eggs are not created equal.. Anyone who has seen the tall, orange yolk, viscous white, and tough shell of a true pastured egg knows they’re profoundly different. So has anyone who’s tasted one. This has been vigorously denied by the American Egg Board and the Egg Nutrition Council, primarily representing conventional egg farmers, which assert that eggs from giant smelly barns are nutritionally equal to their pastured counterparts.
In 2007, the magazine Mother Earth News decided to test that claim. They sent for pastured eggs from 14 farms around the U.S., tested them for a number of nutrients, and compared them to the figures listed in the USDA Nutrient Database for conventional eggs. Here are the results per 100 grams for conventional eggs, the average of all the pastured eggs, and eggs from Skagit River Ranch, which sells at my farmer’s market:
Conventional: 487 IU
Pastured avg: 792 IU
Skagit Ranch: 1013 IU
Conventional: 34 IU
Pastured avg: 136 - 204 IU
Skagit Ranch: not determined
Conventional: 0.97 mg
Pastured avg: 3.73 mg
Skagit Ranch: 4.02 mg
Conventional: 10 mcg
Pastured avg: 79 mcg
Skagit Ranch: 100 mcg
Omega-3 fatty acids:
Conventional: 0.22 g
Pastured avg: 0.66 g
Skagit Ranch: 0.74 g
Looks like the American Egg Board and the Egg Nutrition Council have some egg on their faces…
Eggs also contain vitamin K2, with the amount varying substantially according to the hen’s diet. Guess where the A, D, K2, beta-carotene and omega-3 fatty acids are? In the yolk of course. Throwing the yolk away turns this powerhouse into a bland, nutritionally unimpressive food.
It’s important to note that ”free range” supermarket eggs are nutritionally similar to conventional eggs. The reason pastured eggs are so nutritious is that the chickens get to supplement their diets with abundant fresh plants and insects. Having little doors on the side of a giant smelly barn just doesn’t replicate that.