Egg Digestability

[daf2]

I have heard several mixed opinions and views on raw eggs. I was wondering if anyone had read any articles on it. I found one here: http://www.fnri.dost.gov.ph/htm/eggmyths.htm

[daf2]

The only place that i have heard raw eggs are not digested has been on forums, never in an article or reputbale source.

[YellowJacket]

The only place that i have heard raw eggs are not digested has been on forums, never in an article or reputbale source.

So forums and abstracts from peer review journals are now irrelevant? I used to think that it was common knowledge that eating raw eggs was pointless and in fact dangerous. Goes to show that common knowledge isnt always so common.

[daf2]

thanks...that was exactly what i was looking for. I always ate eggs cooked but for a few years i was having them in my morning shake raw and i was criticized by several people so i was heistant to continue.

good info

[daf2]

yes i will continue to eat them raw. most times i have at least three in the morning with my shake, but sometimes ill decide to cook them. I ate them raw for the past three plus years or so except the past couple months.

[Curls4dGirls]

Addressing the fear of salmonella contamination, it is important to understand where the fear comes from. Some eggs are contaminated with salmonella, but the cause comes from a chicken that is unhealthy. It is also important to mention that the average infected egg is only one in 30,000. Even though the odds of eating an infected egg in your lifetime is realitively small, if

Based on your stat, if you eat 3 raw eggs per day 5 days per week for 1 year, then your chances of salmonella infection are 1 in 40.

If you eat raw eggs at that rate for 5 years, then your chances of salmonella infection increase to 1 in 8. For 10 years, 1 in 4.

:bbq:

[Control]

Based on your stat, if you eat 3 raw eggs per day 5 days per week for 1 year, then your chances of salmonella infection are 1 in 40.

If you eat raw eggs at that rate for 5 years, then your chances of salmonella infection increase to 1 in 8. For 10 years, 1 in 4.

:bbq:

Check out the big brain on Brad! :bravonew:

[YellowJacket]

yes i will continue to eat them raw. most times i have at least three in the morning with my shake, but sometimes ill decide to cook them. I ate them raw for the past three plus years or so except the past couple months.

Not to mention all 3 of them are going to waste.

[Severedties]

So forums and abstracts from peer review journals are now irrelevant? I used to think that it was common knowledge that eating raw eggs was pointless and in fact dangerous. Goes to show that common knowledge isnt always so common.

\
Where are the abstracts from the peer review journals. Nobody has posted them up. So the only info in this thread, specifies that it is fine to eat them raw.

[Chadd77]

Check out the big brain on Brad! :bravonew:

Great movie!




Sorry... Back to the egg discussion. :D

[Friggemall]

Biotin, also known as vitamin H or B7 and C10H16N2O3S (Biotin; Coenzyme R, Biopeiderm), is a water-soluble B-complex vitamin which is composed of an ureido ring fused with a tetrahydrothiophene ring. A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin is important in the catalysis of essential metabolic reactions to synthesize fatty acids, in gluconeogenesis, and to metabolize leucine. It is commonly found in pyruvate dehydrogenase as a carrier of HCO3-.

General overview

Biotin is used in cell growth, the production of fatty acids, metabolism of fats, and amino acids. It plays a role in the Krebs Cycle, which is the process in which energy is released from food. Biotin not only assists in various metabolic chemical conversions, but also helps with the transfer of carbon dioxide. Biotin is also helpful in maintaining a steady blood sugar level. Biotin is often recommended for strengthening hair and nails. Consequently, it is found in many cosmetic and health products for the hair and skin.

Hair problems

Biotin supplements are often recommended as a natural product to counteract the problem of hair loss in both children and adults. However, there are no studies that show any benefit in any case where the subject is not actually biotin deficient. The signs and symptoms of biotin deficiency include hair loss which progresses in severity to include loss of eye lashes and eye brows in severely deficient subjects. Of note, shampoos that include biotin might be more effective if they were drunk instead of poured over the head as the absorption of biotin through the skin is limited (but drinking shampoo might cause other problems that would offset any hair growth benefit).

Cradle cap (seborrheic dermatitis)

Children with a rare inherited metabolic disorder called phenylketonuria (PKU; in which one is unable to break down the amino acid phenylalanine) often develop skin conditions such as eczema and seborrheic dermatitis in areas of the body other than the scalp. The scaly skin changes that occur in people with PKU may be related to poor ability to use biotin. Increasing dietary biotin in the diet has been known to improve seborrheic dermatitis in these cases.

Diabetes

People with type 2 diabetes often have low levels of biotin. Biotin may be involved in the synthesis and release of insulin. Preliminary studies in both animals and people suggest that biotin may help improve blood sugar control in those with diabetes, particularly type 2 diabetes.

Biotin deficiency

Biotin deficiency is a rare nutritional disorder caused by a deficiency of biotin. Biotin deficiency can have a very serious, even fatal, outcome if it is allowed to progress without treatment. Signs and symptoms of biotin deficiency can develop in persons of any age, race, or gender. Biotin deficiency rarely occurs in healthy individuals, since the daily requirements of biotin are low, many foods contain adequate amounts, intestinal bacteria synthesize small amounts, and the body effectively scavenges and recycles biotin from bodily waste. However, deficiency can be caused by excessive consumption of raw egg-whites over a long period (months to years). Egg-whites contain high levels of avidin, a protein that binds biotin stongly. Once a biotin-avidin complex forms, the bond is essentially irreversible. The biotin-avidin complex is not broken down nor liberated during digestion, and the biotin-avidin complex is lost in the feces. Once cooked, the egg-white avidin becomes denatured and entirely non-toxic.

Initial symptoms of biotin deficiency include:

1. Dry skin
2. Seborrheic dermatitis
3. Fungal infections
4. Rashes including erythematous periorofacial macular rash
5. Fine and brittle hair
6. Hair loss or total alopecia

If left untreated, neurological symptoms can develop, including:

1. Mild depression, which may progress to profound lassitude and, eventually, to somnolence
2. Changes in mental status
3. Generalized muscular pains (myalgias)
4. Hyperesthesias and paresthesias

The treatment for biotin deficiency is to simply start taking some biotin supplements.

Biochemistry

Biotin is a cofactor responsible for carbon dioxide transfer in several carboxylase enzymes:

* Acetyl-CoA carboxylase
* Methylcrotonyl-CoA carboxylase
* Propionyl-CoA carboxylase
* Pyruvate carboxylase

The attachment of biotin to various proteins, called biotinylation, is an important process in DNA transcription and replication.

Biotin binds very tightly to the tetrameric protein streptavidin, with a dissociation constant Kd in the order of 10-14M. This is often used in different biotechological applications. Until 2005, very harsh conditions were required to break the biotin-streptavidin bond (Holmberg et al, 2005).

[Friggemall]

BIOTIN

Biotin is a water-soluble vitamin, generally classified as a B-complex vitamin. After the initial discovery of biotin, nearly forty years of research were required to establish it as a vitamin (1). Biotin is required by all organisms but can only be synthesized by bacteria, yeasts, molds, algae, and some plant species (2).

FUNCTION

In its physiologically active form biotin is attached at the active site of four important enzymes, known as carboxylases (3). Each carboxylase catalyzes an essential metabolic reaction.

Acetyl-CoA carboxylase catalyzes the binding of bicarbonate to acetyl-CoA to form malonyl-CoA. Malonyl-CoA is required for the synthesis of fatty acids.
Pyruvate carboxylase is a critical enzyme in gluconeogenesis, the formation of glucose from sources other than carbohydrates, for example, amino acids and fats.
Methylcrotonyl-CoA carboxylase catalyzes an essential step in the metabolism of leucine, an indispensable (essential) amino acid.
Propionyl-CoA carboxylase catalyzes essential steps in the metabolism of amino acids, cholesterol, and odd chain fatty acids (fatty acids with an odd number of carbon molecules) (4).

Histones are proteins that bind to DNA and package it into compact structures to form chromosomes. The compact packaging of DNA must be relaxed somewhat for DNA replication and transcription to occur. Modification of histones through the attachment of acetyl or methyl groups (acetylation or methylation) has been shown to affect the structure of histones, thereby affecting replication and transcription of DNA. The attachment of biotin to another molecule, such as a protein, is known as "biotinylation". The enzyme biotinidase has recently been shown to catalyze the biotinylation of histones, suggesting that biotin may play a role in DNA replication and transcription (5,6).

DEFICIENCY

Although biotin deficiency is very rare, the human requirement for dietary biotin has been demonstrated in two different situations: prolonged intravenous feeding without biotin supplementation and consumption of raw egg white for a prolonged period (many weeks to years). Avidin is a protein found in egg white, which binds biotin and prevents its absorption. Cooking egg white denatures avidin, rendering it susceptible to digestion, and unable to prevent the absorption of dietary biotin (7).

Symptoms

Symptoms of overt biotin deficiency include hair loss and a scaly red rash around the eyes, nose, mouth, and genital area. Neurologic symptoms in adults have included depression, lethargy, hallucination, and numbness and tingling of the extremities. The characteristic facial rash, together with an unusual facial fat distribution, have been termed the "biotin deficient face" by some experts (7). Individuals with hereditary disorders of biotin metabolism resulting in functional biotin deficiency have evidence of impaired immune system function, including increased susceptibility to bacterial and fungal infections (8).

Predisposing conditions

Two hereditary disorders, biotinidase deficiency and holocarboxylase synthetase (HCS) deficiency, result in an increased biotin requirement. Biotinidase is an enzyme that catalyzes the release of biotin from small proteins and the amino acid, lysine, thereby recycling biotin. There are several ways in which biotinidase deficiency leads to biotin deficiency. Intestinal absorption is decreased because a lack of biotinidase inhibits the release of biotin from dietary protein. Recycling of one's own biotin bound to protein is impaired, and urinary loss of biotin is increased because the kidneys appear to excrete biotin that is not bound to biotinidase more rapidly (5,7). Biotinidase deficiency sometimes requires supplementation of as much as 5 to 10 milligrams (mg) of oral biotin/day, though smaller doses are often sufficient. HCS is an enzyme that catalyzes the attachment of biotin to all four carboxylase enzymes (see Function). HCS deficiency results in decreased formation of all carboxylases at normal blood levels of biotin, and requires high-dose supplementation of 40 to 100 mg of biotin/day. In general, the prognosis of both disorders is good if biotin therapy is introduced early (infancy or childhood) and continued for life (8).

Aside from prolonged consumption of raw egg white or intravenous feedings lacking biotin, other conditions may increase the risk of biotin depletion. The rapidly dividing cells of the developing fetus require biotin for DNA replication and synthesis of essential carboxylases, thereby increasing the biotin requirement in pregnancy. Recent research suggests that a substantial number of women develop marginal or subclinical biotin deficiency during normal pregnancy (6,9). Some types of liver disease may also increase the requirement for biotin. A recent study of 62 children with chronic liver disease and 27 healthy controls found serum biotinidase activity to be abnormally low in those with severely impaired liver function due to cirrhosis (10). Anticonvulsant medications, used to prevent seizures in individuals with epilepsy, increase the risk of biotin depletion (11,12). See Safety for more information on biotin and anticonvulsants.

The Adequate Intake (AI)

In 1998 the Food and Nutrition Board of the Institute of Medicine felt the existing scientific evidence was insufficient to calculate an RDA for biotin, so they set an Adequate Intake level (AI). The AI for biotin assumes that current average intakes of biotin (35 mcg to 60 mcg/day) are meeting the dietary requirement (1).
Adequate Intake (AI) for Biotin
Life Stage Age Males (mcg/day) Females (mcg/day)
Infants 0-6 months 5 5
Infants 7-12 months 6 6
Children 1-3 years 8 8
Children 4-8 years 12 12
Children 9-13 years 20 20
Adolescents 14-18 years 25 25
Adults 19 years and older 30 30
Pregnancy all ages - 30
Breastfeeding all ages - 35

DISEASE PREVENTION

Birth defects

Recent research indicates that biotin is broken down more rapidly during pregnancy and that biotin nutritional status declines during the course of pregnancy (6). In 6 out of 13 women studied biotin excretion dropped below the normal range during late pregnancy, suggesting that their biotin status was abnormally low. Approximately half of pregnant women have abnormally high excretion of a metabolite (3-hydroxyisovaleric acid) thought to reflect decreased activity of a biotin-dependent enzyme. A recent study of 26 pregnant women found that biotin supplementation decreased the excretion of this metabolite compared to placebo, suggesting that marginal biotin deficiency is relatively common in pregnancy (9). Although the level of biotin depletion was not severe enough to cause symptoms, it was reason for concern because subclinical biotin deficiency has been shown to cause birth defects in several animal species (11). There exists no direct evidence that marginal biotin deficiency causes birth defects in humans. However, the potential risk for biotin depletion makes it prudent to ensure adequate biotin intake throughout pregnancy. Since pregnant women are advised to consume supplemental folic acid prior to and during pregnancy (see Folic Acid) to prevent neural tube defects, it would be easy to consume supplemental biotin (at least 30 mcg/day) in the form of a multivitamin that also contains at least 400 mcg of folic acid.

DISEASE TREATMENT

Diabetes mellitus

It has been known for many years that overt biotin deficiency results in impaired utilization of glucose (13). Blood biotin levels were significantly lower in 43 patients with non-insulin dependent diabetes mellitus (NIDDM) than in non-diabetic control subjects, and lower fasting blood glucose levels were associated with higher blood biotin levels. After one month of biotin supplementation (9 mg/day) fasting blood glucose levels decreased by an average of 45% (14). Reductions in blood glucose levels were also found in 7 insulin-dependent diabetics after 1 week of supplementation with 16 mg of biotin daily (15). Several mechanisms could explain the glucose-lowering effect of biotin. As a cofactor of enzymes required for fatty acid synthesis, biotin may increase the utilization of glucose to synthesize fats. Biotin has been found to stimulate glucokinase, an enzyme in the liver, resulting in increased synthesis of glycogen, the storage form of glucose. Biotin has also been found to stimulate the secretion of insulin in the pancreas of rats, which also has the effect of lowering blood glucose (16). An effect on cellular glucose (GLUT) transporters is also currently under investigation. Presently, studies of the effect of supplemental biotin on blood glucose levels in humans are extremely limited, but they highlight the need for further research.

Brittle fingernails

The finding that biotin supplements were effective in treating hoof abnormalities in horses and swine led to speculation that biotin supplements might also be helpful in strengthening brittle fingernails in humans. Three uncontrolled trials examining the effects of biotin supplementation (2.5 mg/day for up to six months) in women with brittle fingernails have been published (16-18). In two of the trials, subjective evidence of clinical improvement was reported in 67-91% of the participants available for follow-up at the end of the treatment period (16, 17). One trial that used scanning electron microscopy to assess fingernail thickness and splitting found that fingernail thickness increased by 25% and splitting decreased after biotin supplementation (18). Although the results of these small uncontrolled trials suggest that biotin supplements may be helpful in strengthening brittle nails, larger placebo-controlled trials are needed to assess the efficacy of high-dose biotin supplementation for the treatment of brittle fingernails.

Hair loss

Although hair loss is a symptom of severe biotin deficiency (see Deficiency), there are no published scientific studies that support the claim that high-dose biotin supplements are effective in preventing or treating hair loss in men or women.

SOURCES

Food sources

Biotin is found in many foods, but generally in lower amounts than other water-soluble vitamins. Egg yolk, liver, and yeast are rich sources of biotin. Large national nutritional surveys in the U.S. were unable to estimate biotin intake due to the scarcity of data on the biotin content of food. Smaller studies estimate average daily intakes of biotin to be from 40 to 60 mcg/day in adults (1). The table below lists some richer sources of biotin along with their content in micrograms (mcg) (20).
Food Serving Biotin (mcg)
Yeast, bakers active 1 packet (7 grams) 14
Wheat bran, crude 1 ounce 14
Bread, whole wheat 1 slice 6
Egg, cooked 1 large 25
Cheese, camembert 1 ounce 6
Cheese, cheddar 1 ounce 2
Liver, cooked 3 ounces* 27
Chicken, cooked 3 ounces* 3
Pork, cooked 3 ounces* 2
Salmon, cooked 3 ounces* 4
Avocado 1 whole 6
Raspberries 1 cup 2
Artichoke, cooked 1 medium 2
Cauliflower, raw 1 cup 4

*A 3-ounce serving of meat is about the size of a deck of cards.

Bacterial synthesis

The bacteria that normally colonize the colon (large intestine) are capable of making their own biotin. It is not yet known whether humans can absorb a meaningful amount of the biotin synthesized by their own intestinal bacteria. However, a specialized process for the uptake of biotin has been identified in cultured cells derived from the lining of the colon, suggesting that humans may be able to absorb biotin produced by the bacteria normally present in the large intestine (21).

SAFETY

Toxicity

Biotin is not known to be toxic. Oral biotin supplementation has been well-tolerated in doses up to 200 mg/day in people with hereditary disorders of biotin metabolism (1). In people without disorders of biotin metabolism, doses of up to 5 mg/day for two years were not associated with adverse effects (22). However, there is one case report of life-threatening eosinophilic pleuropericardial effusion in an elderly woman who took a combination of 10 mg/day of biotin and 300 mg/day of pantothenic acid for two months (23). Due to the lack of reports of adverse effects when the Dietary Reference Intakes (DRI) were established for biotin in 1998, the Institute of Medicine did not establish a tolerable upper level of intake (UL) for biotin (1). Note: 1 mg = 1,000 mcg.

Drug interactions

Individuals on long-term anticonvulsant (anti-seizure) therapy have been found to have reduced levels of biotin in their blood, and urinary excretion of organic acids consistent with decreased carboxylase activity (2). The anticonvulsants, primidone and carbamazepine, inhibit biotin absorption in the small intestine. Phenobarbital, phentyoin, and carbamazepine appear to increase urinary excretion of biotin. Use of the anti-convulsant, valproic acid, has been associated with decreased biotinidase activity in children (12). Long-term treatment with sulfa drugs or other antibiotics may decrease bacterial synthesis of biotin, potentially increasing the requirement for dietary biotin. Large doses of the nutrient, pantothenic acid, have the potential to compete with biotin for intestinal and cellular uptake due to their similar structures. Very high (pharmacologic) doses of lipoic acid have been found to decrease the activity of biotin-dependent carboxylases in rats, but such an effect has not been demonstrated in humans (4, 24).

LINUS PAULING INSTITUTE RECOMMENDATION

Little is known regarding the amount of dietary biotin required to promote optimal health or prevent chronic disease. The Linus Pauling Institute supports the recommendation by the Food and Nutrition Board of 30 micrograms (mcg) of biotin/day for adults. A varied diet should provide enough biotin for most people. However, following the Linus Pauling Institute recommendation to take a daily multivitamin/multimineral supplement will generally provide an intake of at least 30 mcg of biotin/day.

Older adults (65 years and older)

Presently, there is no indication that older adults have an increased requirement for biotin. If dietary biotin intake is not sufficient, a daily multivitamin/multimineral supplement will generally provide an intake of at least 30 mcg of biotin/day.

REFERENCES

Written by:
Jane Higdon, Ph.D.
Linus Pauling Institute
Oregon State University

Reviewed by:
Donald Mock, M.D., Ph.D.
Professor
Departments of Biochemistry and Molecular Biology and Pediatrics
University of Arkansas for Medical Sciences

Last updated 06/01/2004 Copyright 2000-2004 Linus Pauling Institute

Disclaimer

The Linus Pauling Institute Micronutrient Information Center provides scientific information on health aspects of micronutrients and phytochemicals for the general public. The information is made available with the understanding that the author and publisher are not providing medical, psychological, or nutritional counseling services on this site. The information should not be used in place of a consultation with a competent health care or nutrition professional.

The information on micronutrients and phytochemicals contained on this Web site does not cover all possible uses, actions, precautions, side effects, and interactions. It is not intended as medical advice for individual problems. Liability for individual actions or omissions based upon the contents of this site is expressly disclaimed.

[Friggemall]

I eat raw egg whites mostly through the week though when I'm late, I do cook my eggs on most weekends when I have more time.

[Shibby]

I didn't see where any of that said anything about the protien needing heat or not to make the protien useful.

[Severedties]

I didn't see where any of that said anything about the protien needing heat or not to make the protien useful.

Me either.

I agree it might be unhealthy to eat raw eggs, becasue of the bacterial contamination. But, nobody has ever shown anything that would explain why your body could not digest uncooked egg. Protein is digested in the stomach by acid, this is done independant of heat.