28 replies to this topic

[oehaut]

Egg consumption and the risk of cancer: a multisite case-control study in Uruguay.

BACKGROUND: Previous studies have suggested that egg consumption may increase the risk of colorectal cancer and some other cancers. However, the evidence is still limited. To further explore the association between egg intake and cancer risk we conducted a case-control study of 11 cancer sites in Uruguay between 1996 and 2004, including 3,539 cancer cases and 2,032 hospital controls.

RESULTS: In the multivariable model with adjustment for age, sex (when applicable), residence, education, income, interviewer, smoking, alcohol intake, intake of fruits and vegetables, grains, dairy products, fatty foods, meat, energy intake and BMI, there was a significant increase in the odds of cancers of the oral cavity and pharynx (OR= 2.02, 95% CI: 1.19-3.44), upper aerodigestive tract (OR= 1.67, 95% CI: 1.17-2.37), colorectum (OR= 1.64, 95% CI: 1.02-2.63), lung (OR= 1.59, 95% CI: 1.10-2.29), breast (OR= 2.86, 95% CI: 1.66-4.92), prostate (OR= 1.89, 95% CI: 1.15-3.10), bladder (OR= 2.23, 95% CI: 1.30-3.83) and all cancer sites combined (OR= 1.71, 95% CI: 1.35-2.17) with a high vs low egg intake.

CONCLUSIONS: We found an association between higher intake of eggs and increased risk of several cancers. Further prospective studies of these associations are warranted.

[Skötkonung]

Any speculation on the possible mechanism?

This is an interesting look at the China Study and egg consumption:
http://rawfoodsos.co...ggs-and-diseas/

[oehaut]

Any speculation on the possible mechanism?

I don't

I'm trying to download the paper from the website but it keeps saying that i'm missing plugins. I believe the authors must be giving a plausible explanation.

Maybe you can manage to get it, here

[rwac]

There ya go. Gotta go to the page source.

Attached Files

•  869.pdf   50.92KB   163 downloads

[kismet]

Wow, borderline increased risk at 0-3.5 egg/week. Skimming the paper, this looks pretty solid as far as case-control data goes. Bummer.

[Sillewater]

It does look like a really well-done case-control. Here's a excerpt on the mechanism:

As to the mechanism that may explain a possible detrimental effect of egg intake upon cancer risk the most plausible explanation involves the high cholesterol content of eggs. Higher intake of cholesterol has been shown to increase the formation of secondary bile acids in both humans and animals (Cruse et al., 1979; Hiramatsu et al., 1983) and to enhance the induction of colorectal tumors in animal models (Sakaguchi et al., 1986)....... Our finding that adjustment for cholesterol intake slightly strengthened the association between egg intake and cancer risk suggests that other factors than cholesterol may account for the positive associations we observed. Eggs can also be a source of heterocyclic amines which are formed during high temperature cooking (Layton et al., 1995), however, this mechanism is unlikely to explain much of the elevated risk because most of the results were similarly elevated for both fried eggs and boiled eggs. As for the other cancer sites, we are currently not able to point to a biologically plausible mechanism.

It could be that the bile acids play a role (I provide various links in my blog over here: http://hanswuhealth....e-on-fiber.html).

I also thought it could be the oxycholesterol but they found similiar effects for both fried and boiled eggs. Maybe there is a threshold effect and boiling eggs is enough, or maybe its just that increasing dietary intake of cholesterol is enough (dietary cholesterol does increase cholesterol levels in those with low intakes, e.g. vegetarians, Seventh Day Adventists). This is a great study because of the wide variety of dietary intakes in Paraguay (as mentioned in the paper). Other cancers may result from lysosomal accumulation and dysfunction (1). This is something I came upon while looking at abstracts from Futuremedicine (interesting articles there all the time). And Knopp et al also has some interesting findings (beyond just that in insulin sensitive folks dietary cholesterol increases serum cholesterol). In (2) they found increased CRP and amyloid A. Whether CRP plays an important role as a biomarker is yet to be determine (3). Also (3) has some interesting data for those inclined.

The paper also has some other interesting data such as alcohol intake decreased risk, and also meat intake decreased risk. However both was not significant.

[1] http://www.futuremed...journalCode=clp

[2] Circulation. 2005 Jun 14;111(23):3058-62. Epub 2005 Jun 6.Cholesterol feeding increases C-reactive protein and serum amyloid A levels in lean insulin-sensitive subjects.Tannock LR, O'Brien KD, Knopp RH, Retzlaff B, Fish B, Wener MH, Kahn SE, Chait A.

[3] J Am Coll Cardiol. 2010 Sep 21;56(13):1034-41.Association of combinations of lipid parameters with carotid intima-media thickness and coronary artery calcium in the MESA (Multi-Ethnic Study of Atherosclerosis).Paramsothy P, Knopp RH, Bertoni AG, Blumenthal RS, Wasserman BA, Tsai MY, Rue T, Wong ND, Heckbert SR.

[Skötkonung]

The types of cancer are strange... oral cavity and pharynx? What ingredient of eggs could be causing cancers of the digestive track, the oral cavity in particular.

• Other lifestyle factors not corrected for by the study authors (they mentioned most participants are low-income)
• Oxycholesterol (are these carcinogenic?)
• Contaminants (PCBs, Dixons, pesticides, etc)
• Glycotoxins such as heterocyclic amines (we know these are carcinogenic)

Perhaps some combination of the above? Poor people buy cheap factory eggs (contaminated) and fry them up (oxidated cholesterol, glycotoxins). But then again, they found similar associations with boiled eggs.

The authors propose that cholesterol intake is what causes cancer, but it is my understanding that cholesterol intake (in many people) has little influence on total cholesterol. Is it possible that hyper-responders to dietary cholesterol are causing cancer incidence to be higher in the egg consuming group? I don't know.. But I love my eggs

[Sillewater]

The authors propose that cholesterol intake is what causes cancer, but it is my understanding that cholesterol intake (in many people) has little influence on total cholesterol. Is it possible that hyper-responders to dietary cholesterol are causing cancer incidence to be higher in the egg consuming group? I don't know.. But I love my eggs

If you look up some of Knopp et al stuff on cholesterol they found that in insulin sensitive folks dietary cholesterol does raise serum cholesterol. Also in folks with already low cholesterol, dietary cholesterol raises serum cholesterol (look for study done on Seventh Day Adventist). Maybe something to do with absorption Knopp suggests that insulin resistance decreases absorption, or has to do with the fact that in most people they already consume a lot of choletserol and one egg doesn't matter (Seventh Day Adventists are vegetarian). I also don't see any baseline, but since its a poor country they may not get a lot of choletserol in their diet anyways, thus making them a good group to study dietary cholesterol.

Edited by Sillewater, 21 March 2011 - 08:07 PM.

[Skötkonung]

The authors propose that cholesterol intake is what causes cancer, but it is my understanding that cholesterol intake (in many people) has little influence on total cholesterol. Is it possible that hyper-responders to dietary cholesterol are causing cancer incidence to be higher in the egg consuming group? I don't know.. But I love my eggs

If you look up some of Knopp et al stuff on cholesterol they found that in insulin sensitive folks dietary cholesterol does raise serum cholesterol. Also in folks with already low cholesterol, dietary cholesterol raises serum cholesterol (look for study done on Seventh Day Adventist). Maybe something to do with absorption Knopp suggests that insulin resistance decreases absorption, or has to do with the fact that in most people they already consume a lot of choletserol and one egg doesn't matter (Seventh Day Adventists are vegetarian). I also don't see any baseline, but since its a poor country they may not get a lot of choletserol in their diet anyways, thus making them a good group to study dietary cholesterol.

The idea that insulin sensitivity is some how connected to cholesterol uptake doesn't make sense to me.

Cholesterol researcher Dr. Maria Luz Fernandez of the University of Connecticut's Department of Nutritional Sciences summarized the results of a number of studies testing the effects of egg consumption on blood cholesterol levels. In children aged 10-12, in men aged 20-50, in premenopausal and postmenopausal women, in whites and hispanics, the same basic finding persists: two or three eggs per day has little or no effect on the blood cholesterol levels of over two thirds of the population.

Dietary cholesterol provided by eggs and plasma lipoproteins in healthy populations.
"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."

When hyperresponders (which constitute less than a third of the population) eat egg yolks, their cholesterol levels do go up. LDL, and HDL both go up equally, so there is no change in the ratio of LDL to HDL, or of LDL to total cholesterol, both of which are considered better measures of the risk of heart disease than the total concentration of cholesterol.

Edited by Skötkonung, 21 March 2011 - 11:09 PM.

[yoyo]

I would be interested in arachadonic acid as a causal mechanism.

Do the cells lining upper GI tract get their energy from circulatory system or do they directly absorb from food?

[Sillewater]

The idea that insulin sensitivity is some how connected to cholesterol uptake doesn't make sense to me.

Cholesterol researcher Dr. Maria Luz Fernandez of the University of Connecticut's Department of Nutritional Sciences summarized the results of a number of studies testing the effects of egg consumption on blood cholesterol levels. In children aged 10-12, in men aged 20-50, in premenopausal and postmenopausal women, in whites and hispanics, the same basic finding persists: two or three eggs per day has little or no effect on the blood cholesterol levels of over two thirds of the population.

Another study carried out in 18 healthy lacto-vegetarian Indians demonstrated an increase in blood cholesterol in subjects after 4 weeks of consuming one boiled egg per day [23]. However, the mean LDL-C and HDL-C were not different after 8 weeks of egg consumption although some hyperresponders still presented elevations in total cholesterol after this period of time [23].

To evaluate whether insulin resistance with or without obesity influences the response to dietary cholesterol [24], 197 healthy subjects participated in a randomized crossover design and were fed no, two or four eggs per day for 4 weeks with a 1 month washout between periods. The subjects were classified as insulin-sensitive (n = 65), insulin-resistant (n = 75) and obese insulin-resistant (n = 58). Insulin-resistant and insulin-sensitive subjects had a significant increase in LDL-C of 7.8 and 3.3% only, respectively, after consuming four eggs while obese insulin-resistant subjects had no changes in LDL-C when consuming no, two or four eggs. In contrast HDL-C was significantly increased for all groups even after the consumption of two eggs. These studies suggest that dietary management of obese insulin-resistant individuals could focus more on restricting calories rather than dietary cholesterol [24].

While insulin resistant and sensitive (I'm assuming non-obese) experienced increase. Would like more baseline data though.

[Skötkonung]

3.3% is pretty insignificant. If you had a LDL-C measurement of 100 mg/dL, that would be a increase of 3.3. Plus HDL went up comparatively more, so it looks like the ratio between HDL and LDL improved.

I think eggs are probably contaminated by industrial pollutants, judging by the types of cancers associated with egg consumption. They are by proportion (over 70%) largely fat and fat is a good carrier for PCBs. Chicken feed is often contaminated with these pollutants and it is probably concentrated in the chicken's eggs... just as it is concentrated in the milk of cows that eat similarly contaminated foods. Think about how many egg recalls have been issued due to contaminated feed...

Recently there was a UK / Germany egg recall for unacceptably high levels of industrial pollutants.

Update on dioxin contamination of pasteurised liquid eggs

Friday 7 January 2011
quiche

The Food Standards Agency is providing further information about the distribution of pasteurised liquid whole egg to the UK from the Netherlands that may have been made with eggs contaminated with dioxins.

The pasteurised liquid whole egg (that is including the white and yolk) was produced using eggs from Germany that could contain levels of dioxins that are above the legal limits. These eggs were subsequently mixed with non-contaminated eggs to produce pasteurised liquid egg, an ingredient used widely in the manufacturer of cakes.

This pasteurised liquid egg has been supplied to two manufacturers in the UK. These are:

* Kensey Foods, Cornwall – a division of Samworth Brothers
* Memory Lane Cakes Ltd, Cardiff – a division of Finsbury Food Group

These manufacturers used the pasteurised liquid egg to produce a range of short shelf life cakes and quiches, which were supplied to the major UK supermarkets.

There is no food safety risk from eating these products. The majority of products will have been sold and most have passed their 'use by' or 'best before' dates. In light of this information some supermarkets are choosing to voluntarily remove the small amount of products that are still in date.*
The science behind the story

Dioxins and polychlorinated biphenyls (PCBs) are chemicals that get into our food from the environment. They have no immediate effect on our health but can cause problems if they are absorbed into our bodies at high levels for long periods.

Foods high in animal fat, such as milk, meat, fish and eggs (and foods produced with them) are the main source of dioxins and PCBs although all foods contains at least low levels of these chemicals. The levels of dioxins and PCBs in any one individual's diet will vary depending on the amounts and types of foods they eat.

The risk to health comes from eating food with high levels of dioxins and PCBs over a long period. They have been shown to cause a wide range of effects in certain animals, including cancer and damage to the immune and reproductive systems, although it appears that people may be less sensitive.

http://www.food.gov....n/dioxinupdate2

A good reason to not eat eggs from a factory farm.

Edited by Skötkonung, 21 March 2011 - 11:50 PM.

[Sillewater]

3.3% is pretty insignificant. If you had a LDL-C measurement of 100 mg/dL, that would be a increase of 3.3. Plus HDL went up comparatively more, so it looks like the ratio between HDL and LDL improved.

I think eggs are probably contaminated by industrial pollutants, judging by the types of cancers associated with egg consumption. They are by proportion (over 70%) largely fat and fat is a good carrier for PCBs. Chicken feed is often contaminated with these pollutants and it is probably concentrated in the chicken's eggs... just as it is concentrated in the milk of cows that eat similarly contaminated foods. Think about how many egg recalls have been issued due to contaminated feed...

I agree that pollutants may play a role.

Regarding the increase in LDL. I would like to see more data regarding that part of the study. Can't draw many conclusions from the sparse numbers they provide.

However this study found similiar numbers:

Arterioscler Thromb Vasc Biol. 2003 Aug 1;23(8):1437-43. Epub 2003 Jun 19.


Effects of insulin resistance and obesity on lipoproteins and sensitivity to egg feeding.
Knopp RH, Retzlaff B, Fish B, Walden C, Wallick S, Anderson M, Aikawa K, Kahn SE.

This one also found increase:

J Nutr. 2006 Apr;136(4):971-6.


High cholesterol intake modifies chylomicron metabolism in normolipidemic young men.
César TB, Oliveira MR, Mesquita CH, Maranhão RC.

But as you say the LDL/HDL ratio was maintained. The only problem I have with this reasoning is the fact that one of HDLs important beneficial effects is to help with the efflux of cholesterol from the cell. If HDL has to increase because LDL increases then to me that is bad. Based on the lysosome paper I cited in my above post (http://www.futuremed...journalCode=clp) if more cholesterol passes through the lysosome more cholesterol can get trapped leading to lysosomal dysfunction and accumulation of various by-products (e.g. lipofuscin).

I think for now it is prudent to keep dietary cholesterol low (not just because of the effects of normal cholesterol but also oxidized cholesterol). For me to consume cholesterol I need evidence that it is indeed beneficial, not just neutral.

[Skötkonung]

I think for now it is prudent to keep dietary cholesterol low (not just because of the effects of normal cholesterol but also oxidized cholesterol). For me to consume cholesterol I need evidence that it is indeed beneficial, not just neutral.

Didn't you just post some evidence of a benefit? Cholesterol favorably raises HDL over LDL. That improves ones cardiovascular risk profile. Fear of oxidized cholesterol seems not well founded and your future medicine article is in vivo (show me evidence in something living).

Edited by Skötkonung, 22 March 2011 - 12:51 AM.

[Sillewater]

Didn't you just post some evidence of a benefit? Cholesterol favorably raises HDL over LDL. That improves ones cardiovascular risk profile. Fear of oxidized cholesterol seems not well founded and your future medicine article is in vivo (show me evidence in something living).

Got none. This is just my take and its as far as I have taken it for now. Maybe in the future I'll realize dietary cholesterol is beneficial

[ajnast4r]

Any speculation on the possible mechanism?

This is an interesting look at the China Study and egg consumption:
http://rawfoodsos.co...ggs-and-diseas/

my guess is the unfavorable change in the distribution of fats & nutrients in grain fed vs pastured or omega3 type eggs.

grain fed eggs have significantly more AA than omega3 or pastured eggs:

http://www.sciencedi...44c7c4a63fef3e3

http://library.wur.n...viewFile/356/75

Edited by ajnast4r, 26 March 2011 - 11:54 PM.

[Forever21]

Not that I consume eggs, but for someone who does, should this study cause his to watch his eggs intake, lower it down perhaps or should he start making sure he's eating orange eggs. (from free-range, grass/flax fed chickens)

[Skötkonung]

Not that I consume eggs, but for someone who does, should this study cause his to watch his eggs intake, lower it down perhaps or should he start making sure he's eating orange eggs. (from free-range, grass/flax fed chickens)

I certainly wouldn't eat eggs that are conventionally produced, and I wouldn't eat any eggs that are preprocessed (powered, heat treated, or separated). And if I was cooking my eggs any other method than hardboiling, I would make sure to use saturated fat / EVOO and not to overcook them.

[Jay]

Any speculation on the possible mechanism?

This is an interesting look at the China Study and egg consumption:
http://rawfoodsos.co...ggs-and-diseas/

my guess is the unfavorable change in the distribution of fats & nutrients in grain fed vs pastured or omega3 type eggs.

grain fed eggs have significantly more AA than omega3 or pastured eggs:

http://www.sciencedi...44c7c4a63fef3e3

http://library.wur.n...viewFile/356/75

Not worried about AA consumption. We get little of it after all -- and less than we used to. LA consumption is a worry though... Just because one of the elongation products of LA is AA doesn't mean that normal dietary AA is bad. I know that was the initial mechanistic speculation but recent evidence (and reevaluation of old evidence) makes that less probable now. I try to select eggs that have less LA.

Edited by Jay, 31 May 2011 - 10:00 PM.

[yoyo]

Any speculation on the possible mechanism?

This is an interesting look at the China Study and egg consumption:
http://rawfoodsos.co...ggs-and-diseas/

my guess is the unfavorable change in the distribution of fats & nutrients in grain fed vs pastured or omega3 type eggs.

grain fed eggs have significantly more AA than omega3 or pastured eggs:

http://www.sciencedi...44c7c4a63fef3e3

http://library.wur.n...viewFile/356/75

Not worried about AA consumption. We get little of it after all -- and less than we used to. LA consumption is a worry though... Just because one of the elongation products of LA is AA doesn't mean that normal dietary AA is bad. I know that was the initial mechanistic speculation but recent evidence (and reevaluation of old evidence) makes that less probable now. I try to select eggs that have less LA.

My impression was we get a lot more, because of increased precursor linoleic fat in our food animals' diets.

If it isn't the AA produced from linoelic fat, what makes it bad? The two other thing of note are it is a precursor to GLA, which seems mostly antiinflammatory, and its rather high potential for oxidation.

[madanthony]

Any speculation on the possible mechanism?

This is an interesting look at the China Study and egg consumption:
http://rawfoodsos.co...ggs-and-diseas/

*I* have always had a speculation about that. Eggs are a prime source of methionine and the average American diet is deficient in B vitamins to handle that methionine. I'll bet if the study took into account homocysteine value and uMMA levels they would find that with adequate active B vitamins (methylfolate, methylcobalamin, P5P, TMG, B2) (also copper, zinc, as used by methionine synthase) that the cancer statistics show cancer only in those w/o proper methylation.
Mad
(I eat eggs every day w/o fail. My family eats eggs every day w/o fail. We don't get cancer.
My homocysteine is 6.1 (perfectamento) and my uMMA is in range).

[Luminosity]

IT'S THE HORMONES IN FACTORY FARMED EGGS.

[InquilineKea]

What if you're an ovo-vegetarian? (or in other words, if you'd otherwise be a vegan if you didn't eat eggs?)

[neue regel]

Egg cholesterol is not that bad at a 2-3 eggs/per week level. Don't be fear-mongeing.

[Danail Bulgaria]

Are there people here, who eat alot of eggs?

[SloMoSandy]

Are there people here, who eat alot of eggs?

About 10-15/a day here... (mostly the whites.. Tho' I eat like one or two yolks too..)..

Edited by VidX, 01 November 2011 - 01:55 PM.

[AgeVivo]

throwing an idea: the egg white is full of methionin => avoid egg white

methionin is needed to make every protein (AAA). slight speculation: more methionin leads to a) more uncontrolled protein synthesis compared to the rate of protein degradation, leading to increased protein amyloidosis and other troubles in the cells => more cancers b) more possibility for cells to develop proteins very fast => for tumors to grow fast
(reminder: methionin-restriction extends mouse and rat lifespan, and is used in hospitals to inhibit tumor growths in humans; seems to lead the cells to spare proteins and recycle them (autophagy))

Edited by AgeVivo, 01 November 2011 - 09:22 PM.

[Danail Bulgaria]

I have another idea: the egg contains cholesterol. Cholesterol is proven to enchance the chances of catching the cancers listed in the beginning of the topic.

[frederickson]

making sweeping lifestyle modifications on the basis of a case-control study is absolutely foolish.

i have not had time to read the full text. can anyone report what covariates were included in the model? observational studies like this are almost invariably flawed by insufficient adjustment for potential confounders. the effects of generally healthy/unhealthy lifestyle practices are rarely fully accounted for in the regression models. since eggs are "unhealthy" in the eyes of the masses, i have a hard time believing that the authors fully adjusted for the lifestyle practices that may have differed between those who avoid eggs "in the name of health". this, along with confirmation bias, is one of the reasons that i think nutritional epidemiology has caused more problems that it has solved. and i am a nutritional epidemiologist