In my recent post on 'Meat', I included two studies by Erin Richman. Those studies also looked at eggs. A natural response to those studies might be to stop eating eggs. I think that a little perspective is called for.
In the Health Professionals Follow-up Study [1]:
"Men who consumed 2.5 or more eggs per week had an 81% increased risk of lethal prostate cancer compared with men who consumed less than 0.5 eggs per week ..."
Relative risk by number of eggs consumed in a week:
<0.5 = 1.00 (reference)
0.5-1.4 = 1.33
1.5-2.4 = 1.49
>2.4 = 1.81
In the CaPSURE study [2]:
"Greater consumption of eggs ... was associated with 2-fold increases in risk in a comparison of extreme quantiles ..."
Relative risk by median number of eggs consumed in a week:
0.4 = 1.00 (reference)
1.0 = 1.17
3.0 = 1.06
5.5 = 2.02
This relative risk table is less well-behaved here. Not sure what one can actually deduce from it, except by ignoring the middle numbers.
Richman notes that:
"egg consumption {was} positively associated with less healthy lifestyle behaviors and worse clinical characteristics, including higher mean BMI, smoking, and Gleason sum 8–10 at diagnosis"
{"less healthy lifestyle behaviors" sounds very judgmental to me, coming from an author who is, essentially, trying to figure out what that means after PCa diagnosis.}
The association with such "lifestyle behaviors" requires that that the analysis control for them. e.g. eliminate any confounding effect of BMI. The extent to which this occurred is not clear.
U.S. per capita egg production in 2014 was 260.7. 40% of eggs go directly to the food industry. One assumes that the studies somehow quantified egg intake from bought baked goods.
Only a small percentage of eggs bought by the end-consumer end up on the breakfast plate, but I don't know the actual fate of the 60% used at home - cookies, cakes, muffins, pancakes, etc, versus a simple over-easy egg. But, it seems to me that context is crucial.
In January, the new "Dietary Guidelines for Americans" was released. [3]:
"... longstanding limits on dietary cholesterol were ... removed, a victory for the nation’s egg producers, which have long argued that cholesterol from eggs ... is not a major health concern."
"For many years, the dietary guidelines have recommended that Americans limit their intake of dietary cholesterol to 300 milligrams a day – slightly less than the amount in two eggs – which scared many people away from egg yolks, shellfish and other cholesterol-rich foods. While the latest guidelines dropped that longstanding limit on dietary cholesterol, the panel also noted that Americans should “eat as little dietary cholesterol as possible” to lower their risk of cardiovascular disease."
"The Physicians Committee for Responsible Medicine, which advocates a vegan diet, announced that they were filing a lawsuit against the government over its decision to drop the 300-milligram cholesterol limit from the guidelines."
While many complain about food industry lobbyists who seek to link production capacity to the food pyramid, thereby ensuring the status quo, I find it especially galling that an activist group of vegan doctors would have any say at all.
But the above story points out a problem with any study of eggs & PCa - health-conscious men have been programmed, over decades, to believe that a daily egg might lead to CVD. Egg abstainers tend to have other "healthy" habits that might confound study findings. We would expect a lower BMI, e.g. Those who eat egg white omelets probably run 5 miles before breakfast & don't light up afterwards. LOL
The case against cholesterol in PCa is very strong. PCa cells have a greater uptake than normal cells. Cholesterol content is associated with aggression. In terms of LDL cholesterol, the VLDL fraction facilitates uptake. But the liver makes a ton of cholesterol & a daily egg is neither here nor there, in terms of total cholesterol.
David Perlmutter MD:
"Cholesterol is vitally important for brain function. While your brain represents about 2-3% of your total body weight, 25% of the cholesterol in your body is found in your brain, where it plays important roles in such things as membrane function, acts as an antioxidant, and serves as the raw material from which we are able to make things like progesterone, estrogen, cortisol, testosterone and even vitamin D."
Realistically, it takes a statin drug to reduce PCa cholesterol, since, if uptake is insufficient, the cells will begin to manufacture it. A statin can stop that.
Richman offers a potential smoking gun other than cholesterol:
"A plausible mechanism that may explain our observed association between eggs and prostate cancer progression is high dietary choline. Egg consumption is a determinant of plasma choline, and higher plasma choline was recently reported to be associated with a greater risk of prostate cancer (50, 51). Malignant prostate cells have higher choline concentrations than do healthy cells, and choline kinase is overexpressed in prostate cancer (52–54). In addition, because of the increased uptake of choline by progressing prostate tumors, radiolabeled choline is used to identify early prostate cancer recurrence (55). No studies have examined dietary choline and prostate cancer risk or progression ..."
Most will know that PCa differs from other cancers in that a radio-labeled glucose PET scan is not very useful for imaging. PCa prefers fatty acids for energy. Choline levels in PCa cells tend to be high. Hence the interest in radio-labeled choline as an imaging agent.
What if we were to limit choline intake? Choline is an essential dietary element. "Most common signs of choline deficiencies are fatty liver and hemorrhagic kidney necrosis." [Wiki] I am certainly not going to flirt with deficiency. Without outright deficiency, PCa cells will be able to take up what they need.
"Choline and its metabolites are needed for three main physiological purposes: structural integrity and signaling roles for cell membranes, cholinergic neurotransmission (acetylcholine synthesis), and a major source for methyl groups via its metabolite, trimethylglycine (betaine), which participates in the S-adenosylmethionine (SAMe) synthesis pathways."
"The adequate intake (AI) of choline ... for adult men is 550 mg/day."
A large egg has 147 mg. [Wiki] Three large eggs = 441 mg - 100 mg short of the daily AI.
(One lb broccoli has 182 mg. 8 oz cod has 180 mg. Is nothing safe? LOL)
From the Richman quote above:
"plasma choline was recently reported to be associated with a greater risk of prostate cancer (50, 51)"
"51" is a spurious link - nothing to do with PCa.
"50" is also spurious, in a sense. Choline is an honary B vitamin. The B vitamins are crucial for maintaining the SAM (aka SAMe) cycle. Deficiencies in folate (or the synthetic folic acid analog) or a cofactor such as vitamin B12, can lead to less SAM. As witnessed by elevated homocysteine.
Adequacy of folate & cofactors lead to SAM sufficiency. SAM is the universal methyl donor in the body. PCa cells have high levels of methyl. The cells want to be hypermethylated. The promoter regions for tumor suppressor genes are methylated (silenced) in most PCa cells.
From study "50" [4]:
"The results of this large prospective study suggest that elevated plasma concentrations of choline and vitamin B2 may be associated with an increased risk of prostate cancer."
Other studies that have looked at one-carbon metabolism (the SAM cycle is part of that) have noted PCa risk with folate or vitamin B12 - or protection from elevated homocysteine. It's all the same thing: it's better if the SAM cycle is impaired. The apparent increased risk with choline is actually the risk that comes with the SAM cycle operating according to specs. It is choline inadequacy that protects.
Low levels of choline may very well be protective against PCa, but that's kind of a scorched earth approach, with risks elsewhere. Well, ADT is something of a scorched earth therapy, so who am I to reject it?
-Patrick
[1] cancerpreventionresearch.aa...
[2] ajcn.nutrition.org/content/...
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