Why the Egg-Cancer Link?
Two million men in the U.S. are living with prostate cancer — but that’s better than dying from prostate cancer. Catch it when it’s localized and the five-year survival is practically guaranteed, but once it really starts spreading, chances drop to one in three. “Thus, identification of modifiable factors that affect the progression of prostate cancer is something that deserves study,” noted Dr. Erin Richard and colleagues at Harvard. So, they took more than a thousand men with early stage prostate cancer and followed them for a couple years to see if there was anything in their diet associated with a resurgence of the cancer, such as spreading to the bone.
Compared to men who hardly ate any eggs, men who ate even less than a single egg a day had a significant 2-fold increased risk of prostate cancer progression. The only thing worse was poultry consumption, with up to four times the risk of progression among high-risk men. They think it might be the cooked meat carcinogens that for some reason build up more in chicken and turkey muscle than in other meats. For more on these so-called heterocyclic amines, see my videos: Heterocyclic Amines in Eggs, Cheese, and Creatine?, Estrogenic Cooked Meat Carcinogens, and PhIP: The Three Strikes Breast Carcinogen.
But what about the eggs? Why would less than once-a-day egg consumption double the risk of cancer progression? “A plausible mechanism that may explain the association between eggs and prostate cancer progression is high dietary choline,” the researchers suggested. Egg consumption is a determinant of how much choline you have in your blood, and higher blood choline has been associated with a greater risk of getting prostate cancer in the first place. So the choline in eggs may both increase one’s risk of getting it and having it spread.
Studies have associated choline consumption not just with getting cancer and spreading cancer, but also with significantly increased risk of dying from it. Those who ate the most had a 70% increased risk of lethal prostate cancer. Another recent study found that men who consumed two and a half or more eggs per week — that’s just like one egg every three days — had an 81 percent increased risk of lethal prostate cancer.
Maybe that’s why meat, milk, and eggs have all been associated with advanced prostate cancer—because of the choline. Choline is so concentrated in cancer cells that doctors can follow choline uptake to track the spread of cancer throughout the body. But why may dietary choline increase the risk of lethal prostate cancer? Dietary choline is converted in the gut to trimethylamine (see my video Carnitine, Choline, Cancer and Cholesterol: The TMAO Connection), so the Harvard researchers speculated that the TMAO from the high dietary choline intake may increase inflammation, which may promote progression of prostate cancer to a lethal disease.
In one of my videos, Eggs and Choline: Something Fishy, I talked about what trimethylamine might do to one’s body odor.
In the New England Journal of Medicine, the same Cleveland Clinic research team that did the famous study on carnitine repeated the study, but instead of feeding people a steak, they fed people some hard-boiled eggs. Just as they suspected, a similar spike in that toxic TMAO. So it’s not just red meat. And the link between TMAO levels in the blood and strokes, heart attacks, and death was seen even in low-risk groups like those with low-risk cholesterol levels. Thus, because of the choline, eating eggs may increase our risk regardless of what our cholesterol is.
It’s ironic that the choline content of eggs is something the egg industry actually boasts about. And the industry is aware of the cancer data. Through the Freedom of Information Act, I was able to get my hands on an email (which you can view in my video, Eggs, Choline, and Cancer) from the executive director of the industry’s Egg Nutrition Center to an American Egg Board executive talking about how choline may be a culprit in promoting cancer progression. “Certainly worth keeping in mind,” he said, “as we continue to promote choline as another good reason to consume eggs.”
With regard to the prevention of prostate cancer progression, chicken and eggs may be the worst foods to eat, but what might be the best? See my video Prostate Cancer Survival: The A/V Ratio.
To prevent prostate cancer in the first place, see videos such as:
- Reducing Cancer Risk In Meateaters
- Industrial Carcinogens in Animal Fat
- Is It the Diet, the Exercise, or Both?
What about reversing cancer progression? See Dr. Ornish’s work Cancer Reversal Through Diet?, followed up by the Pritikin Foundation: Ex Vivo Cancer Proliferation Bioassay. Flax may help as well (Flaxseed vs. Prostate Cancer).
-Michael Greger, M.D.