The New York Times online Health section yesterday reported (Gina Kolata) that eggs have been implicated in increasing the risk of heart disease by the same mechanism that evoked fear in meat eaters just two weeks ago.
Trimethylamine N-oxide (TMAO) in the News Again
Researchers found that the lecithin in egg yolks is digested to choline which is metabolized by gut bacteria to become TMA and then to the liver, to trimethylamine N-oxide (TMAO) — the very same substance that is metabolized from the carnitine in red meat. This risk was broadcasted all over the media two weeks ago — causing unnecessary concerns about eating red meat.
In the study published in the New England Journal of Medicine the researchers concluded that,
The production of TMAO from dietary phosphatidylcholine is dependent on metabolism by the intestinal microbiota. Increased TMAO levels are associated with an increased risk of incident major adverse cardiovascular events. (Funded by the National Institutes of Health and others.)
Choline from Egg Yolks is Converted to TMAO by Gut Bacteria
This started out to be a study of the relationship of gut bacteria to cardiovascular risk. Suddenly there are tons of studies involving gut bacteria — which is a good thing — but maybe not.
As I am definitely not an expert at reading some of these technical studies, I take my advice from people who are experts and can pull apart fact from fiction.
Dr. Jeff Leach from the American Gut Project
One of my favorite scientists is Dr. Jeff Leach who is currently running the American Gut Project. If anyone knows about gut bacteria, he does. In his typical charming and humerous writing style, in this article called “From Meat to Microbes to Main street: is it time to trade in your George Foreman Grill?”, he completely debunks the carnitine association to cardiac risk.
To give just one example of his criticism of the study that associated carnitine from red meat with cardiac risk, he discusses the part of the study in the cohort of 2,595 men and women undergoing elective cardiac evaluation. The researchers found an association between TMAO concentrations in serum and cardiovascular risks. The relationship between raised TMAO and caradiac risk was highest in the group/quartile of 650 individuals. Dr. Leach points out the stats of this group:
Average age of this group/quartile was 61, 80% were male, were overweight to obese on average, one out of three had diabetes, 75% were hypertensive, a whopping 77% were smokers, numerous medications like statins and beta-blockers were the norm, and every biomarker of a crappy diet was elevated, as well as biomarkers of inflammation. In short, these folks were a mess.
Dr. Leach goes on to say,
It’s important to note the TMAO association was just that, an association – among many. At this point it might be useful to mention that even though the researchers are focused on red meat, an amazing assortment of foods can generate levels of TMAO higher than that reported for red meat. To name a few: potatoes, peas, peanuts, eggs, mushrooms, bread, squid, prawn, crab, halibut, cod, herring, tuna and an assortment of other fishy things. So, who’s to say that red meat is responsible for the higher concentrations of TMAO in the sickest quartile of these 2,595 people? If a TMAO association is the issue, then we might want to start issuing warnings to the general public that omega-rich fish are now off the menu, as well as carrots and peas. Remember, correlation does not equal causation
I think we can extrapolate the information from these criticisms to include this new study about the TMAO from the lecithin in egg yolks — as Dr.Leach mentioned above.
Additionally, there is this excellent article from Chris Kresser that links the many writers who have debunked this meat fiasco.
The Bottom Line
As I have said before, Red Meat Won’t Kill You — and neither will eggs. But poor science will.
Eat plenty of cholesterol and saturated fat rich foods like red meat and eggs. Just make sure the animals are humanely raised on pasture.
What do you think about all this? Leave a comment and let me know!