Proceed with Caution

Your gut is full of microscopic creatures known as microbes. Among other things, they are critical to digestion. You've probably seen yogurt advertised as containing "live active yogurt cultures," and these do help your gut microbes to thrive, keeping everything running smoothly. This is also why many people experience diarrhea when they take antibiotics: they kill the good digestive microbes along with the germs that are causing whatever illness you've been prescribed the antibiotics to treat.

Studies in animals have established that those intestinal microbes process a substance called choline, which is part of lecithin, to create trimethylamine-N-oxide (a mouthful we'll just call TMAO), which encourages artherosclerosis (plaque formation in the arteries). Researchers at the Cleveland Clinic have confirmed this in humans through two studies recently published together in the New England Journal of Medicine (2013;368(17):1575-1584).

In the first study, 40 healthy adult men and women ate two whole, large hard-boiled eggs, which contain about 250 milligrams of choline apiece. Before and afterwards their blood and urine was tested for TMAO. The participants were then prescribed two different antibiotics to take daily for one week, then they returned to the lab and repeated the blood and urine testing before and after eating eggs. This allowed the researchers to compare the effects of the antibiotics on the amount of TMAO in the urine and to conclude that the intestinal microbes were definitely responsible for the production of TMAO by metabolising choline.

In the second study the researchers were able to obtain blood samples and TMAO levels from over 4,000 patients who were receiving cardiac catheterization at the clinic. After three years the researchers were able to access the patients' records to find out which patients experienced what is known as "a major cardiovascular event," i.e., stroke, heart attack, or death, and compare their TMAO levels with those who did not have a major cardiovascular event.

After taking into account many variables, from age to whether they were on certain medications and the progression of their heart disease, the researchers found that those with the highest TMAO levels were 43% more likely to experience a stroke, heart attack, or death than those with the lowest TMAO levels.

What this means for you

In their conclusion the researchers noted that the major sources of choline in the diet - eggs, liver, beef, and pork - are already considered foods to be enjoyed with caution and moderation. Should you cut them out of your diet completely? Not unless you want to for reasons other than the amount of choline they contain. You can still safely enjoy your eggs, liver, beef, and pork - in moderation.

First posted: May 1, 2013