I’ve been writing a lot about choline lately. Most recently, my article entitled “Nonalcoholic Fatty Liver Disease: A Silent Epidemic of Nutritional Imbalance” contained a major section on the role of dietary choline in protecting against fatty liver disease, which itself is a powerful and independent risk factor for heart disease.
I also wrote a series dealing more specifically with choline and fatty liver over at The Daily Lipid, which culminated in my post on this blog, “Why Is My Cholesterol So High on This Diet?”
Likewise, Dr. Emily Deans has recently been writing about the role of choline in mental health, something I had covered in less detail in my 2007 article on pregnancy nutrition.
It may be of concern, then, that a recent paper published in Nature suggests that dietary choline may be contributing to heart disease:
Yikes! Are we to eat liver and egg yolks to support our liver health and mental health only to wind up with heart disease as a result?
Here’s a diagram representing the hypothesis that these authors have offered us (image from the associated commentary by Rak and Rader):
The authors argue that dietary choline, found mostly as phosphatidylcholine, enters the intestine where our gut bacteria convert it to free choline and then to trimethylamine, a gas that smells like rotting fish. Then our livers detoxify the trimethylamine to an odorless product called trimethylamine oxide (TMAO). While this prevents us from walking around smelling like we’ve been swimming in a barrel full of fermenting cod livers, the authors argue that TMAO fills our arteries with plaque.
In support of this hypothesis, the authors showed that blood levels of choline, its metabolic byproduct betaine, and TMAO all correlated with the incidence and severity of cardiovascular disease in humans, although this was not prospective data showing that the occurrence of these compounds in the blood early in life predicted the development of heart disease later in life.
They also showed that feeding mice phosphatidylcholine did in fact produce TMAO, but only in the presence of gut bacteria. Further, feeding mice five-fold or ten-fold higher concentrations of choline chloride than they would ordinarily receive, or simply feeding them TMAO itself, increased atherosclerotic lesion size, and atherosclerotic lesion size correlated with blood levels of TMAO.
There’s just one major problem with this hypothesis. Studies in humans have shown that neither phosphatidylcholine nor choline-rich foods produce detectable increases in trimethylamine.
Here’s a figure from a 1983 study by Ziesel and colleagues showing urinary excretion of trimethylamine after supplementation with different types of choline in humans:
The third bar in each panel represents the excretion of trimethylamine in the urine. Choline chloride and choline stearate led to the production of large amounts of trimethylamine, but lecithin (phosphatidylcholine), the main form of choline found in food, led to only a small increase.
It turned out, however, that their lecithin was contaminated with some trimethylamine. If they “cleaned” it to remove the contamination, shown in the fourth panel, the lecithin did not increase urinary excretion of trimethylamine at all.
A 1999 study by other authors came to similar conclusions. They looked at the urinary excretion of both trimethylamine and its detoxification product TMAO in humans. They found that 60 percent of free choline and 30 percent of carnitine, another potential precursor, was excreted in the urine as one of these two products, but that neither betaine nor phosphatidylcholine converted to either product at all.
In fact, these authors even fed 46 different foods to humans and looked at the subsequent excretion of trimethylamine and TMAO. Choline-rich foods like liver and eggs did not produce any increase in urinary trimethylamine or TMAO over control levels. In fact, even carnitine-rich meats failed to increase excretion of these compounds. The only foods that increased excretion of TMAO were seafoods, which naturally contain some trimethylamine, giving them their “fishy” smell.
Here is a representative selection of seafoods and other animal foods:
Here we see that only seafoods, naturally contaminated with trimethylamine, increase the urinary excretion of trimethylamine and TMAO in humans. Liver, eggs, and meat do not.Â
These authors explained their results by citing research showing that the enzyme phospholipase A cleaves phosphatidylcholine, or lecithin, into a compound called lysolecithin in the small intestine where it is efficiently absorbed. By contrast, other forms of choline travel to the colon where gut bacteria make enzymes that convert them to trimethylamine.
Should we presume, then, that it is not liver and egg yolks, but rather fish and shellfish that contribute to heart disease? Perhaps, although this seems doubtful given that populations such as the Kitavans eat plenty of fish, even in fermented form, yet appear to be free of heart disease.
In order to even begin supporting such a hypothesis, we would have to first see to what degree eating seafood leads to the accumulation of TMAO in the blood, and here we only have urinary data. If the kidneys efficiently dispose of TMAO into the urine after eating seafood, TMAO may be unlikely to accumulate in the blood for any length of time.Â
Indeed, the massive increases in urinary trimethylamine and TMAO following meals rich in seafood suggests that our kidneys excrete these compounds very efficiently.
So how, then, should we interpret the correlation between heart disease risk and plasma concentrations of choline, betaine and TMAO in humans?
Blood levels of choline are currently considered an emerging marker for destabilization of coronary plaques or ischemia in acute coronary syndrome, as reviewed here. During the process of blood clotting, inflammatory enzymes release choline from membrane phospholipids in order to also generate phosphatidic acid, which is used as an important signaling molecule. Elevated blood levels of choline, then, and perhaps its metabolite betaine, could simply reflect an inflammatory or pro-clotting environment.
Elevated TMAO could reflect dietary trimethylamine or TMAO from seafood, but it could also reflect impaired excretion into the urine, or enhanced conversion of trimethylamine to TMAO in the liver.Â
The enzyme Fmo3 carries out this conversion, mainly in the liver, as reviewed here. There are a number of genetic variants affecting the activity of this enzyme, some of which appear only in certain ethnicities, and the enzyme also processes a number of drugs used to treat psychoses, infections, arthritis, gastro-esophageal reflux disease (GERD), ulcers, and breast cancer. Iron or salt overload may also increase the activity of the enzyme. TMAO could, then, be a marker for ethnicity, drug exposure, genetically determined drug efficacy, or other conditions.
If we had strong epidemiological evidence showing that consumption of fish and shellfish early in life is associated with an increased risk of developing heart disease later in life, then the animal studies reported in the Nature article would present a strong justification for considering the hypothesis that trimethylamine contaminating these foods is somehow increasing the risk of heart disease.
Yet, we do not have that. Alas, we instead have evidence that islanders who eat traditional diets containing fish tend to be free of heart disease.
Perhaps future work will in fact elucidate a role for harmful gut bacteria in increasing TMAO levels and subsequent development of heart disease, in which case the clear implication would be that we should figure out how to normalize the gut bacteria. Right now, we have no evidence that eating choline-rich animal foods increases TMAO at all, so a hypothesis dependent on this apparently fictitious process is as yet an impotent one.
Pass the liver and egg yolks please. And maybe some folks fasting for Lent may say pass the fish, shrimp or octopus. Consuming these choline-rich foods will produce much better mental health than worrying in the face of contrary evidence that they are clogging your arteries.
Brilliant as usual, Chris. Every time one of these supposedly conclusive studies comes out and gets reported, everyone seems to have a knee-jerk reaction–in this case, to regard choline as evil. Why do they never seem to give equal time to analysis/studies which show the original study to be faulty?
Nice one. I hadn’t gotten to that paper yet, beyond noting that the amount of choline they fed to the mice was massive. Needless to say, I was finding their claims hard to swallow on that basis alone…
What is your opinion on choline supplements such as choline bitartrate?
So, I am confused, is supplemental choline intake, such as in the form of choline chloride or bitartrate still undesirable?
Also, the data citing Carnitine’s potential conversion into undesirable TMAO, could this be applicable towards supplemental Carnitine usage, but also and more particularly, to the usage of Acetyl-L-Carnitine supplementation? This has distressing potential.
Nice work Chris. I don’t know how anyone can keep up with you: ) I am also bothered a lot by the whole data mining premise of this “metabolomics” paradigm. It is statistically bogus and likely to lead to spurious corellations when “screeining” for so many metabolites.
Chris,
Glad you shed some light on this. I was suspicious of this new paper when I first saw it last Friday on the Science Daily website.
Unfortunately, I am not a big fan of liver/organs and eggs. Because of this, I don’t think I get enough choline in my diet. On the flip side I am probably taking in a little more fructose than I should but I am working on reducing that..
In the meantime however, I was wondering if you thought supplementing with choline would be beneficial? I was considering choline citrate versus phosphatidylcholine to reduce my pill burden. I can get one 650mg tablet of Choline Citrate which supposedly has 221mg of actual Choline. I would be interested in your thoughts.
Thanking you in advance.
Respectfully,
John M.
God Bless you sir! I need to take PPC (polyenylphosphatidylcholine) for liver disease and the Nature article was quite distressing.
I had read before that choline chloride was the wrong way to supplement choline, and phosphatidylcholine was the way to go. Your data seems to support this theory.
Easy there lil pony. As consistently brilliant as the reviews and studies you (thankfully) put forth are….they’re all gonna come gunnin fur ya…layin waste to their horse-hauckus studies–as your rather knowledgably lucid and objective insights so often trend–these vain and competitive greedy black-hearts will want some pay-back, couldn’t you imagine?
Of course, there is always that, but please, keep your course as I’m somehow certain you will….and keep feedin on truly good healthy food cause you’re gonna need all the energy you can, what with clearin the PhD and fightin off all the overwhelming preponderance of frauds out there; not to mention discovering stuff that can be of genuine benefit for those well-enough-tuned to keep an ear to the heavens and earth.
You’re one very usefully contributing life, from my humble perspective, anyway, which is
how we should all learn to live our lives: to
contribute to the fulfillment of an eventual harmony here on this planet…amongst all living things. One way or another, life ultimately is tethered to the language that the nature of the universe speaks, and not the notional nonsense of so many weakened minds divin for dollars to get through the day. Yes, everybody’s gotta eat…but exactly what? Find the best answer to that question for one’s self and family, and sustainable health often prevails…and always with the caveat that everyone is different, so don’t get too enamored and cocky with one of our greatest impediments to significant and meaningful learning: Beliefs…as they come and go as do the sea’s changing tides.
So again, my gratitude for your fine research efforts and the sharing of, and,
All the best, especially inHealth,
Mark
Responses to Cynthia, Stephan, Cliff, EC Seiler, Dr. Harris, John M, John, and Mark L.
First, I apologize for the late reply everyone!
Cynthia, thanks! I think part of the problem is lack of people doing the critical analysis and submitting it. If I have time, I’ll write a letter if it’s not past their deadline when I can.
Stephan, thanks! A little hard to swallow indeed.
Cliff, I would only use phosphatidylcholine.
EC, yes I would stick to phosphatidylcholine. Acetyl-L-carnitine may act differently than the carnitine they used, as does food carnitine. I will try to look into it.
Dr. Harris, thanks! On the data mining, I think they offered it some legitimacy here because they went out with a specific hypothesis to look for the association in a different cohort. Of course, that still doesn’t indicate causation.
John M, you can make up for choline by getting more B6, B12, folate, and betaine. If you supplement with choline, I would, in light of this data and the *potential* for harm, stay on the safe side and stick with phosphatidylcholine.
John, you’re welcome and thanks!
Mark L, thank you so much for your kind words.
Hello Chris…..Any likelihood that supplemental brands of PC, such as NOW Foods or Jarrow, could be contaminated with TMA? Also, does a supplement such as DMAE or CENTROPHENOXINE pose a problem, it would not seem to me as it does as it is rejected for breakdown by gut flora and does not require this conversion process. Also, does DMAE and CPX serve as an essential dietary Choline source, or would PC supplementation/intake still be advisable to achieve AI? All the best!
Hi EC,
I would ask the company about contamination. Seafood has such contamination, however, and I eat it. I would get choline from food, unless you have some condition that choline might treat in higher doses, in which case I’d use PC because it most closely mimics what is found in food, unless there are clinical trials showing superiority of something else for some therapeutic use.
Chris
p.s. Were you able to determine whether ALCAR should pose any problem, seems like it should be OK to me….?
Hi EC,
I haven’t been able to look into it yet, but will write about it when I get a chance. I’d favor consuming liver, heart, and so on for some of these more obscure nutrients, but I’ve supplemented with acetyl-l-carnitine and R-alpha-lipoic acid in the past and felt good from it.
Chris
Interesting. What about strokes? Looking at these maps it seems that coastal and island populations that would typically eat a lot of fish also have a lot of strokes. Is TMAO a risk factor for strokes?
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_16_death_from_stroke.pdf
http://www.who.int/cardiovascular_diseases/en/cvd_atlas_15_burden_stroke.pdf
Great read. I was quite concerned when I read those studies as I’ve been taking a lecithin supplement and wasn’t sure now how safe it was. Each serving contains 2g of Phosphatidylcholine along with 1g of Phosphatidylinositol. Is that safe?
Thanks
Chris, you seem to say that much excretion (such as with the choline chloride) does indicate the potential for ill health. However, you later suggest it might simply indicate efficiency of the body to get rid of TMAO? Obviously we can’t have it both ways? Meanwhile, the authors of the observational study did correlate choline, betaine, and TMAO with cardiovascular problem. Are you saying that the authors with their “excretion measurement” didn’t measure something meaningful to their conclusions. And therefore you say that choline is probably healthy?
Hi Mike,
Yes, I can have it both ways, at least in the senses in which I was using the data. If TMAO is efficiently excreted into the urine, then it is unlikely to cause harm except in people where its excretion is impaired, thus causing its accumulation in plasma or other tissues. However, in a crossover trial with the same subjects, who clearly would have similar efficiency of excretion from one food to the next, the absence of any excretion suggests that no TMAO is generated. In any case I took these in the context of other data, and not alone. The fact phosphatidylcholine doesn’t seem to generate TMAO is consistent with our understanding of how it is absorbed. The fact that seafood seems to generate it is consistent with the fact that seafood is contaminated with it. And so on. If TMAO is a problem, then it is likely to be the seafood that should be problematic. So this has to be interpreted within the context of other data suggesting whether seafood contribute to heart disease, and so far the precise opposite argument has prevailed, and for good reason.
I don’t know what “excretion measurement” you’re talking about. I provided examples of confounders that could account for some of these associations.
Chris