I received several questions about Lecithin on Facebook and this blog after my last post on Emulsifiers. I cited one study that I found for illustration purposes:
Dietary carnitine (present predominately in red meat) and lecithin (phosphatidyl choline) are shown to be metabolized by gut microbes to trimethylamine (TMA), which in turn is metabolized by liver flavin monoxygenases (especially FMO3 and FMO1) to form trimethylamine-N-oxide (TMAO). High levels of TMAO in the blood strongly correlate with cardiovascular disease and associated acute clinical events.Dietary modification of the microbiome affects risk for cardiovascular disease.
Many of the questions came from the belief that lecithin helps heal the gut. My goal is to see what has been found in studies listed on PubMed – my gold standard for separating urban-(medical)-legend from reasonable facts. I first look at conditions: There was nothing for Chronic Fatigue Syndrome.
Irritable Bowel Syndrome
There are no studies except with boswellia where it was used as a delivery mechanism.
- Oral administration of a lecithin-based delivery form of boswellic acids (Casperome®) for the prevention of symptoms of irritable bowel syndrome: a randomized clinical study.
- Supplementation with a lecithin-based delivery form of Boswellia serrata extract (Casperome®) controls symptoms of mild irritable bowel syndrome.
“The most promising approach in UC seems to be the use of probiotics or the natural compound lecithin as a stabilizer of mucus structure to enhance the barrier…. ongoing phase III study … “Improvement of a ‘Leaky’ Intestinal Barrier. 
Note: that we have an “or” and “seems to be” — so no concrete results yet.
“Children with CD frequently consume food additives, and the impact on disease course needs further study. ( Mean exposures per day for xanthan gum was 0.96 ± 0.72, carrageenan 0.58 ± 0.63, maltodextrin 0.95 ± 0.77, and soy lecithin 0.90 ± 0.74. )”Children with Crohn‘s Disease Frequently Consume Select Food Additives. 
Note: The authors are stating concerns about all of these food additives for Crohn’s Disease children
In randomized controlled studies, delayed-release lecithin [phosphatidylcholine (PC)] was proven to be clinically and endoscopically effective, which now awaits a phase III authority approval trial.Lecithin as a therapeutic agent in ulcerative colitis. 
- Phosphatidylcholine (lecithin) and the mucus layer: Evidence of therapeutic efficacy in ulcerative colitis? 
- ” Topical supplement of PC by a delayed-released oral PC preparation is effective in resolving inflammatory activity of UC and may develop to a first-choice therapy for this disease. “
- Managing ulcerative colitis in remission phase: usefulness of Casperome®, an innovative lecithin-based delivery system of Boswellia serrata extract.
Note: There were no results published for the phrase III study. If there are old studies indicating positive results and plans for more studies, but nothing is published, THEN most researchers would conclude that no positive results were obtained and thus the study was not published because it failed to produce intended results.
Issues Associated with Lecithin
lecithin, choline, and carnitine) are converted by closely related gut bacterial TMA lyases to TMA, which is absorbed and converted predominantly by flavin mono-oxygenase 3 to the toxic trimethylamine N-oxide (TMAO). TMAO causes atherosclerosis in animals and is elevated in patients with coronary heart disease.New Insight into the Dietary Cause of Atherosclerosis: Implications for Pharmacology. 
- Gut microbiota-dependent trimethylamine N-oxide (TMAO) pathway contributes to both development of renal insufficiency and mortality risk in chronic kidney disease.
- Idiopathic autoimmune hemolytic anemia due to lecithin overdose: a case report. 
- Lecithin supplements and breast cancer risk.
No scientifically valid clinical studies exist on the safety and efficacy of high-dose lecithin supplementation in nursing mothers or infants.Lecithin. Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US)
- [Resistance to vitamin K antagonist revealing interaction with soy lecithin]. – “interaction between oral anticoagulants and food supplement that is increasingly used.”
- ” On the other hand, the super lecithin and linseed oil that were characterized by low omega-6 to omega-3 ratio (about 1) reduced the blood lead concentration [in rats]” 
It appears that some early studies saw improvement when a delayed- release dosage of lecithin was used (no information on the dosage). As these studies were on what appear to be a potential commercial product, the missing phrase III studies suggest that positive results were not found. What is more interesting to infer is the decision to use delayed release — it implies there were issues seen with direct lecithin (which likely were not published but known to the researchers).
There are reports of lecithin overdose and drug interference. There are no safety studies to determine what dosage is beneficial (and what level is harmful).
I conclude that current published evidence does not support the use of lecithin supplements.