Oil and Water: The Hidden Life of Phosphatidylcholine

The molecule that keeps the peace

Imagine your cells as little water balloons. To keep their membranes intact when they meet oily fats or harsh bile acids, they recruit a peacekeeper: phosphatidylcholine (PC). It's the emulsifier nature invented—half loves water, half loves fat—first isolated from egg yolk by Théodore Gobley, who mapped its chemistry over three decades in the 1800s. Without PC, oil and water refuse to meet; with it, they make truce. ^[1][2]

When choline runs low, the liver pays

PC is also your body's main delivery truck for fat export from the liver. The truck—VLDL—can't roll without PC in its outer shell. Deprive humans of choline (the backbone used to make PC), and fat piles up in the liver within weeks; enzymes leak into blood; muscles ache. Re-introduce choline and the damage reverses. Controlled depletion–repletion studies and guidance from European authorities cemented this: most adults need roughly 400 mg/day of choline, more in pregnancy. ^{[12][7][8][9]}

Clinicians learned this the hard way. In the 1990s and 2000s, patients on long-term parenteral nutrition (hospital feeding) developed fatty liver because their formulas lacked choline. Adding choline—or lecithin/PC—raised blood choline, melted liver fat on CT within 2–4 weeks, and lowered ALT/AST; stop the choline and fat crept back within ~10 weeks. That's a transformation story written in scans. ^{[10][11][16][14][15]}

"We thought people didn't require choline... I took choline away and most men and post-menopausal women developed fatty liver or muscle damage. That work proved humans require choline," said nutrition scientist Steven Zeisel, recalling how deficiency in people overturned textbooks. ^[6]

NAFLD: supportive role, not a silver bullet

Because choline shortages impair fat export, researchers tested essential phospholipids (soy-derived PC mixtures, often called EPL or PPC) in nonalcoholic fatty liver disease. A 2020 systematic review and network meta-analysis found that, across small trials (4–72 weeks), adding EPL to standard care tended to reduce ALT by ~11–29 U/L and lower triglycerides and total cholesterol; authors urged larger trials to confirm. ^[3][4][5]

A 2024 phase IV trial now underway is giving 1,800 mg/day of Essentiale (EPL) for six months to measure liver fat by elastography—exactly the kind of study needed to move from promise to proof. ^[19][20]

Bottom line: in NAFLD, PC-rich EPL looks promising as an adjunct—especially alongside diet and movement—but it's not established disease-modifying therapy. ^[3]

Bile's bodyguard: why PC matters to gall and bile ducts

Every minute, bile acids—nature's detergents—flow through tiny ducts. To keep those soaps from dissolving your own tissues, the liver flips PC into bile via the ABCB4 (MDR3) transporter, where PC and bile acids form mixed micelles that soften bile's sting and stabilize cholesterol. Genetic glitches in ABCB4 strip PC from bile, leading to gritty stones (LPAC), pregnancy cholestasis, and duct injury; recent structural biology shows exactly how ABCB4 recruits and moves PC, and how some drugs can clog this pump. Think of PC here as the bubble-wrap that keeps bile's detergents from scratching the pipes. ^{[21][22][23][26][27]}

The gut barrier twist: coating the mucus

Another surprising place PC works is on top of the colon's mucus—a water-shedding layer that keeps resident microbes from rubbing the lining raw. In ulcerative colitis (UC), this PC coat runs thin. Early trials with a delayed-release PC (LT-02) that survives the stomach hinted that topping up the mucus PC might calm symptoms and promote mucosal healing, especially at higher doses (~3.2 g/day). ^[18]

But science is a detective story with wrong turns. In 2024, two larger, international, double-blind trials found no significant benefit in inducing remission and only faint maintenance signals; the induction study stopped early for futility. Safety looked good, but efficacy didn't replicate. The idea—rebuilding a hydrophobic mucus shield—remains elegant; the drug, so far, hasn't delivered. ^[17][13]

"Intestinal mucus serves as the first line barrier... a deficiency of mucus phosphatidylcholine predisposes to inflammation," wrote gastroenterologist Wolfgang Stremmel in a 2024 review, making the mechanistic case even as clinical results stay mixed. ^[24]

The paradox you should know: choline, microbes, and TMAO

PC delivers choline, and gut microbes can turn choline into TMAO, a compound linked in human cohorts to higher cardiovascular risk and platelet reactivity. A Cleveland Clinic team showed supplemental choline can raise TMAO and heighten platelet responsiveness—one plausible route to more clotting risk in some people. Yet TMAO biology is nuanced: microbiome gene counts don't reliably predict who makes TMAO, and foods that raise TMAO (like fish) often associate with better heart outcomes. The signal is there; the context matters. ^[25][^19a][^13a]

Where this leaves a health-conscious reader

• If your diet skimps on choline-rich foods (eggs, meats, some fish, soy), meeting the 400 mg/day choline target—through food or choline-bearing supplements like PC—helps the liver do its core job: export fat safely. ^[7][8]
• In NAFLD, EPL/PC may improve enzymes and lipids as add-ons to lifestyle changes. Expect gradual effects over months, not days. Watch for larger trials. ^[3][19]
• For UC, modified-release PC remains experimental; the largest trials to date didn't meet endpoints. ^[17]
• Be wary of a cosmetic detour: PC/deoxycholate "fat-dissolving" injections (often sold as PCDC). FDA warns they're unapproved and have caused scars, infections, and deformities; only deoxycholic acid (Kybella) is approved—and only under the chin, in clinical hands. ^[28][29][30]

Practical notes you can use

• Typical clinical research doses vary by goal: UC trials used 1.6–3.2 g/day of modified-release PC; a current NAFLD trial uses 1.8 g/day of EPL. Over-the-counter lecithin products often provide grams of PC but far less choline than pure choline salts—adjust expectations accordingly. ^[18][17][19]
• Timeline: in deficiency states (e.g., parenteral-nutrition–related), imaging changes appeared within 2–4 weeks; in NAFLD studies, benefits accrued over 8–24+ weeks. Stopping can let problems creep back within weeks to a few months. ^[10][11][16]
• If you have cardiovascular disease or high TMAO, focus on whole-diet patterns (more plants, fish, fiber) and discuss choline/PC dosing with your clinician; the microbiome's response varies by person. ^[25][^2a]

A closing thought

Phosphatidylcholine doesn't behave like a typical "supplement." It's more like infrastructural material—grease in the gears and bubble-wrap on the pipes. Where systems are starved of choline or stripped of PC, restoring it can set physiology right. Where systems are already stable, adding more brings diminishing returns—and, occasionally, new questions. The story began in an egg yolk; it continues in your liver, bile, and gut, one careful trial at a time. ^[1]