The Mitochondrial Roots of Fatty Liver — and How Choline Helps

• Mitochondrial dysfunction is a central feature of fatty liver disease — The two most significant drivers in modern diets, ethanol and LA, each produce toxic aldehyde byproducts when metabolized in the liver. Ethanol is converted into acetaldehyde, while LA breaks down into 4-hydroxynonenal (4-HNE), both of which are highly reactive and damaging to mitochondria.

These aldehydes bind to proteins, phospholipids, and mitochondrial DNA, impairing oxidative phosphorylation and reducing the liver’s ability to generate ATP. Over time, this impairs the liver’s capacity to oxidize fats, leading to lipid accumulation inside hepatocytes.

• Mitochondrial damage triggers inflammation and disease progression — As mitochondrial membranes are damaged by these aldehydes, the inner membrane loses integrity and protein complexes responsible for energy production are disrupted. The resulting decline in ATP production coincides with increased leakage of reactive oxygen species (ROS), compounding oxidative stress.

Mitochondria begin to release signals that activate immune responses, including mitochondrial DNA and other damage-associated molecules. This triggers hepatic inflammation, contributing to the progression from simple fat accumulation to steatohepatitis and, eventually, fibrosis or cirrhosis.

• Ethanol and LA follow the same toxic pathway — Figure 1 below illustrates the shared toxicity pathway of ethanol and LA, showing how both compounds drive the same cascade of mitochondrial injury, oxidative stress, and inflammatory signaling.

Although one source is traditionally viewed as “alcoholic” and the other “nonalcoholic,” the internal damage they cause is nearly identical at the cellular level. This overlap helps explain why researchers now advocate for abandoning the alcohol-based distinction in favor of a unified diagnosis under the umbrella of MASLD.

• LA plays a particularly insidious role in this progression — Once incorporated in cell membranes, LA becomes highly vulnerable to damage when the liver is under oxidative stress. 4-HNE sticks to important proteins inside mitochondria and interferes with how they work.

It also disrupts the normal signals that help mitochondria adapt to stress and throws off their ability to divide or repair themselves. These changes weaken the liver’s energy system, making it harder for the liver to cope with damage or recover from injury.

• Fatty liver affects all body types and backgrounds — National Health and Nutrition Examination Survey (NHANES) data show that fatty liver is prevalent across a wide range of ethnicities and body types. The table below shows this demographic spread, underscoring the reality that liver fat accumulation is a systemic issue tied to modern dietary and lifestyle patterns, not a condition confined to specific groups.

• The importance of redefining fatty liver disease — Redefining fatty liver disease in terms of mitochondrial health and metabolic overload offers a more biologically coherent understanding of what drives this global epidemic. It shows that the real issue is the liver’s declining ability to produce energy and repair itself, especially when it’s being hit by harmful compounds. Learn more about mitochondrial damage and liver dysfunction in “Unveiling the Dual Nature of Fatty Liver Disease.”

• Choline is absorbed in the gut and routed according to the body’s needs — Specialized transporter proteins help choline cross the intestinal wall and enter the bloodstream. From there, choline enters cells and follows several metabolic routes, depending on the body’s needs.

A large portion is directed toward the synthesis of phospholipids, especially phosphatidylcholine (PC), which is the most abundant phospholipid in mammalian cell membranes. Roughly 95% of the body’s choline is stored in this form.

• Choline enables the export of fat from hepatocytes — To help the liver export fat, choline is turned into phosphatidylcholine (PC) through a multi-step process called the CDP-choline pathway, as shown in Figure 2. First, an enzyme called choline kinase adds a phosphate group to choline, turning it into phosphocholine. Then, another enzyme uses a molecule called CTP to activate phosphocholine, creating CDP-choline, the key building block of PC.

This middle step is the most tightly controlled part of the pathway, acting as a checkpoint for PC production. In the final step, CDP-choline is joined with a fat-based molecule called diacylglycerol (DAG), forming PC, which the liver then uses to build membranes and ship fat out of the cell.

• Choline prevents fat buildup and strengthens cellular membranes — Once formed, PC is inserted into cellular membranes and packaged into very-low-density lipoproteins (VLDLs), which transport triglycerides from the liver into circulation.

As shown in Figure 3, this process begins in the endoplasmic reticulum, where PC enables the early steps of VLDL assembly. Triglycerides from lipid droplets are added, and the VLDL particle then matures in the Golgi apparatus before being exported into the bloodstream. Without enough PC, this pathway breaks down, fat accumulates inside hepatocytes, and the liver loses its ability to regulate lipid metabolism and maintain structural integrity.

• Choline contributes to the synthesis of phosphatidylethanolamine (PE) — PE makes up 20% to 30% of total membrane phospholipids and is especially enriched in mitochondrial membranes, where it plays a key role in energy metabolism. PE can also be made inside mitochondria through a different route.

This alternative pathway produces PE right where it’s needed most — at the center of energy production. In addition, the body can convert PE into PC by adding methyl groups, a process that depends on nutrients like folate, vitamin B12, and methionine. These nutrients help carry out essential chemical reactions that connect choline metabolism to gene regulation, detoxification, and cardiovascular support.

• Maintaining a healthy PC:PE ratio for normal membrane behavior — Since PC and PE are two major building blocks of cell membranes, their shape matters. PC has a large, wide head that helps membranes stay flat and firm, like a smooth sheet.

PE, on the other hand, has a smaller head that lets membranes curve and bend, which is needed to form bubble-like structures called vesicles that move materials around the cell. The balance between PC and PE helps control how flexible or rigid the membrane is, which affects how cells grow, send signals, and remove damaged parts.

When the body doesn’t make enough PE, mitochondria become stressed and less efficient at making energy. This can lead to more damage from unstable molecules called free radicals. On the flip side, increasing PE levels, such as by supplementing with ethanolamine, has been shown to help cells clean up waste, boost energy production, and even extend lifespan in some studies, suggesting it may support healthy aging and metabolism.

• Choline also supports methylation by being oxidized to form betaine — Betaine is a compound that helps add chemical tags called methyl groups to other molecules. This process turns homocysteine into methionine, which the body then uses to make S-adenosylmethionine (SAM), a key helper in many reactions. These methyl tags support important functions like repairing DNA, making neurotransmitters, and controlling inflammation.

• The liver not only stores fat during choline deficiency but also loses functional integrity — The image below illustrates the hepatic consequences of choline deficiency. The healthy hepatocyte shows a strong membrane, working mitochondria, and very little fat inside.

The steatotic hepatocyte, by contrast, is swollen with fat droplets, has damaged mitochondria, and shows signs of membrane breakdown. This highlights how low choline intake disrupts fat processing and energy production in the liver, setting the stage for fatty liver disease.

• Choline fuels the nervous system as the precursor to acetylcholine — Acetylcholine is a neurotransmitter required for learning, memory, and muscle coordination. It plays a major role in both the central nervous system and peripheral motor control.

Because neurons only produce acetylcholine if enough choline is available at their synaptic terminals, inadequate choline intake can impair cognitive performance and motor function. Researchers continue to study choline’s therapeutic value in neurological conditions such as Alzheimer’s disease and other neurodegenerative disorders.

• Choline is essential for fetal development and infant brain growth — During pregnancy, maternal choline supports the development of the fetal hippocampus and other brain regions involved in memory and learning. Studies show that children of mothers who consumed higher levels of choline (up to 930 milligrams per day) performed better on cognitive tasks.

Methylation processes that shape the fetal epigenome also rely on choline, alongside folate and vitamin B12. If any of these nutrients fall short, methylation capacity drops and homocysteine levels may rise, increasing the risk of neural tube defects and long-term developmental changes.

• Methylation pathways depend on choline-derived betaine — Through its conversion to betaine, choline sustains the body’s one-carbon metabolism, which regulates gene activity, neurotransmitter balance, and membrane synthesis. This methylation support also extends cardiovascular protection. When choline or betaine levels fall short, methylation falters, homocysteine builds up, and the risk of metabolic disturbances increases.

• Choline maintains gallbladder and bile function — PC makes up 10% to 15% of bile lipids and helps keep cholesterol dissolved, preventing the formation of gallstones. Without enough choline, bile composition becomes unstable, which increases the risk of gallstone formation and fat malabsorption. In animal models, choline deficiency leads to gallbladder dysfunction, abnormal bile flow, and impaired fat digestion.

• Genetic and life stage factors increase choline needs — Nearly 40% of women carry a gene variant that reduces their ability to synthesize choline internally and elevates their choline demand, which raises their dietary requirement. At the same time, aging reduces the liver’s capacity to make choline and increases reliance on dietary intake. These factors help explain why many older adults and pregnant women are particularly vulnerable to deficiency.

• Current choline guidelines aim to prevent damage, not optimize health — The current adequate intake (AI) levels in the table below were set by the Institute of Medicine in 1998 and are meant to prevent overt liver injury, not to optimize long-term mitochondrial performance or metabolic resilience. These values vary by age, sex, and physiological demand.

• Several factors increase choline requirements beyond the baseline — As shown in the table above, women of childbearing age may have lower choline needs if estrogen is high, as estrogen stimulates endogenous choline synthesis. But in postmenopausal women or those with low estrogen, dietary choline becomes more important. Genetic variations also matter, as certain polymorphisms reduce the body’s ability to make or recycle choline, raising the risk of liver dysfunction on low-choline diets.

• Metabolic stress raises choline demand across the board — During pregnancy, choline needs spike due to fetal brain development, placental transport, and maternal methylation load. In individuals with fatty liver, diabetes, or obesity, choline is rapidly used for membrane repair, detoxification, and mitochondrial phospholipid replenishment, making deficiency more likely even at modest intake levels.

• Diet also plays a major role — Plant-based diets typically supply far less choline than omnivorous ones, since the richest sources, such as egg yolks, liver, and red meat, are often limited or excluded. Eggs are especially important, as one yolk provides about 125 milligrams of choline, and they remain the most practical dietary source for most people. But decades of anticholesterol messaging discouraged egg consumption, unintentionally contributing to widespread choline deficiency.

• Egg access has also become more difficult — Avian flu outbreaks, supply chain disruptions, and shifting animal welfare policies have led to higher prices and limited availability in some regions. These barriers, combined with growing public pressure to adopt plant-based diets, have made it harder for many people to meet their choline needs through food. Without eggs or liver in the diet, most people fall far below optimal intake unless they supplement.

• Cut back on vegetable oils and eliminate alcohol intake — Your first step is to stop feeding your liver the compounds that are breaking it down. LA is the primary fat in processed vegetable oils like soybean, corn, sunflower, safflower, and canola oil.

You’ll also find it in margarine, mayonnaise, salad dressings, fast food, chips, crackers, granola, and nearly every ultraprocessed snack. Ethanol, the active ingredient in alcohol, is also used in many extracts, sauces, and processed flavorings. Removing these inputs reduces the stress on your liver and helps restore its ability to produce energy and clear fat.

• Increase your dietary choline consumption — Once you’ve removed the damaging inputs, your liver needs raw materials to rebuild. The table below shows the best dietary sources of this nutrient, with pastured eggs and grass fed organ meats being the highest.

While some plant foods, like soybeans, broccoli, cauliflower, and Brussels sprouts, contain modest amounts, they usually aren’t enough on their own. If you’re on a plant-based diet, you’ll need to be especially mindful about including high-choline foods or considering supplementation to close the gap.

• Supplement with choline when diet falls short — If you’re not getting enough choline through food, supplementation becomes an important option. Different forms of choline offer distinct benefits depending on how your body uses them. The table below compares these forms based on their choline content, absorption, biological activity, and clinical relevance. Understanding the differences can help you choose the right supplement to support liver recovery and overall metabolic health.

Standard choline supplements like choline bitartrate are poorly absorbed and tend to elevate trimethylamine N-oxide (TMAO), a compound linked to cardiovascular risk. I recommend opting for more bioavailable forms such as citicoline (CDP-choline) or alpha-GPC, which bypass this problem and efficiently raise PC and PE.