Choline is an essential nutrient that is neither a vitamin nor a mineral, although it is often grouped together with the B vitamins. While the liver can synthesize some choline, it cannot make enough to meet physiological needs. That is why choline is considered an essential nutrient that must be consumed through the diet.
Where to Find Natural Choline
Choline is found in many different foods, with highest levels found in animal-based protein like organ meats. While there is no recommended daily allowance (RDA) established for choline, the Daily Value (DV; found on nutrition facts labels) for choline is 550 mg per day. However, the Food and Drug Administration (FDA) does not require food companies to call out choline content on a food label unless it has been added to the food.
The following foods are rich sources of choline:
- Animal sources: beef and beef liver, egg yolks, chicken and chicken liver, fish roe, salmon, cod, pork, shrimp, cow’s milk
- Vegetables: broccoli, green peas, collard greens, brussels sprouts, shiitake mushrooms, cauliflower, potatoes
- Beans and legumes: navy beans, lima beans, soybeans
Choline’s Functions in the Human Body
Despite being officially recognized by the Institute of Medicine as an important nutrient relatively recently (1998), choline is known for a wide range of critical roles in the human body, including roles in methylation, cell membrane structure, cell signaling, and brain health.
Choline plays an important role in methylation: the transfer of one carbon methyl group from one molecule to another. This action either activates or deactivates that molecule and is instrumental in gene expression. In fact, methylation is the process by which human epigenetics regulates gene expression. Choline is a methyl donor, along with betaine, methionine, and folate, and it is crucial to keeping the methylation process running smoothly. Methylation plays an important role in:
- Cell division; DNA and RNA synthesis
- Detoxification and hormone biotransformation
- Neurotransmitter biosynthesis
- Central nervous system (CNS) development and neural tube formation
- Histamine clearance
- Phospholipid synthesis
- Myelination of peripheral nerves
Choline is a key nutrient for methylation because it can be oxidized to betaine. Betaine is an important methyl donor which participates in the remethylation of homocysteine to methionine. This process is an alternative pathway that mimics the B12-folate pathway for homocysteine remethylation.2 This specific role underscores the importance of choline to cardiovascular health, since elevated homocysteine levels are a risk factor for cardiovascular disease. However, the data related to choline and cardiovascular health is mixed.
Cell Membrane Structure and Signaling
Choline is used to synthesize phosphatidylcholine and sphingomyelin, two major phospholipids that form the structure of cell membranes. Sphingomyelin also forms part of the myelin sheath that envelops nerve fibers and facilitates the transmission of nerve signals. Choline is also a precursor of the neurotransmitter acetylcholine. This neurotransmitter is important for many brain and nerve functions, including:1
- Skeletal muscle control
- Circadian rhythm
Lipoprotein Transport and Metabolism
When dietary fats and cholesterol are absorbed, they are carried to the liver by lipoproteins called chylomicrons. Once in the liver, these dietary fats are packaged into different kinds of lipoproteins called very low-density lipoproteins (VLDL) for transportation out of the liver through the bloodstream to the rest of the body. Phosphatidylcholine synthesis is required for VLDL formation; without enough of it, fat and cholesterol can accumulate in the liver.1
Choline’s Role in Pregnancy, Postpartum Women, and Infants
While folate tends to get the spotlight when it comes to key pregnancy nutrients, choline is receiving more well-deserved attention. In 2017, the American Medical Association advised that prenatal vitamins should contain choline, though most prenatal formulas do not. The following year, the American Academy of Pediatrics referred to choline as a “brain-building” nutrient and recommended pediatricians ensure pregnant woman and young children get adequate amounts of choline.3
The adequate intake (AI) established for adults of child bearing age is 425 mg per day, 450 mg per day during pregnancy, and 550 mg per day during lactation. However, some research suggests these levels are inadequate, finding that 930 mg per day provided improvements to several pregnancy outcomes, including reduced neonatal stress, faster processing speed in infants and improved memory in children at age 7.3
Choline is necessary for fetal development, specifically brain and neural tube development. Choline also plays an important role in placental function, including transportation of macronutrients. Other roles of choline in fetal development include:3
- Large amounts of choline and choline-derived phospholipids are necessary to support rapid growth, cell division and myelination of neurons
- Acetylcholine influences proper brain development, including development of the hippocampus, the part of the brain related to learning, memory, and attention
- As a methylation nutrient, choline influences genetic expression, and adequate prenatal intake may have lasting protective effects on health
Choline during infancy is just as important as during pregnancy for continued developmental growth of the newborn. During lactation, maternal choline requirements increase even more because choline is passed in large amounts to the child via breast milk.3,4 Choline in breast milk increases two-fold during the first week after birth and remains stable beyond six months.2
Studies suggest that choline may have a wide variety of preventative effects on various body systems, including cardiovascular, brain, and liver health.
As methyl donors, choline and folate support healthy homocysteine metabolism. Elevated homocysteine is a known cardiovascular risk factor and may contribute to the development of atherosclerosis and blood clots.1,5 However, as noted above, research related to choline and cardiovascular disease risk is mixed.
Non-Alcoholic Fatty Liver Disease (NAFLD)
Phosphatidylcholine is required for VLDL particle synthesis and function. Choline deficiency, resulting in insufficient phosphatidylcholine, may result in fat accumulation in the liver (hepatic steatosis) and NAFLD.1,6
Choline may be an important nutrient for neurological health. Research suggests a link between higher choline intake and improved cognitive function, including verbal and visual memory.7 Other studies have shown that people with Alzheimer’s disease have lower levels of the enzymes that convert choline to acetylcholine, an important neurotransmitter. Therefore, it’s been suggested that increasing dietary choline may reduce symptoms of dementia and improve cognitive function.8 While observational trials have demonstrated enhanced cognitive performance, more research is needed to clarify choline’s potential role in neurological diseases.
Who Needs Extra Choline?
While overt choline deficiencies are rare, some people are more at risk for choline deficiencies or insufficiencies than others.
- Pregnant and breastfeeding women
- Postmenopausal women; estrogen is a cofactor in the biosynthesis of phosphatidylcholine. Since postmenopausal women have lower estrogen concentrations, they have higher requirements for choline than premenopausal women do9
- Those who drink excessive alcohol may require higher amounts of choline, according to animal studies10
- Endurance athletes; choline levels drop significantly during and after endurance exercise, such as marathon running. Supplementing with lecithin has been shown to stabilize choline levels, but it is unclear whether this may improve athletic performance11
Choline may be a nutrient best consumed through food, as consuming excessive amounts can lead to “fishy” body odor, vomiting, excessive sweating and salivation, low blood sugar, and liver damage. The upper tolerable limit for choline is 3,500 mg per day for adults.5
Considering choline’s importance and the vast number of foods that contain choline, this nutrient is certainly one to watch.