PEMT — Your Internal Choline Factory
PEMT (phosphatidylethanolamine N-methyltransferase) is an enzyme in the liver
that produces phosphatidylcholine | A major component of cell membranes and bile, essential for fat transport from the liver (PC) from phosphatidylethanolamine using three
sequential methylation reactions. Phosphatidylcholine is a critical component of
cell membranes, bile (needed for fat digestion), and VLDL particles (which
transport fat from the liver). PEMT is the body's primary internal source of
choline, reducing dependence on dietary intake.
The Mechanism
The Val175Met variant | Valine-to-methionine substitution at position 175 of the protein (p.Val175Met) (rs7946) substitutes valine with methionine at position 175
of the PEMT protein. The T allele (Met) reduces enzyme activity by approximately
30%, meaning less phosphatidylcholine is produced internally. This shifts the
burden to dietary choline sources. Each methylation reaction requires one
S-adenosylmethionine (SAM) | SAM is the body's universal methyl donor molecule, so PEMT activity is also
dependent on overall methylation capacity. Notably, the T allele is very common
in Europeans (75% frequency) but much rarer in East Asians (24%).
The Gender Dimension
PEMT is an estrogen-responsive gene — estrogen upregulates its expression. This
means premenopausal women with PEMT variants may be partially protected by their
estrogen levels. However, postmenopausal women with PEMT variants face a
particularly high risk of choline deficiency because they lose both the genetic
capacity and the hormonal support for internal choline production.
The Evidence
A clinical trial at UNC Chapel Hill | da Costa KA et al. FASEB J 2006 — common genetic polymorphisms affect the human requirement for the nutrient choline demonstrated that women with PEMT variants
who consumed a low-choline diet developed liver dysfunction (fatty liver, elevated
liver enzymes) significantly more often than women without the variant. A
Japanese study | Song J et al. PEMT Val175Met and NASH susceptibility, 2007 confirmed that the variant is significantly more frequent
in NASH patients. More recent research shows sex-specific effects | PEMT rs7946 polymorphism and sex modify choline effect on hepatic steatosis risk, 2023
where adequate dietary choline intake modifies the risk of hepatic steatosis
differently in men and women.
Practical Implications
Egg yolks are the most practical dietary source of choline (about 150mg per yolk).
Liver is even richer but less commonly consumed. If you carry the T allele,
deliberately including choline-rich foods daily is one of the simplest and most
impactful dietary strategies informed by your genetics. This is especially
important if you also have MTHFD1 variants (rs2236225), which independently
increase choline needs.
Interactions
PEMT interacts with MTHFD1 (rs2236225) — both variants increase choline
requirements, and the combined effect can be substantial. It also interacts
with MTHFR (rs1801133), as PEMT activity depends on SAM from the methylation cycle.
All genotypes
Normal PEMT activity — normal choline production
Your PEMT enzyme functions normally, producing phosphatidylcholine (an important membrane component) from other building blocks. This reduces your need for dietary choline. About 35% of Europeans share this genotype.
Reduced PEMT activity — increased choline need
You carry one variant allele, which reduces PEMT activity. This means you need more choline from your diet. About 47% of people share this genotype.
Low PEMT activity — high dietary choline need
You have two copies of this variant. Your ability to make phosphatidylcholine internally is reduced, making dietary choline much more important. About 18% of people share this genotype.