Choline

Choline is an essential nutrient that was only recognized as such in 1998 — very late compared with the vitamins. It is neither a vitamin nor a mineral, and because the body makes a small amount of it in the liver, for years it was considered “not needed from food.”

Today the picture is different, and the key finding is surprising: according to dietary surveys, only a few percent of the population reach adequate intake of choline. It is one of the most lacking nutrients in the Western diet — largely because of falling consumption of eggs, its main source.

Dosage and sources

One egg provides about a quarter of a woman’s daily intake — which also explains why vegans and vegetarians are at higher risk.

Benefits (Pros)

1. Fetal brain development

This is the best-established and most urgent role. Choline is needed for development of the hippocampus — the memory region — and for methylation processes in the fetus. Controlled human trials have shown that higher choline intake in pregnancy was linked to better cognitive function in the baby. Choline is the forgotten nutrient of pregnancy nutrition, alongside folic acid and iron.

2. Acetylcholine — a neurotransmitter

Choline is the raw material for acetylcholine, the neurotransmitter of memory, learning and neuromuscular transmission.

3. Cell membranes

Phosphatidylcholine is the most abundant phospholipid in the body’s cell membranes, and a major component of lecithin.

4. The liver — preventing fatty liver

Choline is needed to make VLDL — the particle that carries fat out of the liver into the blood. Without it, fat gets stuck in the liver, and this is a documented mechanism: studies in which volunteers were deprived of choline showed development of fatty liver within weeks, which reversed once choline was restored.

5. Methyl donor

Alongside folic acid and B12, choline (via betaine) takes part in the methylation cycle that breaks down homocysteine.

Downsides and Side Effects (Cons)

1. TMAO — the open debate

Certain gut bacteria convert choline (and carnitine) into TMA, which the liver converts into TMAO. High blood levels of TMAO have been linked in observational studies to cardiovascular risk.

What to know before drawing conclusions:

• Causation has not been proven. It is not known whether TMAO causes harm or is a marker of something else.
• Fish raise TMAO more than eggs or meat — and fish are consistently linked to lower cardiovascular risk. This is a contradiction the theory struggles to explain.
• The makeup of the microbiome determines the amount of conversion more than the amount of choline does.

The currently accepted conclusion: there is no justification for avoiding choline-rich foods because of TMAO.

2. Fishy body odor at high doses

High doses of choline supplements (above 3.5 grams) produce excess TMA that is excreted through sweat and breath — a characteristic fishy body odor. This is also the mechanism of the rare genetic disease trimethylaminuria.

3. Other side effects at high doses

Nausea, diarrhea, excessive sweating and a drop in blood pressure.

4. Populations at risk of deficiency

• Vegans and vegetarians — the densest sources come from animals.
• Pregnant women — the need rises just when the supply from the diet stays the same.
• Postmenopausal women — estrogen boosts the liver’s own production of choline, so its decline increases dependence on diet.
• Carriers of polymorphisms in the PEMT gene — lower efficiency of the body’s own production.

5. Supplements — when they make sense

For most people, one to two eggs a day solve the problem without a supplement. Supplementation is relevant for vegans and for pregnant women who don’t eat eggs — preferably with professional advice.

Summary

Choline is the nutrient most people don’t know about and most don’t get enough of: only a few percent of the population reach adequate intake. It is needed for acetylcholine, for cell membranes, for clearing fat from the liver — and above all for fetal brain development, where it is considered the forgotten nutrient of pregnancy nutrition. The solution is very simple: eggs. One egg provides 147 mg — about a quarter of daily intake — mostly in the yolk. As for the worry about TMAO: it is not well founded enough to justify avoiding choline-rich foods.