Choline and creatine draw from the same methyl-group budget

A large egg carries about 147 milligrams of choline, and nearly all of it sits in the yolk that gets poured down the sink the moment a recipe calls for liquid egg whites.¹³ People make that swap for protein-per-calorie reasons. Creatine synthesis also draws on SAM-derived methyl groups that support phosphatidylcholine synthesis. A secondary analysis of a randomized trial in arsenic-exposed Bangladeshi adults found that creatine did not significantly prevent a decline in plasma choline, so creatine should not be counted as a dietary choline source.⁴⁵⁸

01Choline and creatine compete for the same methyl groups

The body runs most of its methylation reactions off a single currency, S-adenosylmethionine, or SAM, made from the amino acid methionine. SAM hands off a methyl group to whatever reaction needs one, then becomes S-adenosylhomocysteine, which gets broken down to homocysteine and either recycled back to methionine or cleared through a separate pathway. The system only works if enough methyl groups keep entering it.⁴⁵

Two of the biggest draws on that pool are phosphatidylethanolamine N-methyltransferase, or PEMT, which builds phosphatidylcholine, the body's own backup route to choline, and guanidinoacetate N-methyltransferase, or GAMT, the last step in endogenous creatine synthesis. Older estimates put creatine synthesis at more than 70 percent of the body's SAM-derived methyl group use. A 2006 reanalysis by Stead and colleagues in the American Journal of Clinical Nutrition argued that figure was too high because PEMT-driven phosphatidylcholine synthesis had been undercounted, and revised creatine's share down while identifying choline synthesis as the other major consumer of the same pool.⁴ Researchers still argue over the exact split between the two pathways, but both draw from the same account.⁴⁵

02How much choline liquid egg whites remove

Choline sits almost entirely in the yolk. USDA food composition data puts a large egg at roughly 147 milligrams of choline, with the white contributing a small fraction of that and the yolk carrying the rest.¹³ Pour off 200 grams of liquid egg whites for a high-protein breakfast scramble and the choline number changes dramatically because the yolks are gone.³

The Adequate Intake for choline is 550 milligrams a day for adult men and 425 milligrams for adult women, set by the National Academies from depletion and liver-function data because the evidence was too thin to support a full Estimated Average Requirement.¹ Wallace and Fulgoni's analysis of NHANES 2009 to 2012 data found that only 6.6 percent of adults 19 and older met that target for usual choline intake from foods, meaning roughly 93.4 percent had usual food intakes below the AI.² Two whole eggs already cover more than half the adult female AI.¹³ A whites-only version of the same breakfast covers almost none of it.³

03The methyl-group cost of making creatine without a supplement

Published estimates place endogenous creatine synthesis in healthy adults at roughly 1 to 2 grams per day. It follows a two-step pathway that starts with arginine and glycine forming guanidinoacetate in the kidney, then finishes when the liver's GAMT enzyme methylates that guanidinoacetate into creatine using a SAM-derived methyl group.⁵⁶ That synthesis runs whether or not a person eats meat or fish, and it runs harder in people with more muscle mass to maintain, because creatine degrades to creatinine at a rate roughly proportional to the size of the muscle creatine pool. Dietary creatine downregulates how much endogenous creatine the body has to build from scratch.⁵⁶

That downregulation is why creatine has been proposed as a methyl-group-sparing intervention.⁵ Skip the supplement and the body still has to build some of the creatine it needs. Endogenous synthesis requires methyl transfer through GAMT, which draws on the same system used by PEMT.⁴⁵

04Creatine supplementation did not reliably protect choline status

The biochemical mechanism is established. Whether it produces a measurable choline benefit is a separate question, and the secondary analysis built to test it directly gives a different answer than the biochemistry alone suggests.⁴⁵⁸

Peters and colleagues analyzed 458 participants across four treatment groups for 12 weeks: placebo, 3 grams per day of creatine, 400 micrograms per day of folic acid, and the combination of creatine and folic acid.⁷ Creatine supplementation lowered plasma guanidinoacetate compared with placebo, which is the expected signature of downregulated endogenous creatine synthesis. It did not lower plasma total homocysteine on average across the full sample.⁷

A companion analysis from the same trial looked directly at plasma choline in 605 adults.⁸ It compared 400 and 800 micrograms per day of folic acid with placebo, creatine with placebo, and creatine plus 400 micrograms of folic acid with 400 micrograms of folic acid.⁸ Choline fell 6.6 percent in the placebo group over the 12 weeks. The creatine group's decline was smaller, at 2.6 percent, but the difference between creatine and placebo did not reach statistical significance. Folic acid groups prevented the measured decline, while creatine alone did not produce a statistically significant effect.⁸

The shared biochemical pathways are established. The clinical significance of competition between them remains uncertain.⁴⁵⁸ This 12-week secondary analysis in arsenic-exposed Bangladeshi adults found that lowering endogenous creatine synthesis did not reliably translate into protected choline status. The 12-week trial did not test lifters cutting choline through liquid egg whites while loading creatine. Until direct evidence in that population exists, treat creatine as biochemically connected to choline status and track choline separately.⁸

05How to cover choline while keeping liquid egg whites

Liquid egg whites remain a useful protein tool. Creatine remains one of the best-supported supplements in sports nutrition for reasons that have nothing to do with choline.⁶ Count each choice separately when planning choline.

If liquid egg whites are the protein anchor, the choline decision still runs through food. A yolk or two most days, a soy or fish serving a few times a week, or a sized supplement when the diet genuinely cannot close the gap all work. No trial cited here supports counting the creatine already in the shaker as choline coverage.