Why Endurance Athletes' Brains Run Low on Choline

Why Endurance Athletes' Brains Run Low on Choline

Run a marathon and your blood chemistry changes in ways you can feel but rarely name. One of those changes involves choline, a nutrient most athletes never think about. The link between choline endurance exercise and the wall runners hit late in a race is older and better documented than you might expect.

Back in the 1980s, MIT researchers measured plasma choline in runners crossing the finish line of the Boston Marathon. The numbers dropped sharply. That finding kicked off four decades of questions about whether your brain and muscles are quietly running short on a key raw material when you push hardest.

Here is what the science actually says, and what it does not.

Key Takeaways

• Marathon running drops plasma choline by around 40%, first documented in Boston Marathon runners in the mid-1980s.
• Choline is the precursor to acetylcholine, the neurotransmitter that tells your muscles to fire.
• Low choline may reduce acetylcholine release at the neuromuscular junction, which could contribute to fatigue.
• Supplementation prevents the drop, but most studies show it does not reliably improve endurance times in well-fed athletes.
• Many adults already fall short of recommended choline intake before they lace up.

What Choline Actually Does in an Athlete's Body

Choline is the building block for acetylcholine, the chemical signal that crosses the gap between your nerves and your muscle fibers. No acetylcholine, no contraction. That makes choline relevant to every stride, pedal stroke, and stroke of the pool.

Your body makes a small amount on its own, but most of it comes from food. The Food and Nutrition Board recommends an adequate intake of 425 mg/day for adult women and 550 mg/day for adult men, according to the Linus Pauling Institute at Oregon State University. Eggs, liver, and protein-rich foods carry the heaviest loads.

Most people do not hit that number. Survey data analyzed in a study published in a National Institutes of Health journal found that egg eaters take in nearly double the choline of non-eaters, and that suboptimal intake is common across the population. So plenty of athletes start a long session with a tank that was never full.

The Choline Depletion Running Story Starts in Boston

Plasma choline drops roughly 40% after a marathon. That is the headline finding, and it has held up.

The original work came from L.A. Conlay and Richard Wurtman's group at MIT, who measured decreased plasma choline concentrations in marathon runners and published the result in the New England Journal of Medicine in 1986. A later review noted that runners of the 1985 and 1986 Boston Marathon showed a 40% drop in plasma choline levels, per a paper archived in a National Institutes of Health database.

This is the plasma choline marathon effect in a nutshell. The longer and harder the effort, the lower the reading tends to go. One review noted a negative relationship between time spent cycling and plasma choline concentrations, with longer bouts pulling levels down further.

Why does it happen? Your body burns through choline to keep acetylcholine production going, and it also pulls choline into other pathways under metabolic stress. The supply side cannot always keep pace with demand.

Choline, Acetylcholine, and the Fatigue Question

A drop in choline may reduce acetylcholine release at the neuromuscular junction, which could blunt the signal that drives muscle contraction. This is the mechanism researchers keep circling back to.

A 1992 follow-up from the same MIT lineage found that changes of similar magnitude to those seen in marathon runners have been shown to reduce acetylcholine release from the neuromuscular junction in vivo. In plain terms, the size of the choline drop matters because it lands in a range that can affect how well your nerves talk to your muscles.

That connects acetylcholine muscle function directly to the choline you eat. The neuromuscular junction is one of several spots where transmission can fail during heavy exercise, contributing to peripheral muscle fatigue.

So the theory is clean. Lower choline means less acetylcholine, which means weaker signaling, which means choline fatigue late in a race. The data, though, is messier than the theory.

Does Supplementing Choline Improve Performance?

Supplementing choline reliably prevents the exercise-induced drop, but it does not consistently make trained athletes faster. This is the part the supplement marketing tends to skip.

A study on trained cyclists found that choline ingestion raised blood levels by 37 to 52% within an hour, and neither group depleted choline during exercise when supplemented. The plumbing worked. The performance payoff did not show up in well-conditioned riders.

Other work points the same direction. A controlled trial found that choline supplementation did not improve endurance in highly trained cyclists, though it helped explosive strength during a short, intense fatiguing task. The benefit seems to depend on who you are and what you are doing.

Here is the honest read on choline athletic performance:

• If you already eat enough choline, topping up may not move your race times.
• If you start depleted or run very long efforts, replacing what you lose makes more sense.
• The clearest gains so far show up in strength and high-intensity tasks, not steady-state endurance.

How to Keep Your Choline Topped Up

Food is the simplest fix. Eggs are the standout, since egg eaters take in close to double the choline of people who skip them. Liver, beef, chicken, fish, and dairy all contribute.

If you train long and often, pay attention during heavy weeks. Choline depletion running is most relevant for marathoners, ultra runners, and long-course triathletes, not someone jogging three miles. Match your intake to your workload.

Supplements like CDP-choline and alpha-GPC raise blood choline quickly, but the evidence says they shine more for cognitive sharpness and strength than for shaving minutes off a long run.

The Bottom Line on Choline and Endurance

Long, hard exercise lowers plasma choline, and the steepest drops show up after events like marathons. Because choline feeds acetylcholine, the nutrient sits close to the machinery of muscle contraction, which is why researchers have studied it as a fatigue factor for nearly forty years.

The practical takeaway is calmer than the mechanism suggests. Eat enough choline, lean on eggs and protein, and pay extra attention during your highest-volume blocks. For most athletes, that covers it. The performance miracle that early supplement hype promised never quite arrived, but the nutrition fundamentals are sound and worth respecting.

Frequently Asked Questions

How much does plasma choline drop during a marathon?

Plasma choline falls roughly 40% in marathon runners, based on measurements taken from Boston Marathon participants in the mid-1980s by MIT researchers. The exact size of the drop varies with the length and intensity of the effort. Longer, harder sessions tend to pull levels lower, while shorter or moderate workouts may not deplete choline meaningfully.

Does low choline actually cause fatigue?

It may contribute. Choline is the precursor to acetylcholine, the neurotransmitter that signals muscles to contract. Research shows that drops in choline similar to those seen after a marathon can reduce acetylcholine release at the neuromuscular junction. That said, fatigue during endurance exercise has many causes, and choline is only one piece of a larger picture.

Will taking a choline supplement make me faster?

Probably not if you already eat enough choline. Studies on trained cyclists show supplementation prevents the exercise-induced choline drop, but it does not reliably improve endurance times in well-conditioned athletes. The clearest benefits appear in explosive strength and high-intensity tasks rather than steady-state endurance running or cycling.

What foods are highest in choline?

Eggs are the standout source, and people who eat them take in nearly double the choline of those who do not. Beef liver is exceptionally rich, followed by other meats, poultry, fish, and dairy. Plant sources like soybeans and cruciferous vegetables contribute smaller amounts. A varied diet built around protein usually covers your needs.

How much choline do I need per day?

The Food and Nutrition Board sets adequate intake at 425 mg per day for adult women and 550 mg per day for adult men, per the Linus Pauling Institute. Many adults fall short of these numbers, especially those who avoid eggs. Endurance athletes training long hours may want to pay closer attention during high-volume weeks.

Is choline depletion a concern for short workouts?

No. The sharp choline drops documented in research come from prolonged, strenuous efforts like marathons and long cycling bouts. Shorter or moderate sessions do not appear to deplete choline in a meaningful way. If your training is brief or low intensity, choline status is far less of a factor than it is for ultra-distance athletes.

The Pre-Session Tool the Choline Story Leaves Out

Choline depletion is a nutrition problem, and the fix is on your plate. Eat your eggs, fuel your long efforts, and the chemistry mostly sorts itself out. None of that addresses the other thing athletes want before a hard session: a sharp, steady head and quick reaction time without the wired feeling that wrecks pacing.

That is where Roon fits. It is a sublingual pouch with four ingredients working together: 80 mg caffeine, 60 mg L-theanine, 25 mg methylliberine (Dynamine), and 5 mg theacrine (TeaCrine). It absorbs in 5 to 10 minutes and is built for 6 to 8 hours of focus with no jitters, no crash, and no tolerance buildup.

To be clear, Roon is not a choline source and it will not refill what you burn during a marathon. It is a focus tool, not a fueling strategy. If you want a clear pre-session edge to pair with smart nutrition, try Roon before your next training block.

Written by Roon Team