FUEL FOR THOUGHT & EXERCISE PERFORMANCE: Acetylcholine VS. Dopamine
By Robert Schinetsky
Pre workout supplements are an interesting breed.
Their purpose is pretty straightforward -- to supply the body with nutrients to support and augment performance through a variety of mechanisms, such as improving ATP production, delaying the onset of central/peripheral fatigue, and increasing feelings of alertness, focus, and concentration.
Yet, despite its simplicity, pre workout supplements are some of the most botched products on the market, especially when you consider the scores of pre workouts on the market that contain ingredients that confer little-to-no known performance benefits, such as L-glutamine, BCAAs, and L-arginine.
One of the aspects most, if not all, pre workout supplements seek to enhance/optimize is the body’s neurotransmitter network.
Neurotransmitters are chemical messengers that transmit signals from nerve cells to target cells that are located in muscles, glands, or other nerves. They ultimately impact how we perceive, interact, and react to the various stimuli in our environment.
When it comes to pre workouts, specifically, products usually key in on boosting levels on one or two neurotransmitters, namely dopamine and acetylcholine.
Today, we take a closer look at these two neurotransmitters and which one, if any, should be the focus of your pre workout supplement needs.
Acetylcholine Promoting Supplements
Acetylcholine is most commonly referred to as the “learning neurotransmitter” due to its involvement in (you guessed it) learning as well as memory and focus. It also plays a key role in muscle contractions as well as the mind-muscle connection.
At the heart of acetylcholine is choline -- an essential nutrient responsible for several vital functions in the body particularly in regards to cell membranes, which are composed of phospholipids (phosphatidylcholine). Phospholipids aid the overall structural integrity of a cell membrane.
Choline is also heavily involved in central nervous system signal transmission (sending signals from the brain to the muscles) and lipid metabolism and utilization.
Here are several common supplements included in pre workouts to boost acetylcholine levels in the body:
Choline bitartrate is perhaps the most common form of supplemental choline on the market. It’s also one of the cheapest as well. Choline bitartrate is ~41% choline by weight, which means in 1000mg of choline bitartrate, you’re getting 410mg of actual choline.
Typically, it’s included in pre workouts and/or nootropics to enhance acetylcholine levels in the body, which should promote greater learning, memory, and focus.
However, choline bitartrate doesn’t cross the blood-brain barrier, which means it won’t have much of an effect in increasing brain levels of acetylcholine.
Furthermore, research has found no benefit of choline bitartrate supplementation for exercise to exhaustion at 70 or 150% of VO2 max.
Doses used in the trial were 2.43 grams of choline bitartrate, which is 2-4 times higher than the dose included in most pre workout supplements (500-1000mg).
Another form of choline found in dietary supplements, though not as common as it once was, is choline citrate, which contains 50% choline. So, for every 1,000mg of choline citrate ingested, you’re getting 500mg of actual choline.
As was the case with choline bitartrate, choline citrate has been studied for its potential benefits in improving exercise performance, particularly during prolonged exhaustive exercise, which is when choline levels may be depleted.
However, research finds that even after 4 hours of rigorous exercise choline citrate conferred no additional benefit compared to placebo for either run time to exhaustion or squat tests.
The dose of choline citrate used in this particular study was 8.4 grams! That’s over 4 times what you’ll find as the max dose of choline bitartrate used in pre workouts these days!
Now, researchers have put forth that that reason choline salts may not have been shown useful for improving performance could be due to lack of bioavailability or the exercise wasn’t exhaustive enough to deplete choline concentrations to any meaningful degree, which means supplementing with choline wouldn’t offer much benefit as there’s no deficiency that needs to be rectified.
Transitioning away from the choline salts into the realms of choline-containing supplements that offer superior bioavailability (as well as added expense) brings us to Alpha-GPC.
Alpha-GPC is able to cross the blood-brain barrier and is converted to phosphorylcholine, where it can then serve as a source of choline for acetylcholine synthesis.
And, some studies indicate it may improve cognitive function compared to placebo, particularly using high doses (1000-1200mg alpha-gpc) in those with cognitive decline.
Regarding its performance-boosting potential, acetylcholine is responsible for the action potential that stimulates a muscle to contract. Based on this, it’s believed that supplementing with alpha-gpc (or some other acetylcholine-boosting nutrient) could enhance performance by increased muscle contraction, leading to greater power and strength output.
To date, that theory remains to be fully elucidated; however, a pair of recent studies involving dietary supplements containing 300mg or 150mg of alpha-GPC noted improvements in reaction time and vertical jump power.[4,5]
Note: it’s worth mentioning that both of the supplements used in the aforementioned studies included additional ingredients besides alpha-GPC.
A more recent study, in which subjects were given 600mg alpha-GPC, noted improvements in muscle strength during an isometric mid thigh pull assessment.
Lastly, a 2017 study testing 200mg and 400mg doses of alpha-GPC administered 30 minutes before testing did not demonstrate any changes in psychomotor vigilance performance.
As it stands, more research is needed regarding the utility of alpha-gpc and resistance-training. It may have some benefit regarding vertical or countermovement jump, but the research is far from conclusive.
Another popular (and equally expensive) form of supplemental choline, especially those who dabble in the realm of nootropics and cognitive performance, is CDP-choline (citicoline).
CDP-choline is another form of highly bioavailable choline that can readily cross the blood-brain barrier. It’s ~18% choline by weight, which might lead you to believe it’s ineffective compared to alpha-gpc, or even choline bitartrate. However, once it’s digested, cdp-choline separates into cytidine and choline.
The body can use cytidine to produce uridine, a molecule that serves as a major component of RNA and a promoter of DNA repair and cell growth. Uridine may also help stabilize dopamine activity at the receptor level.
Furthermore, uridine is needed to synthesize the phosphatidylcholine (PC) in neuron membranes, and it assists with neuron repair.
In terms of human research, CDP-choline has shown benefit for improving brain ATP production (up to 14%) as well as improved attention and psychomotor speed and reduced impulsivity in adolescents.
To date, there is no research investigating CDP-choline’s ability to improve physical exercise performance.
Thus far, we’ve discussed ingredients that directly work to increase acetylcholine levels by increasing serum concentrations of choline. Up next, are a pair of supplements that work to enhance acetylcholine concentrations indirectly.
First, is huperzine A -- an alkaloid naturally occurring in Toothed Clubmoss.
Huperzine A functions as an acetylcholinesterase inhibitor. Acetylcholinesterase is the enzyme that breaks down acetylcholine. By inhibiting this action, acetylcholine remains active longer in the body, which would support improved memory (and by extension muscle contraction).
As with CDP-choline, there is no exercise-specific data on huperzine.
It’s being investigated as a potential treatment for Alzheimer’s disease, and it has been found to improve memory in learning tasks in school children.[9,10]
However, as it stands there is no substantial body of evidence that huperzine A could improve cognitive function or physical performance in the context of exercise or resistance training.
DMAE (Dimethylaminoethanol) isn’t as popular as it once was in pre workout supplements, but you’ll still see it pop up from time to time.
It is naturally produced by the body and contains one less methyl group than a molecule of choline. DMAE has the ability to reduce build-up of beta-amyloid -- the “age pigment,” which is known to impair cognitive function and is implicated in age-related cognitive decline.
Due to having one less methyl group than choline, DMAE is noted to more easily cross the blood-brain barrier. However, it doesn’t directly increase acetylcholine levels in the brain.
DMAE may increase acetylcholine levels by inhibiting choline metabolism in other tissues of the body which may limit the amount of choline used by other tissues, leading to greater choline levels in the bloodstream.
Researchers have also suggested it may coax your cholinergic receptors to be more active, thereby leading to more acetylcholine.
To date, studies in humans have found the DMAE may be beneficial for improving behavior and attention span in children with ADHD as well as improving symptoms of cognitive decline in individuals with mild cognitive impairment.[15,16]
But, when it comes to improving exercise performance specifically, the data is lacking.
The final acetylcholine-promoting agent to be discussed is acetyl-l-carnitine (ALCAR).
Carnitine is a well-known compound, frequently found in weight loss aids due to the fact that carnitine facilitates the delivery of fatty acids into the mitochondria where they can then be oxidized (burned) for energy.
Despite the mechanism making sense, the data showing that regular L-carnitine improves weight loss to any meaningful degree is mixed at best.
Acetyl-L-Carnitine is an “enhanced” form of carnitine that’s been acetylated. This allows it to cross the blood-brain barrier and supports acetylcholine synthesis.
ALCAR also supports energy metabolism in the brain and confers neuroprotection due to its ability to scavenge free radicals and protect against oxidative stress, which can contribute to cognitive decline.[18,19]
However, as we’ve mentioned before with the other ingredients covered thus far, there is a succinct lack of evidence denoting any benefits with ALCAR and exercise performance.
Can it be helpful for cognitive health long term?
But, will it help you train harder or last longer in the gym?
The data simply isn’t there yet.
Potential Concerns About Carnitine + TMAO
TMAO (trimethylamine-N-oxide) is created when our gut bacteria metabolize certain nutrients, including choline, betaine and carnitine -- all of which are prevalent in animal-based proteins.
A number of studies have found an association between increased levels of TMAO and an increased risk for clot-related events, including heart attack and stroke.[20,21,22]
Long-term supplementation of L-carnitine has also been noted to induce an increase of fasting plasma trimethylamine-N-oxide (TMAO) levels.
However, other studies in humans have noted that while L-Carnitine does increase TMAO levels, it doesn’t increase markers of atherosclerosis, inflammation, or oxidative stress.[24,25,26]
Still, researchers make it clear that “additional studies focusing on long-term supplementation and its longitudinal effect on the TMAO metabolism and cardiovascular system are needed.”
Most recently, a 2021 population study, including an average follow-up of 8 years, noted that elevated plasma levels of TMAO, as well as its precursor -- choline, predict incident risk for cardiovascular disease development independent of traditional risk factors.
The Bottom Line on Acetylcholine and Exercise Performance
Based on the current body of evidence, there doesn’t appear to be convincing evidence or a need to supplement with acetylcholine-promoting agents prior to exercise.
A number of studies have found that choline supplementation (in various forms) has little-to-no significant impact on physical exercise performance or mental aspects of performance, including reaction time, logical reasoning, vigilance, spatial memory, or working memory.
This may be due to the fact that choline or acetylcholine doesn’t appear to be the key limiting factor in performance.
For instance, previous research has found that even after 4 hours of exhaustive exercise there was not a significant depletion in plasma choline, nor was there any benefit obtained from supplementing with 8+ grams of choline citrate (yielding 4,000+mg of choline).
The take home here is that getting after it in the gym from 60-90 minutes is unlikely to deplete choline or acetylcholine levels to any meaningful degree, which indicates there likely isn’t much benefit to supplementing with acetylcholine-promoting agents pre training.
Dopamine Promoting Supplements
Dopamine, commonly referred to as the “motivation and reward” molecule, is the principal catecholamine/neurotransmitter that’s directly involved in motor control and has been identified as being important to increased and maintained efficiency of exercise-trained humans.
It is created from the amino acid tyrosine, which can cross the blood-brain barrier, and is transformed into L-3,4-dihydroxyphenylalanine (L-DOPA) via tyrosine hydroxylase, which is then ultimately converted to dopamine by dopa decarboxylase.
Note: this is why AML Pre Workouts contain both L-Tyrosine as well as L-Dopa (from velvet bean) as it provides the raw material needed to support dopamine synthesis.
Beyond its role in motor control, decision-making, motivation and reward, dopamine also plays an important role in cardiovascular and renal function, which impacts heart rate, blood pressure, muscle tone, visual processing, calcium homeostasis, and protein synthesis.
Additional research has found that dopamine confers ergogenic effects as it increases heat storage and hyperthermia tolerance during exercise.
On the flip side, depletions in the concentration of dopamine in the brain as a result of prolonged exercise has been linked with the onset of central fatigue based on the animal and human studies.[31,32,33]
While some earlier research has found no significant improvements in physical performance after tyrosine supplementation[34,35,36], later studies indicate that tyrosine supplementation can enhance working memory, cognitive tasks, and tolerance to stress under stressful situations, such as military operations or sleep deprivation.[37,38,39,40]
Additional research provides evidence that tyrosine supplementation prior to exercise may improve vigilance and reaction time, indicating improved cognitive function.
A 2015 review concluded that tyrosine supplementation may effectively “enhance cognitive performance, particularly in short-term stressful and/or cognitively demanding situations.”
Taken together, the current body of evidence suggests that supplementing with tyrosine before stressful situations (such as intense physical exercise) can help maintain higher levels of performance and help attenuate decrements in performance associated with depleted dopamine levels.
For these reasons, Advanced Molecular Labs builds its pre workout supplements around a robust matrix of ingredients all keyed in on promoting greater dopamine concentrations, including the likes of L-Tyrosine, L-Dopa, Folic Acid, and of course the base of all the best pre workout supplements -- caffeine.
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