When learning about muscle metabolism, the example used is seemingly always sprints vs. walking or light jogging. It’s essentially a comparison between high-intensity and low-intensity training – anaerobic vs. aerobic conditions. And, in dealing with metabolism between these two conditions, it’s easy to fall into the trap that high-intensity training equals anaerobic, while low-intensity training equals anaerobic. Things aren’t so dichotomous in the body – while one condition predominately utilizes fuel differently, it’s never so black and white. Now, given that I’ve talked about glycolysis in painful detail in this series, let’s discuss what happens under anaerobic conditions.
Here’s glycolysis in a nutshell:
Glucose + 2 NAD+ + 2ADP + 2 Pi –> 2 NADH + 2 pyruvate + 2 ATP + 2 H20 + 4 H+
For all intents and purposes, let’s assume total anaerobic conditions (just remember it isn’t quite so). Under these training conditions, your muscles rapidly start making ATP, primarily through glycolysis. That’s because the TCA cycle (the energy generating pathway after glycolysis) is relatively slow. By putting your body under high-intensity conditions, you’ve created a demand for energy quickly. And so, glucose is broken down to pyruvate and this pyruvate accumulates and converts to lactate, depleting NAD+ in the process. Your body has a way of recycling this – the enzyme lactate dehydrogenase.
Lactate dehydrogenase converts pyruvate and NADH into NAD and lactate – we call this homolactic fermentation. Lactate is the anion coming from the dissociation of lactic acid. Lactic acid is an alpha hydroxy acid (its hydroxyl neighbors its carboxyl group), so it’s relatively strong. As such, it can lower the pH in your muscles – something you can certainly feel. This feeling acts as a signal from the muscle, letting you know that too much lactic acid is building up. Too much lactic acid can, in fact, destroy the muscle (but keep this statement in context).
The accumulation of hydrogen ions from the dissociation of lactic acid (and thus, a drop in pH) slows glycolysis down, disrupts the recycling of phosphocreatine, and prevents your muscles from contracting as forcefully. Supplements like beta alanine, carnosine, and bicarbonate buffer against this. I’ll discuss this shortly. But first, how does your body naturally handle the buildup of lactate?
The Cori Cycle
Your muscles aren’t really designed to handle lactate. So, they pass the recycling duties off to the liver. Your muscles convert lactate to the amino acid alanine and dump it into the bloodstream. Your liver then picks this alanine up and converts it back to lactate, then to pyruvate, and then to glucose (or something else in a different context). This glucose can then be used to fuel the strenuous activity your muscles are enduring by going through glycolysis. This is the Cori Cycle. By doing this, you’re incurring an oxygen debt, which will be paid post-workout.
Staving Off the pH Drop
Carnosine is a di-peptide (two amino acids linked together) made up of beta alanine and histidine. It has a host of benefits for the body ranging from gut, liver, and eye health to improved immune and even cognitive function. But how does it buffer against acidosis? Carnosine has an imidazole ring as part of its structure – this ring gives it the ability to buffer against hydrogen ions. Fast twitch muscle, the type of muscle fiber that is taxed greatly during anaerobic glycolysis, can store plenty of carnosine. Increasing muscle carnosine levels should, then, help to delay the onset of fatigue following high intensity exercise.
As I said, beta alanine is one out of the two components that makes up carnosine. And, it happens to be the rate limiting factor in carnosine production. Supplementing with beta alanine has shown to increase muscle carnosine levels as much as 80% (Culbertson, 2010). Because of this, there’s an idea that beta alanine might be a superior supplement for buffering against acidosis. But why not just take more carnitine?
Carnosine vs. Beta Alanine
There’s debate between which is superior, but in the context of performance, I’d have to cast my vote for beta alanine. It’s counterintuitive, but if you’re goal is to increase intramuscular carnosine stores, thereby delaying the time it takes for the muscle to fatigue, beta alanine will actually do a better job than carnosine supplementation. This is because, when consumed orally, carnosine is rapidly metabolized by an enzyme called carnosinase. Once broken down, its components remain and have to be pieced together to generate carnosine once again. By taking the limiting factor, beta alanine, as a supplement (and you should already have plenty of histidine), you can avoid the extra step. It’s likely that this can be overcome through higher dosing of carnosine, but that’s hardly the solution (and beta alanine is inexpensive).
Beta Alanine and Growth Hormone
Those who know their biochemistry well know that growth hormone is released in response to lactic acid. So, the concern that beta alanine supplementation and its possible negative impact on growth hormone is warranted. However, it’s important to understand that beta alanine isn’t targeting lactic acid. Rather, it’s buffering against the hydrogen ions that are created as a result of lactic acid production. The body then, is able to sustain longer bouts of muscular contractions despite the buildup of lactic acid. If anything, since the body is able to handle higher amounts of lactic acid due to beta alanine supplementation, wouldn’t this allow for an even greater growth hormone response?
Beta alanine can be a decent performance enhancer, but there are some things to consider when taking it. First, timing seems to play a role – when combined with carbohydrate and protein, carnosine levels are enhanced (Baguet, 2009). Second, there seems to be some evidence that creatine may have a synergistic or at the very least, additive effect alongside with beta alanine because of its ability to increase muscle phosphagen levels. This should further combat the effects of fatigue by increasing anaerobic and aerobic capacity. Whether or not they work synergistically or independently of each other requires some more research.
I’ve seen on several forums that some are concerned about taurine and beta alanine being competitors. To that, I’d say to always keep things in context – it’s never a black and white situation. While it is true that the two share the same transporter (SLC6a6), this is a matter that simply has been exaggerated. Unless the dose of beta alanine is quite high (in which case, extreme nausea will be more of a concern) there should not be a problem with taurine absorption. Studies have used doses as high as 6.4 grams/day (much more than I would recommend) or more and didn’t find any interactions with taurine (Dawson, 2002).
And so, to close this off, I’d recommend taking ~3 grams of beta alanine with your pre-workout meal. This seems to be enough, when taken consistently, to notice its effects. Supplementing with beta alanine can take several weeks to kick in, so don’t expect anything immediately. There is an interesting effect, called paresthesia, with beta alanine and becomes much more noticeable the higher the dose is. It can best be described as a “pins and needles” type feeling. This isn’t an allergic reaction. It shouldn’t be too obnoxious of feeling if the dose is kept around 3 grams and the sensation diminishes relatively quickly.
If you have any questions regarding anything I’ve covered here, feel free to reach me at firstname.lastname@example.org.
Baguet, A., Reyngoudt, H., Pottier, A., Everaert, I., Callens, S., Achten, E., & Derave, W. (2009). Carnosine loading and washout in human skeletal muscles. Journal of Applied Physiology, 106(3), 837–842. doi: 10.1152/japplphysiol.91357.2008
Culbertson, J. Y., Kreider, R. B., Greenwood, M., & Cooke, M. (2010). Effects of beta-alanine on muscle carnosine and exercise performance: a review of the current literature. Nutrients, 2(1), 75–98. https://doi.org/10.3390/nu2010075
Dawson, J. R., Biasetti, M., Messina, S., & Dominy, J. (2002). The cytoprotective role of taurine in exercise-induced muscle injury. Amino Acids, 22(4), 309–324. doi: 10.1007/s007260200017