Let’s look more specifically at some of the BCAA myths out there and the real science behind muscle growth.
While BCAAs are vital for energy production and muscle metabolism, BCAAs alone do not stimulate muscle protein synthesis.
Leucine is particularly popular in the supplement industry because it is known to be a key regulator of the rate of protein synthesis.
It not only gets incorporated into protein itself, but it can activate the molecular processes that are involved in initiating the process of protein synthesis2.
The idea behind BCAAs and leucine supplements is that spiking leucine levels will initiate the metabolic processes for protein synthesis and increase protein turnover.
Let’s look at why this doesn’t work as you might think it would:
You can think of leucine as a the key to the car, but you still need enough gas to go anywhere.
The best way to stimulate protein synthesis is to take a balanced profile of EAAs that is optimal for protein synthesis, this is the most potent and effective method because it not only starts the process but also gives the body the building blocks it needs to follow through the whole process4.
Other ways to stimulate the body is high quality dietary protein, resistance training, and anabolic hormones like growth hormone and testosterone. These aren’t as effective because you still need to ensure that you have a sufficient amount of amino acids available in the system to complete the protein synthesis process.
When we exercise the oxidation of leucine increases within the body naturally.
The dip in leucine is an issue for a couple reasons:
BCAA were thought to minimize serotonin activity by boosting the leucine in the body and thus helping with mental focus and performance. Logically this makes sense, but what happens when you spike leucine levels in the blood?
The body has regulatory mechanisms that helps maintain the EAA ratio in the blood (pg27) An enzyme is activated that degrades the amount of leucine, but it also degrades the other BCAAs in the process as well. You’re left with decreased concentrations of all your BCAAs which will limit the rate of protein turnover.
Even if you take a supplement with all three BCAAs, it still offsets the natural ratio of EAAs in the amino acid pool thus BCAAs do not have a demonstrable beneficial effect on protein synthesis5.
Most people take BCAA supplements before and during their workouts when the body is already primed to oxidize BCAAs like leucine so you’re left with no measurable effect6.
To get an increase in protein turnover and get the most benefits out of your workout it is best to supply the body with a balanced ratio of EAAs. The perfect ratio will not disturb the body or signal it to oxidize any of the EAAs. Taking an EAA will also increase the production and functioning of mitochondria.
Aerobic:Take EAA within 1 hr after
Resistance: Take EAA 30min before & Take EAA after
When taken alone, without the other 6 EAAs, BCAAs actually have an adverse effect on muscle protein synthesis as they throw off the body’s amino acid pool and trigger the degradation of all the BCAAs within the system.
