‘Why do you always insist that I reach my protein macro everyday? What makes it so important?’ A common question with a very simple answer, so read on!
In order to build muscle you need what are known as branch chain amino acids. One of those BCAA’s is called leucine. Leucine helps improve muscle growth better than all the others types, but there’s a threshold you need to reach before this amino acid can actually work.
Leucine is an essential amino acid and is found in protein sources such as egg whites and animal protein. Leucine stimulates muscle growth by activating a muscle building pathway called mTOR (mechanistic target of rapamycin). Elevated leucine levels alert mTOR that there are sufficient nutrients and amino acids for muscle building. If you do not have enough leucine in your body, mTOR gets disabled. And this makes it extremely important that you reach the leucine threshold if you want to help your muscles grow.
So how do I do this?
In order for your body to utilize this muscle-building power of leucine, you have to consume enough of it. Your body absorbs 100% of the amino acids we consume but only a very small percentage of that actually goes to muscle building: other organs and muscles in our bodies also require amino acids.
When you eat protein, amino acids are distributed through your digestive tract to your liver, kidneys, cardiac and smooth muscles, but also to tissues like the skin. To reach a leucine threshold, where the amount of amino acids you consume are used to synthesise skeletal muscles instead of being delegated to the rest of the body, you need to make sure you are consuming enough protein with a high leucine content at one time.
And does this change as I age?
Yes indeed, the older you get it becomes more necessary to consume higher concentrations of leucine in order to get the benefits. This is because when you are younger you are more sensitive to the mTOR pathway, the older you get the less sensitive you become.
It also seems that once you have reached your personal leucine threshold there is a so-called ‘refractory period’: the body must use the amino acids it already has before it can begin to use more as it enters the body. To achieve this threshold and to make sure you are getting the most out of your nutrients, it seems to be best to eat a larger amount of protein in one meal, and then ‘replenish’ your body with protein after four to five hours instead of constantly eating small amounts of protein throughout the day.
How much leucine are we talking about?
The amount of leucine contained in a protein needed to achieve this threshold, according to current research, is between 26 and 41 percent leucine, or 3.2- 4.4 gram. For reference: a 4.7oz steak will provide you with this amount of leucine, as will 5 large eggs.
So there you have it! Do you have any questions about this? You can contact me here: