Amino Acids and Nitrogen's Role in Making Gains


The versatility of amino acids in the body is pretty impressive. From facilitating chemical reactions, providing structure to your bones, muscles, skin and hair, to defending against infections and forming certain hormones. No wonder they were named proteins: ‘of prime importance’.

Does this mean proteins also deserve the top billing in our diets? What are the best sources of high-quality protein? How much protein should you consume in order to build/maintain muscle mass? Let's dig into the wonderful world of science and nutrition and find out!

What is protein?

Protein is made up of 20 amino acids (9 of which are essential) and is the only macro nutrient that provides nitrogen to our bodies.

What is so important about nitrogen you might ask? It is essential for all the processes mentioned above. Furthermore nitrogen balance is a determinant of whether or not all the necessary ingredients are there for muscle protein synthesis (MPS). Studies show if this level is positive – muscle is able to be built. If it is negative – it's likely that muscle protein is being degraded.

What happens if you don't consume enough protein?

Let's think of muscle as your body’s protein storage heap. Any bodily process that needs an amino acid, and there isn’t a free one circulating around the body, will require for some muscle to be broken down in order for the more important process to take place. So, consuming enough protein for normal body functions is essential, and keeping a positive nitrogen balance – that is consuming more protein than what is generally required – primes your body for building muscle.

What's the RDI of protein?

Generally, for maintenance and normal workings the body, the recommended daily intake (RDI) of protein per day is only between 0.7 – 1.0g per kilogram of body weight. Athletes require more, depending on intensity and volume of training.

One thing to note here is that training tends to swing you towards negative nitrogen balance. So, the more intense your training, the more protein you need for recovery or ‘to swing you back into positive nitrogen balance'.


The big question: How much protein do you need for muscle growth?

The current evidence suggests a minimum of 1.6g per kilogram per day and the upper intake of 2.2g.

What’s the difference and which number should you aim for? If you’re just starting to train and increase your protein intake, 1.6g will easily suffice. In this case anything above your regular intake will result in MPS! More seasoned lifters would fall closer to the upper level intake.

Personally, I’d recommend the higher intake just in case – the countless studies done on high protein diets and their supposed links to liver and kidney dysfunction have all come back as negative: high protein diets do not result in organ dysfunction! So, you are safe to consume more than 2.2g per kilogram of body weight per day, however anything over that number has not shown to be more effective and result in higher MPS.

How much protein can you absorb from a meal?

One question that I constantly get asked is ‘how much protein can you absorb from a meal?’

Simple answer: all or most of it depending on the meal, unless you have issues with your gastrointestinal tract (GIT).

Dietary protein gets degraded into peptides and then into amino acids along the GIT (mainly stomach and small intestine) with the aid of hydrochloric acid and digestive enzymes, and therefore gets absorbed only as small peptides and single aminos via specific carriers (depending on the amino acid).

I think that question comes from the misconception that only about 25g of protein “is used for muscle, so any more is just waste”.

So, let's reword the question to help us get to the heart of the matter and what we really want to know: “How much protein do you need to consume in a meal for maximum MPS?”

Some of the amino acids will go to synthesizing your nails, hair, hormones, enzymes, and even glucose (blood sugar - a carbohydrate) if you’re on an extremely low carb diet (the process is called Gluconeogenesis). So, we need to ensure there are enough essential amino acids to go around for all those processes and for positive nitrogen balance during the pre-prandial state (fancy way of saying during a fast or between meals).

A brand new study on just this question was published earlier in the year (I urge you to read the full study), and suggests splitting your protein across a minimum of four meals for maximum MPS – that is 0.55g per kilogram of body weight per meal if we’re aiming for the 2.2g figure discussed earlier.

Here's an example of how I would set my day up based on what we’ve discussed so far:

  • For an 80kg person: 80 * 2.2 = 176 (round up for nice whole numbers = 180g per day)
  • Substitute 30g for post-workout shake and BCAA/EAA during training: 180 – 30 = 150
  • 150 split into 4 meals = 37.5g per meal; and since I barely ever get the exact amounts in my meals, I prefer to work within a range: 35 – 40g per meal.
  • Choose your protein sources and ensure they’re high-quality.

What're the best quality sources of protein?

To conclude, let's look at what some high-quality proteins are. They’re complete proteins, that is they have all the essential amino acids.

All animal products are complete proteins: chicken, beef, pork, eggs, dairy, whey, casein etc. However, only some plants are sources of complete proteins: quinoa, buckwheat, chia, soy and hemp seed.

Most plants lack one or two EAAs so eating two of them together makes a complete protein. For example: rice is low in lysine and high in methionine, while beans (and chickpeas and lentils) are low in methionine and high in lysine.

Also, ever wondered why all the highest quality vegan protein powders are a combination of pea and rice proteins? Straight pea or rice protein powder needs to be fortified with the missing amino in order to be a high-quality source. If you're looking for a great source of this, check out Bioflex Nutrition'sBioLife.


Information relating to MPS is in regards to positive calorie balance, all EAAs and essential nutrients (fats and carbs included).

In other words, while you do need to be in positive nitrogen balance to build muscle, you also need to be eating enough calories and other macros, with the majority of your protein coming from high-quality sources coupled with training. You can eat all the protein you want, without exercise to stimulate MPS you’ll just be excreting the excess nitrogen.