The Role of Nitrogen Balance in Building Muscle

Proteins – both the ones you eat and the ones in your body (like your muscle tissue) – are made up of building blocks called amino acids, which contain nitrogen.

In order to build muscle, it’s important to balance the protein you eat with the protein your body naturally loses every day in order to reach your goals.

Where does nitrogen in the body come from?

Nitrogen comes from the proteins you eat. When you eat proteins such as meats, eggs or beans, they are broken down during digestion into individual amino acids which can be used by the body to make other body proteins. The structure of all amino acids includes an “amino group” which is the portion of the amino acid that contains nitrogen and supplies nitrogen to the body.

What does nitrogen balance mean?

Every day, nitrogen comes into your body from the proteins in your diet and is lost naturally in waste from your urinary and digestive tracts, sweating and shedding of hair or skin cells.

Nitrogen balance refers to the balance between the nitrogen coming into the body and the nitrogen that is being lost. When you are in nitrogen balance, it means that the amount of nitrogen going in and the amount that is leaving the body are roughly the same. Most healthy adults are in nitrogen equilibrium, which means that the amount of protein they are taking in is enough to maintain and repair body proteins. Any excess nitrogen is simply excreted from the body.

But this balance can be tipped. When someone is in negative nitrogen balance, it means that more nitrogen is leaving the body than is coming in. Therefore, the body is losing protein and does not have adequate nitrogen to build and repair cells and tissues. This may happen when someone suffers serious burns or injuries, but it can also happen on extreme diets where calories, protein or both are in very short supply. Without enough calories or protein to keep the body functioning properly, the body may be forced to break down its own protein sources for fuel (such as your muscle).

On the other hand, there are instances where you can be in positive nitrogen balance. In these situations, the body is growing in some way, so it is retaining more nitrogen than it is losing. A pregnant woman, a growing child or someone who is gaining muscle mass would all be in positive nitrogen balance. When the body is in positive nitrogen balance, the body is retaining nitrogen so it can use it to build and repair tissues, such as muscle, or to manufacture other important body proteins such as hormones.

Muscle Development and Nitrogen Balance

For individuals who are aiming to build muscle mass through a combination of strength training and proper diet, adequate protein is necessary to encourage muscle repair and growth. For strength athletes, protein needs have been estimated to be about 1.5 to 2 grams of protein per kilogram of body weight (one kilogram = 2.2 pounds). So, for an 80 kg (175 pound) athlete, 120 to 160 grams of protein per day would be recommended.1

Ensuring you get enough protein is only part of the story, though. It’s also important that you spread your protein intake over the course of the day and consume the best types of protein to maximize muscle protein synthesis. Ideally, protein intake should be distributed evenly over meals and snacks, and special attention should be paid to getting adequate protein immediately after training. After a workout, dairy protein sources such as whey and casein are suggested, since they are rich sources of branched chain amino acids – a particular group of amino acids that stimulate muscle growth and recovery* after a workout.

It’s also important to consume enough calories in order to tip nitrogen balance in your favor. Sometimes an athlete may cut too many calories in order to quickly build muscle and lose fat at the same time. But when calories are cut too much, some of the protein that is being eaten might be used for fuel, rather than to build and repair muscle. Rather than “burning the candle at both ends”, it’s important to take in a balanced diet that also provides enough carbs and fats for fuel, so that protein can be used to build lean mass and help you achieve your goals.

1Thomas DT et al. Med Sci Sports Exerc 48:543, 2016.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.