Nitrogen Retention

Nitrogen Retention

Nitrogen retention has been spoken about in respect to preserving gains both off cycle and during a cut already, but at user request I decided to help out and split out the subject of nitrogen retention into its own thing. Because it’s important, is often covered, and is often over-simplified.

Firstly, what is Nitrogen?

Atomic number 7. Very abundant in the universe.

Well, thanks Incy. But that’s not useful.

Muscles are partially made up of the stuff.

Skeletal muscles contain approximately 75% water, 20% protein, 1–10% fat, and 1% glycogen. The biochemical properties of the major muscle components (i.e., myofibers, connective tissue, and adipose tissue) are described in the following.

Per kg of muscle, 200 grams is protein. Of that protein, 32 grams is nitrogen.

Nitrogen Balance

Positive nitrogen balance is necessary to maintaining and building muscle: Positive nitrogen balance is associated with periods of growth, and tissue repair. This means that the intake of nitrogen into the body is greater than the loss of nitrogen from the body, so there is an increase in the total body pool of protein.

Negative nitrogen balance is associated with periods of fasting. This means that the amount of nitrogen excreted from the body is greater than the amount of nitrogen ingested.

Calculating Your Nitrogen Balance

It’s surprisingly difficult, and methods used are treated as approximations. However a rough estimate of nitrogen balance can be made. Kinda.

Nitrogen Balance = Protein intake/6.25- (result of urinary area nitrogen test) - 4

Average range of urinary area nitrogen test is between 12-20. If consuming 180g of protein daily, this would (on average) lead to a positive nitrogen balance of 4.8-12.8g.

Surely increased muscle mass would change this formula and requirements for maintaining balance, right?

Seems reasonable, and don’t call me Shirley. While there is some evidence that athletic folks surprisingly need less protein (and by proxy, nitrogen), I’m not sure this extends to absolute units such as ourselves, where a large amount of muscle is going to require an increased amount of protein & nitrogen for maintenance.

I did some digging and found a study that looked at relationship between BMI and Proteinuria. 50% of this study were overweight, with higher BMI having a positive relationship with protein excretion. I would take this as indicative that the greater the mass the more the need for protein (and nitrogen).

What Things Can We Do To Improve NO Balance?


PEDs increase nitrogen retention:

IT HAS been demonstrated by a number of workers (1, 3–5, 7, 8, 10–14, 20, 21) that testosterone propionate causes a retention of nitrogen and other tissue-building elements in human beings, thus confirming older observations of Kochakian (15) on castrate dogs. Methyl testosterone administered orally has similar effects (6, 13, 20, 22, 24). The anabolic effects of the androgens have been reviewed comprehensively by Kenyon, Knowlton and Sandiford (9).

When a patient is given a constant nitrogen intake, the administration of testosterone propionate or methyl testosterone causes a decrease in the urinary nitrogen and no appreciable change in fecal nitrogen, so that increased amounts of nitrogen are retained. Inorganic phosphorus and sulphur in the urine are similarly affected by testosterone propionate. Phosphorus is retained approximately in the ratio to nitrogen of 1:10. The ratio of nitrogen to sulphur estimated as retained often approximates the normal proportion of these elements in body protein.

There’s a bunch of other PEDs (Clen for example, and most likely SARMs) which may impact nitrogen balance but I’m less sure on. So I’m going to completely gloss over that, and just leave it out there that other compounds likely have similar effects.


The IM crowd may have other data to share on this item, but per the introductory quote periods of fasting are generally associated with negative nitrogen balance.


Your largest GH spikes during sleep. In men approximately 70% of the GH pulses during sleep coincide with short wave sleep, and the amount of GH secreted during these pulses correlates with the concurrent amount of SWS. Short Wave Sleep aka deep sleep. Basically, get good quality sleep. GH is important because it improves nitrogen balance.

The logical question for many after reading that would be what is the effect of MK677? As expected, MK677 reverses diet induced catabolism.

Over the Counter Supplements

When I was still new to weightlifting and thought Arnold was natty, I would take every supplement from GNC my paycheck could support. Including, but not limited to, BCAAs and Nitric Oxide. Is there any erogenic benefit here with these OTC supplements which increase nitrogen?

  • BCAA’s - probably. The data is kinda mixed due to clinicians being more concerned with survival rates when using BCAAs in wasting cases (AIDs, burn victims), but I did find a few examples of it clearly increasing nitrogen balance and a equal number of studies where it did little if anything.
    • In one of the clearer cases (and in animals, so easier to control diet and outside influences), four groups were split between (control, 1) a diet where 17.5% of caloric intake was protein, (2) a diet enriched in BCAA (supplement of 8.5%, valine/leucine/isoleucine ratio 1:1:1), (3) a diet enriched in casein (supplement of 8.5%) and (4) a normal diet. Nitrogen retention was similar in groups 1 & 2 (high protein and high BCAA respectively), but reduced to 63% and 44% of group 1 in groups 3 & 4. Conclusion here is that yes, oral supplementation of BCAA likely improves nitrogen balance AND that a diet high in protein also works for maintaining positive nitrogen balance.
  • Citrulline (and Arginine) - Cirtulline significantly increased nitrogen balance in comparison to sham and controls. The levels can distinctly be seen to increase from about day 5 of supplementation onward, and provided a significant increase. As part of this same study, arginine was also measured and found to do an OK job, but definitely not as effective as Citrulline. Citrulline converts to arginine in the liver, so no need to supplement with both - just pick one if you wish to supplement.
  • Nitric Oxide (excl. aminos i.e. when they do not include Citrulline or Arginine which they often do) - While NO supplements may have a range of other benefits, its benefit to Nitrogen balance was not data I could find with a somewhat mixed set of results on performance enhancement, ranging from improving endurance to having no impact whatsoever:

Increase Protein

Protein is a good source of nitrogen: meat, dairy, eggs, nuts and legumes. When coming off-cycle, increase your protein intake to at least 0.82g/lb (if you’re not already exceeding this) and preferably more if you can manage it (see below). This is an increase on the amount that is strictly necessary for muscle growth for most folk, but high protein meals have been shown to increase anabolism.

6.25g of protein represents approximately 1g of nitrogen.

How Much Protein Do I Really Need To Maintain Positive Nitrogen Balance?

Credit to /u/mike_hunt_hurts for locating this excellent journal article.

Firstly, the more protein you bring in, the more you lose, but it will still have an overall incremental benefit to nitrogen balance.

Second, meta data indicates that protein intake of 2.3-3 g/kg per day will definitively result in a positive nitrogen balance. For a 100kg /220lb male, that's 230-300 grams of protein per day, which is a metric shit ton of protein and considerably more than the 1g/kg of bodyweight that I often see in literature, and still more than the 1g/lb broscience that is generally advised within weight lifting groups.

Assuming that 300 grams of protein daily is feasible, is it healthy specifically in respect to kidney function? There's really no evidence that high protein diets worsen kidney function in healthy adults(and it may actually improve it), although those with kidney disease may see decline in kidney function.

An increase in protein is also associated with improvements with body composition:

Our results showed that a shift from a spontaneous protein intake of 0.9 g protein/kg/d to 1.4 g protein/kg/d over a 10-d period using dietary supplements was associated in this population with an increase in both the fat-free mass and net protein synthesis

So What?

In my own experience, the only time I have really needed to be concerned with nitrogen balance is when coming off cycle and/or when cutting. Beyond that, I find my own protein intake is sufficient for progressively gaining muscle. I would consider supplementing with Citrulline based on the data I was able to find. A 2 month supply is about $15, so not in any way cost prohibitive for most.

High amounts of protein are a base requirement for maintaining nitrogen balance considering nitrogen is found in protein sources. A high protein diet would not need any supplementation to maintain positive nitrogen balance.