Friday, January 30, 2015

How much protein does one need to be in nitrogen balance?

The figure below, from Brooks et al. (2005), shows a graph relating nitrogen balance and protein intake. A nitrogen balance of zero is a state in which body protein mass is stable; that is, it is neither increasing nor decreasing. It seems that the graph was taken from this classic study by Meredith et al. The participants in the study were endurance exercisers. As you can see, age is not much of a factor for nitrogen balance in this group.

Nitrogen balance is greater than zero (i.e., an anabolic state) for the vast majority of the participants at 1.2 g of protein per kg of body weight per day. To convert lbs to kg, divide by 2.2. A person weighing 100 lbs (45 kg) would need 55 g/d of protein; a person weighing 155 lbs (70 kg) would need 84 g/d; someone weighing 200 lbs (91 kg) would need 109 g/d.

The above numbers are overestimations of the amounts needed by people not doing endurance exercise, because endurance exercise tends to lead to muscle loss more than rest or moderate strength training. One way to understand this is compensatory adaptation; the body adapts to endurance exercise by shedding off muscle, as muscle is more of a hindrance than an asset for this type of exercise.

Total calorie intake has a dramatic effect on protein requirements. The above numbers assume that a person is getting just enough calories from other sources to meet daily caloric needs. If a person is in caloric deficit, protein requirements go up. If in caloric surplus, protein requirements go down. Other factors that increase protein requirements are stress and wasting diseases (e.g., cancer).

But what if you want to gain muscle?

Wilson & Wilson (2006) conducted an extensive review of the literature on protein intake and nitrogen balance. That review suggests that a protein intake beyond 25 percent of what is necessary to achieve a nitrogen balance of zero would have no effect on muscle gain. That would be 69 g/d for a person weighing 100 lbs (45 kg); 105 g/d for a person weighing 155 lbs (70 kg); and 136 g/d for someone weighing 200 lbs (91 kg). For the reasons explained above, these are also overestimations.

What if you go well beyond these numbers?

The excess protein will be used primarily as fuel; that is, it will be oxidized. In fact, a large proportion of all the protein consumed on a daily basis is used as fuel, and does not become muscle. This happens even if you are a gifted bodybuilder that can add 1 lb of protein to muscle tissue per month. So excess protein can make you gain body fat, but not by protein becoming body fat.

Dietary protein does not normally become body fat, but will typically be used in place of dietary fat as fuel. This will allow dietary fat to be stored. Dietary protein also leads to an insulin response, which causes less body fat to be released. In this sense, protein has a fat-sparing effect, preventing it from being used to supply the energy needs of the body. As long as it is available, dietary protein will be favored over dietary or body fat as a fuel source.

Having said that, if you were to overeat anything, the best choice would be protein, in the absence of any disease that would be aggravated by this. Why? Protein contributes fewer calories per gram than carbohydrates; many fewer when compared with dietary fat. Unlike carbohydrates or fat, protein almost never becomes body fat under normal circumstances. Dietary fat is very easily converted to body fat; and carbohydrates become body fat when glycogen stores are full. Finally, protein seems to be the most satiating of all macronutrients, perhaps because natural protein-rich foods are also very nutrient-dense.

It is not very easy to eat a lot of protein without getting also a lot of fat if you get your protein from natural foods; as opposed to things like refined seed/grain products or protein supplements. Exceptions are organ meats and seafood, which generally tend to be quite lean and protein-rich.


Brooks, G.A., Fahey, T.D., & Baldwin, K.M. (2005). Exercise physiology: Human bioenergetics and its applications. Boston, MA: McGraw-Hill.

Wilson, J., & Wilson, G.J. (2006). Contemporary issues in protein requirements and consumption for resistance trained athletes. Journal of the International Society of Sports Nutrition, 3(1), 7-27.


WilliamS said...

"Having said that, if you were to overeat anything, the best choice would be protein, in the absence of any disease that would be aggravated by this."

I take it you do not agree with Ron Rosedale's strong warning against high protein intake, i.e, that it accelerates aging and degeneration by signaling nutrient abundance and thus favoring fecundity over self-preservation.

Ned Kock said...

Hi William. If excess animal protein caused accelerated aging, you’d see accelerated aging among cultures that consume significant amounts of seafood. Usually what happens is the opposite.

Ned Kock said...

Looking at this post, one theme that comes to mind is this – you don’t need a whole lot of protein to be in nitrogen balance. What is the best gauge of the amount of protein needed? In healthy individuals it is this – how hungry you are for protein-rich foods.

WilliamS said...

"If excess animal protein caused accelerated aging, you’d see accelerated aging among cultures that consume significant amounts of seafood."

According to Rosedale's view, that'd only be true if the total protein consumption were excessive, i.e., >>1g/kg LBM (depending on activity levels and some other factors). Just eating seafood as opposed to other protein sources wouldn't matter.

Also, as you no doubt know, Rosedale believes we can have longer, healthier lifespans than ancestral cultures did by directing metabolism, via food choices, toward repair and regeneration rather than reproduction. Of course he cannot prove this, but he makes a very interesting case.

Anonymous said...

I also have to take issue with the suggestion that overeating protein is benign. I believe Rosedale is right and once again 10 years ahead of everyone else. Even a cursory review of the science of mTOR makes it very clear how dangerous protein overconsumption is. Possibly even worse than high carb eating.

John said...

There are a few issues I have with protein recommendation studies. They are rarely done in muscular or elite athletes. Extrapolating from beginners or endurance athletes to people deadlifting triple bodyweight or running a 10.5sec 100m is dubious. I haven't tested this long term, but I am pretty confident I would lose muscle at 100g protein per day (5'9, 185)

There are a few studies with weightlifters [the sport of weightlifting], and they seem to all show that more protein is better. Even if studies don't show statistical significance, the trend is almost always still there.

When you think about how much actual protein is in a pound of muscle, it seems odd that one would need 1g/lb of bodyweight for progress. Perhaps other nutrients are important as well, like vitamin A and zinc?


Regarding aging, I think Rosedale is just pushing his pet theory to be honest. His argument isn't bogus, but those results are inconsistent [protein and aging]. One study in rats even showed that calorie restriction but high protein worked best: they had better aging indicators than regular calorie restricted rats, in addition to more strength and a better body composition. Methionine restriction and tryptophan restriction give impressive results sometimes.

Also, one is likely to enjoy a higher quality of life with higher metabolic rate and higher body temperature--just an educated guess though.

Morris said...

From memory, a 65kg male requires about 27g of protein/day to replace losses according to NAS Dietary Intake Ref Guide (basis for Dept of Agriculture Dietary Recommendations). Protein loss is apparently the only food substrate which can be accurately measured. Can you comment on this? If true then it is strange indeed as the “normal” turnover is multiples of that

Ned Kock said...

Hi Morris. Studies using adult individuals who conduct primarily endurance exercise tend to overestimate protein turnover. Factors such as young age (particularly during growth spurts) and resistance exercise would stimulate protein retention, bringing the protein requirement for nitrogen balance down significantly.

Audacity17 said...

"and carbohydrates become body fat when glycogen stores are full"

This has become somewhat of an obsession of mine. For about a decade I bought into the carbs cause insulin and insulin causes you to be fat mindset. Then after reading some of Ray Cronise's blog, he points out that people burn a 50/50 mix of fat and glucose. He believes what people perceive to be hunger is actually cravings. From what I can tell, he puts clients on a low fat, low calorie diet combined with thermal loading. So, based on my calorie burn of 4300 calories per day, I figured my use of carbs to be 2150, or 438 grams, and fat to be 2150, or 239 grams.

But, at what level are my glycogen stores when I eat? And what gets filled up first? And when I eat my carbs...was I already at 80 percent full? For example, I assume that when blood sugar rises, the body first checks the liver to be full, then the muscles, and finally if there is excess in the blood, it's converted to fat. Wouldn't glycogen stores be lowest in the morning, especially if you didn't eat many carbs at night? And wouldn't that indicate the best time to eat carbs is in the morning? The Leangains/Warrrior Diet/Carb Backloading crowd disagrees. They do suggest carbs after strenuous weight training though.
Tim Ferriss in his book, The Four Hour Body, observed that when he ate meat at night, it blunted his blood sugar response in the morning. I actually tried eating mostly carbs, with little fat at breakfast and lunch. Then, meat and green veggies at dinner. I lost weight and felt less hungry during the day, but it was psychologically hard at night.

js290 said...

Converting excess protein into glucose produces a lot of nitrogen which has a metabolic cost as well.

Fat is really the free fuel. Fortunately, Nature endowed us with negative feedback loops that prevent us from overeating protein and fat.

Also, the "caloric" value is rather meaningless as food provides more than just energy. It also provides information about the environment, i.e. what to do with that energy.

donny said...

I think nitrogen balance can be misleading.

Take somebody who's been on a three-week fast. That person can be in positive nitrogen balance on a protein intake that would have had them previously in a strongly negative nitrogen balance. Or take somebody, put them on a 40 grams a day protein diet. They may lose lean mass for months, before eventually approaching equilibrium, or even a positive balance. That doesn't necessarily mean that they're eating adequate protein--just adequate to prevent further loss of lean mass.

Weight train, and you may be in a more positive nitrogen balance, even without increasing protein intake. Increased protein might accelerate muscle gain, but should this be interpreted as an increased protein requirement? Brad Pilon has suggested that sometimes, the extra protein might just get a person to their full potential a little sooner--but they might end up at the same plateau, if a little sooner, that a person eating a bit less protein does. Rate-limiting isn't necessarily potential-limiting. Although most people are impatient enough to want to get there sooner.

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