Thursday, December 30, 2010

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. 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.

References

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.

27 comments:

Glenn said...

Interesting as always, Ned. The numbers are actually higher than I expected. 136 grams for a 200 lb guy is a bit lower than what most bodybuilders shoot for (more like 150 - 200), but it's not way off. Plus... do you think those studies take into account the higher metabolic rate of a heavily hypertrophied physique (not a distance runner!) and the increased energy requirements of someone who weight trains intensely 5 days a week?

Elenbaas said...

I know excess protein aggravates Kidney disease, but can it CAUSE kidney disease or similar? Randy

Ned Kock said...

Hi Glenn. These numbers assume that total calorie needs are met. So, for example, a 155-lb person who spends 3500 calories per day will need 84 g if the extra calories are coming from other sources (e.g., fat). Otherwise this person will need a higher protein intake. Total caloric expenditure varies widely from person to person, based on lean body mass, amount and intensity of exercise, and NEAT (among others). Actually NEAT plays a major role, more than lean body mass per se, although I think these two measures are correlated.

Ned Kock said...

Hi Elenbaas. The evidence that excess protein causes kidney disease is very slim. The byproduct of protein digestion, urea, is not toxic per se. (See link below for a study where large amounts of urea were administered to hemodialysis patients for several months, with no adverse health effects.)
http://www.ncbi.nlm.nih.gov/pubmed/5008253

Also very slim is the evidence that excess protein leads to a decrease in bone density. In fact, research suggests that increased protein consumption is associated with an increase in bone density, as long as it is animal protein:

http://aje.oxfordjournals.org/content/155/7/636.abstract

Anne said...

Interesting article because yesterday I was trying to work out my intake of protein, fat and carbs per day. I'm 49.5kg, BMI 18.6. I eat a low carb diet and get approximately 50g carbs per day, 145g protein and 120g fat. It seems an awful lot of protein compared to what you're talking about - I suppose it's okay ?

Ned Kock said...
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Ned Kock said...

Hi Anne. Let me preface my comment by saying that I am not a medical doctor. Having said that, no, I don’t think your relatively high intake of protein is a problem. Most of it is oxidized, which is fine. A lot of it is used to synthesize albumin, which ensures that serum albumin levels are high. Since free fatty acids bind to albumin, high serum albumin levels are necessary for proper body fat burning.

People talk about the “metabolic advantage” of LC. If you look at it with an open mind, LC does provide a sort of metabolic advantage. But that is because of the replacement of carbs with protein, not because of the replacement of carbs with fat. Maybe that is why Dr. Eades’s site is called “protein power”.

Whether a high protein intake makes one live longer I don’t know, but certainly the opposite extreme (a diet that makes one obese) will shorten lifespan.

David Isaak said...

Related to this post and the previous one--and harking back to our discussions of whey--here are a couple of recent studies on BCAAs. The first is on leucine and muscle synthesis:

http://jn.nutrition.org/content/140/12/2145.abstract

The second is on the inverse relationship between obesity and BCAA intake (purely epidemiological, and uses BMI to define overweight, but interesting nonetheless):

http://jn.nutrition.org/content/early/2010/12/15/jn.110.128520.abstract?sid=b147675d-614d-4d45-92e3-485326a99c98

Ned Kock said...

Hi David, thanks for the links. Your comments are always very much appreciated.

Indeed, BCAAs seem to provide a signal to the body for protein synthesis, and that appears to be related to the mTOR pathway. I believe that this is particularly true of leucine. What is difficult to establish based on most of the research so far is whether that signal is not simply due to insulin. BCAAs are highly insulinogenic, and insulin also stimulates protein synthesis through the mTOR pathway.

Still, the studies are interesting. The Torrazza et al. would be even more interesting if the pigs could not have had an insulin response, or if the insulin response was controlled for. In the latter case, the multivariate effect of BCAA supplementation could become very weak or disappear; because the insulin response would likely vary across pigs. The results of the Qin et al. study with humans were not that surprising, as they were looking at BCAA content in food, and BCAAs are essential AAs.

Another issue to consider when looking at BCAA supplementation is the empirical evidence on protein digestion rate and protein accretion. Usually in comparisons between whey and casein supplementation, over time and together with strength training, the latter leads to more muscle gain; as long as it is in the context of a balanced diet with plenty of BCAAs coming from food sources. This happens even though whey has a higher BCAA content than casein.

Finally, there is evidence that aged cheese is a healthier source of casein than supplements, at least as far as rats are concerned. Yes, cheese also comes with fat, a good fat (saturated) but in high quantity, and some moderation is needed. The first link below is to a study with rats; the second is a summary of some very interesting comments by Jack C. on aged raw milk cheese.

http://healthcorrelator.blogspot.com/2010/05/cheese-consumption-visceral-fat-and.html

http://healthcorrelator.blogspot.com/2010/05/cheeses-vitamin-k2-content.html

David Isaak said...

The cheese posts were fascinating. Lucky for me that I love cheese.

Most bodybuilders I've talked to about nutrition use both casein and whey, but most of them take their casein before bed. Their focus is all on digestion speed, and they believe they get better results if they consume a slow-digesting protein before sleep, so their bodies continue to be bathed in amino acids during their overnight fast.

I've never seen anything about the timing of protein synthesis for muscle building. Is there any reason to believe that more or less of it goes on during sleep?

Ned Kock said...

Most of the research on timing agrees that a 2-3 h window after the exercise session is crucial for protein intake. Casein seems to be more effective than whey because it is slow release. But there is research suggesting that a constant influx of amino acids, as in an IV drip with an AA solution, does not lead to increase muscle protein accretion. That is, the research is a bit contradictory in this respect.

At night both growth hormone and testosterone levels are elevated. So the possible combination of elevated protein synthesis (from strength training earlier in the day) and slow-release AAs makes it a good idea to ingest casein-rich foods in the evening, particularly of the day one exercises.

js290 said...

Ned,

doesn't excess protein get converted to glucose via gluconeogenesis? If so, it seems like it'd be more prudent to moderate the protein intake to the levels you suggest and increase the amount of fat intake. I think this is where Dr. Rosedale differs from Drs. Eades.

The overdosing of protein by bodybuilders seem to be a rather superstitious activity if indeed your calculations are correct on protein requirements.

Anonymous said...

Hi Ned
Thanks for yet another interesting post. Can you comment re the view of biologist Ron Mignery (author of the e-book “Protein Cycling Diet”) that the minimum (basal) protein requirement of a 170lb male is 25gm/day based on N2 loss measurements? His motivation is to minimize risk of neurogenerative disease in susceptible people by inducing neuronal cell autophagy via protein deprivation diet. He claims that since the risks of protein insufficiency/excess are so asymmetrical, standard protein requirements are overstated. How can the discrepancy (roughly 3:1 protein) be reconciled? Can there be that much uncertainty in the science?
Morris

LeonRover said...

Hey Ned

I did a little arithmetic on the reported daily diet for Kitivans by Lindeberg and calculated their daily protein intake is 1.1 - 1.2 gm/kg

I guess none of 'em is in the gym.

Ned Kock said...

Hi js290.

Yes, that is about the only path for protein to become body fat, but that conversion only happens very rarely. Much more rarely than the conversion of carbohydrates to body fat, starting with lipogenesis in the liver when glycogen stores are full. The liver makes fat with excess carbohydrates, secreting that fat in VLDL particles. Excess protein, on the other hand, is not turned into fat by the liver.

Gluconeogenesis usually happens at rest when liver glycogen is depleted, or during an intense exercise session when lactate becomes available to the liver. In both situations body fat cells are in FFA release mode, basically in a state of physiological insulin resistance. So they don’t make body fat from blood glucose in any significant way; or, rather, the release of fat from adipocytes is higher than any possible small accretion via GLUT4-mediated lipogenesis.

(I’ll continue on a separate comment.)

Ned Kock said...

(Continuation from previous comment.)

A third situation, which is more on the abnormal end of the scale, is chronic stress. Here catabolic hormones (e.g., cortisol) stimulate gluconeogenesis without the body really needing the extra glucose. But even in this third case, body fat cells will be in FFA release mode.

So protein virtually never becomes body fat. The large amounts of protein consumed by bodybuilders will not become skeletal muscle; a significant proportion of the extra protein will become fuel. Remember that protein is satiating, so one cannot consume too much of it.

A high protein diet is the closest thing we have to an ideal diet for losing body fat. Whether such a diet increases longevity I don’t know. There is some evidence that increases in animal protein intake are associated with increases in longevity, but the max intake in the studies I’ve seen is not that high. I need to do more research on this.

Ned Kock said...

Hi Morris. Below is a link to a “knol” by Ron Mignery, which has links to other chapters and I think covers the main concepts. It is good stuff, and well argued; in a scholarly yet accessible way. I found a few peer-reviewed articles by him, but they were on different topics.

http://knol.google.com/k/ron-mignery/protein-cycling-diet-1/2s3nmvrwklbxs/3

This is an issue that I plan on addressing on separate post, soon to be up, but I think that by “pulling both ways” you can also make autophagy work, and in a less costly way. By “pulling both ways” I mean stimulating protein synthesis with strength training and at the same time restricting calorie intake, in a cyclical way. This effectively creates a temporary starvation response that stimulates not only body fat loss but autophagy, while nitrogen balance is raised by strength training. No undesirable long-term adaptations occur, due to the cycling.

(I’ll continue on a separate comment.)

Ned Kock said...

(Continuation from previous comment.)

Periodic protein restriction, which is what Mignery advocates, may also work. But as I’ll show also in a future post, there is evidence that increased animal protein intake is associated with increases in bone density and longevity. So the price of autophagy mediated by severe periodic protein restriction may be too high.

Mignery mentions calorie restriction as a foundational idea, which he uses to support his method. The idea of calorie restriction leading to increased longevity is one that I don’t think hold much water. Here is a post that explains why, and also includes some data:

http://healthcorrelator.blogspot.com/2010/10/china-study-ii-does-calorie-restriction.html

Ned Kock said...

Blogger was not allowing me to enter long comments, so I had to break them down. I hope this didn't mess things up too much.

WilliamS said...

Ned, I'm curious to hear why you apparently disagree with Dr. Ron Rosedale, who strongly recommends limiting protein consumption to reduce cancer risk and increase longevity. Avoiding overstimulation of the mTor pathway is one of his concerns. As you probably know, he argues that saturated and monounsaturated fats are the only truly nontoxic macronutrients that can be freely consumed without danger.

(I'm new to your blog, so my apologies if you've already commented on this topic. I searched your blog for commentary on Dr. Rosedale and did not find anything other than a reference to his website.)

Ned Kock said...
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Ned Kock said...

Hi William. Yes I’ve seen that, and also evidence from trials with curcumin and other substances that suppress mTOR signaling pathways. But most of the related data is unclear in my view; often it seems that cancer must have advanced somewhat. When cancer has progressed beyond a certain point it seems that almost any excess nutrient feeds it; e.g., studies show that carbs and vitamins seem make it more aggressive.

Also, the idea that the excess consumption of animal protein is tied to cancer is strongly countered by empirical evidence from various isolated populations whose intake of protein was very high, and yet had very low incidence of cancer. These include various groups of Eskimos, Native Americans, and tribal Africans.

Finally, if that were true than I would expect to see a much higher incidence of cancer among natural bodybuilders, who tend to consume tons of protein.

fat burners said...

Your graphical representation for required proteins is very clear to make a health body.

buy viagra said...

Proteins are very important to our body and to be healthy, so we must try to eat most of them we are able to.

Anna K. said...

Ned, you said that "If a person is in caloric deficit, protein requirements go up. If in caloric surplus, protein requirements go down."

do you have some studies to back this up?

It could be that under a prolonged caloric deficit the body will adjust and require less because it will use the available protein more efficiently in addition to utilizing autophagy.

Anna K. said...
This comment has been removed by the author.
Anna K. said...

Ned, if you get a chance to comment on the above, thanks.