Protein for Athletes

How much protein should athletes consume?

Bodybuilders have long known that consuming extra protein makes it easier to add muscle. Yet low protein dieting can enhance immunity against viruses and bacteria, and extends lifespan in animals.

The Perfect Health Diet, because we’re positive toward saturated fats and starches, will often lead to lower protein consumption than other Paleo diets that restrict fatty or starchy foods. So it’s natural that some athletes and bodybuilders have asked how to optimize protein intake.

Robert recently asked about this, but let’s look specifically at the case of Advocatus Avocado:

I believe my performance improved (albeit marginally–the differences aren’t large) when I allowed my protein/carb/fat ratios to remain consistent despite my high caloric intake, which is ~3,600 calories/day. In other words, I had a sense of better performance when I lowered my fat% to around 65 and allowed around 200g/day of protein (I work out 2-3x a week for an hour).

At 3,600 calories per day, 65% fat is 2340 calories; 200 g protein is 800 calories; that leaves 460 calories carbs. How do these compare with Perfect Health Diet recommendations for athletes?

Nitrogen Balance, Exhaustion of Benefits, and Toxicity

There are a few magic numbers for protein intake that we want to be aware of:

  • Nitrogen balance. Nitrogen comes into the body in dietary protein and leaves the body in urine as ammonia, urea, and uric acid after proteins are metabolized. So when a person is in nitrogen balance, the amount of dietary protein matches the amount of metabolized protein, and the protein content of the body is unchanged. Very likely, the muscle content is unchanged too.
  • Exhaustion of benefits. We want to find the “plateau region” for nutrients. Athletes want to know: at what level of protein intake does protein no longer help build muscle?
  • Toxicity. At what level of protein intake does protein begin to damage health?

Luckily Ned Kock of the superb Health Correlator blog has done much of the work for us in his post “How much protein does one need to be in nitrogen balance?.”

He presents this chart, from a book on Exercise Physiology [1]:

There’s a great deal of variability across persons. Some people are in nitrogen balance at protein intake of 0.9 g/kg/day; others need as much as 1.5 g/kg/day. At 1.2 g/kg/day, half the sample was in nitrogen balance.

Various factors influence the interpretation of this data:

  • The sample was of endurance athletes. Endurance exercise increases protein needs, so most people would reach nitrogen balance at lower protein intakes. Resistance exercise doesn’t require as much protein: Experienced bodybuilders are typically in nitrogen balance at 1.2 g/kg/day. [2]
  • Most of the sample probably ate a high-carb diet. Glucose needs were met from dietary carbohydrates. Low-carb dieters would need additional protein for glucose manufacture.
  • As Ned states, in caloric deficit, protein needs are increased; in caloric surplus, protein needs are decreased. If you’re restricting calories for weight loss, expect to need a bit more protein to avoid muscle loss.
  • Supplementing leucine “increased protein synthesis and decreased protein breakdown” [2], thus leading to nitrogen balance at lower protein intakes.
  • The point of nitrogen balance is dynamic: if everyone in the sample ate 0.9 g/kg/day, then they’d eventually get into nitrogen balance at 0.9 g/kg/day. The body adjusts to conserve muscle at given food availability.

The average person needs much less protein to be in nitrogen balance. The US RDA for protein, 0.8 g/kg/day, was set so that 97.5% of Americans would be in nitrogen balance. [2] But just to be conservative, and because we’re developing advice for athletes, let’s consider 1.5 g/kg/day as the protein intake that brings our athletes into nitrogen balance.

What about the protein intake that exhausts benefits?  At what intake is muscle synthesis no longer promoted?

Ned, citing a review paper [2], offers the following answer: “[P]rotein intake beyond 25 percent of what is necessary to achieve a nitrogen balance of zero would have no effect on muscle gain.”

On my reading it’s not so easy to infer a clear answer, but let’s go with this. If so, then muscle gains would be exhausted at 1.25*1.5 = 1.875 g/kg/day even for the most strenuous athletes.

What about toxicity?

We deal with this in our book (p 25). At a protein intake of 230 g/day (920 calories), the body’s ability to convert ammonia to urea is saturated. [3] This means the nitrogen from every additional gram of protein lingers in the body as ammonia, a toxin.

Clearly marginal dietary protein is toxic, via ammonia poisoning, at this intake level. A reasonable estimate for where toxicity begins is between 150 to 200 g/day.

Putting it together: A prescription for athletes

Let’s say our athlete is an 80 kg man. Then maximum muscle gain will be achieved at a protein intake of 1.875*80 = 150 g/day. Toxicity will begin somewhere between 150 to 200 g/day. So the “plateau region” where all the benefits, and none of the toxicity, are achieved is between 150 g/day and some protein intake not much above 150 g/day.

The plateau region is quite narrow! What this tells us is that athletes should consume about 150 g/day protein.

This assumes a high-carb diet, so that no protein is needed for gluconeogenesis. The body utilizes about 600 calories/day of glucose, plus another 100 calories per hour of intense training.

With carb intakes below 600 calories/day, additional dietary protein would be needed, because protein would be consumed nearly 1-for-1 with the missing carbs.

So we can summarize these results as follows:

  • On a high-carb diet (>600 calories/day), 600 protein calories/day maximizes muscle gain.
  • On a low-carb diet (<600 calories/day), 1200 carb+protein calories/day maximizes muscle gain.

Looking back at Advocatus Avocado’s personal experience, he eats a low-carb diet with 460 carb calories per day. We predict therefore that he would need 740 protein calories a day to maximize his muscle gain (plus up to another 100 calories per hour of training, to replace lost glycogen).

Advocatus says he needs 800 protein calories/day to maximize muscle gain. Close enough for blog work!

At these protein intake levels, Advocatus is probably experiencing mild ammonia toxicity. He might slightly improve his health by eating a few more carbs, and cutting his protein intake a bit.

He might also find that leucine supplementation would reduce his protein needs a bit.

Overall, however, I think his experiences are consistent with our framework for understanding nutritional needs. Those who are content with maintaining an ordinary person’s muscle mass can get by with relatively low protein intakes of 0.8 g/kg/day or less. But muscle-building athletes need high protein intakes, around 1.9 g/kg/day, to maximize the rate of muscle gain. If they eat low-carb, they may need even more protein. Such high protein intakes are likely to exceed the threshold of toxicity.

References

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

[2] 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.

[3] Rudman D et al. Maximal rates of excretion and synthesis of urea in normal and cirrhotic subjects. J Clin Invest. 1973 Sep;52(9):2241-9. http://pmid.us/4727456.

Leave a comment ?

101 Comments.

  1. Here’s an interesting but contrary take on the origin of protein requirements by Dr. Ron Mignery, in his e-book (http://knol.google.com/k/ron-mignery/protein-cycling-diet/2s3nmvrwklbxs/1#. Mignery’s motivation is to minimize protein to reduce risk of neurological disease in susceptible people.
    He says in Chap. 10 “One thing you discover when you try to formulate a low protein diet the difficulty of finding suitable foods. When the national Academy of Science established its Recommended Daily Allowances for protein, it started with the amount of protein and its breakdown products lost by the average adult male body per day (link 20) . Since nitrogen is found in proteins but not fats or carbohydrates, its measure serves as a close measure of protein. Obligatory urinary nitrogen losses at about 37 mg/kg/day, fecal nitrogen losses at 12 mg/kg/day, perspiration, hair, fingernails, and sloughed skin nitrogen losses at 3 mg/kg/day and other losses at 2 mg/kg/day imply a protein loss of 0.34g/kg/day or 0.15g/lb/day. Any net recovery from the diet beyond that in the absence of growth is converted to carbohydrate (sugar) and burned for energy or then converted to fat. Of course energy is as legitimate a need as any other and there is nothing bad about getting it from protein, unless you have a condition like some kidney diseases for which a low protein diet is indicated….
    Increasing the 0.34 minimum as a safety margin, the World Health Organization recommends 0.45 grams/kg/day of protein. Doubling this the United States Department of Agriculture recommends 0.8 grams/kg/day for average healthy adults. For adults ranging from 100 to 200 lbs this is around 20 to 40 grams per day using the WHO number, 40 to 80 using the USDA number.” The reference (link 20) is not available without a fee.

  2. Thanks Paul. I was waiting for you to blog about this. It seems there are many other bloggers also blogging about the protein sparing effects of glycine contained in gelatin to offset the negative effects of methionine. Chris Masterjohn and Matt Stone just recently released a post on the benefits of gelatin.

    Increasing my protein intake usually always makes me feel shitty, and going anywhere over 115 grams always gives me terrible body odor. Ammonia maybe? Either way it seems that as a soccer player I should really focus on increasing my fat and carbs to perform better and hopefully pack on some healthy weight. But if my total calories go up so does my protein intake. I would have to consume tons of fat to reach my caloric goal without going overboard on protein. Not that I mind, I love fat!!

  3. Nice one, Paul!

    I came very close with figuering out my requirements. 145g of each protein and carbs is what I strive for, including the 30g of BCAA’s.
    This comes out as 20/60/20 % for P/F/C by calories.
    At times the carbs may fall short.

  4. Advocatus Avocado

    I love the smell of ammonia in the morning! (It smells like victory.)

    Thanks very much, Paul, for your analysis.

    I’m around 92kg, so it looks like I may be able to put the protein to better use than the example, though it appears the toxicity remains an issue. I’ll titrate the protein and carbs according to your recommendation and let you know (should you care) how it turns out.

  5. Extremely helpful article, Paul… thank you!

  6. Hi Paul,

    I’m 81 kg and I’m doing resistence training for 30min (x2 a week) to build muscle.

    I eat 120g carbs and 40g animal proteins a day (I can’t tollerate more proteins than that) with a lot of coconut oil (4.5TBS).

    After 2 months my weight hasn’t changed so I’m wondering if I’m doing something wrong.

    Do I have to count also vegetable proteins (peas etc)?

  7. Paul,

    Nice analysis. All of the protein thoughts I have seen hinge on nitrogen balance. Not sure if the performance benefits are more than athletes internalizing whey powder marketing. I’m not aware of any good literature on protein intake effecting real world endpoints, like performance measures or body composition.

  8. Hi Paul

    Good analysis on what is specifically “protein synthesis” for muscle gain. However, there are several other “athletic” functions for protein such as mitochondrial biogensis, glycolytic enzymes and peptide hormones. Yet no study (as far as I’m aware) has looked at the protein amounts for an athlete based on these functional requirements ?

    Thus, in much the same way that your book shows how there are other uses and needs for carbohydrate other than just simple energy production, can the same be not said about protein ? i.e. it is not just needed for muscle synthesis ??

  9. For those who don’t like absolute values and prefer per kg values to work with, the 150 to 200 grams a day converts to about 2.6 to 3.6 g/kg/day (taken from Cordain’s most recent paper).

  10. Hi Morris,

    Thanks for the Mignery analysis and the WHO protein estimate.

    As I pointed out, there is no fixed point of nitrogen balance: eat 0.45 g/kg/day and the body will adjust its protein recycling and metabolism to achieve nitrogen balance at 0.45 g/kg/day.

    There are complex benefits and costs to increasing protein intake. So this thread is really only for those power athletes who place muscle above every other consideration.

    We’re fans of protein restriction in other contexts.

    Hi Robert,

    Yes, I’m interested in the glycine too. I do believe that eating “tails to nails” amino acid ratios, not just muscle meat, is beneficial.

    Getting into the individual amino acids raises a lot of issues … and we’ll have to do it … nice to see Chris and Matt getting into it.

    Hi Franco,

    Sounds like a healthy muscle-maximizing diet!

    Hi Advocatus,

    Thanks, will be interested in hearing your experience!

    Hi Kratos,

    That’s not far from what I usually do … though I am going to experiment with intermittent higher protein.

    I don’t know why you say what you are doing is “wrong” … you are just at the opposite extreme of our plateau ranges!

    You are taking 640 calories carb+protein which is just enough to meet minimum needs. You are in ketosis which spares a bit of glucose. Your body has been forced to adapt to conserve protein.

    With limited protein it’s going to be hard to gain muscle … but as I said, the point of nitrogen balance is dynamic and with ketosis your body can achieve nitrogen balance at very low protein.

    I don’t think pea proteins are sustaining you! It’s your body’s adaptations.

    Why is higher protein intolerable to you? What happens?

    Hi stoic,

    The literature doesn’t provide much solid guidance, but I trust Ned, so I’ll go with his interpretation.

    Hi Barry,

    Yes, there are many influences of protein on the body, and we have a broad “healthy range” for protein, so there is plenty of room to explore the pros and cons of various protein intakes.

    It can get fairly complex, especially once we start varying the amino acid composition with gelatin, BCAA/leucine supplements, etc.

    It might be worth exploring the issues you raise to see, e.g., how protein needs might vary between endurance and resistance athletes.

    Best, Paul

  11. Hi Paul,

    40g is the max tollerable aumount because:
    1) I don’t eat eggs (they make me tired)
    2) I don’t eat dairy (seems to trigger acne)
    3) I don’t tollerate all red meats (they triggers inflammation for me)

    So my only safe source of animal proteins is chicken but after eating it for years I can’t stomach lot of it anymore, it makes me nauseous!

    I should also limit meat proteins because them raise my uric acid over the range.

    So it is a very complicated situation for me!

    Do you think it’s a waste of time exercising if I can’t eat more proteins?

  12. Ciao Kratos!

    I would also be interested to know why only 40g of protein? Sounds awful little for muscle building!
    What is your main protein source? What are the symptoms when eating more then this? Maybe try adding BCAA’s? Never hear somebody having problems with pure BCAA.

    Btw, I don’t count protein in veggies, they are little and not very bio-available. Just in meat/fish, milk/cheese, eggs and maybe nuts (but I actually don’t eat much of those anymore). For peas, mmh, I think you could count those, but are you eating that much peas?

  13. @Kratos,

    we were cross-posting!
    What’s about fish?
    Reading baout your condition, I think you will far well with BCAA’s! Try them.

  14. And, about the eggs: did you try raw yolk only, without the whites? The whites do contain some anti-nutritions some people can’t tolerate well.

  15. Hi kratos,

    I don’t think the exercise is useless, if you stop exercising you’ll lose what muscle you have. But if your goal is muscle gain, you need more protein.

    Franco’s suggestions are good.

  16. Ciao Franco!

    We posted at the same time. lol

    I don’t eat a lot of peas, maybe 10g of vegetable proteins (130g).

    I haven’t eaten fish during last year because I have an IGG sensitity to almost all of them.
    Maybe after a year my IGG come down, I should retry them. Buona idea!

    I never tryed egg yolk alone but I don’t think that eating only yolks I can get a lot of proteins (most of them is in the white).

    Thanks for the BCAA advice, I’ll try them!

  17. Yes, one yolk has just 2.7-3.0g, but that’s high quality! Plus you get the choline and a bunch of vitamins for free.
    I have 4 of them in my shake everyday.
    Another protein source could be: whey hydrolisate (essentially enzymatically pre-digested whey with 0 fat/carb). Much much easier digested then the standard whey or any other milk-derived product but of course a bit pricy.
    Buona fortuna!

  18. @Kratos: eat your proteins raw not cooked… digestion problems will disappear guarantee it….search for Aajonus Vonderplanitz for more info.

    http://theprimaldiet.nourishedmagazine.com.au/author/theprimaldiet/
    http://www.wewant2live.com/
    http://www.rawpaleoforum.com/

  19. http://bodyrxradio.com/show-archives/the-bodyrx-show-015/

    Must listen for anyone interested in the “protein for athletes” topic. One of the best natural bodybuilders Layne Norton and Dr.Scott Connelly discuss this topic. Layne has a PhD specializing in muscle protein metabolism…

  20. art ayers and ray peat seem to differ in their fish oil pros and cons,both respected men in theie fields but i am a little confuse with their conflicting advice re omega 3.can you shed any light on this pleas Paul or anyone else
    thanks

  21. This seems to support what I’ve found. I’m eating 60-120g of protein a day with 100-150ish g carbs and I’ve been able to add muscle easily. I’m 140 lbs and averaging 3-4 hours of tennis + fitness a day.

  22. Hi Stas,

    Thanks much! I’m listening now.

    Hi chris,

    An omega-3 post is coming. If you want me to address specific points, leave links to the Art Ayers and Ray Peat posts for me.

    Hi Abby,

    I think those are great intake levels for a tennis player. Supportive of muscle gain and no toxicity.

    I’m glad to hear you’re playing so much tennis! I take it your knee is fixed?

    Best, Paul

  23. Yes! I’m almost 100 percent, but the last bit is coming. Hopefully I’ll be able to play tournaments soon. I’m looking to get recruited by harvard actually.

  24. Cool! If you come here we’ll have to meet up.

  25. we have seen that for a 80kg guy the area is small already. but from the post it seems that whilst the nitrogen balance scales with bodyweight whilst the toxic amount does not. the implication is that a 120kg (no fat) bodybuilder can choose to be not in nitrogen balance, or in the toxic range?
    or, to make it more concrete, what is the recommendation for a 120kg body-builder?

  26. Hi Thor,

    You’re right, there’s no guarantee that the two regions don’t overlap. This is particularly true in people with cirrhosis or fatty liver, who have a reduced ability to turn ammonia into urea. See http://www.ncbi.nlm.nih.gov/pubmed/7450564.

    In paper [3], they actually say that urea synthesis scales per kg body weight to the 3/4 power. This means that if your body weight doubles, urea synthesis capacity increases by 68%.

    For a 120 kg lean athlete, it’s quite possible that the protein intake that delivers maximum muscle synthesis exceeds the toxicity threshold.

    I guess you have to decide what it is you want to optimize. Muscle gain, or toxin avoidance? We don’t really know the long-term health effects of low-level chronic ammonia toxicity.

    Best, Paul

  27. It might be worth remembering, as Paracelsus would likely point out, that when talking about the toxicity of a substance, one has to invariably talk about its non-toxicity or beneficial nature at lower dosages. I’m not sure where the safe plateau range is, but at some blood concentration ammonia is toxic to certain pathogens (like ecoli). So, it might be good at times to have a bit more ammonia than at other times. Just a thought.

  28. Hi Paul

    Since your on the subject of protein. What do you think of rice proteins like Sun Warrior or Thorne?

    Thanks for the great blog and your great reader interaction!

    SJ2

  29. Hi SJ2,

    There’s nothing wrong with them that I’m aware of, but unless you’re a vegan, I don’t see much reason to take complete protein supplements.

    I would rely on meat/fish/eggs for protein and then BCAA or leucine supplements if you want extra muscle synthesis support or ketosis.

    Best, Paul

  30. I have to say, there’s no lean (10%BF) 120kg bodybuilder I ever saw who doesn’t have “chemical support”.
    This “support” is also known to increase protein synthesis dramatically.
    So, ammonia will be his smallest health problem in the long run.

  31. Paul,I feel you hit the nail smack on the head here…

    “”For a 120 kg lean athlete, it’s quite possible that the protein intake that delivers maximum muscle synthesis exceeds the toxicity threshold.

    I guess you have to decide what it is you want to optimize. Muscle gain, or toxin avoidance? We don’t really know the long-term health effects of low-level chronic ammonia toxicity.””

    I have kidney issues and actually feel pain in my kidneys at times from over consumption of protein.I had an online diet guru write me out a diet at one time and he had me eating 300gms of protein a day.In a matter of two days I was toxic and developed gout and severe kidney pains with a strong feeling of malaise.I found over the yrs that if I lowered my protein to levels where I didn’t feel this way I would suffer in gym with a slow lowering of strength every week.

    But at other times I would up the protein and get pains that were tolerable and would make some nice strength gains in gym.I started to wonder if you have to kinda feel sick to succeed in bodybuilding.Lowere the protein somwehat and over time the gains would slow and then stop.I now feel that as you pointed out in above statement….do you want to be muscular and lean and have a les comfortable life with a most likely shortened lifespan or do you want to live longer but be pudgy and soft….your choice. 🙂

  32. Hi Wolfstriked,

    So sorry you got bad advice. 300 g is way too much protein — twice our recommended maximum.

    But I believe you can add muscle just as fast at 150 g protein, if some of it is a leucine supplement and you eat 150 g carbs and some coconut oil.

    There are more knobs to turn than just total protein.

    If you try it my way, let me know how it turns out. I am curious.

    Best, Paul

  33. Thanks Paul,300gms is what this guy prescribes and it does give amazing results.People get shredded on his diet.You also eat 40gms of carbs(all starch)and on workout days you drink a PWO shake of 50gms whey(on top of the 300gms normal)spiked with 80gms dextrose.Just not for me as I feel way toxic eating like that.Though I will add that a week into it I was having days where my body seemed to not have any issues with that much protein.Maybe the body gets used to it?

    Right now I am trying 100gms protein and 150gms on WO days which is every other day.I WO’ed yesterday and felt toxic LOL.My eyes get red and I just feel very bad…like I hard a hard drinking night.But I wanna look good body wise so…..

  34. It appears from the comments that supplemental BCAAs count in adding up protein grams. Is this indeed the case?

    I started a ketogenic diet to combat frequent migraines. So far, so good. However, since I am in the early stages, I am rigorously tracking my C:F:P intake to see what levels of Carb and Protein I can intake and still be in high levels of ketosis. To date, I have not been including BCAAs in the protein count.

  35. Hi Todd,

    I’m glad it’s working! I assume you’ve read of Rob Sacks’s experiences with the ketogenic diet for migraines: http://perfecthealthdiet.com/?p=1543.

    As for your question: Well, BCAAs are protein! But whether they should be counted depends on your purpose for counting.

    You might look at our ketogenic diet series, http://perfecthealthdiet.com/?p=2479 and http://perfecthealthdiet.com/?p=2638, for info on how you can remain in ketosis with a higher protein and carb intake by including coconut oil and leucine supplements in your diet.

    If you’re counting calories in order to judge how ketogenic your diet is, it may make sense to distinguish BCAAs from complete protein since leucine makes the diet more ketogenic whereas complete protein makes the diet less ketogenic.

    In general, ketogenic diets are healthier when they have more carb+protein. Supplemental leucine can help you add in more complete protein or carbs for a given level of ketosis, and thus improves the health of the diet. It’s good you are taking BCAAs.

    Best, Paul

  36. Paul,

    It was the Rob Sacks story that inspired me to give it a try. I had been on high doses of Topiramate for a couple of years, and I wanted to get off it. Emily Deans’ blog had a great post on what happens in the brain when you are in ketosis:

    http://evolutionarypsychiatry.blogspot.com/2010/08/your-brain-on-ketones.html

    Interestingly, the three effects, including the production of more GABA, are all very similar to what Topirmate is thought to do.

    It took me a couple of months to taper off the Topiramate, and I started my ketosis with a three day water fast (I was targeting 7 days but got invited to a job interview, for which I needed to be well-fed and energized) Now I on the ketogenic diet, with great results so far.

    If I make it another 10 days without a headache, I think I will be able to show a statistically significant effect. I’m very optimistic.

    Todd

  37. Hi Paul,

    http://weighttraining.about.com/od/nutritionforweights/qt/protein_howmuch.htm

    “Yet the other useful information that can be gleaned from the numbers above is that with an average protein absorption of, say, 7 grams/hour, a theoretical absorption is limited to around 168 grams each day (24×7). If accurate, it makes the 400 gram/day protein diets look entirely unnecessary at best.”

    So if we wait about 5 hours between meals we should limit proteins to 35g x meal (7gx5).

    If these data are correct eating more than 35g of proteins a meal can be harmful because most of them will be fermented by bacteria.

  38. Hi snaider,

    Hmmm, that’s interesting.

    On the one hand, since we think protein intakes above 150 g/day are toxic and have little benefit, it would make sense that the intestine would have evolved a tendency (under normal conditions) to stop absorbing protein above that intake.

    On the other hand, we know that when fat and carbs are scarce the Inuit could get rabbit sickness, from ammonia poisoning. So in starvation or fat+carb starvation, the intestine must absorb toxic levels of protein.

    So, I would conclude: As long as they’re eating high calorie diets with plenty of fat and carbs, bodybuilders who eat extra protein may not be poisoning themselves – just excreting their protein supplements in feces.

    But if they cut their fat and carb intake, then they may well start poisoning themselves.

    Either way, I would respect the 150 g or so upper limit.

    I doubt it’s necessary to divide protein into 35g doses. A large dose can probably linger in the digestive tract long enough to be absorbed.

  39. Paul and Snaider,

    Does protein get fermented in the gut???
    I thought that’s just the case with fiber.
    In any case, I take in 80% of my ~140g of protein/day in a 2-3 hour window without any ill-effects.

  40. Hi Franco,

    Glutamine can be metabolized by bacteria in the gut but most amino acids can’t. So most excess protein would be excreted, not fermented.

    I’m a bit surprised by limits to absorption because I haven’t heard of protein in feces, but I haven’t looked into the literature either.

  41. Hi Franco,

    I know that protein eaters bacteria are no good ones: they produce a lot of toxins.

    http://en.wikipedia.org/wiki/Putrefaction
    http://en.wikipedia.org/wiki/Gut_flora

    “Another, less favorable type of fermentation, proteolytic fermentation, breaks down proteins like enzymes, dead host and bacterial cells, and collagen and elastin found in food, and can produce toxins and carcinogens in addition to SCFAs. Thus, a diet lower in protein reduces exposure to toxins”

    In a lot of epidemiologic studies meat is linked to gastrointestinal cancer that may be due to these toxins.

    I took Carnitine (an aminoacid) and it gave me a putrid odour of feces and gas, it is mainly degraded by bacteria rather than absorbed:

    http://www.chm.bris.ac.uk/motm/carnitine/Carnitine.htm

    “In contrast to humans, bacteria possess enzymes to catabolize carnitine. Intestinal bacteria degrade most of the orally supplemented carnitine”

  42. Thanks Paul and snaideer,

    Snaider,
    the first link just gives an overview of gut flora. I didn’t find “protein fermentation” there, except this strange statement about putrefaction. Did you check the sources (2)(7) they gave for this? One is a very suspicious pdf without mentioning of the author of said paper speaking about the benefit of fiber the second is a study about gut flora where just the abstract is available. Can’t judge that.
    The second link(putrefaction)descripes decomposition of the human body after dead. It has nothing to do with meat in my stomacch, except you believe in the vegan hype that it’s rotting there for weeks which has no physiological base as far as I know.
    I get rid of my feces everyday.
    I have no problems whatsoever with large amounts of meat in one sitting. No gases with meat(beef, pork, chicken, fish/shrimps) only too! Also feces seem compact but healthy (not painful to excred).
    If I have gas and loose stool I can always, with no fail, track this down to too much vegetable fiber like found in cabbage, onions or even green bananas (in short “carbohydrate fermentation”!) or food additives (e.g. carageenan).

    Never trust wikipedia! At least not at first glance.

  43. Question that’s always bugged me about this whole “nitrogen balance” thing, and let me know if I am totally off base here. By volume, the majority of the air we breathe is nitrogen, something like 75% as far as I know. This nitrogen definitely gets into our bloodstream, it becomes a major concern when we go scuba diving deep and too frequently. Would this not confound the measurement of “nitrogen balance” in our body?

  44. Hi Geoff,

    Atmospheric nitrogen is N2, the molecular form, which is chemically stable. It doesn’t add to or subtract from the body’s nitrogen balance — it just gets exhaled.

    The trouble in diving is that the nitrogen dissolves in the blood at high pressures and then if you come up too fast you have very high pressure gas in your blood vessels that can’t get out, except by a sort of explosion. You have to come up slowly enough to let the nitrogen make it from blood to lungs, from whence it can be exhaled.

    So issues with atmospheric nitrogen are physical, not chemical.

    Best, Paul

  45. Leucine Intake (dosage)? Hi Paul, I have a ‘three parter’ that i hope you can address if possible;

    Part one; do you have a recommendation for calculating Leucine supplementation?
    I’ve seen a recommendation on a supplier web site of 0.1g per kg (bodyweight not lean mass) per day. So for our 80kg athlete example, that would be 8 grams of Leucine per day.

    & part two of the question, still using the 80kg athlete example, could we then adjust his protein intake down, which is (for this example) 1.9 g/kg/day or 152 grams before any Leucine supplementation.

    & part three, would there be a need to adjust….or would there be a benefit in adjusting carb intake when supplementing with Leucine.

  46. Hi Darrin,

    I don’t have specific recommendations. I think this is largely a matter for personal experimentation at this point. I think 8 g/day should be safe and would probably be beneficial for athletes, but can’t guarantee it.

    I would reduce consumption of other protein as leucine is supplemented, if intake is near our upper limit for safety of 150 g/day.

    I wouldn’t bother adjusting carb intake for leucine. In principle some of the leucine could replace some carbs, but at 8 g/day leucine we’re talking only 30 calories, of which maybe 10 calories might replace glucose. That’s a small fraction of your carb intake.

    Best, Paul

  47. Paul,
    Any citations for “enhance immunity against viruses and bacteria”? We’re writing an academic paper on something similar and I remembered that line from this article.
    Thanks!
    Nick

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