Thursday, February 18, 2010

30g of protein per meal for optimal muscle building? That Depends - a lot

ResearchBlogging.orgLess and More? Yes, when talking protein. Have you encountered any of these questions? How much protein can i eat at a sitting? What's the right amount of protein to eat? How much protein can i absorb? These are questions in the fitness world that get asked all the time - especially by folks who want to optimize their muscle growth. The answer seems to be "less than you think, but more often"

We know there's a usual formula (even that's been debated at a Protein Roundtable - but not by much) about how much protein to take in in a day - let's just say for now it's 2-2.5 g per kg (based on work in 2006), or about a g/pound (nice mix of metric and imperial there) which has been pretty much the standard recommendation for some time, newly validated. As the authors note, that's about 176 g of protein a day for an 80kg person " This is well below the theoretical maximum safe intake range for an 80 kg person (285 to 365 g/d)."

Intriguingly, there's a newish study out to show that 30g of protein derived from real food is about all the protein one can reasonably ingest in a sitting that will support muscle or protein synthesis is 30g. There are certain conditions attached to this statement that we'll discuss below.

Also Note, muscle protein synthesis here is being looked at in a particular context. We're talking about what resting muscle can use to handle the ongoing breakdown and build up of muscle proteins. This is potentially different than a body builder working out to build lots of mass. In other words, we're looking at a kind of baseline max.

SO 30g of whole protein or, in the case of this study, a 113g serving of lean beef (about 4oz). That's pretty close to the traditional portion size of a piece of meat the size of a deck of cards.

We can eat more protein at one meal, but the authors would argue, it ain't doing anything for muscle building/protein synthesis of resting muscles. Here's the overview of the research:
A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscle Protein Synthesis in Young and Elderly Subjects

T. Brock Symons PhD, Melinda Sheffield-Moore PhD, Robert R. Wolfe PhD and Douglas Paddon-Jones PhDCorresponding Author Contact Information, E-mail The Corresponding Author
Accepted 30 January 2009.
Available online 21 August 2009.


Ingestion of sufficient dietary protein is a fundamental prerequisite for muscle protein synthesis and maintenance of muscle mass and function. Elderly people are often at increased risk for protein-energy malnutrition, sarcopenia, and a diminished quality of life. This study sought to compare changes in muscle protein synthesis and anabolic efficiency in response to a single moderate serving (113 g; 220 kcal; 30 g protein) or large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Venous blood and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion (0.08 ╬╝mol/kg/min) of L-[ring-13C6] phenylalanine in healthy young (n=17; 34±3 years) and elderly (n=17; 68±2 years) individuals. Mixed muscle fractional synthesis rate was calculated during a 3-hour postabsorptive period and for 5 hours after meal ingestion. Data were analyzed using a two-way repeated measures analysis of variance with Tukey's pairwise comparisons. A 113-g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a threefold increase in protein and energy content, there was no further increase in protein synthesis after ingestion of 340 g lean beef in either age group. Ingestion of more than 30 g protein in a single meal does not further enhance the stimulation of muscle protein synthesis in young and elderly.
The authors cite their motivation for the study in part as a balance to previous work that showed 10g of EAA's at a go was all the body could make use of - that amounts beyond that signalled no greater muscle synthesis (or synthesis of muscle protein, more formally). So what about getting those EAA's from a whole food like "113 g lean beef, 30 g protein, 10 g EAAs, 220 kcal." Turns out that it *seems* it doesn't matter from whence one gets those EAA's, that's the max the body can use for " a maximal acute protein synthetic effect."

Indeed, in the discussion of their results at 30g the authors also speculate
In terms of stimulating muscle growth, it therefore seems likely that under resting/nonexercising conditions, consumption of more than 30 g protein in a single meal is not justified. Indeed, it may well be the case that a slightly smaller meal would produce a similar protein synthetic responseIn terms of stimulating muscle growth, it therefore seems likely that under resting/nonexercising conditions, consumption of more than 30 g protein in a single meal is not justified. Indeed, it may well be the case that a slightly smaller meal would produce a similar protein synthetic response.
Considerations: Could even less protein, in other words, have as much of a protein synthesis response as the 30g? Note the caveats given: if we're talking at rest and without exercise. The authors' participants were people who (a) didn't change their diet for the 72 hours leading up to the study (b) didn't do any activities for that period. THe study notes only that they were healthy people in a range of ages, not whether any were jocks or sedentary. Also, the average weight (plus or minus 7kg) was about 80kg in the "young" group and about 78 in the "elder" group. We also don't know what the lean mass is of any of the participants, or perhaps more fundamentally, how amount of protein might be impacted if one weights 20kg less or more than the study average?

One Feeding. The authors offer even more caveats: the researchers only looked at the ingestion of the whole protein - not at it mixed up with more food, as we usually get it, or after exercise. They say:
Perhaps the most obvious is the fact that a single menu item, such as a serving of lean beef, is seldom eaten alone. As noted, there are some data suggesting that elders may have a less robust protein synthetic response to the combined ingestion of protein and carbohydrate than their younger counterparts (25). This has yet to be explored in the context of an actual mixed-nutrient meal, but warrants further investigation. Further, there is the potential of an added protein synthetic response if protein were to be consumed in close temporal proximity to physical activity (29,30).
25 E. Volpi, B. Mittendorfer, B.B. Rasmussen and R.R. Wolfe, The response of muscle protein anabolism to combined hyperaminoacidemia and glucose-induced hyperinsulinemia is impaired in the elderly, J Clin Endocrinol Metab 85 (2000), pp. 4481–4490.
29 S.M. Phillips, J.W. Hartman and S.B. Wilkinson, Dietary protein to support anabolism with resistance exercise in young men, J Am Coll Nutr 24 (2005), pp. S134–S139.
30 M. Sheffield-Moore, C.W. Yeckel, E. Volpi, S.E. Wolf, B. Morio, D.L. Chinkes, D. Paddon-Jones and R.R. Wolfe, Postexercise protein metabolism in older and younger men following moderate-intensity aerobic exercise, Am J Physiol Endocrinol Metab 287 (2004), pp. E513–E522.
In other words the researchers only tested protein synthesis effects when chewing meat in isolation of other food stuffs. Yes that's right, that's all they got: a 90% lean beef patty. And yes, "this project was supported by funding from the National Cattlemen’s Beef Association Checkoff Program" But it was also funded by the NIH center on aging. And considering the findings suggest that less is just as good as more, it's not doing the cattleMEN's association a great service.

Where's the Beef for Application? What is intriguing to me in this study is how one would balance optimal absorption of protein with the amount of protein we're supposed to ingest - especially if remotely active. so our 80kg guy is going for 180ish grams of protein, at max 30g whole protein a meal.

So, let's say our person has three meals a day. 30g per meal, that's only 90g protein, total. That's half the protein our fella needs, according to the usual saw of .8-1g protein/pound of person.

Or what about folks who eat only one meal a day? That's one more potential problem with the evening feast beyond say glucose effects, then, perhaps? They may pig out on protein, but it's still 30g a shot for muscle synthesis this study would suggest. Read on.

Frequent Feedings for Optimal Muscle Building? Er...
Could this max 30g of whole protein be one more argument for the value of frequent meals during the day(s one eats -one may fast)? Consider one of the core heuristics of Precision Nutrition (discussed here): at each feeding make sure to have
  • some greens
  • some healthy fats
  • some protein
  • (starchy carbs only post workout).
6 feedings at 30g a shot would be just right for our 80 kg hero. Indeed, the study authors seem to suggest this approach as the Good One:

We suggest that instead of a single, large protein-rich meal, ingestion of multiple moderate-sized servings of high-quality protein-rich foods over the course of a day may represent an effective means of optimizing the potential for muscle growth while permitting greater con- trol over total energy and nutrient intake.
Full Disclosure: What the authors do not say is what the minimal times are between feedings such that one can make use of that full 30 again. They do state that the "post-ingestion period" is three hours. They did not however retest meal ingestion at that time to see what would happen with another dose. And that's fine for this study that was looking at size of dose for max possible effect, but it does mean we're speculating about repeats - grounded speculation, but still less tested.

Though there is a 2007 8 week trial that shows that lean mass didn't change to any statistically significant degree, whether people got all their daily protein in one meal or three a day. Whether folks were training or not was not considered. So the question comes up: are acute responses (measures taken at time of ingestion) related to longitudinal responses?

And what if Less is More? May be time to highlight again that we're talking about protein synthesis here, not protein absorption. Absorption amounts (2-2.5g/kg body weight) may be greater than required amounts for protein synthesis. An interesting question still kinda out there is if 30g is the max for resting muscle for a more or less 80kg person, what's the least amount to still get this max effect?

What about Work Outs? Things get really interesting if we consider pre and post training nutrition with carb/protein periworkout nutrition, as in this study where participants were fed slightly more than 30g protein pre AND post workouts (along with creatine and carbs). These researchers didn't test the amounts of protein they used (related work in this 2009 study suggests it's 20g post workout - thanks Kevin Greer for the ref); they just looked at whether there was a better effect with pre and post supplementation than not. They did sorta hit the maximal usable amount, which is cool, but it might be too much too soon to be fully absorbable for muscle synthesis.

Or maybe - maybe - the effect was from the Creatine and Carbs + Protein and not just the protein (another few views on protein+ creatine vs carbs + creatine [one] or pro+cho vs pro+cho+cr[another]). Dang.

What happens if we OD on protein? Can we? We know that if we're in caloric deficit, protein is getting oxidized for fuel before going to protein synthesis, right? And likewise if we eat too much of it, it gets deaminiated and the amonia gets peed out, which has been a concern/question regarding toxicity of overdoing protein:
High protein diets on the other hand advocate excessive levels of protein intake on the order of 200 to 400 g/d, which can equate to levels of approximately 5 g · kg-1 · d-1, which may exceed the liver’s capacity to convert excess nitrogen to urea. Dangers of excessive protein, defined as when protein constitutes > 35% of total energy intake, include hyperaminoacidemia, hyperammonemia, hyperinsulinemia nausea, diarrhea, and even death (the “rabbit starvation syndrome”[link added -mc]).
Hence the 2-2.5g/kg recommendation. Other excess ingestion of protein has protein used for glucose conversion, and we know if we don't need all the available sugar, well heck, it's stored as fat.

Summing Up?
What do we know from this study: that measured over three ours post ingestion, it doesn't matter whether an 80kg person eats 30g or three times that, that 30g of whole protein was the most that could be utilized for muscle protein synthesis in their resting muscle at a feeding.

What the authors are NOT saying: 30g of protein is needed every 2-3 hours for muscle growth. It seems kinda the opposite: less protein may be needed for acute muscle protein synthesis.

Where we mayn't be able to Generalize: While the authors suggest therefore that a strategy is to spread protein intake over the day, the 1 meal a day vs 3 meals a day study suggests that lean mass holds over time whether following this strategy or not. SO why spread out protein uptake??

If we move from protein synthesis at rest to muscle building, other work seems to suggest that even when working out that (a) just working out and (b) creatine may be more important for packing on muscle than protein. This latter point is one that Eat STop Eat author Brad Pilon makes in his ebook How Much Protein (thanks to Chris Highcock for pointing this book out to me).

So what can we say? well, what the authors also say is of note is that there's been concern that elderly eating low protein diets, mixed with other nutrients may have a blunted protein synthesis. This study suggests that there's no age related effect of upping protein to a certain point, regardless of age. Ok. So both elderly and younger types respond the same to acute protein intake when just eating protein. Good to know.

But once again a lovely finding of an acute response and a seeming logical conclusion (spread protein out over the day) doesn't seem to hold on its own in the larger context as a prescription for action. We may find though that benefits of protein supplementation have other functions than just mass related - like recovery and immune function. More food for future thought.


Related Posts

select citations
Bilsborough S, & Mann N (2006). A review of issues of dietary protein intake in humans. International journal of sport nutrition and exercise metabolism, 16 (2), 129-52 PMID: 16779921

Symons, T., Sheffield-Moore, M., Wolfe, R., & Paddon-Jones, D. (2009). A Moderate Serving of High-Quality Protein Maximally Stimulates Skeletal Muscle Protein Synthesis in Young and Elderly Subjects Journal of the American Dietetic Association, 109 (9), 1582-1586 DOI: 10.1016/j.jada.2009.06.369

CARLSON, O., MARTIN, B., STOTE, K., GOLDEN, E., MAUDSLEY, S., NAJJAR, S., FERRUCCI, L., INGRAM, D., LONGO, D., & RUMPLER, W. (2007). Impact of reduced meal frequency without caloric restriction on glucose regulation in healthy, normal-weight middle-aged men and women Metabolism, 56 (12), 1729-1734 DOI: 10.1016/j.metabol.2007.07.018

Cuthbertson, D. (2004). Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle The FASEB Journal DOI: 10.1096/fj.04-2640fje

KERKSICK, C., RASMUSSEN, C., LANCASTER, S., STARKS, M., SMITH, P., MELTON, C., GREENWOOD, M., ALMADA, A., & KREIDER, R. (2007). Impact of differing protein sources and a creatine containing nutritional formula after 12 weeks of resistance training Nutrition, 23 (9), 647-656 DOI: 10.1016/j.nut.2007.06.015


Unknown said...

can you comment or extrapolate for larger folks? i mean 6 meals@ 30g/meal works perfectly for the weight you chose. What about a 100kg trainee? Also, what would be your opinion re: minimum spacing of meal timing to maximize protein synthesis? Have you seen any studies on this? I mean for the 6 meal example...if sleep wasn't an issue, you'd have a trainee eating every 4 hours. Given that most of us aspire to sleep for 8 hours, we then are looking at every 3.2 hours with an 8 hour period of fasting (aka sleep). What if it's every 2 hours and then your trainee sleeps/fasts for 14 hours?

dr. m.c. said...

Hi Peter, you're asking a great question. I've asked a phd in nutrition to come back on this for you.

In the meantime, i agree that weight MAY be a factor, but not sure by how much. The participants in this study conveniently weighed around 80kg plus or minus 8 pounds.

If we up that to 200-250g for our trainee at 100kg, as per the forumula on not toxifying yourself with protein and still able to absorb it, that's 41g of protein a feeding rather than 30. Who knows? perhaps if mass does have a bearing on absorption that's a reasonable increase for protein synthesis too and not just absorption? I don't know. Time to email the authors!

The thing i take away from this is that spreading out protein over the course of the day is a good idea for protein synthesis.

The other thing i take away from this is that exact amounts taking into account activity and other foods one may be eating hasn't been directly tested - and so it's likely more than this - how much more, dunno, but perhaps again less than we thought.

And yes, pretty much eating every few hours is one approach that's been showing grand results.

You raise a great point about meal frequency and nutrient timing if you only are awake for 10 hours (your 14 hour fast/sleep).

In that case, it doesn't seem entirely reasonable to try to cram in 6 feedings, does it? if for no other reason that if you're only up for 10 hours you're not likely to have the same energy requirements as someone who's up for 16?

What i dig about your question is that it teases out the remarkable variables that inform real living, and that most of the time research offers heuristics/directions rather than single factor prescriptions.

In this case, this study seems to be one more that says More is not More.

I'm hoping geogie fear will have a moment to come on over for this question. Thanks a bunch.


Unknown said...

thanks for the response. My takeaway from reading the study (as is the case with most studies on nutrition/training) is to come up with ideas for 10 more studies that I wish someone would do. ;)

I wasn't clear about the 14 hour fast/sleep...I didn't mean to imply that the trainee was sleeping 14 hours. Just perhaps sleeping 8-9 and not eating breakfast, for instance.

Thank you for the thoughtful response and the asking around on behalf of my questions. I've been enjoying your blog for quite sometime now and appreciate your work.

Georgie Fear, RD, CPT said...

Wow, there's a lot here to touch on....

1. Absorption for larger folks.

You will "absorb" virtually all the protien you eat - the digestive system is quite efficient. The question is how much can you assimilate into muscle vs deaminate and do other things with.

2. Spreading protein over the course of the day is generally helpful for maintaining muscle mass. As far as minimum meal timing, you can't force the muscles to take up more protein just by packing lots of it in.

The amount that will be used for protein synthesis is regulated by so many other things: hormones, (GH, insulin, T, cortisol...etc) and stimulus provide by weight training . Also, calorie/energy intake is the big picture - if carbs are in short supply, protein will be used for generating glucose.

For larger or smaller folks, use recommendations based on g/kg.


dr. m.c. said...

Georgie, thanks

would you care to comment (please) on the study above about the one mealers doing just as fine it seems with protein all in one sitting vs 3 feeding group?

how can this be if timing is important??


Unknown said...

Wait... mc, I think your post is a bit confusing at the beginning. One of the questions you list is "What's the right amount of protein to eat?", and then you say "We know there's a usual formula... about how much protein to take in in a day - let's just say for now it's 2-2.5 g per kg (based on work in 2006)". But in the abstract for the study, they write "A suggested maximum protein intake based on bodily needs, weight control evidence, and avoiding protein toxicity would be approximately of 25% of energy requirements at approximately 2 to 2.5 g · kg-1 · d-1, corresponding to 176 g protein per day for an 80 kg individual on a 12,000 kJ/d diet" (emphasis mine). Now, unfortunately, I cannot seem to get access to the full article through my university, but I get the impression that 2-2.5 g per kg is not the answer the authors suggest for the question "What's the right amount of protein to eat?" but only "How much protein can I absorb?". The study is meant to show that the theoretical maximum is much higher than the practical maximum. Isn't that right?

dr. m.c. said...

mark no intended confusion
there are several articles being discussed, and you've referenced two:
the first one is just about known non-toxic levels of protein that can be ingested.
- the other how much of ingested protein can be used in one sitting for protein synthesis in particular under very specific circumstances.

sorry it was confusing. was trying to make the case in the article that there is a difference between how much we can eat (and what happens to it in the body, of which protein synthesis is a part)
- and how much apparently can be used for protein synthesis in a single feeding window.

that's all

hope that helps

dr. m.c. said...

mark, ps, georgie's comments here also speak to this point about complete use of protein vs fraction can be used for protein synthesis


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