Everything you need to know about protein

[RottenWillow]

We have a ton of info on this board about carbs. A lot about fats too. But what about protein?

One can never achieve a hard body without protein. You can cardio yourself from now until doomsday and you will stay Pilsbury Doughgirl soft unless your body gets sufficient amounts of good quality protein to maintain (and possibly increase) skeletal muscle.

What is protein? What makes one protein source better than another? When should I eat it? How much should I eat? If you can't answer these questions, read on ladies.



The following essential information about protein are excerpts from Lyle McDonald's website where he is expounding on the nature of protein. The original thread is exhaustive and beyond the scope of a basic knowledge reference thread. Hopefully I have included everything you need to know to make wise, informed protein consumption decisions.



What Are Good Sources of Protein? - Introduction

In recent years, thanks to emerging research, diet books and popular articles, the general public is starting to become aware of something that many athletes (especially bodybuilders) have been saying for a while: higher protein diets are better for weight/fat loss and improved health.

Between those two groups, a question that often comes up is “What are good sources of protein?”

So, in my usual way, I’m going to dissect the question and look at all of the factors that go into determining what constitutes a good source of protein. And with that out of the way, let me start answering the question “What are good sources of protein?”


Digestibility: Before a protein can be used by the body, it has to be digested and absorbed into the bloodstream for use by the body. Proteins vary in their digestibility and, logically, a protein that is poorly digested will be a poor source simply because less of what’s being eaten is being made available to the body.

Protein Quality: In one sense, the topic of protein quality could be used as an overall look at many of the other topics I’m going to discuss. In general, protein quality is a measure of how well or poorly a given protein is used by the body.

Amino Acid Profile: Again, tying in with the issue of protein quality, there is the issue of the amino acid profile of a given protein. For background, amino acids are simply the building blocks of protein, and there are 18-22 distinct amino acids depending on who you talk to (not all sources recognize all of the amino acids). Each one is found in differing proportions in different food protein sources and, under certain circumstances, that profile will affect how it is used in the body or how it functions.

Presence or Absence of Other Nutrients: While often ignored, the presence or absence of other nutrients in a given protein source also impacts on how good of a protein it may be. For example, some protein sources contain high levels of iron, B12 and zinc while others do not; the presence of absence of the omega-3 fatty acids (fish oils) may also be relevant. Calcium is also a consideration.

 

[RottenWillow]

A Primer on Protein Digestion

The majority of protein digestion occurs in the small intestine where protein is broken down into smaller and smaller amino acid (AA, the building blocks of protein) chains via a variety of protein digesting enzymes. You can think of proteins as being a long chain of the AAs, the enzymes basically act like scissors, cutting the chains into smaller and smaller bits.

Now, the above makes it sound like all ingested protein gets into the bloodstream after digestion but this is far from the case. No process in the human body works at 100% efficiency and this is one of them. For various reasons, a proportion of all ingested nutrients will escape digestion, continuing through the intestine to eventually end up in your poop. Fat is typically absorbed with up to 97% efficiency and carbs can vary quite a bit depending on what you’re talking about. But what about protein?

So, for example, they might feed someone 50 grams of protein and then see how much comes out the other end. Let’s say that 5 grams of protein show up in the poop. That means that 45 grams of the 50 grams ingested were actually absorbed and that protein would have a digestibility of 90% (45 grams absorbed/50 grams ingested = 0.90 * 100 = 90%).

The research on this is extremely clear and I’ve reproduced the chart from The Protein Book on the digestibility of common foods below.




Food Source............................................ ..Protein Digestibility (%)
Egg..............................................................97
Milk and Cheese............................................ .....97
Mixed US Diet............................................. ......96
Peanut Butter........................................... ........95
Meat and Fish............................................. ......94
Whole Wheat............................................. ........86
Oatmeal.........................................................86
Soybeans........................................ ................78
Rice......................................... ...................76

Source: National Research Council. Recommended Dietary Allowances, 10th ed. National Academy Press, 1989.




Looking at the chart above, two major things stand out. The first is that, contrary to the occasional vegetarian claim, vegetable source proteins have a significantly lower digestibility than animal source proteins.

The second is that commonly available animal-source food source proteins have extremely high digestibilities, 94-97%. This means that for every 100 grams of protein consumed, 94-97 grams are being digested and assimilated by the gut. (Note from RW: This is a big part of why I always advise people NOT to count wheat and bean protein when calculating their macros.)

 

[RottenWillow]

What Are Good Sources of Protein?



Whole Foods vs. Protein Powders

Whole food proteins are generally contained within a matrix of connective tissue and such (e.g. think of the chewing that you have to put into eating meats such as beef, tuna, or chicken) and that alone will slow the process of digestion down. Basically, even without direct data, I’d expect most whole food proteins to be slowly digesting proteins.

Research using whole food meals find that amino acids are still be released into the bloodstream up to 5 hours after eating them; this certainly supports the idea that whole food proteins take a long time to digest. Other researchers have suggested that a given meal will maintain the body in an anabolic state for 5-6 hours so clearly whole food proteins aren’t digesting particularly quickly.

Basically, the majority of proteins that people who aren’t obsessed athletes will be eating are going to be slowly digesting proteins.


The primary exception that I’ve examined, of course, is whey protein which digests quickly; soy isolate is also a fast protein (another that I’ll mention briefly in a second is pea protein hydrolysate). Now, whey has some nice characteristics in terms of its amino acid profile (discussed in a later segment of this article), it may improve immune system function, and have other functional health benefits. Outside of athletes, life extension folks and the obsessed health types, I’m not sure that whey protein powder is going to make up a major source of protein for the majority of people.

However, this brings me in a very roundabout way to a related topic having to do with protein powders and the different forms that they come in.

Types of Protein Powder: Concentrates, Isolates and Hydrolysates

Protein powders come in three primary forms which are isolates, concentrates and hydrolysates. Protein concentrates typically contain roughly 80% protein with 5-6% carbohydrate and fat while isolates may contain up to 90% protein. Hydrolysates are simply isolates or concentrates which have been pre-digested (digestion of protein is called hydrolysis) by subjecting them to specific enzymes. Practically speaking, you will typically pay the least for a protein concentrate, more for an isolate and the most for a protein hydrolysate. Because of the presence of free form amino acids in protein hydrolysates, they often have a more bitter taste than either concentrates or isolates.

There is no advantage to whey or casein hydrolysates in terms of digestion speed. None. Well, unless you think paying three times the price and accepting an often bitter taste is an advantage.

Is Faster Digestion Better?

Although this question would pretty much never come up with regards to general health and nutrition, it is one that is relevant to sports nutrition (and as noted in part 2, older individuals may obtain beneifts from fast proteins). Is it better for protein to be quickly digesting or slowly digesting?

Of course the answer is context dependent and depends on what the goal is. For the majority of applications, I hope that readers get the basic idea that I think slower digesting proteins, or a mix of slow and fast are generally superior to fast proteins by themselves.

This is especially true for non-athletic applications where I think most should simply stick with whole food proteins most of the time anyhow; in the context of a mixed meal, that will mean that the proteins being consumed will digest slowly.

 

[mattya802]

I saw you mention in one of your other posts that timing is everything and you should be taking your BCAA's as soon as you wake and protein 30 minutes after. How about pre and post workout timing? Before bed timing? Any advice there?

 

[RottenWillow]

What Are Good Sources of Protein? - Protein Quality

Essentially, protein quality simply refers to how well or how poorly a given protein is used by the body once it has been digested. Clearly, any protein that escapes digestion (as discussed in What are good sources of protein? - Digestibility) can’t do anything in the body but that doesn’t mean that all of the protein that is digested automatically works the same in the body.


Method of Measuring Protein Quality


Biological Value(BV): BV is one of the more common methods of measuring protein quality and tends to be the one that is seen the most so I’m going to give it the most discussion. BV is simply a measure of how much of the protein actually entering the bloodstream is retained in the body (e.g. used for proteins synthesis or what have you); that is it takes digestibility into account. I’d note that some of the protein (again, researchers are actually measuring nitrogen going in vs. out but that’s not important here) that gets into the bloodstream comes back out in the urine.

Since BV is comparing protein in vs. out, the highest possible value for BV would be 100, that would mean that 100% of the protein that got into the bloodstream is being used by the body (note again, some protein won’t be digested in the first place). No protein has a BV of 100 and claims that whey have a BV of 140 are simply nonsense (they are based on a misreading of a specific paper); this would suggest that for every gram of protein from whey that is eaten, the body somehow stores 1.4 grams of protein. An impossibility.

BV is measured by feeding subjects a protein free diet for three days and then giving them a measured amount of protein, the amount that comes back out in the urine and poop and skin and such are then estimated and BV is calculated. This type of study is called a nitrogen balance study and, for a variety of reasons can be very inaccurate. Again, more detail can be found in The Protein Book.

I’d note that BV is typically tested at very low protein intakes, far below what the average American (and certainly any athlete would eat). Eating more protein lowers the apparent BV which has led to some humorously bad interpretations of BV. As well overall energy intake drastically affects BV; if you eat more calories, apparent BV goes up, if you eat less, apparent BV goes down.

Because of this, BV has a lot of practical problems. It’s very accurate under conditions of low protein intake but caloric has to be meticulously controlled. At the types of high protein intakes seen in most modern countries, as well as with athletes, BV doesn’t tend to say very much.

Net Protein Utilization (NPU): NPU is extremely similar to BV. But while BV is comparing the amount of protein that is actually digested to the amount that is stored in the body, NPU simply compares the amount of protein eaten to the amount stored in the body. Put differently, BV takes digestion and actual absorption of protein into account; NPU doesn’t. This doesn’t make NPU very useful.

Protein Efficiency Ratio (PER): PER is a measure of the amount of weight gain (in grams) in rats compared to their protein intake. It’s always measured in young growing rats and, frankly, has about zero relevance to human physiology.

Protein Digestibility Corrected Amino Acid Score (PDCAAS): The PDCAAS is the newest method of scoring protein quality and is the one most in common use. Like chemical score it compares the amino acid profile to some reference protein; as well it it takes into account digestion. Somewhat interestingly, proteins that were scored as low quality (such as soy protein) achieved a much higher score via the PDCAAS. This is actually in line with research showing that quality soy proteins work just fine for supporting basic human protein needs.

PDCAAS does have a couple of problems, however. The first is that the highest score possible is set at 1.0, no protein can score above that value regardless of the apparent quality. Basically, scores higher than 1 are simply rounded back down.


Does Protein Quality Matter?

Which brings me to my major commentary about the issue of protein quality: I consider it essentially irrelevant. I noted above that BV, for example, is measured at very low levels of protein intake and this tends to hold true for many of the other methods. Protein quality is measured under conditions of low intake because the primary application of protein quality has to do with ensuring adequate nutrition for people who don’t have enough food. Which means that it stops having much relevance at high intakes.

That is to say, small differences in protein quality make an absolutely massive difference if you’re talking about someone in the third world who is eating small amounts of a single source of poor quality protein and doing so in the context of insufficient total caloric intake in the first place.


Athletes tend to get really obsessive about the issue (and of course supplement companies pander to that) but at a protein intake of 1-1.5 grams per pound of lean body mass coming from mixed high quality sources, quality just won’t matter. There is much more discussion of this in The Protein Book.

One possible exception to this is dieting; (RW note: I added the bold) when calories are restricted, the way the body uses protein can change and different proteins may be specifically beneficial (the dairy proteins whey, casein or simply milk are valuable in this regards for reasons outside the scope of this article).

 

[RottenWillow]

What are Amino Acids?

Amino acids are simply the building blocks of protein. Depending on which reference source you use, there are 18-22 different amino acids that occur in the human food supply. Whole food proteins are simply long chains of these amino acids bonded together. Typically whole food proteins are extremely long chains of amino acids, as I discussed in What are good sources of protein? - Digestibility, these long chains are cut into smaller and smaller chunks during digestion until only single amino acids and chains of 2-3 amino acids are actually absorbed.


Essential vs. Non-essential Amino Acids

I should note that the amino acids are usually subdivided into essential amino acids and inessential or non-essential amino acids. It’s important to note that both are absolutely essential for life, the term inessential/non-essential simply means that those amino acids don’t need to be obtain from the diet; the body can make them. The essential amino acids can only come from the diet; hence they are ‘essential’.y


Why do Amino Acids matter?

Now, as mentioned in What are good sources of protein? - Digestibility, after being broken down in the gut and intestine, proteins then appear in the bloodstream as amino acids. These are then used in the body for various processes such as the synthesis of new proteins.

Your heart, liver and many other organs are made of protein, skeletal muscle contains about 20% protein (most of it is actually water), your hair and skin is made of protein, there are numerous enzymes and liver proteins made in your body every day; all are synthesized from incoming amino acids from the diet.


BCAA: A Primer

The branched chain amino acids (BCAA) refer to three individual amino acids, leucine, isoleucine and valine. They are so named because of their branching structure. It’s been known for years that they are treated differently in the body than the other aminos; while other aminos can all be degraded in the liver, BCAA metabolism is fairly specific to skeletal muscle. In a very real sense, BCAA are muscle food. I should note that while BCAA are primarily used in the muscle, they can also be burned there directly for energy.

The BCAA can not be made within the body and must be obtained by the diet. In that context, I’d note that all high quality proteins actually contain quite a bit of BCAA. Proteins such as meat typically contain about 15% BCAA by weight (e.g. 100 grams of protein will provide about 15 grams of BCAA) while dairy proteins such as whey and casein contain more. Some forms of whey contain as much as 25% BCAA by weight (e.g. 100 grams of whey protein will provide 25 grams of BCAA), casein comes in at about 20%.

Glutamine: A Primer

Glutamine is a non-essential amino acid (e.g. under normal conditions it can be made in sufficient amounts) although under conditions of very high stress (trauma, burn injury), the body may need more. Crafty supplement manufacturers have tried to liken heavy training to that level of stress which is, frankly, absurd.

Glutamine plays a number of roles in the body, early research showed that it could stimulate protein synthesis when added to cell culture. Glutamine is also involved in immune system function, I’ll talk about this further on. Glutamine is also involved in acid-base balance, some have suggested its consumption on a high-protein diet to help buffer acid production. I suggested glutamine for GH release (GH has some fat mobilizing properties) in The Ultimate Diet 2.0.


As noted above, BCAA can be burned in skeletal muscle directly (and this increases when glycogen has been depleted) and this tends to produce ammonia which the body buffers by converting to glutamine to be sent to the liver. Basically, glutamine is used by the body to transport amino from muscle to other places where it can be disposed of; glutamine is also used heavily by the gut, immune system and kidneys.

 

[RottenWillow]

I saw you mention in one of your other posts that timing is everything and you should be taking your BCAA's as soon as you wake and protein 30 minutes after. How about pre and post workout timing? Before bed timing? Any advice there?

Hey, sorry I missed your post.

Actually I think I said I felt that timing was the single most important consideration in protein consumption. Quality and quantity are very important too, but I'd personally be willing to get less of either of the above if it meant I could get exactly the timing I consider best.

In the post right above your original one Lyle is talking about whole food protein releasing aminos up to 5 hours after consumption. That's why you want your bedtime protein to be a whole food source. Unless you want to get up during the night to eat like some pro BB'ers do, you want a relatively heavy protein/carb/fat meal just before retiring. The fat retards gastric emptying and will give you an even longer trickle of aminos into your bloodstream during that long fast that occurs while you're sleeping. Then close the gap quick when you wake up with some BCAA's, a rapidly digesting protein powder, or Gear. (not a commercial, but I've used the latter and it is fantastic)

I personally drink a pre-workout shake, not post. About 2 to 2.5 hours before I hit the iron I drink about 50g of protein and about 50g of carbs in a very low fat drink (which speeds gastric emptying). The aim is for the aminos to be just beginning to pass through the small intestine into my bloodstream right when my muscles need them. I can always take a little dextrose right after the workout to trigger an insulin spike, since the carbs are in the process of emptying into the intestine. I think waiting until after the workout to drink your protein and carbs is too late.

 

[ledhead]

Hey, sorry I missed your post.

Actually I think I said I felt that timing was the single most important consideration in protein consumption. Quality and quantity are very important too, but I'd personally be willing to get less of either of the above if it meant I could get exactly the timing I consider best.

In the post right above your original one Lyle is talking about whole food protein releasing aminos up to 5 hours after consumption. That's why you want your bedtime protein to be a whole food source. Unless you want to get up during the night to eat like some pro BB'ers do, you want a relatively heavy protein/carb/fat meal just before retiring. The fat retards gastric emptying and will give you an even longer trickle of aminos into your bloodstream during that long fast that occurs while you're sleeping. Then close the gap quick when you wake up with some BCAA's, a rapidly digesting protein powder, or Gear. (not a commercial, but I've used the latter and it is fantastic)

I personally drink a pre-workout shake, not post. About 2 to 2.5 hours before I hit the iron I drink about 50g of protein and about 50g of carbs in a very low fat drink (which speeds gastric emptying). The aim is for the aminos to be just beginning to pass through the small intestine into my bloodstream right when my muscles need them. I can always take a little dextrose right after the workout to trigger an insulin spike, since the carbs are in the process of emptying into the intestine. I think waiting until after the workout to drink your protein and carbs is too late.

IMO no carbs before bed stores as fat especially if you your doing morning cardio on a empty stomach the goal is to burn as much fat as possible. Secondly, Your pre work-out drink should be 1 hr or 1 1/2 before hitting the iron.Also the carbs should be complex slow burning so you have fuel to train, simple carbs burn to quick, maybe a little during training for insulin spike. Other then that great post....

 

[RottenWillow]

IMO no carbs before bed stores as fat especially if you your doing morning cardio on a empty stomach the goal is to burn as much fat as possible. Secondly, Your pre work-out drink should be 1 hr or 1 1/2 before hitting the iron.Also the carbs should be complex slow burning so you have fuel to train, simple carbs burn to quick, maybe a little during training for insulin spike. Other then that great post....

I don't understand what you're trying to say in your first sentence.

As for pre-workout drink, I'd say an hour is definitely too close to vigorous exercise. I think people would tend to unnecessarily interfere with digestion. Plus I suspect you're looking to exploit the insulin spike interval, but that's not really the topic of this thread. After an hour you're not yet absorbing any aminos through your small intestine.

Yes I agree pre-workout carbs should be lower GI. I use rolled oats which have a moderately low GI, 50g of which raises my blood glucose from 95-100 to about 125-130 mg/dl in about 45 minutes.

 

[ledhead]

I don't understand what you're trying to say in your first sentence.

As for pre-workout drink, I'd say an hour is definitely too close to vigorous exercise. I think people would tend to unnecessarily interfere with digestion. Plus I suspect you're looking to exploit the insulin spike interval, but that's not really the topic of this thread. After an hour you're not yet absorbing any aminos through your small intestine.

Yes I agree pre-workout carbs should be lower GI. I use rolled oats which have a moderately low GI, 50g of which raises my blood glucose from 95-100 to about 125-130 mg/dl in about 45 minutes.

The first sentence I was pointing out that you gave advice to eat carbs before you went to bed, which is a no-no if your trying to get into shape, it stores as fat,and the objective is burning fat whch is easier when you don't eat carbs before bedtime. Sorry to get off topic! But I still disagree with the timing thing
2 to 2 1/2 hrs is way to long before you workout I might agree slightly an 1 maybe is too close but no mor than 1 1/2. Logic being fuel for your workout. And plenty of time to digest. That digest theory is pure speculaton as far as I"m concerned... Some BB take in 100 grams of protein every 2 1/2 hrs. And they say you can only absorb 50 grams every 2 hrs... Not trying to debunk your thread at all.. But nothing is written in stone..