Protein Slows Digestion? Nope.

By Jordan Feigenbaum MS, Starting Strength Staff, CSCS, HFS, USAW Club Coach

In response to this gem of an article. I answered this on the Starting Strength nutrition forum, but I thought I’d repost it here. The article’s claims are italicized and my responses are in bold. 

The food that we consume is absorbed and its nutrients are subsequently sent to different organs through the blood.

The food that we consume is absorbed and its nutrients are subsequently sent to different organs through the blood. Not really the case literally. Protein and carbohydrates get absorbed as amino acids and monosaccharides through the small intestine’s brush border> into the enterocyte (cell)> into the portal vein> to the liver first before going anywhere else, then they get distributed based on lots of factors.

Fats get absorbed as fatty acids directly into the enterocyte (cell) and packaged into the chylomicron (with cholesterol, phospholipids, etc.)> into the lymphatic system> into the venous circulation and then go to some tissues, but mainly those who express high levels of mitochondria for beta oxidation or peroxisomes for long chain fatty acid oxidation. Principally, these are the liver and skeletal muscle.

However, a slow or sluggish digestive system isn’t able to perform its assigned function effectively. That is why a person experiencing a bout of slow digestion is bound to feel extremely uncomfortable post lunch or dinner. Nausea, bloating and vomiting are the most common symptoms of sluggish digestive system that occur after having meals.

Notice they do not define a normal GI transit time for a mixed meal, a slow GI transit time for a “bad” meal, nor do they distinguish between a pathologically slow state like gastroparesis or ileus or obstruction and a “slow” transit time occurring due to a specific meal composition. Yes, there is a marked difference.

Constipation or common digestive problems like diarrhea and irritable bowel syndrome can make the digestive system sluggish.

Diarrhea is actually the GI contents moving too fast. IBS has physiological symptoms of a combination of diarrhea, constipation, abdominal pain, and abdominal bloating. Seems like it might not make the digestive system sluggish, right? Though if you’re constipated, sure (and fiber and/or some probiotics tend to improve symptoms by increasing motility and osmotic pressure in the intestine to propel the contents)

Although protein is good for health, excessively high amounts of protein in the diet can slow down the digestive health. This is because, the body has to really work to digest protein.

Not the case at all. Proteins are initially broken down via the acidic pH of the stomach (and further in the small intestine by pancreatic enzymes that are all part of our normal physiology) and are absorbed very rapidly into the portal circulation. Whey, for instance- spikes blood plasma levels of amino acids (digestive end products of protein) within 20 minutes of ingestion.

Mixed meals confound the “speed” component, i.e. what is the fat content (slows gastric emptying), fiber content (soluble slows, insoluble speeds), total kCal content (larger is slower), tonicity of the meal (isotonic empties faster than hypo or hyper tonic from the stomach to the small intestine), etc. In addition, the hormonal milieu at the time with respect to previous meals also influence gastric transit time. Ghrelin, for instance- increases when you’re hungry and increases the motility of the gut.

Don’t forget about existing food in the GI tract. See how this is quite complicated to talk about? Let’s not forget about drugs….

At any rate, Carbohydrate rich and protein rich foods empty at about the same rate, but normal gastric emptying following a meal is 2-6 hrs….so yea- perhaps this whole article is a bit silly, eh?

Unlike simple carbohydrates, proteins are heavy, hence are not easy to digest and so when its presence is alarmingly high in everyday meals, the consequence is a slow digestive system.

Now this is easy to see that this is wrong…

People with intestinal problems such as Crohn’s disease tend to have a sluggish digestive system besides bowel dysfunction (diarrhea or constipation), vomiting and stomach pain. In this condition the lining of the small and large intestine are inflamed. However, in most cases, the swelling infiltrates in the inner layers of the bowel tissue. This chronic inflammatory disease considerably slows down digestion as the food tends to move at a very slow pace through the intestine.

Fuark. Crohn’s is, currently, a dysregulation of inflammation in response to bacteria in the walls of the GI tract, which results in proinflammatory substances causing direct mucosal injury.

Crohn’s usually presents with diarrhea, fatigue, weight loss, and crampy abdominal pain plus oral ulcerations, perianal fissures, perirectal abscesses, and malabsorption BECAUSE THE FOOD CAN’T BE ABSORBED BECAUSE IT’S MOVING at a normal speed but the mucosa can’t absorb it.

A point to note that although food is digested in the stomach, most of the digestion occurs inside the intestine. Experts say that the intestine is the place where nutrients are observed and eventually circulated in the bloodstream to various parts of the body. However if the food stays for longer time in the stomach, this can affect the digestion process. This condition is known as gastroparesis, in which the stomach takes more time to transfer the ingested food to the intestine. This happens because the stomach muscles that are assigned the task of pushing the food to the intestine, lose their ability to work efficiently. Gastroparesis is the result of malfunctioning of the vagus nerve that regulates movement of muscles lining the stomach wall.

Most common KNOWN causes of gastroparesis:

1) diabetes mellitus
2) idiopathic
3) post-surgical (especially if vagus nerve damaged)

Other causes:

-etoh and tobacco, weed
-infection (mono, chagas, rotavirus)
-CNS injury like a tumor or cerebrovascular event
-PNS pathology (parkinson’s or guillan barre)
-other issues (cancers, hypothyroid, lupus, intestine obstruction, portal hypertension, HIV, stroke and migraines)

So…yea, protein is UNLIKELY to be the cause of “slowed” gi emptying….


7 Rules to Optimize Protein Intake

By Jordan Feigenbaum MS, CSCS, Starting Strength Staff, USAW CC, HFS

In general, I am not a fan of rules, dogma, or rigid guidelines. That being said, what follows are what I consider to be the most important variables when it comes to optimizing protein intake for anyone. While there are sure to be inter-individual variability, these “rules” are pretty spot on. Without further ado…..

1) You will eat enough protein each meal. Optimal protein intake per meal will be the amount of protein that yields ~3-4g of leucine, a branched-chain amino acid (BCAA). 3-4g of leucine per meal has been shown to maximize muscle protein synthesis. If it’s maximized, it can’t go any higher with additional protein, right? This is also, of course, assuming that the protein you’re consuming either contains all the essential amino acids (like all animal derived proteins do) or you have eaten a protein rich meal within the past 4-6 hours that had all of the EAA’s present in abundant amounts. Just to give an example, whey protein (the KING of all proteins) has ~3g of leucine per 20g serving whereas brown rice protein has 3g of leucine per 40g serving. While these two doses are equivalent in their potential to drive muscle protein synthesis, they are not equivalent in calories, which may be a consideration you wish to make if you’re calorie restricted. (Note: many protein manufacturers have different leucine/serving ratios but this is a fairly accurate estimate based on most protein supplements).
2) You will optimize meal frequency. Somewhere along the line people started espousing the mantra “eat every two hours to stoke the metabolism” or “so you don’t become catabolic”, with catabolism meaning breaking down– in this case skeletal muscle- to use their constituents elsewhere in the body.  Problem with these recommendations with respect to protein intake is that there is a known refractory period to muscle protein synthesis (MPS), which we can think about on a gross level as muscle growth/recovery/building. Every time a large enough dose of protein is ingested, i.e. one that provides enough leucine and EAA’s to push the MPS reaction over the edge, there’s a 3-5 hour refractory period that must transpire before another dose of protein (at a meal/shake/etc) will yield another bout of MPS. This means that if you ate a protein rich breakfast at 8am, then ate again at 10am, the meal at 10 am would contribute nothing to MPS and then, by definition- it would be stored away as energy -either glycogen or fat depending on other variables. Ultimately, we should be waiting longer between protein dosings to optimize our results. MPS is obviously important for the athlete, but it’s also important for the gen pop- particularly the aging population who is at risk for sarcopenia, decreased work capacity, and thus a host of other comorbidities (e.g. diabetes from decreased skeletal muscle buffering of blood glucose). The literature suggests that the aging population actually sees fantastic results with higher protein intakes and they even use whey protein shakes in many of their interventions.

tl;dr-Eat 3-5x per day tops, spread out 3-5 hours.
3) You will determine optimal protein intake by taking rules 1 and 2 into consideration with total calorie intake, age, and gender. It intuits well, given rules 1 and 2, that the optimal protein intake per day is initially based on how much protein a person needs per meal to maximize MPS multiplied by the number of meals they will have per day. Other factors that are taken into consideration to increase or decrease the protein prescription (new book title?) for an individual includes the following modifiers:
a)Gender- The more male someone becomes, the more sensitive to amino acids they are, in general. This would allow a male to need slightly less protein per pound than a weight and age-matched female. That being said, lean body mass weight also plays a role in the amount of leucine needed per meal to maximize MPS, but this is literally a variation of 0.5-1g tops for a range of bodyweights between 100lbs-300lbs, so we don’t take it into consideration and 3-4g is very safe.

b) Age- In general, the more someone ages the less sensitive they become to protein, so protein levels should go up over time slightly.

c) Dietary Preferences- As the quality of protein increases (based on bioavailability, protein digestibility amino acid corrected score, and amino acid profile) the total protein needed to optimize protein intake goes down. Similarly, the more vegan someone is, the more protein they require, i.e. the more calories from protein they require to get the same effect as their meat-eating, bone crushing, bacon frying counterparts. In short, the lower quality your protein sources are (lentils/rice/veggies/wheat/soy) the more protein you require for the same effect. This is an important consideration for those who are calorie restricted/limited.

4) You will not listen to bro’s who tell you that you only need x gram of protein/day. First off, we’re definitively NOT talking about protein needs here. Protein needs refers to what you NEED to not be deficient- not to optimize performance, aesthetics, or health but merely to survive. So yea, not what we’re talking about. Secondly, the amount of protein you actually need is a fairly complex answer based on everything we’ve discussed above. Do you really think the dude with the cut-off tee who maxes out on bench press every Monday and squats high (or more likely-leg presses) has taken all this into consideration before word vomiting his opinion to you while you foam roll? Doesn’t it make more sense that he noticed your new Lululemon yoga pants (if female) or is admiring your handsome combover (if male)? Seems more likely to me…

5) You will not listen to the bros who tell you that you can only absorb x gram of protein/meal. The poor bro, he can’t catch a break. So this oft-repeated nonsense goes around and around and just will not die…until TODAY. Let me be crystal clear, you absorb and use virtually 100% of everything that enters your gastrointestinal tract from your mouth. If you don’t, you’ll know it because you’ll be having watery diarrhea post-prandial (after a meal) since the undigested and unabsorbed food will act osmotically to draw water into the large intestine and then well, you know what happens after that. Look, we’ve done the tracer studies and know that when you eat any amount of protein at a meal it all gets absorbed. All of it. Actually 110-120% of it. Yep, MORE THAN 100%. That’s because the cells the line the  bowel, the enterocytes, make proteins themselves. These are called endogenous (made within the body) proteins and yep, they’re absorbed too. Yes Virginia, if you eat 100g of protein at a meal you’ll absorb it all. Yes, it will take longer than if you only ate 20g, but you’ll absorb the first 20g of protein from the 100g at the same rate as 20g on it’s own provided they have similar total fat content and fiber content within the entire meal. That being said, the time course to which a meal is absorbed matters little to anyone, unless they compete or train multiple times per day.

6) You will not get lured into buying expensive protein with sub optimal amino acid profile. People, if you’re paying more than ~10 dollars/lb of protein you’re getting duped, as the manufacturer is preying on your ignorance. Whey is the king protein, period. It’s better than the 100 dollar fish protein from a certain manufacturer who is big in the land of shirtless dudes and vibram 5 finger clad women. Why? Because its amino acid profile is better, i.e. it has more BCAAs (leucine/isoleucine/valine) and a higher concentration of essential amino acids. Also, it’s cheaper…so that seems to be a good point in and of itself. Whey trumps casein on satiety, MPS rates, and time that it keeps plasma (blood) amino acid levels elevated. In other words, all the nonsense the bro at GNC regurgitates about casein being a slow digesting protein that is good to take at night because it slowly releases amino acids from the GI tract is BS. Well, to be fair to him (bro) or her (bra?), it [casein] does more slowly release amino acids into the blood stream from the gut, but it’s TOO SLOW to actually raise blood amino acid levels high enough to effectively drive muscle protein synthesis unless you dose it much higher than whey, which is the king of proteins. Also, whey keeps you fuller, longer (satiety) than casein, and it’s CHEAPER. Yep, whey is better than egg protein, beef protein, hemp protein (sucks), rice protein (sucks), pea protein (double sucks), and soy protein (double sucks). Whey protein concentrate, one of the cheapest options out there is where everyone should start for whey supplementation. If it doesn’t upset your GI tract, then stay there and never look back. If it does- and it will in some who are sensitive to an amino acid fraction (beta lactalbumin) – switch to whey protein isolate, which has this fraction removed. Whey protein concentrate (WPC) might actually be superior to whey protein isolate (WPI) because b-lactalbumin is a very concentrated source of leucine- so I prefer WPC in those who can tolerate it. No Virginia, WPI doesn’t always mean better and as you just learned- more expensive is not always better.

7) You will not fall into the trap of megadosing protein, because gainzZz? So far we’ve described why it’s hard to put a firm number on optimal protein intake based on numerous variables. That being said, there is definitely an upper limit- though not for the reason your doctor will try to justify. Most physicians, PA’s, nurses, etc. will all try to recite the urea cycle and scream stuff about ammonia at you whilst telling you that your kidneys and/or liver will fail with high levels of protein intake. I think every time they do this an angel gets its wings because it occurs too frequently and is so far removed from what actually happens in vivo (in the body) that I assume it’s just a religious ritual that all health care providers learn in school and pay homage to periodically. While I do not have time to layout the entire metabolic pathway for ammonia and urea, the two  toxic byproducts of protein metabolism that supposedly build up an will harm your kidney and/or liver, I will briefly state that in a healthy person- there is no upper limit for protein intake, as the excretion (removal) rate of these toxins is massively upregulated in an adaptive way that is not harmful, but is a response to a hormetic stressor, i.e. something that disrupts our homeostasis. There is no evidence of any kidney or liver damage when the excretion pathways upregulate either. Similarly, in end stage renal disease, those who ate a “very low protein diet” had worse outcomes than those who ate either a “moderate protein” or “low protein” (but higher than very low) diet. This indicates, to me at least, that protein and its metabolism is not harmful to the kidney- even if it’s function is reduced. More data continues to accrue exposing other harmful factors to the kidney, namely elevated blood sugar in those patients who don’t deal with glucose very well….perhaps because they haven’t optimized their protein intake yet 🙂

I say all this sort of tongue-in-cheek, as I do think there is an actual upper limit to useful protein intake, i.e. there is an inflection point where increased protein dosing does not yield improvements in performance, muscle protein synthesis, aesthetics, etc. This point is obviously different for many people, but I could make a pretty strong argument to avoid intakes in excess of 300g or so for anyone who is under 350lbs. Think about the 200lb bro- replete with cut off tank- who eats 400g of protein per day. While only a fraction (maybe half- depending on sources, age, etc.) will actually contribute to MPS, the other half is getting burnt (oxidized) or converted to carbohydrates and/or fat for storage. These processes are all controlled by enzymes, who will adapt (of course) to the stress imposed upon them. If/when these enzymes upregulate, i.e. increase in number and activity, the body becomes more efficient at using protein for fuel (oxidation to yield energy) and/or converting it to carbohydrates and fat. Similarly, such a robust protein intake concomitantly decreases intake of other substrates to a degree, i.e. carbohydrate and fat intake will be lower in a person who eats 400g of protein than if that same person only ate 200g of protein. This all sums to create a situation where a person is very good at breaking down protein as fuel and, God forbid, should his protein level ever significantly drop below 400g for an extended period of time- like if he were to spend a week at the Jersey Shore and only consume 100-150g of protein/day- then theoretically protein turnover would continue to be elevated since the body’s enzymatic ability to break down protein is so upregulated. Just some food for thought.


Top 10 Mistakes People Following Starting Strength Make

By Jordan Feigenbaum MS, Starting Strength Staff, CSCS, HFS, USAW Club Coach


1) Not reading the book

Seriously, most people who are doing “Starting Strength Novice Progression” have never even read the book. They got the “routine”, replete with rows in place of power cleans, of the Internet and are 100% unprepared for what this program requires. Further, because they have not read the book and thus, are lacking in understanding the rationale- the WHY- behind the program, they do a bunch of inappropriate things as seen in the other 9 items below. Bompa, Issurin, and Zatsiorisky all agree that explaining to an athlete the “why” behind the “what” is important for compliance. If you want to do Starting Strength Novice Progression, you need to read the book. Period.

2) Starting too heavy.

This is usually a result of a failure to read the book, however there are still some people that will start too heavy because the heavier you start the faster you’ll get strong, right? Wrong. What we’re aiming to do is use the smallest effective dose to stimulate the maximum potential response. In lifting terms, we want you starting with a weight that begins to challenge your ability. This can be gauged, roughly, by when the speed of the bar slows down or the technique suffers slightly. If the former happens, then you’ve just done a set of 5 reps that is heavy enough to drive the adaptations we want, i.e. strength, neuromuscular coordination, hypertrophy, etc. If the latter happens, however, we need to back the weight down just a tad in order to preserve proper form (see below).

3) Having poor technique.

This mostly stems from people not doing Step 1, i.e. reading the book, OR not watching all the videos, reading all the articles, etc. on the site, YouTube channel, or various other mediums. Bottom line is, if you’re technique is not good you’re going to see less than optimal results through any training program, period. When compounded by the fact that this program aims to get you as strong as possible in the shortest amount of time, things start to escalate quickly. It would behoove any person to see a Starting Strength Coach within their first week of training just to hammer this all out. If that’s not possible, post a form check on the Q/A the coaches so graciously run.

4) Eating like a bird.

I was thinking about putting this as number one, but alas, I thought the other things were actually more important and, specifically, doing number 1 would take care of this number. Look, if you’re a 16-23 year old male and <165 lbs, you need to gain a significant amount of body weight, like yesterday, in order to be facilitate the fastest rate of strength and muscle size acquisition. This is done through food, like LOTS of it. I’ve already written extensively about this topic in this article, so I suggest checking that out. Look, here’s the simple fact:

You have one chance in your life to put on muscle at an almost unnatural rate. This moment in time also coincides with the ability to gain a tremendous amount of strength, if you’ll only eat to facilitate this process. For 3 months forget about your abs so you can build the ice chest to put the 6-pack in.

The older, heavier, or more female you get away from this “ideal Starting Strength candidate” the less extra food you need to drive these processes. Again, see the article linked above “To Be a Beast” for more discussion on this topic.

5) Not resting long enough between sets.

After 3 minutes, approximately 80% of your muscle’s ATP has been replenished, at 5 minutes, approximately 95% is back in the game, and at 8 minutes ~ 100% is there. Don’t try to hit PR’s, which happen everyday on this program, with 80% of your muscles’ energy available.

6) Adding in too much bullshit.

Remember that we’re using the minimum effective dose to get the maximum response here. Adding in a bunch of extra stuff dilutes the “effective dose” AND spreads the body’s available resources for adaptation to the “dose” too thin for optimal results for a novice trainee. Of course, as you become more “trained” and thus, can tolerate more volume, frequency, and intensity, you’ll be able to add more exercises, sets, reps, etc. 

If, on the other hand, you add too much tomfoolery TOO SOON in your training career, you run a very serious risk of attenuating (diminishing) your adaptive responses to training, thus blunting your progress.

The take home, keep it simple Santa (K.I.S.S.- I don’t like calling people stupid, normally). The big five, squat, bench press, press, deadlift, powerclean plus chins, curls, and back extensions will work beautifully for your dedicated novice progression. Read the book to see implementation, or this excellent article on Fitocracy by Michael Wolf.

7) Resetting a million times.

Sometimes you just have to call a spade a spade and realize it’s time to move on. Whether it’s due to not enough food, not enough recovery, or poor technique, etc. you just need to either get some help or move on. If you’re not progressing every training session, you’re no longer on the Novice Progression anyway, so don’t be married to it if it’s not working for you (and you’re doing all the necessary things to make it work).

That being said, having a training program that revolves around the big 5 and some HIIT (if necessary) is the best base template you could hope for, with rep ranges, total volume, and frequency all reflecting an individual’s needs and goals. Put simply, you could do a lot worse than to keep resetting over and over again, but do you really want to stay weak? Figure out the limiting reagent and nip it in the bud. Grow. Progress. Profit.

8) Missing workouts (and not adjusting accordingly).

Simple enough, right? If you miss a workout on this program you are, by default, failing to provide a stimulus for your body to adapt to. This adaptation response is what is used to drive the next training day’s progress. Thus, if you miss a day you shouldn’t be expecting to “go up” in weight the next training day, although in the beginning this is more feasible. Moreover, novices tend to de-train more quickly than advanced trainees, as they’ve had less cumulative exposure to the lifts, progression, etc. and thus, it’s not unusual to see some of these detraining or deconditioning effects if a person misses a workout.

So, what do you do if you miss a workout? Simply repeat the last workout you did and start from there. If you miss a series of workouts and are a true novice, you’ll just start all over again. I really shouldn’t have to say this, but how about just not missing workouts?

9) Reading too much bullshit.

Bro 1: “Hey man, did you see that new exercise on today?”

Bro 2: “Nah, bro. What was it?”

Bro 1: “It’s like this weird lunge thing with kettlebells. All the Russians used to use it and that’s why their legs are so jacked. I heard Klokov invented it!”

Bro 2: “Dude, this is awesome. We don’t have to do squats today then. Let’s do like 40 minutes of mobility, to make sure we activate all our muscles during training, then do Klokov lunges with kettlebells.”

Bro 1: “Yea, squats are so old-school. said these were better for hypertrophy anyway. I don’t care about being strong, I just want to LOOK strong.”

Sadly, this sort of crap happens everyday in gyms (CrossFit and black-iron gyms are not exempt from this either) across the country. People mistake “new” or “proprietary” with “better” and try to reinvent the wheel. Look boys and girls, barbells are the most efficient way to load the human musculoskeletal system and stress the body. Because it’s the most efficient*  way to stress the body, it’s the most efficient at causing the body to adapt and these adaptations are more robust than any other silly shit your “guru” is pushing.

*ef·fi·cien·cy: noun, plural ef·fi·cien·cies.

1. the state or quality of being efficient; competency in performance.
2. accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort: The squat is increasing Christy’s exercise efficiency by working all the muscles of her legs and trunk instead of wasting hours doing isolation/activation bullshit.
3. the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage.

10) Being a p*ssy.

Any program that’s designed to add weight to the bar 3x a week is going to be hard, make no bones about it. If you want it to be easy or, more commonly, easier week to week you need an attitude check.

“It never get’s easier, you just go faster”- Greg LeMond

Booze and Barbells Part II

By Jordan Feigenbaum MS, Starting Strength Staff, CSCS, HFS, USAW CC

In case you missed part one of this three part series, click here. In today’s blog entry we’re going to talk about how alcohol affects skeletal muscle and the sex steroid, testosterone. Things can get pretty complicated in a hurry here, but what I aim to do is provide some basic science background for my readers as well as how a certain stressor, i.e. alcohol, can alter the internal milieu. I actually just used the words “internal milieu”, which describes the internal environment of the human body just so I could provide the following quote to pay homage to my previous physiology professors:

“The stability of the internal environment [the milieu intérieur] is the condition for the free and independent life”- Claude Bernard

The concept of the internal environment being important for physiological normalcy and a rationale for the human body’s homeostatic underpinnings was later expanded upon by Walter Canon’s characterization of homeostasis in 1932. He [Canon], proposed four characteristics of homeostasis as follows:

  1. Constancy in an open system, such as our bodies represent, requires mechanisms that act to maintain this constancy. Cannon based this proposition on insights into the ways by which steady states such as glucose concentrations, body temperature and acid-base balance were regulated.
  2. Steady-state conditions require that any tendency toward change automatically meets with factors that resist change. An increase in blood sugar results in thirst as the body attempts to dilute the concentration of sugar in the extracellular fluid.
  3. The regulating system that determines the homeostatic state consists of a number of cooperating mechanisms acting simultaneously or successively. Blood sugar is regulated by insulin, glucagons, and other hormones that control its release from the liver or its uptake by the tissues.
  4. Homeostasis does not occur by chance, but is the result of organized self-government.

It is important to appreciate the homeostatic mechanisms that the human body possesses in order to maintain an “even keel”, as without redundant pathways in place things can go awry in a hurry. At any rate, while the overall concept of the internal milieu and it’s influences on homeostasis are critically important, further discussion of it would preclude our look at just how alcohol/ethanol can alter skeletal muscle metabolism and testosterone levels. To begin, let’s talk a bit about skeletal muscle.

One of the most common effects of alcohol on striated muscle, i.e. skeletal and cardiac muscle, is fiber atrophy or reduction in size. Skeletal and cardiac muscle are both striated, as they have repeating sarcomeres and appear (under the microscope) to have alternating “light” and “dark” bands.

Screen shot 2013-06-12 at 6.07.19 PMSmooth muscle on the other hand, which is found in lots of places like the walls of the vascular system and the GI tract, do not appear striated under a microscope because they lack the organized, repeating structure of the sarcomere.

At any rate, striated muscle size is a result of the balance of protein synthesis and protein breakdown. In other words, the net flux of protein reflects the protein being built (synthesized) and deposited minus the protein being broken down and metabolized. If something were to either increase protein synthesis or inhibit (prevent) protein breakdown, their would be a net gain in protein levels. On the other hand, if the rate of protein breakdown is increased OR the synthesis of new protein is inhibited, there will be a net loss of protein. In general, a net gain of protein within muscle tissue results in hypertrophy (increased size) and a net loss of protein in the muscle tissue results in atrophy.

Ethanol tends to decrease striated muscle protein synthesis [1]. Interestingly, the resulting atrophy appears to be greatest in Type IIB fibers, which are a subtype of the fast-twitch muscle fibers that produce high amounts of force, contract rapidly, and are anaerobic. Some researchers actually classify type II muscle fiber atrophy as part of a diagnostic criteria of alcoholic myopathy, however this selective decrease in size also occurs in other issues like calorie malnutrition, neuropathy, etc. Additionally, only about 33% of chronic asymptomatic alcoholics show significant type II fiber atrophy without malnutrition, neuropathy, etc. although other studies report 40-60% of alcoholics presenting with significant atrophy [1]. Urbano et al. goes head to head with Preedy et al in the following quotes:

In fact, it [ethanol] is the most frequent cause of toxicity to striated skeletal and cardiac muscle in adults in dose dependent fashion [1].

“Due to the ethanol-induced reduction of muscle phosphorylase activity, decreased rates of protein synthesis and whole-body protein metabolism by 15–30%, predominantly in type II fast-twitch anaerobic fibers that utilize glycolytic metabolism.Type I fibers were not overly affected and there was no clear decrease in muscle protein breakdown [5].

As far as how this occurs on a cellular level, it appears as though ethanol consumption disrupts the translation of would-be muscle-protein RNA, but not it’s transcription. For background information, muscle protein synthesis signalers (like eating a protein-rich meal or training) increase the transcription of certain DNA to muscle protein RNA. Muscle protein RNA is then translated into muscle protein, which is shuttled to it’s target and deposited as muscle. Through increased binding of a variety of different regulatory sites on the muscle protein RNA, translation is decreased and total muscle protein synthesis decreases [2].

Measuring decreases in total muscle protein synthesis can be tricky in the laboratory settings, as most of the time a total nitrogen balance measurement is used. Remember, protein is the only macronutrient with nitrogen as a component. Therefore, it intuitively makes sense that the amount of nitrogen taken in minus the amount of nitrogen excreted can give insight into the nitrogen balance of a person or animal. Unfortunately, some people take this sort of information as definitive with regards to what is actually happening in the muscle specifically. Remember, all tissues (lungs, gut, kidney, visceral organs, etc.) are made up of protein, which are also turned over regularly and thus influence total body protein and nitrogen balance. Lang et. al. provide a nice quote describing this:

However, whole body measurements represent the sum of many vastly different organ systems (e.g., muscle and nonmuscle protein synthesis and hepatic secretory protein synthesis) and provide little information concerning individual processes or tissues.

So while total body nitrogen balance tells us what’s happening on a body wide or systemic level, it does not tell us what’s happening in just the muscle tissue. Muscle protein turnover, in sum, makes up less than 30% of total body protein turnover anyway [3]. Other studies, however, have shown that with acute alcohol intoxication muscle protein synthesis decreases in skeletal muscle, heart, intestine, bone, and skin. Additionally, chronic ethanol exposure has been demonstrated to decrease skeletal muscle protein synthesis in rats [4, 5]. It appears that ethanol exposure is potentially harmful to overall protein synthesis, as described in the following quote:

“However, experimental and clinical studies have clearly demonstrated that ethanol itself is a direct noxious agent to heart and skeletal muscle in a progressive, cumulative, and dose-dependent manner, an effect independent of nutritional, vitamin, or mineral factors.”-[Nguyen et al. (6)]

There are only a couple of things left to discuss with respect to actual skeletal muscle function and ethanol. First, muscle glycogen concentration tends to increase in chronic alcohol patients because glycogen cannot be degraded as efficiently. This is due to a partial inhibition of the biochemical pathway for glycogenolysis (glycogen breakdown) as well as glycolysis (glucose breakdown) [5]. In contrast, acute alcohol exposures tend to decrease glycogen storage, especially post workout as some of the mechanisms used to store glycogen in skeletal muscle are inhibited and instead fatty acid production is increased. These effects are independent of acetaldehyde toxicity, which was discussed in part one of this series [5].

Ethanol and acetylaldehyde also tend to increase formation of reactive oxygen species due to their effects on vitamin metabolism. Reactive oxygen species (ROS) tend to increase cellular damage and stress in the skeletal muscle, thus increasing damage to cells of the muscles which may increase atrophy.

Moving along, let’s start our discussion about alcohol and testosterone production by covering the general overview of testosterone production in vivo (in the body). This will give us some background to what is normal so we can consider the effects of ethanol on the internal milieu and homeostasis.

Gonadal-AxismennewestNormally, males produce testosterone in the Leydig cells of the testes from cholesterol via increasing leutinizing hormone (LH) activity within the testes. LH increases an enzyme called cholesterol desmolase, which is responsible for converting cholesterol to pregnenolone. Pregnenolone will go on to be converted through various enzymes to testosterone and thus, but first it needs to be formed from cholesterol. Thus, increasing the enzymatic activity of cholesterol desmolase helps to increase testosterone production.

Naturally, one would ask well what increases LH? Gonadotropin releasing hormone (GnRH) is secreted by the hypothalamus in the brain. GnRH is released into blood vessels that carry this peptide to the anterior pituitary gland (hypothalamic-hypophysial portal system). GnRH is normally secreted in a pulsatile fashion, i.e. it is not constant. It acts on certain cells in the anterior lobe of the pituitary gland (gonadotropes) to cause them to manufacture and release LH, which is also released in a pulsatile fashion. LH is released into the systemic (body-wide) circulation where it ends up traveling to the testicles and causing the Leydig cells to pump out testosterone, as described above.

As discussed at the beginning of this post, most, if not all of the body’s pathways are tightly regulated to keep it on an “even-keel”. Let’s explore this now that we know the testosterone-producing pathway. Testosterone produced by the Leydig cells provides what’s known as “negative feedback” on the hypothalamus and cells of anterior lobe of the pituitary, effectively decreasing secretion of GnRH and LH. Thus, when testosterone levels are high, GnRH and LH levels are low. Conversely, when testosterone levels are low, the frequency and amplitude of GnRH pulses are increased. A downstream effect of this is increased LH release and thus, increased signaling to the Leydig cells to produce more testosterone because the negative feedback signaling is removed.

As we’ll see in the upcoming discussion of ethanol’s effects, perturbation at any level of this pathway can result in deleterious effects. So, how does ethanol affect testosterone production and/or signaling?

As it turns out, ethanol exposure appears to lower GnRH levels, which leads to reduced LH secretion from the anterior pituitary and reduced testosterone production by the Leydig cells of the testes [7]. Mechanistically, this occurs because a hormone normally produced in the testes and hypothalamus at very low levels, β-endorphin (an endogenous opiod), normally only slightly suppresses testicular testosterone production and release. In the hypothalamus, β-endorphin results in decreased GnRH release. Adams and Cicero have shown an increase in β-endorphin after acute alcohol exposure [10]. Naltrexone, a treatment currently used in alcoholism to decrease alcohol cravings, blocks B-endorphin activity and may prevent reduced testosterone levels. Three other ways ethanol affects active GnRH levels is through acetalaldehyde, which is toxic, disturbing nerve impulses outside the hypothalamus that signal GnRH production WITHIN the hypothalamus, and finally, ethanol appears to interfere with processing of the inactive GnRH precursor to the active GnRH form according to Uddin et al.

LH levels actually decrease with alcohol exposure, which is not what we’d expect. Harkening back to our homeostatic mechanism discussion, if testosterone production falls, we’d expect GnRH and LH levels to increase to “right the ship”. However, as discussed above GnRH levels actually decrease and so do LH levels. Mechanistically, the decreased LH levels appear to be due to the toxic affect of ethanol directly on the anterior pituitary gland where LH is released by interfering with GnRH’s signaling of LH production in the cells that they act on (gonadotropes). Another effect of ethanol on LH that causes it’s decrease is that alcohol in the blood tends to result in the anterior pituitary gland’s production of less potent LH variants, thus decrease the level of LH in the blood and the quality of LH in the blood too.

A study done by Steiner and colleagues in 1996 found that when males were given a 15-percent alcohol solution that was administered every 3 hours, around the clock, together with a diet replete with protein, vitamins, folic acid, and minerals (total daily alcohol dose was 220g or 3g/kg body weight, which equals 15 drinks) that the testosterone levels in the men’s blood declined 5 days into the study and continued to fall over the entire period. This was attributed to a decrease in testosterone production in the Leydig cells of the testes and increased removal rate of testosterone from the blood via catabolic processes. On the other hand, Southren et al. found that the increased testosterone catabolism or breakdown is only present in men without liver disease, whereas the clearance is decreased in men with liver disease.

Numerous studies in human and animal models have since confirmed reduction in testosterone levels after either acute or long term alcohol exposure. Acute alcohol ingestion appears to result in a significant reduction in testosterone levels that lasted for 96 hours in a rat model [9].

Sarkola and Eriksson actually found that testosterone can increase in men exposed to a low dose of ethanol, although this is a transient effect due to the predomination of decreased liver clearance of testosterone from the blood compared to the decreased testosterone production in the testes. Unfortunately, during the latter stages of elimination of alcohol or when alcohol has been completely eliminated, testosterone production decreases even more. Similarly, in higher doses of alcohol consumption, e.g. 1.5g/kg, the decreased production of testosterone predominates over the transient decreased clearance rate of testosterone. This has been confirmed by experiemental evidence from Välimäki et al in 1990 and Ylikahri et al. in 1974 [10].

Another interesting finding is that alcohol abuse and subsequent impaired testosterone production tends to result in testicular atrophy/shrinkage, which occurs in about 75% of men with advanced cirrhosis [10]. The atrophy most likely results from the toxicity on the testes, decreased LH and FSH production, and other confounding factors causing decreased sperm cells and sperm production.

Finally, and perhaps one of the more important ways alcohol effects testosterone’s activity and blood levels is that ethanol exposure tends to increase aromatization of testosterone and testosterone precursors. Aromatase is an enzyme that converts testosterone to estrogen and thus, increased aromatization results in increased conversion of testosterone to estrogen. Additionally, the immediate precursors to testosterone, androstenedione (Mark McGwire?) can be “aromatized” to another estrogen subtype called estrone. Scientific evidence points to this “increased aromatization” as a byproduct of increased estrogen production and not a decrease in estrogen clearance [10]. Aromatization is not a good thing above physiological normal (homeostatic) levels in men, as the authors conclude:

“In addition to causing breast enlargement, estrogens appear to exert a negative feedback effect on LH and FSH production and may thereby contribute to alcohol’s suppression of those key reproductive hormones.”

While alcohol certainly has some benefits, which we’ll get to I PROMISE, it’s important to know the deleterious effects that alcohol can have on the internal milieu, especially as it pertains to training. Again, I’ll leave you with my favorite axiom related to alcohol consumption and training:

“If you’re drinking enough to get drunk, you’re drinking enough to mess with your results.”


Until next time.


1)  Urbano-Marquez, A.; Fernandez-Sola, J. Effects of alcohol on skeletal and cardiac muscle. Muscle Nerve 2004, 30, 689-707.

2) Lang, CH, Wu, DQ,  Frost, RA. Inhibition of muscle protein synthesis by alcohol is associated with modulation of eIF2B and eIF4E. American Journal of Physiology-Endocrinology and Metabolism 1999, 277, 268-276.

3) White JP, Baynes JW, Welle SL, Kostek MC, Matesic LE, et al. (2011) The Regulation of Skeletal Muscle Protein Turnover during the Progression of Cancer Cachexia in the ApcMin/+ Mouse. PLoS ONE 6(9)

4) Preedy V. R.,Peters T. J.,Patel V. B.,Miell J. P. (1994) Chronic alcoholic myopathy: transcription and translational alterations. FASEB J. 8:1146–1151

5) Preedy V. R., Peters T. J. (1990) Changes in protein, RNA, DNA and rates of protein synthesis in muscle-containing tissues of the mature rat in response to ethanol feeding: a comparative study of heart, small intestine and gastrocnemius muscle. Alcohol Alcohol. 25:489–498.

6) Nguyen VA, Le T, Tong M, Silbermann E, Gundogan F, de la Monte SM. Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy. Nutrients. 2012; 4(8):1058-1075.

7) Vatsalya Vatsalya, Julnar E. Issa, Daniel W. Hommer, and Vijay A. Ramchandani. Pharmacodynamic Effects of Intravenous Alcohol on Hepatic and Gonadal Hormones: Influence of Age and Sex. Alcohol Clin Exp Res. 2012 February; 36(2): 207–213.

8) Sarkola, T. and Eriksson, C. J. P. (2003), Testosterone Increases in Men After a Low Dose of Alcohol. Alcoholism: Clinical and Experimental Research, 27: 682–685

9) Steiner, J., Halloran M.M., Jabamoni K., Emanuele, N.V., Emanuele, M.A. Sustained effects of a single injection of ethanol on the hypothalamic-pituitary-gonadal axis in the male rat. Alcoholism: Clinical and Experimental Research 20:1368–1374, 1996.

10) Emanuele, N.V., Emanuele, M.A. (1998) Alcohol’s Effects on Male Reproduction. The Alcohol and Other Drug Thesaurus. Vol. 22, No.3.