Hi guys, haven't seen y'all in a while! I've been busy as a bee, studying away. I wanted to pop in and drop some knowledge, hopefully have a positive effect on everyone's muscular endeavors. I couldn't neatly fit this into any of the subtopics in diet/nutrition, so mods help me out if I've put this in the wrong spot. I want to talk about protein: what it is and how it works, in relation your body as well as your food. I also have an important note on the effect of heat in both cooking and production/processing of whey protein.

PROTEIN:
It's in every cell of your body, it's in most of the foods we eat, and it's what makes up those flashy muscles we all chase. So clearly, it's pretty important for us meatheads to have at least a passing knowledge of this stuff. But many people don't understand it clearly, so my aim is to assemble a dearth of information into a cohesive, somewhat easily digestible post. I've just finished an intense round of biochem courses, and I've been inspired to help the good people of eroids understand just what's going on with our favorite macronutrient. I'm by no means a real doctor (yet), and I will let you know when I'm not totally sure about something.

Structure:
Most of us know that protein is composed of amino acids. There are 20 principle, proteinogenic amino acids that I've recently been forced to memorize. I won't get into essential vs nonessential, because really they're all essential to a healthy diet ;-) Also, I think it's rather common knowledge around here that our bodies can't synthesize certain "essential" amino acids. Moving on... Amino acids are linked together, in sequence, by a very special chemical bond: the peptide bond. This type of bond is so important because it allows proteins to take on various shapes. Primary structure is the sequence of AA's in a polypeptide, the specific order of AA's in a long, tangled string of 'em. Secondary structure refers to how those sequences take on basic shapes such as alpha helices, beta sheets, and beta turns. Tertiary structure refers to the overall shape of the protein molecule, what does the jumble of beta sheets and alpha helices look like? Many times it's globular, a bumpy, ugly looking spherical shape. A lot of enzymes are globular. Other times the tertiary structure is filament-like, which you should recognize as the shape of ACTIN and MYOSIN (microfilaments), which are rope-like proteins that slide together and pull apart to give your muscles eccentric and concentric contraction. Other filament proteins include keratin (nails, hair, hooves for some of you folks), elastin (lungs, circulatory vessels, ear cartilage), and microtubules (important for genetic replication and intra/extracellular transport). Quaternary structure indicates that a certain protein or enzyme has tertiary subunits, often assembled in symmetrical fashion. Hemoglobin (Hb) has quaternary structure; it's a tetramer (4 subunits) that has an iron ion in the middle. Not all proteins have quaternary structure. Myoglobin (Mb) is a monomer (1 subunit) and thus has no quaternary structure, which I believe is what allows it to bond more tightly to oxygen. The tradeoff for "looser" binding with oxygen is hemoglobin's cooperative binding characteristic; as each additional oxygen binds, it becomes more attracted to other oxygens, hence the sigmoidal shape of the oxy-hemoglobin dissociation curve. Both Mb & Hb have mostly alpha helices in their secondary structure, and those helices fit together quite similarly. But interestingly, the primary sequences of these two are pretty dissimilar.

Vocab time!
- Polypeptide: a sequence of more than one AA.
- Denaturing/Denaturation: breaking apart some, most, or all of these bonds. Often done in a lab, but also in your body (constantly).
- Enzymes: things that speed up (catalyze) chemical reactions.
- Fun fact: enzymes make you not drunk after being very drunk, they're the reason alcohol is only kinda toxic. An enzyme (alcohol dehydrogenase) turns ethanol into acetaldehyde (a highly toxic, unstable, free-radical forming molecule), and another enzyme (aldehyde dehydrogenase) turns that into acetic acid (the acid molecule we dilute with water to make vinegar), which is a precursor to acetyl CoA, which is then transported to and burned (with oxygen) in your mitochondria (during krebs cycle). So alcohol really is fuel, it's the 4th macro, and per gram it gives you a number of calories somewhere in between protein/carbs and fats.

Function:
Everyone knows protein is what your muscles are mostly made of, but what many people don't know is that most enzymes in your body are proteins (A few enzymes are catalytic RNA molecules). Proteins are the structural building blocks of your muscles. They also form structural components of your skin, epithelial cells, they're all over your dick, and especially deep down inside that gigantic gas tank you call a stomach. We literally use proteins (and salty acid) to break down proteins. Our body maintains what you could imagine as an "amino acid pool" in a constant cyclical process: ingestion, digestion (which includes physical disassembly/mastication, & denaturation), uptake (absorption of AA's & small polypeptides through intestinal walls), and synthesis; rebuilding of specific polypeptides/structural proteins, with the goal of eventual (re-)construction of cells and tissues. I don't yet know much about uptake or synthesis, and I know very little about excretion of proteins. I'll get a handle on that stuff after a few more years of school. Suffice to say that current literature indicates your body has an absolute limit of protein grams that it can utilize per unit of time, at a generally constant rate (not accounting for more severe anabolic/catabolic states such as recovery/weightlifting). Juicing will almost certainly increase that max amount, as well as the rate of its utilization.

Food:
We literally eat the muscle of dead animals in order to gain muscle. If only the ancient shamans were correct in assuming we could do this with brains. Alas, this is not the case. But I digress... Your meats and dairy will have the highest amount of protein relative to fat and carbs. But it may come as a surprise to learn there are plants, somewhat edibles ones, that contain very high amounts of protein. This should make sense, since we just learned that protein functions to maintaining structure and catalyze reactions in living tissues. Plants are alive, they have some very rigid structures, and they too need enzymes or other proteins to function. Most plants use forms of carbohydrate for structure (think cellulose, starch, fiber), throw in some proteins and you get very rigid plants bits. My favorite edible plant, shelled edamame (soybean), is particularly high in protein. Dairy comes from animals, so it makes perfect sense that it would have lots of protein in it, but that also comes with a healthy dollop of fats and carbs. Most of you probably derive the vast majority of your protein from animal sources, so I'll focus on that from here onward.

Meat:
Eating carved up animal flesh is great! When decently prepared, it smells like amazing with a side of holy crap I want some, and it tastes like everything that is good and wholesome in life. Probably because we've been eating animals since the beginning of forever. We've evolved a deep love for ripping apart the flesh of all types of animals, from tiny foraging rodents and small game birds to giant herd animals and larger, much tastier birds. The leaner your cut of meat, the more precisely you can control your protein intake levels. If you know there's pretty much no fat in your meat, then you can carefully add/remove carbs and fats in a cyclical fashion, and derive the greatest muscle gains from your yum-yums. I want to make specific note about how we digest meat. Heating meat doesn't "kill" animal protein, or render it ineffective... quite the opposite. It's an initial round of slight denaturing, which is the very function of that roiling vat of salty hydrochloric acid you call a stomach. If you overcook your meat, fear not! Your aren't wasting your protein's usefulness, you've simply denatured it slightly more and sucked out all the juicy moisture than makes it so delicious. In fact, with eggs, cooking actually congeals the aqueous suspension of albumin (a protein), thus making the protein more bio-available. I haven't verified this in literature, but I'm 99% sure about this statement. But that's not to say raw meat is not as good; sushi is freakin' AWESOME! It gives your stomach's enzyme producing tissues exercise, making them do a little more work to denature the more whole protein. However, the absolute amount of digestible raw protein is most likely less than what it is for cooked protein, simply because your tummy has to do more work. This means you need more raw eggs in that protein shake to get the same amount of useful protein as compared to making a decent omelette.

A note on Whey Protein:
I suspect that while some whey protein supplements are high quality, you aren't going to digest all, or maybe even half of the total grams of protein you're ingesting. Here is where I'm using my current scientific knowledge to form an unproven, but very likely hypothesis based on two reasons: first reason is that protein powders are likely more fragmented forms of whey, and they are almost ubiquitously mixed into liquid shakes, which means it quickly passes through your system, and not all of the protein will be absorbed in the intestinal lining. My dad's a doctor and whenever he'd see me drinking protein shakes he would laugh and say "son you're just shittin' and fartin' your money away!" Well this isn't exactly the entire story, but there is some truth to his statement in that those are the two primary modes of protein excretion. After all, we want an excess of, rather than a deficiency in protein intake. My second reason is that high heat is a cheap, fast way to process whey into a usable, shelf-stable solid powder form. Whey in its most natural form is a liquid, and the processing equipment necessary to make it solid is much more expensive and time consuming. I learned the cold process is called "cross flow microfiltration", it's done using expensive ceramic filters, and there's lot's of waste generated when using this method. So most manufacturers blast it with heat to get their $$ real quick without losing much of the raw precursor material (liquid whey). User k-boom hinted at this idea, and learn't me all about that process. Look for the 3rd comment of this thread: https://www.eroids.com/forum/training-nutrition-diet/supplements/best-pr...

So there ya have it, PROTEIN! The wonderful macro, a meathead's best friend, the wonderful mistress I love to put my tongue all over every morning. If you have any questions, I'll try to answer them. If I'm wrong or have misrepresented something, please correct me and back it up with references so we can all better our knowledge of this wondrously essential component of life.