“But Dude, I’m Eating Only Brotein!?”

Intro:

If I had a dollar for everytime I saw, heard, or read something along the lines of “just eat protein to get leaner” or “eat protein if you wanna lift big weights” I would be writing this article on a newer laptop, in a versace robe, with a Victoria’s Secret model feeding me a choice assortment of fresh tropical fruit. Alas, I am in a library typing this on an 11 year old laptop, wearing an Old Navy T-shirt, drinking a Monster. Nonetheless, I have come here today to dismantle the many myths about protein metabolism and shine some light on why just eating a lot of protein will not make you strong or jacked.

Let’s first establish what a protein is. Proteins are made of amino acids that are joined together and eventually folded and cross-linked into their final form. They make up our muscles, they transport important molecules like oxygen, and amino acids even make up some of our most important hormones like insulin. Protein, however, is most known for being the macromolecule of choice for the average gym goer. So, let’s talk about what happens when you pound that 35g protein shake after a workout. As protein enters the body, it passes through the mouth, esophagus, and esophageal sphincter as it reaches the stomach and later the small intestine. When it reaches the stomach, the Pancreas releases CCK and Secretin causing the release of digestive enzymes. A group of zymogens (inactive forms of enzymes) are activated by enteropeptidase and begin to break down the peptide structures that make up the ingested proteins. These enzymes are peptidases (protein specific enzymes), and attack different areas of the peptide chain, eventually freeing up amino acids. Once the protein is degraded to free amino acids, the amino acids can be absorbed through the small intestine. After being absorbed, the amino acids have one of three fates, be synthesized into new proteins, be degraded into waste products, or be converted to other substances in order to be used for energy.

Protein Synthesis (Which type of protein?):

Everyone has heard of the “anabolic window,” and it is definitely a real thing. In terms of protein synthesis, most pathways are active during a four hour period after a meal. This is the ideal destination for gym goers as the amino acids consumed by the body are converted to muscle mass and other protein derivatives necessary for proper bodily function. Let’s talk for a second about what type of protein is ideal. When I was in Biochemistry, my professor explained the differences between whey protein and casein and how they can be used for optimal nutrition. He referenced a 1997 study that measured amino acid levels in the blood after Whey protein and then after Casein. The study found that whey protein produced higher levels of amino acids in the blood for about 2 hours after ingestion. The casein, on the other hand, was absorbed at a slower rate. This led to lower initial levels, but actually resulted in longer levels of elevated amino acids as well as a greater net release. If you look at protein with the goal of muscle growth, then Whey would be recommended immediately before or after a workout. Casein would be better around bedtime or if you are going to go a long time without consuming protein and still want to have elevated amino acid levels by the time your workout comes around. Now, let’s talk about how much protein you should be eating to maximize muscle growth. Many people recommend 1 gram per lb of body weight, and this is not necessarily false as it is a good target to shoot for. If you look at the results of many studies trying to figure out the optimal range, it seems that the consensus is 1.6 g per kg of body weight (0.73 g per lb). This means that the average 190 lb man would need 139 g to achieve close to maximum benefits. Now, what about those people that only eat protein and consume 200 g per day when they weigh only 180 lbs. Well, let’s take a look.

No Protein Left Behind:

If there are too many amino acids to be used in their normal state, they can be oxidized in order to create energy for the body. This process is started by either a transamination (transfer of an amino group) or a deamination (removal of an amino group). The resulting structure can be further metabolized to important molecules like pyruvate and acetyl coA which can be used to generate ATP. So what about this amino group? Well, let’s first discuss what an amino group is. An amino group consists of an ammonium molecule (NH4+), and it is actually toxic to the body. The ammonium is generally processed through the Urea Cycle, and is excreted in the urine in the form of urea. The urea cycle will increase production as more amino acids are consumed in the diet, so eating more amino acids than your body can use will only result in an uptick in the urea cycle, not an extra storage of muscle mass. The body does not store free amino acids, so breaking the bank on 250g of protein a day really just is not worth it.

Protein as a Primary Energy Source:

I am going to very briefly touch on using proteins as an energy source. As previously mentioned, amino acids can be modified to generate molecules like pyruvate which are used to generate ATP. This process does not regularly take place under what we would consider “normal circumstances.” Typically, amino acids are broken down in the body during fasted conditions, typically over 24 hours after the last meal. At this point in time, most of the body’s glycogen stores are empty and a new source of energy is required. Amino acids are used to make glucose and ketones during this time, while others are used to make different proteins that are necessary to life (i.e. structural proteins, hemoglobin, etc.). It is very uncommon to get to a point where proteins are being used as a primary energy source, so it is much more common for excess amino acids to be shuttled to the urea cycle out of sheer excess.

Recap:

As you can see, an overconsumption of protein will not provide any real benefit to your health or your ability to grow muscle. Oftentimes, when it comes to the body, any excess nutrient will be excreted as our bodies are phenomenal at regulating ourselves. As long as you keep your caloric intake in a healthy range and reach the 1.6 g/kg recommendation on protein intake, you should be able to see near optimal results. Reaching your daily protein intake is important, but the people who are eating an excessive amount are either uneducated on protein metabolism or are just doing it for show.

Sources:

Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrère B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14930-5. doi: 10.1073/pnas.94.26.14930. PMID: 9405716; PMCID: PMC25140.

Nunes, E. A., Colenso-Semple, L., McKellar, S. R., Yau, T., Ali, M. U., Fitzpatrick-Lewis, D., Sherifali, D., Gaudichon, C., Tomé, D., Atherton, P. J., Robles, M. C., Naranjo-Modad, S., Braun, M., Landi, F., and Phillips, S. M. (2022) Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults, Journal of Cachexia, Sarcopenia and Muscle, 13, 795–810, https://doi.org/10.1002/jcsm.12922