Your Body On: Protein

Because amino acids are not only the building blocks of protein

Where do I get my protein? The truth is, a lot of places. Chickpeas, tofu, eggs, greek yogurt, lentils, nuts and maybe the occasional Beyond Burger. For you, it might be a bit different, including more or less animal-based sources. The similarity between you and I is that we are likely already consuming enough protein.

However, “High Protein” became a potent nutritional buzzword this past-year. From gracing sugary cereal boxes to enticing your green smoothie with a $1.50 add-in, the media and food industry made it seem as if we can never get enough of this “holier-than-thou” macronutrient.

So, what exactly is the hype about protein? Do we really need more protein than before? Should we take BCAA’s? What types of plant-based proteins are the best? What the heck even is protein?

Similar to my article all about carbohydrates, this article will delve into the basics, common questions and misconceptions surrounding protein, delivered in an unbiased and evidence-based approach — because nutritional science consistently shows us that there is no single best diet for human consumption.

Are amino acids only the building blocks of muscle protein?

When we think of amino acids, we traditionally simply know them as the building blocks of muscle protein. While this is intuitive, and mostly true, the reasons for ensuring you meet all your essential amino acids goes beyond simply building muscle.

Amino acids are chains of carbon, with an ammonia group and a carboxylic acid group. Strictly dietary speaking, the most important type of amino acids are essential amino acids. As humans, we lack the enzymatic machinery to synthesize 9 out of the 20 amino acids to meet our bodies needs. Therefore we must acquire these amino acids through diet. A way to remember this is that essential amino acids are “essential” to obtain through diet.

Snack-break: The nine essential amino acids are valine, phenylalanine, histidine, lysine, methionine, tryptophan, isoleucine, threonine and leucine.

Once the protein we eat is digested into amino acids, they can be used for energy, protein synthesis, or other biosynthesis pathways. This means that amino acids are not only the building blocks of muscle-protein.

Amino acids are not only the building blocks of muscle protein.

What are the other functions of amino acids?

Amino acids can be metabolized into neurotransmitters, such as seretonin from tryptophan. Seretonin is our “feel-good” neurotransmitter, and can also regulate our intestinal movement. The amino acid is converted into seretonin primarily in our gut microbiome.

There are numerous other examples of other uses of amino acids. Epinephrine is derived from tyrosine, and helps us activate our fight-or-flight response. Creatine is synthesized from three amino acids; glycine, arginine and methionine and supplies ATP energy molecules to our muscles. Histamine is derived from histidine, and is released during an allergic reaction.

Similarly, combinations of different strands of amino acids to create protein is not solely destined for protein found in our muscles.

Protein synthesis can also include enzymes, transport proteins, and hemoglobin, which is a carrier for oxygen molecules in our red-blood cells. In fact, a deficiency in histidine (an essential amino acid) will disrupt the protein synthesis of hemoglobin, potentially resulting in anemia.

How does protein and BCAA’s stimulate muscle-protein synthesis?

Muscle-protein synthesis (MPS) is stimulated by the ingestion of essential amino acids. Strong research has consistently shown that the essential amino- acid leucine plays a key role in stimulating MPS, especially after performing resistance training. MPS is stimulated when leucine activates mTORC1, a receptor in our cells which is responsible for nutrient metabolism, including protein synthesis.

Leucine is a branched-chain amino acid (BCAA), which refers to it’s chemical structure. Isoleucine and valine are also BCAA’s, and all BCAA’s are essential amino acids. Knowing that BCAA’s stimulate MPS, sport nutrition supplement companies have been quick to market “BCAA supplements” to enhance MPS.

Solely consuming BCAA’s stimulates MPS 50% less than those consuming a nutrition supplement with all essential amino acids.

However, BCAAs appear to work best when they are consumed alongside other essential-amino acids. In fact, one study showed that solely consuming BCAA’s results in stimulating 50% less MPS compared to 100% whey protein.

The bottom line? BCAA supplements are not required for stimulating MPS. A complete source of protein, including whole foods, is best for stimulating MPS.

Why can’t I simply eat more protein to build more muscle?

We know that essential amino acids, including BCAA’s, stimulate MPS, but how could it be increased? Unfortunately, simply eating more protein, even if it has an optimal amino acid profile will not increase MPS.

We need to create a reason for our muscles to synthesize more protein, which can be achieved through stressing our muscles in a new workout regime (especially resistance training), encountering a sickness or injury (although not recommended) and the normal growth experienced in children.

Muscle-protein synthesis can only be increased if we create a metabolic need for it.

Furthermore, protein has no official storage space in our body. Unlike carbohydrates which are stored as glycogen and fat which is stored away in adipose tissue, extra dietary protein does not equate to extra protein synthesis “stored” into our muscles. Instead, it can cause weight-gain as the extra carbon-backbones are converted into triglycerides for fat storage.

Not convinced that our muscles don’t store protein? Think of it this way. Our muscles serve many functions — strength, stability, immune function and even heat. Therefore, tapping into our muscles for protein and energy compromises functionality. This may happen under periods of starvation or increased protein needs and inadequate intake, such as after surgery.

Knowing all this, how can I ensure my diet covers all essential amino acid and protein needs?

While the nutritional science may seem overwhelming and sometimes confusing, the bottom line concerning adequate protein intake while achieving an optimal amino acid profile is quite simple: Eat a variety of protein containing foods.

Foods with a complete amino acid profile can include both animal and plant sources of protein. Notably, quinoa and soy are complete sources of plant-based proteins, however amino-acid digestibility of these foods may be decreased due to fibre and other non-nutritional components.

If you are seeking a nutritional supplement, such as in the form of a protein powder, ensure it contains all essential amino acids and ideally at least 2.7 g of leucine per serving. Supplements containing whey or pea protein isolates may be the best choice due to their complete essential amino acid profiles, and high leucine content.

Remember that whole protein foods also contain BCAA’s. For example, 100g of chicken contains approximately 8 g of BCAAs, while 1/2 cup of greek yogurt will provide 5 g.

Snack break: Why are complete proteins so important? Protein synthesis can be though of as an “all-or-nothing” process. Even if we lack 1% of the amino acids required, the remaining 99% amino acids present will be degraded, and the protein will not be synthesized.

A strong, bottom line.

While protein nutritional jargon is fed to us by the spoonful these days, it is reassuring to know that most healthy individuals can meet their protein needs through whole foods, such as the protein sources described above.

For athletes, or those with increased nutrient needs such as growing children and those recovering from illness, requirements can be much higher where consulting with a Registered Dietitian can help ensure that you are meeting your needs.

Also, remember that the best diet for you is one that is sustainable. This year, instead of focusing on the singularity of one macronutrient over another — consider your nutritional goals, lifestyle, cooking skills, current disease management and quality of life.

Hungry for more? Be sure to read my article Your Body On: Carbohydrates

Kristen Sunstrum is a dietetics student who believes nutrition extends beyond healthy foods.