There is an ever-growing demand, trend and popularity for vegetarian diets. Mainstream media and social networks are becoming active hubs for creating diet divide, pitting both sides of the argument against each other. The role of capitalism and corporate greed is also playing a role in this divide with many Netflix shows and other docuseries pushing a plant based/vegetarian agenda as superior for performance and health. It must also be noted that the same also exists for omnivore diets.
On the other hand, governments are dashing to improve food availability and sustainability. While at the same time, they are aiming to meet climate promises by minimizing the impact that animal farming has on the planet. But is there a need for such divergence with respect to perceived diet superiority?
I don’t think so. However, some important questions must be addressed.
What is a protein?
What are the roles of protein?
What is protein quality?
Can you obtain adequate protein from plant-based sources?
What are the downsides of plant-based protein?
A protein is compound built on carbon, hydrogen, oxygen and nitrogen. Amino acids are the building blocks of all proteins. Amino acids are bound by peptide bonds and when amino acids are joined together, they are called polypeptides of up to 300 amino acids. There are 20 dietary amino acids and these amino acids code for all proteins.
Of these 20 dietary amino acids, 11 of these are non-essential amino acids. What this means is that our body can create them. The remaining 9 amino acids are essential amino acids, meaning that we must obtain them from the diet. As muscle is mostly protein and they contain all the essential amino acids, meat is seen as good protein source. Plant based protein sources contain the exact same amino acids but in varying quantities and often do not contain all the essential amino acids.
When all amino acids are not present, the source is termed an incomplete protein source.
It is always thought that the only role of protein is growth and repair and the likely reason for this is due to marketing campaigns that people get exposed to and thus associates' protein with growth and growth only.
Indeed, a major regulatory role of protein is growth and repair, however protein has many other roles in the body including:
Providing structure to all cells in the human body and being an integral part of muscle, bone, skin, hair and nails.
Acting as enzymes that accelerate biochemical reactions, vital for the provision of energy for muscle contraction.
Transporting and storing substances, for example in our blood, oxygen is transported by the protein hemoglobin!
Functioning as hormones that regulate different roles in the body such as the release of insulin from the pancreas which regulates our blood glucose levels
Signaling and send messages in the body, like the insulin receptor in the cell membrane of a muscle cell is bound by insulin released from the pancreas which signals to increase the uptake of glucose into the muscle cells.
Contracting our muscles! The proteins in our muscles turn chemical energy stored in the bonds of ATP into mechanical work!
Supporting immune health by the creation of antibodies to fight infections!
The quote “Everything we do, everything we are and everything we become depend on the action of thousands of different proteins” Houston (2006) always comes to mind when thinking about protein. Protein’s role is not isolated to just growth!
A major part of the plant vs animal-based protein debate is on quality, but what is protein quality? Protein quality refers to the type of amino acid and the quantity of the amino acids present in a food. A protein source is deemed higher quality when all essential amino acids are present.
The “protein digestibility corrected amino acid score” (PDCAAS) is a ranking system for protein sources where it ranks foods on a scale of 0-1 with 1 being the highest quality source. A protein source quality is also typically ranked by how effective it is at stimulating muscle protein synthesis. Animal based foods rank higher here as they contain higher amounts of the essential amino acids.
But are the amino acids in plant based different than animal based? No, in fact they are identical to those found in animal-based sources. The difference pertains to the type and abundance of the essential amino acids in the food source. Plant based foods are typically lower in abundance and do not contain all the essential amino acids meaning individual sources are lower in quality.
The significance of this is that vegetarians are at risk of incomplete protein intake, whereby they do not obtain adequate amounts of all essential amino acids and thus can interfere with normal protein synthesis. Many vegetarians have marginal protein intakes and do not meet optimal intakes. They are at risk of deficiency.
This is typically only an issue in those who do not pay attention to their dietary choices. Many vegetarians have the required awareness to meet their protein demands by combining protein sources to meet all essential amino acid intakes, these are termed complimentary proteins.
Contrary to popular belief, you can obtain adequate protein from plant-based sources. The caveat to this is that it requires better dietary planning, using complimentary sources to balance the amino acid profile. This is essential as most plant-based protein sources are not as high in protein as animal-based sources and that without adequate diversity, they may not obtain adequate amounts of certain essential amino acids.
A recent case study by Daniel Davey highlighted that even in an elite sport setting that an individual can maintain performance levels, lean muscle mass and health while undertaking a plant-based diet. The key aspects to ensuring success according to Davey was support networks, dietary planning and understanding.
While it is possible to obtain adequate protein from a vegetarian diet, there can be some drawbacks, and these would appear to be more concerning for those who are looking to increase lean tissue mass. It is a well-known fact that the digestion, absorption, aminoacidemia and stimulation of muscle protein synthesis is better with isolated proteins compared to whole-food proteins. Coincidently, isolated proteins differ with respect to the same variables when comparing isolated plant-based proteins and animal-based proteins.
This is largely down to protein the kinetics and signaling.
When comparing identical amounts of whey, casein and soy protein, whey has the greatest ability to stimulate muscle protein synthesis, while soy has a greater ability to stimulate MPS compared to casein. In conjunction to this, and most concerning, is the finding that soy protein appears to inhibit mTORC1, the master regulator of protein synthesis. Due to the apparent impaired anabolic properties of a plant-based approach, supplementation with additional amounts of a plant-based protein is warranted to improve recovery between exercise bouts.
The other major drawback is the careful consideration needed to mitigate nutrient deficiencies (long chain poly-unsaturated fatty acids, iron, iodine, calcium, vitamin D and vitamin B12 that can present when undertaking a plant-based diet. Another major issue that can present include the digestive issue that arise from the large increase of fiber intake.
Awareness of food here is crucial in helping to mitigate this possibility. Finally, and one of the most important external factors includes the social aspect. Social support from peers can be a major factor in adopting a plant-based diet.