Proteins, containing 4 calories per gram, are the most important macronutrient when it comes to overall health and longevity, especially in regards to our clients and their respective goals of improving overall strength and body composition. As the fundamental building blocks of our bodies, proteins are responsible for the structure and function of our cells. They participate in numerous biological processes including hormone production, neurotransmitter activity, enzyme functioning, immune system support, and tissue repair. Additionally, proteins are integral to muscle growth and fat loss, underscoring their importance in the diets we recommend for our clients. By ensuring adequate protein intake, clients can effectively work towards achieving their health and fitness goals.

Structure

Proteins are made of amino acids, which are the building blocks that determine the protein's structure and function within the body. There are a total of 20 different amino acids, but only 9 of them are considered essential amino acids (EAAs) because the human body cannot produce them and must obtain them through dietary sources. The other 11 amino acids are considered non-essential, as they can be synthesized by the body. However, all amino acids are essential to body functions and for the body to run effectively and efficiently. The difference simply lies in the composition of amino acids present within the protein source, and are seen as either complete (having all essential amino acids) or incomplete (lacking one or more essential amino acids) proteins.

Complete proteins:

A protein source is considered complete if it contains all 9 essential amino acids in adequate proportions for the body's needs. Complete proteins are typically found in animal-based food sources such as meat, poultry, fish, eggs, and dairy products. However, some plant-based sources, like quinoa, soy, and buckwheat, are also complete proteins.

Furthermore, animal proteins have shown greater anabolic responses in head-to-head comparison with plant protein. Proteins from animal sources generally have a higher EAA and branched-chain amino acid (BCAA) content. Plant proteins have traditionally been regarded as inferior to animal proteins due to their lower proportion of essential amino acids (EAAs) and reduced digestibility, seemingly placing them lower in the protein hierarchy.

Incomplete proteins:

Incomplete proteins, which are common in plant-based sources like legumes, grains, nuts, and seeds, lack one or more of the essential amino acids, or they don't provide them in the necessary proportions.

Despite being incomplete, these proteins can still contribute to a balanced diet when strategically combined with other complementary protein sources to provide all the essential amino acids. This strategy is particularly helpful for those who are vegan or vegetarian.

For instance:

• Legumes (such as beans) are generally low in methionine, an essential amino acid more abundant in grains.
• Grains (like rice) typically lack lysine, which legumes provide.
  

By pairing legumes with grains — beans with rice, for example — a meal is created that includes all nine essential amino acids. This combination compensates for each food's deficiencies, ensuring a balanced intake of all essential amino acids necessary for the body's functions.

Further examples of complementary pairings that yield complete protein sources from plant-based foods include:

• Spinach with Almonds: Spinach is relatively low in methionine and tryptophan, while almonds can help balance this with their higher content of these amino acids.
• Hummus and Pita Bread: Hummus, made from chickpeas, is low in methionine, but when combined with pita bread, a grain, the meal becomes a complete protein source.
• Whole Grain Noodles with Peanut Sauce: Whole grains might lack sufficient lysine, which peanuts provide, making this combination another complete protein option.
  

As an important note; these foods do not have to be consumed together in one meal for the body to utilize them as a complete protein. Consuming these complementary pairings at different times throughout the day still allows the body to utilize the full spectrum of amino acids, as they are pooled together for use as needed.

In summary, the difference between complete and incomplete proteins lies in the composition of essential amino acids present in the protein source, with complete proteins containing all nine essential amino acids and incomplete proteins lacking one or more. Animal proteins, due to their higher EAA content, particularly leucine, and other constituents such as taurine, carnosine, creatine, collagen, and cholesterol, produce a greater anabolic response on a gram-for-gram basis and are more efficient for growth than plant proteins, which can still provide adequate essential amino acids through careful combination in a balanced diet.

Function

The importance of protein in nutrition, and health, cannot be overstated as it is essential for various functions within the body. It is appropriate that the Greek word chosen as the name for this nutrient is Proteos, meaning "primary" or "taking first place." The following are some of the key functions of protein within the human body:

• Tissue formation: Proteins make up the structure of muscles, hair, nails, skin, eyes, and internal organs, providing strength and flexibility to these tissues.
• Hormone synthesis: Non-cholesterol based hormones, such as insulin and growth hormones, are composed of proteins, which help regulate various physiological processes in the body.
• Enzyme production: All enzymes in the body are made up of specific proteins. Enzymes are essential for carrying out numerous biochemical reactions, including digestion, energy production, and DNA synthesis.
• Neurotransmitter synthesis: Neurotransmitters, which are vital for communication between nerve cells, are derived from specific amino acids. For example, serotonin is synthesized from tryptophan, while dopamine is derived from tyrosine.
• Detoxification: Protein aids in the detoxification process, particularly during phase 2 conjugation. Amino acids such as glycine, glutamine, cysteine, methionine, and taurine contribute to this process by helping the body eliminate toxins and maintain overall health.
• Immune system function: Proteins are essential for immune system function, as they are involved in the production of antibodies, which help protect the body from infections and diseases.
• Genetic expression: Proteins are synthesized via DNA-RNA activity, with genetic codes determining the specific proteins required for each cell. This ensures that cells have the necessary proteins to carry out their unique functions.
• Energy production: Although not the primary source of energy, proteins can be broken down into amino acids and converted into glucose or other molecules for energy production when needed.
• Role in Muscle Building: Protein is crucial for muscle gain because it provides the essential building blocks, called amino acids, that your body needs to build and repair muscles. When you exercise, especially during resistance training, your muscles undergo stress and damage, which triggers the need for repair and growth.


Muscle protein synthesis (MPS) is the process where your body creates new muscle proteins using the amino acids obtained from the protein you eat. This process helps repair the damaged muscle fibers and promotes the growth of new muscle tissue, ultimately contributing to muscle gain and increased strength. At the same time, your body is also engaged in muscle protein breakdown (MPB), where existing muscle proteins are broken down into their individual amino acids. This breakdown is a natural part of your body's metabolic processes that happen throughout the day. The amino acids released from MPB can be used for energy or recycled to create new proteins.

To achieve muscle gain, it's important to have a balance between muscle protein synthesis and muscle protein breakdown. This balance is closely related to the concept of positive nitrogen balance. Nitrogen is a key component of amino acids, and your body's nitrogen balance reflects the difference between the amount of nitrogen you consume from protein and the amount your body excretes. A positive nitrogen balance means your body is taking in more nitrogen than it's losing, which is essential for muscle growth.

• MPS < MPB = Loss of muscle Mass
• MPS = MPB = No growth occurred, but no muscle mass was lost
• MPS > MPB = Growth

Intake

In the United States, the Recommended Dietary Allowance (RDA) for protein is established by the National Academy of Medicine (formerly known as the Institute of Medicine). The RDA for protein is 0.36 grams per pound of body weight per day for adults, irrespective of gender. It is crucial to understand that the RDA is based on nitrogen balance studies conducted over 40 years ago on sedentary individuals, which is not the most appropriate method for determining the protein needs of active individuals such as our clients. For instance, a 150-pound woman and a 200-pound man would only require 54 and 72 grams of protein per day, respectively. This recommendation will not sufficiently provide the protein necessary for individuals aiming to optimize body composition, health, or performance.

In the general population, those without specific athletic or body composition-oriented goals, yet aiming for improvements in overall health, should consume protein at a minimal range of 0.54 to 0.73 grams of protein per pound of body weight per day. This is 50 to 100 percent greater than the Recommended Dietary Allowance (RDA) of 0.36 g/lb. To use our previous example of a 150-pound woman, and 200-pound man, the minimum ranges would roughly be 80-110 and 110-145 g/lbs per day, respectively, While better, this will not likely serve the needs of our clients who want to optimize body composition, and increase strength or muscle mass.

The optimal range of protein intake for noticeable change to body composition and/or performance within a relatively short time period, or for those individuals looking to maintain high performance standards over a long period of time will fall within the range of 0.8-1.2 grams of protein per pound of body weight per day. Again, using our ongoing example of a 150-pound woman, and a 200-pound man, this would increase their total daily protein intake to between 120-180 and 160-240 grams, respectively.

When setting up meal plans, it is recommended that you utilize the high end of the range (1-1.2 g/lbs) for those with a higher body fat percentage, and utilize the low end range (0.8-1 g/lbs) for those with a lower body fat percentage — this is due to the client likely being more sensitive to carbohydrates which are not only enjoyable, but offer a protein sparing effect, allowing for the lower intake. A person that is 200 pounds and sub-10% body fat and trying to gain size, can get away with slightly less protein with the addition of carbohydrates in the diet, while another person who is 200 pounds and 40% body fat and in a caloric deficit, will benefit from more protein as it promotes weight loss and is more satiating. It is important to note that the 0.8-1.2 g/lbs range isn't a strict rule, although it serves as a good starting point that will work with most clients. That said, going under the 0.8 g/lbs isn't advised, going over 1.2 g/lbs may be warranted in some situation such as hypocaloric diets.

The upper limit to protein intake per day will be highly independent, so be sure to ask your clients how they are responding to your recommendations. Do not expect them to tell you. A simple way to know if protein intake is too high is with the presence of digestive issues, such as gas, bloating, or loose stool. If this is the case, the easiest thing to do is reduce protein intake recommendations and see what happens. Also, adding a digestive enzyme with all protein meals, as well as switching to easier digested proteins such as eggs or white fish, may help with digestive issues.

Additionally, when it comes to protein sources, there isn't much of a difference between vegan and animal based sources, as long as the total daily amount of complete protein is matched. Research done by Hevia-Larraín and colleagues saw no significant differences in muscular size and strength gains between those consuming protein strictly from vegan sources and a combination of plants and animal sources — this was presumably due to sufficient intake of total daily protein. The caveat here is the total caloric load. Protein from animal sources (a.k.a. meat, dairy, fish, and eggs) will have far less calories per gram when compared to complete protein combinations from plant sources, so be mindful when setting up a meal plan that prioritizes protein from plant sources.

When it comes to intake, the total daily protein amount is most important when it comes to the hierarchy of protein consumption. This is followed by distribution of protein throughout the day, which refers to the spacing or frequency of protein intake over the course of the day, and timing of protein relative to the training bout. For example, there is ongoing research comparing the positioning, timing, and frequency of protein intake across the day, however all of these take a distant backseat to the overall total daily protein amount.

Protein Dosing Cheatsheet

• For General Health: 0.54-0.73 g/lb
• Recomposition (simultaneous fat loss and lean mass gain):
  • For Gen-Pop: 0.8-1.2 g/lb of Total Body Weight
  • For Athletic Population: 1.2-1.5 g/lb of Fat Free Mass

Protein Leverage Hypothesis

The protein leverage hypothesis is a theory in nutritional science suggesting that humans have an innate drive to consume a certain amount of protein in their diet. When people do not consume enough protein, they tend to overeat in an effort to try to meet their protein needs, which can lead to weight gain and other health problems.

This hypothesis is important because it influences food choices and calorie intake, which can impact weight and health. Research has shown that when people consume a diet that is low in protein, they tend to eat more overall calories, likely in an effort to meet their protein needs. Conversely, a diet with adequate protein can promote satiety, helping individuals feel full and satisfied, which may reduce overeating and aid in weight management.

Understanding the protein leverage hypothesis can help coaches create balanced meal plans with appropriate protein levels. By incorporating sufficient protein into the diet, it is possible to maintain lean muscle mass, support various bodily functions, and promote optimal health. Additionally, it can help prevent overconsumption of carbohydrates and fats, which are often present in processed foods, reducing the risk of obesity and related health issues.

Diving deeper