Why is protein so important?

1. Protein is one of the three main macronutrients that makes up the food we eat. (The other two are fat and carbohydrate.)

2. Protein itself is made up of amino acids.

3. Amino acids are the building blocks for most stuff in our bodies. They’re like Legos that can be broken down and re-assembled in different ways.

4. Unlike extra fat (which we can store very easily on our bums and bellies), we don’t store lots of extra amino acids. Protein is always getting used, recycled, and sometimes excreted.

5. If we don’t get enough protein, our body will start to plunder it from parts that we need, such as our muscles.

6. So we have to constantly replenish protein by eating it.

Why do we need it?

Protein is so important that without it, we die or become seriously malnourished. (This protein-deficiency disease is known as kwashiorkor, and we often see it in people who have suffered famines or who are living on a low-protein diet.)

All your enzymes and cell transporters; all your blood transporters; all your cells’ scaffolding and structures; 100 percent of your hair and fingernails; much of your muscle, bone, and internal organs; and many hormones are made of mostly protein. Hence, protein enables most of our bodies’ functions.

Put simply, you are basically a pile of protein.

No protein, no you.

Amino acids

Protein in our food is made up of many different building blocks, or amino acids.

Most people focus on Recommended Daily Allowance (RDA) for total protein, but they don’t think about how much of each amino acid they might need.

If your diet isn’t varied enough, you may be eating enough total protein, but not enough of a specific essential amino acid.

Every day, you need this much of these essential amino acids:

14 mg/kg of histidine - 19 mg/kg of isoleucine - 42 mg/kg of leucine - 38 mg/kg of lysine - 19 mg/kg of methionine + cysteine - 33 mg/kg of phenylalanine + tyrosine - 20 mg/kg of threonine - 5 mg/kg of tryptophan - 24 mg/kg of valine

Of course, you don’t need to spend hours in your kitchen with an eyedropper of lysine solution, carefully calibrating your intake.

Just eat a variety of protein-rich foods and let nature do the rest.

Protein Quality

There are 20 total amino acids, comprised of 9 EAAs and 11 non-essential amino acids (NEAAs). EAAs cannot be produced in the body and therefore must be consumed in the diet. Several methods exist to determine protein quality such as Chemical Score, Protein Efficiency Ratio, Biological Value, Protein Digestibility-Corrected Amino Acid Score (PDCAAS) and most recently, the Indicator Amino Acid Oxidation (IAAO) technique. Ultimately, in vivo protein quality is typically defined as how effective a protein is at stimulating MPS and promoting muscle hypertrophy. Overall, research has shown that products containing animal and dairy-based proteins contain the highest percentage of EAAs and result in greater hypertrophy and protein synthesis following resistance training when compared to a vegetarian protein-matched control, which typically lacks one or more EAAs.

Protein Sources

Milk proteins have undergone extensive research related to their potential roles in augmenting adaptations from exercise training. For example, consuming milk following exercise has been demonstrated to accelerate recovery from muscle damaging exercise, increase glycogen replenishment, improve hydration status, and improve protein balance to favor synthesis ultimately resulting in increased gains in both neuromuscular strength and skeletal muscle hypertrophy. Moreover, milk protein contains the highest score on the PDCAAS rating system, and in general contains the greatest density of leucine. Milk can be fractionated into two protein classes, casein and whey.

Comparison of the quality of whey and casein reveal that these two proteins routinely contain the highest leucine content of all other protein sources at 11% and 9.3%, respectively. While both are high in quality, the two differ in the rate at which they digest as well as the impact they have on protein metabolism. Whey protein is water soluble, mixes easily, and is rapidly digested. In contrast, casein is water insoluble, coagulates in the gut and is digested more slowly than whey protein. Casein also has intrinsic properties such as opioid peptides, which effectively slow gastric motility.

Health benefits of milk-based proteins:

While athletes tend to view whey as the ideal protein for skeletal muscle repair and function it also has several health benefits. In particular, whey protein contains an array of biologically active peptides whose amino acids sequences give them specific signaling effects when liberated in the gut. Not only is whey protein high in β-Lactoglobulin and α-lactalbumin (75% of total bovine whey proteins), but it is also rich in EAAs (approximately 50% by weight). Furthermore, whey protein appears to play a role in enhancing lymphatic and immune system responses.

In addition, α-lactalbumin contains an ample supply of tryptophan which increases cognitive performance under stress, improves the quality of sleep, and may also speed wound healing, properties which could be vital for recovery from combat and contact sporting events. In addition, lactoferrin is also found in both milk and in whey protein, and has been demonstrated to have antibacterial, antiviral, and antioxidant properties. Moreover, there is some evidence that whey protein can bind iron and therefore increase its absorption and retention

Egg protein is often thought of as an ideal protein because its amino acid profile has been used as the standard for comparing other dietary proteins. Due to their excellent digestibility and amino acid content, eggs are an excellent source of protein. While the consumption of eggs has been criticized due to their cholesterol content, a growing body of evidence demonstrates the lack of a relationship between egg consumption and coronary heart disease, making egg-based products more appealing.

One large egg has 75 kcal and 6 g of protein, but only 1.5 g of saturated fat while one large egg white has 16 kcal with 3.5 g of protein and is fat-free. Research using eggs as the protein source for athletic performance and body composition is lacking, perhaps due to less funding opportunities relative to funding for dairy. Egg protein may be particularly important for athletes, as this protein source has been demonstrated to significantly increase protein synthesis of both skeletal muscle and plasma proteins after resistance exercise at both 20 and 40g doses. Leucine oxidation rates were found to increase following the 40g dose, suggesting that this amount exceeds an optimal dose.

In addition to providing a cost effective, high-quality source of protein rich in leucine (0.5 g of leucine per serving), eggs have also been identified as a functional food. Functional foods are defined as foods that, by the presence of physiologically active components, provide a health benefit beyond basic nutrition .

Meat proteins are a major staple in most people diets and, depending on the cut of meat, contain varying amounts of fat and cholesterol. Meat proteins are well known to be rich sources of the EAAs. Beef is a common source of dietary protein and is considered to be of high biological value because it contains the full balance of EAAs in a fraction similar to that found in human skeletal muscle.

A standard serving of 113.4 g lean beef provides 10 g of the EAAs (3.5 g of leucine) and 30 g of total amino acids. Moreover, this 30 g dose of beef protein has been shown to stimulate protein synthesis in both young and elderly subjects. In addition to its rich content of amino acids, beef and other flesh proteins can serve as important sources of micronutrients such as iron, selenium, vitamins A, B12 and folic acid.

For the most part, these quality minerals and micronutrients cannot be as easily obtained through plant-based proteins and/or the bioavailability of these macronutrients from plants is limited. This is a particularly important consideration for pregnant and breastfeeding women. Ultimately, as an essential part of a mixed diet, meat helps to ensure adequate distribution of essential micronutrients and amino acids to the body.

Meat vs. plant based proteins: Is one better than the other?

A highly debated topic in nutrition and epidemiology is whether vegetarian diets are a healthier choice than omnivorous diets. One key difference is the fact that vegetarian diets often lack equivalent amounts of protein when compared to omnivorous diets. However, with proper supplementation and careful nutritional choices, it is possible to have complete proteins in a vegetarian diet. Generally by consuming high-quality, animal-based products (meat, milk, eggs, and cheese) an individual will achieve optimal growth as compared to ingesting only plant proteins.

Research has shown that soy is considered a lower quality complete protein. While soy is considered a complete protein, it contains lower amounts of BCAAs than bovine milk. Additionally, research has found that dietary soy phytoestrogens inhibit mTOR expression in skeletal muscle through activation of AMPK . Thus, not only does soy contain lower amounts of the EAAs and leucine, but soy protein may also be responsible for inhibiting growth factors and protein synthesis via its negative regulation of mTOR. When considering the multitude of plant sources of protein, soy overwhelmingly has the most research.

The Study

A study done by the International Society Of Sports Nutrition published 20th June 2017 provides an objective and critical review related to the intake of protein for healthy, exercising individuals. Based on the current available literature, the position of the Society is as follows:


An acute exercise stimulus, particularly resistance exercise, and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise.


For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d) is sufficient for most exercising individuals, a value that falls in line within the Acceptable Macronutrient Distribution Range published by the Institute of Medicine for protein.


There is novel evidence that suggests higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass).


Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g.


Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs).


These protein doses should ideally be evenly distributed, every 3–4 h, across the day.


The optimal time period during which to ingest protein is likely a matter of individual tolerance, since benefits are derived from pre- or post-workout ingestion; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise.


While it is possible for physically active individuals to obtain their daily protein requirements through the consumption of whole foods, supplementation is a practical way of ensuring intake of adequate protein quality and quantity, while minimizing caloric intake, particularly for athletes who typically complete high volumes of training.


Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS.


Different types and quality of protein can affect amino acid bioavailability following protein supplementation.


Most people should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS).


Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery.


Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.

Coach HB


The Study in full: https://jissn.biomedcentral.com/articles/10.1186/s12970-017-0177-8#Sec15

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