Author: Colleen Gulick, Ph.D (ExPhys), MS, BS (BioE), EIT (ME), CSCS

Deciphering how protein works in the body and determining how much we need to eat to fuel our goals.

What is protein?  

In short: The Swiss Army knife of nutrition. If you mention the words “high protein diet” most people immediately think of athletes and muscle growth.  While muscle growth is certainly an important function of dietary protein, this macronutrient is more versatile than you might expect–kind of like a Swiss Army knife.  Our bodies are made of tens of thousands of different proteins (1).  These proteins aid in many essential bodily functions, such as: supporting the regulation and expression of DNA and RNA, facilitating chemical reactions (most enzymes are proteins), providing support to the body, and coordinating bodily function through hormones (2).  For active individuals, proteins are especially important to support muscle contractions and move essential molecules around the body (such as hemoglobin carrying oxygen) (2).  In order to power these essential functions, most people reach their allotted daily protein requirement from a variety of sources.  Some common high-protein foods include: lean meats, dairy products, tofu, lentils, beans, red meat, quinoa, nuts, spirulina, and seafood.  Protein powder is a common supplement for athletes and people on the move due to its portability, high protein content per volume of food, and capability to enhance athletic performance.  

What makes up a protein?

Amino acids are commonly referred to as the “building blocks of protein” (3).  There are 20 amino acids.  These amino acids bond together to form a protein.  Like Legos combining together to build a toy house, the volume of amino acids and the way in which they bond determine the shape and function of the resulting structure.        

Amino acids are classified as being either non-essential or essential.  There are 11 non-essential amino acids (4).  As the name would suggest, non-essential amino acids can be naturally produced by the body so they are not essential to the human diet.  Essential amino acids, on the other hand, are unable to be naturally produced by the body so they must be obtained from our diet.  There are 9 essential amino acids.  Many foods, like nuts, seeds, vegetables and legumes, are incomplete proteins because they contain some but not all 9 of the essential amino acids.  However, when a food contains all 9 of the essential amino acids it is called a “complete protein”.  Tofu, edamame, tempeh, eggs, beef, poultry and fish are a few common examples of complete proteins.  While obtaining all of the essential amino acids is important, do no limit yourself to only consuming complete proteins.  You can obtain all of your amino acid needs from a variety of sources.  So, if you are eating enough total protein throughout the day, you probably do not need to worry about specifically seeking out complete protein sources.

How much protein do I need?

As with the answers to many physiological questions, the answer to “how much protein do I need” is “it depends”.  The Academy of Nutrition and Dietetics’ guideline for healthy sedentary adults currently recommends 0.8 g of protein per kg of body weight.  However, recent researchers have determined that this volume may be insufficient for many individuals.  Protein needs increase with exercise, pregnancy, age, and illness (5,6).

Athletes

In the hierarchy of protein consumption sedentary individuals require less protein than active individuals.  This makes sense because while everyone needs protein for daily function, sedentary individuals are not performing activities that require muscle repair and rebuilding to the same extent as their gym-going counterparts.  Athletes that are strength training to maintain their current strength should consume 1.2-1.4 g of protein per kg of body weight each day.  This protein intake is typical for many sports while they are in-season such as: 

• Soccer
• Field Hockey
• Pro Pickleball
• Tennis

A higher dietary protein intake (1.6-2 g/kg) is necessary for athletes seeking to increase muscle mass.  This volume is typical for many strength-focused sports and off-season athletes such as: 

• Rugby
• Football
• Discus
• Javelin
• Baseball
• Shot put
• Weightlifting

Endurance athletes should shoot for consuming 1.2-1.6 g/kg.  Endurance activities can include:

• Road cycling
• Triathlons
• Marathons
• OCR
• Cross country skiing
• Orienteering  

Lastly, for athletes in weight control sports that want to minimize their caloric intake while also maximizing their body composition should have a protein intake between 1.4-1.8 g/kg.  Examples of sports that might find this protein range optimal include: 

• Gymnastics
• Wrestling
• Boxing
• MMA
• Judo  

Keep in mind that there is no need to confine yourself to one category.  Athletes should periodize their protein intake throughout the year to suit their goals.  A road cyclist might increase their protein intake (1.6-2 g/kg) in the off season in order to gain as much muscle mass as possible.  Then, as the season approaches, they most likely will increase their volume of road miles and cut down their protein intake (1.4-1.8 g/kg) in order to keep as much muscle as possible while dropping weight.  This optimizes their power to weight ratio for competition.  This modulation of protein consumption can help fuel the body appropriately for the best possible race day performance. 

Who else needs more protein?

Athletes are not the only individuals who benefit from additional protein consumption.  Protein needs also increase with pregnancy, age, and illness (7).  In order to promote the appropriate growth of tissues and organs, pregnant women should consume approximately 1 g of protein per kg of body weight.  Many published studies have demonstrated the need for older adults to have an increased protein intake (8,9).  When compared to their younger counterparts, older adults are less responsive to low doses of amino acid and protein intake (8,9).  In order to preserve muscle mass (which prevents sarcopenia) and help maintain energy balance, healthy adults over 65 years should consume approximately 1.1 g/kg (7).  Older individuals that have had a health setback have an even greater dietary protein need (1.5 g/kg) (7). 

When should I eat protein?

Meal Frequency

Now that we’ve discussed the optimal total protein consumption for the day, let’s break it down into how we accumulate the necessary volume.  For athletes seeking to maximize muscle protein synthesis, consuming 0.25 g of protein per kg of body weight at intervals of 3-4 hours is optimal.  This equates to a dose of 19 and 22 g of protein for the average American adult female (170.8 lbs) and male (199.8 lbs) respectively, consumed every 3-4 hours. (10).

Immediately Before Exercise

Immediately before exercise protein consumption is, frankly, not beneficial for performance.  Other macronutrients will drive performance pre-exercise.  Carbohydrates will be used to power short, high intensity bursts.  The energy for sustained, low intensity exercise will be provided by fat that is already stored in the body.  Thus, protein does not make an impact pre-exercise to the same extent as post exercise. 

During Exercise

Consuming dietary protein during exercise isn’t advantageous for immediately impacting performance since you will predominantly use carbohydrates and fat to fuel muscle contractions.  However, since protein aids in the recovery process, consuming protein throughout the workout can help you get a jumpstart on stimulating muscular adaptation, repair damaged muscle fibers, and enhance anabolic adaptations. A recent study by Gulick et al. shows promise for the notion of consuming protein during the workout in order to enhance insulin like growth factor 1 concentrations (IGF-1, a hormone that signals satellite cells to build skeletal muscle) (11).  The strategy of consuming protein throughout the workout could be particularly useful for weightlifters, track runners, volleyball players, cyclists, and tennis athletes who have breaks and the ability to fuel between sets or efforts.  There needs to be some more research to determine if in-workout protein ingestion is optimal for other hormones as well, but it might be the next big trend in nutrition for muscle protein synthesis.

Immediately After Exercise

The time period immediately after exercise is incredibly important.  Your nutritional choices after exercise will not only help you get the most out of the workout you just completed, but also jumpstarts the recovery process for your next workout.  “The golden hour” is a well-known phrase in athletics and refers to the optimal one hour after exercise in which it is believed that ingesting dietary protein will elicit the greatest increase in muscle protein synthesis.  The optimal dose of protein during this hour is 20-25 grams.  However, if you are in a pinch, as little as 10 g has been shown to have a mild effect on muscle protein synthesis.  Consuming fast releasing carbohydrates (e.g. simple sugars, especially glucose) with your protein will aid in the recovery process.  Breads, pretzels, plain pasta, some cereals, gummy bears, and fruit jello cups are all examples of foods with a high concentration of glucose.  A carbohydrate to protein ratio between 2:1 and 3:1 has been shown to enhance post-exercise glycogen synthesis (12). 

Evening After Exercise

In recent years, research has shown the power of pre-sleep protein ingestion.  Casein protein is a specific type of protein that is slow releasing.  Consuming 30-40 g of casein protein approximately 30 minutes before bed has been shown to increase muscle building overnight via an acute increase in muscle protein synthesis and metabolic rate without influencing lipolysis (breakdown of fats and other lipids by hydrolysis to release fatty acids).  As an added benefit, higher intakes of protein in the evening have been shown to shorten sleep onset latency (13).  Milk protein is approximately 70 to 80% casein protein, so dairy products are great sources of this protein type.  Cottage cheese, cow’s milk, goat’s milk, yogurt, and casein protein powders are all high in casein.  

What happens if I don’t eat enough protein?

Since protein plays such a large role in multiple aspects of physiology, the symptoms of protein deficiency are widespread.  A serious protein deficiency can result in swelling, fatty liver, muscle catabolism, and stunted growth (in children).  A serious protein deficiency is rare in developed countries; however, 1 in 3 Americans aged 50 and older are not meeting the daily recommended protein intake (14).  Individuals who do not meet the daily recommended intake can have skin, hair and nail problems.  Catabolism (a loss of muscle mass) is especially common in the elderly.  The decrease in muscle mass significantly increases the risk of fractures, especially in postmenopausal women (15).  Since proteins aid in our immune defense, an insufficient protein intake can suppress the immune system and open the body up to opportunistic infections (16).  Lastly, protein increases a hormone called ghrelin.  Ghrelin is commonly referred to as the “hunger hormone”.  Thus, when not enough protein is consumed, ghrelin levels are increased and appetite is increased (17).  This is particularly important for individuals who want to lose weight. 

What happens if I eat too much protein?

While insufficient protein intake can have serious health consequences, an overabundance of protein rarely poses a grave health concern.  The population that has the greatest risk of harm from a high protein intake are those people who are predisposed to kidney disease.  For healthy adults, too much protein is largely just ineffective at providing any additional benefit.  Research has shown that, even for high level athletes, protein intakes higher than 3 g/kg/day are not any more effective at building muscle than 2 g/kg.  Once you reach what is termed the “muscle full” threshold, additional protein is not able to be utilized to build protein.  So, this excess protein, and expense incurred, is simply not necessary. 

While an increase in protein can be helpful to reduce ghrelin levels and aid in weight loss, too much protein can hinder weight loss efforts.  Unfortunately, our bodies are not able to efficiently store protein. After a threshold is reached, any additional protein consumed will be stored as fat.  So, while too much protein is rarely a serious health concern, it can be ineffective at muscle protein synthesis and can hamper attempts to lose weight.   

What are the different types of protein?

A Google search of “high protein foods” returns 848 million results.  With so many options how do you choose which powder, bar, or food is best for your needs?  Let’s break down the major protein types in order to better understand the available choices.  The two large categories are plant-based and animal proteins.  The distinction is obvious.  However, the nutritional and health differences that result from the difference in protein source are not as obvious.

The International Food Information Council’s survey reported 28% of people are eating an increased amount of protein from plant sources between 2019 and 2020 (18).  Plant-based eating is on the rise, and for good reason.  Plants with a high protein content, such as beans, nuts, and quinoa, also contain many additional ingredients that are beneficial to our health.  Anti-inflammatory components, especially antioxidants and fiber, protect your cells against free radicals (19).  This protection can lower the risk of cardiovascular disease, cancer, and other diseases (20).  Fruits, vegetables and whole grains are also typically high in fiber, lower in saturated fat and low in cholesterol.  The increased fiber aids in weight control and low saturated fat helps to decrease low-density lipoproteins (LDL cholesterol).  According to the CDC, 38% of U.S. adults (aged 20 or older) have total cholesterol levels higher than 200 mg/dL (less than 200 mg/dL is normal) (21).  High cholesterol levels increase the risk of cardiovascular diseases such as heart disease and stroke (22).  Since heart disease and stroke are two leading causes of death in the U.S., prioritizing foods that lower cholesterol could have a significant impact on your health (21).  Further supporting the importance of protein source, substituting plant protein for animal protein, especially when the animal protein was processed red meat, has been shown to be associated with lower mortality (23).

Consuming plant-based proteins does not only benefit your health, but also aids in the health of the environment.  Climate change and green initiatives are at the forefront of the media.  More than ever, people and companies are making choices based on the ramifications for the plant.  Supporting the growth of plant-based foods is far better for the environment than animal products from a greenhouse gas emissions perspective.  On average, greenhouse gas emissions from plant-based foods are 10 to 50 times lower than emissions from animal products (per 100g of protein) (24).  In addition, consuming plants, as opposed to eating the animals that eat the plants, is much more efficient and cost effective.    

Despite the many beneficial qualities of plant-based foods, there is a large misconception surrounding the protein quality of plant-based proteins.  The quality of a protein is usually determined by the distribution and proportion of essential and non-essential amino acids.  In general, protein from animal sources has a higher quality since they contain higher proportions of essential amino acids.  While most plant-based proteins contain all 20 amino acids, they tend to have a limited amount of essential amino acids.  This means that individuals who consume all of their protein from one plant source are unlikely to consume enough essential amino acids to meet the daily requirements.  However, most of us do not ingest all of our protein needs from eating a single food every day.  A bit of planning can ensure that complementary foods are consumed to meet the essential amino acid requirements.  Combining foods like rice (high in methionine) and beans (high in lysine and thiamine) is one example of a pairing with complementary amino acid profiles.

Athletes may be wondering how plant-based proteins impact their performance.  Plant-based proteins have been shown to be equally effective as a mixed-diet for resistance training induced muscle adaptations (25).  Athletes can consume plant-based proteins and feel confident that they are not sacrificing performance or protein quality.     

What are examples of good sources of protein?

Unlike beef, eggs and shrimp, protein sources from plants can be difficult to identify.  High quality protein sources from seed crops include: quinoa, amaranth and buckwheat.  Lupin, faba bean and lentils are high quality protein sources from legumes.  Other plants with a high protein content include: soybeans (29 g protein/1 cup), red kidney beans (8.6 g protein/100 g), rolled oats (10.9 g protein/100 g), nut mix (23.8 g protein/100 g), hemp seeds (5 g protein/1 tbs), and spirulina (8 g protein/ 2 tbs).  An easily identifiable source of plant-based protein is protein powders.  The benefit of powders, as opposed to whole foods, is that they can contain protein from multiple plant sources in one convenient mix.  In this way, the amino acid profiles can be complementary without the need to consume multiple different foods.  The convenience of a powder is also an advantage.  Plus, powders like ATAQ's provide all of the protein benefits but with no added sugars (which means less bloating for the consumer). 

What should I take away from this article?

• Proteins do more than just muscle contractions. 
• Amino acids are the building blocks of proteins.
• The volume of protein you need is determined by your age, activity level and health status.
• Protein consumption should be spread out throughout the day.
• For athletes, during exercise, immediately after exercise, and before bed are the most important times to consume protein for muscle protein synthesis
• Many Americans do not consume enough protein to meet the daily protein requirements.  This can impact health, risk of fractures (which is especially important for the elderly), and weight loss goals
• Consuming too much protein is rarely a health concern (the exception being for individuals predisposed to kidney disease). 
• Protein can come from either a plant or animal source.
• Consuming a plant-based diet can aid in lowering inflammation and protection against cardiovascular diseases. Plant-based diets are also environmentally friendly.
• When eating a plant-based diet, it is important to obtain your protein from a variety of sources in order to consume a complementary amino acid profile. 
• Plants help build muscle just as well as a mixed protein diet for athletes.
• Plant-based protein powders can provide a convenient way to meet the daily protein requirements without any added sugars.

Reference

(1)    https://www.mpg.de/11447687/W003_Biology_medicine_054-059.pdf

(2)    https://www.eufic.org/en/whats-in-food/article/what-are-proteins-and-what-is-their-function-in-the-body

(3)    https://www.ncbi.nlm.nih.gov/books/NBK557845/

(4)    https://www.rxlist.com/amino_acid_nonessential/definition.htm

(5)    https://www.acsm.org/docs/default-source/files-for-resource-library/protein-intake-for-optimal-muscle-maintenance.pdf

(6)    https://jandonline.org/article/S2212-2672(15)01802-X/pdf

(7)    https://www.eurekalert.org/multimedia/542884

(8)    https://journals.physiology.org/doi/full/10.1152/ajpendo.00488.2005

(9)    https://academic.oup.com/biomedgerontology/article/70/1/57/2947642

(10) https://www.cdc.gov/nchs/fastats/body-measurements.htm

(11 )https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7869853/

(12) https://bjsm.bmj.com/content/55/8/416

(13) https://pubmed.ncbi.nlm.nih.gov/32624442/

(14) https://link.springer.com/article/10.1007/s12603-019-1174-1

(15) https://pubmed.ncbi.nlm.nih.gov/9925137/

(16) https://pubmed.ncbi.nlm.nih.gov/7598064/

(17) https://pubmed.ncbi.nlm.nih.gov/16400055/

(18) https://foodinsight.org/wp-content/uploads/2020/06/2020-Food-and-Health-Survey-.pdf

(19) https://pubmed.ncbi.nlm.nih.gov/31037277/

(20) https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/multimedia/antioxidants/sls-20076428

(21) https://www.ahajournals.org/doi/10.1161/CIR.0000000000000757

(22) https://www.heart.org/en/health-topics/cholesterol/about-cholesterol

(23) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5048552/

(24) https://www.science.org/doi/abs/10.1126/science.aaq0216

(25) https://journals.lww.com/acsm-msse/Fulltext/2019/06001/Does_Exclusive_Consumption_of_Plant_based_Dietary.2367.aspx