The Ultimate Guide to Protein

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What is protein?  

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.  Our bodies are made of tens of thousands of different proteins.  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.  All of these functions manifest in results that we can see: muscle growth, weight control, healthy skin, hair, and nails.

 

For active individuals, proteins are especially important to support muscle contractions and move essential molecules around the body (such as hemoglobin carrying oxygen).  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, seafood, and protein powders. 

 

What makes up a protein?

Amino acids are commonly referred to as the “building blocks of protein.”  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.  As the name would suggest, non-essential amino acids can be naturally produced by the body so they are not essential to consume through diet.  Essential amino acids, on the other hand, are unable to be naturally produced by the body so they must be obtained from our food.  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 not 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? 

Your protein needs are dependent upon your current stage of life and your health goals. Sedentary individuals would be the class of adults with the lowest protein needs because they perform the least amount of activity and thus, do not need to build, power, or repair as much as their highly-active peers. The Academy of Nutrition and Dietetics’ guideline for healthy sedentary adults currently recommends 0.8 g of protein per kg of body weight. It should be noted that the recommended dietary allowance (RDA) is the amount of protein that is the minimum needed to prevent malnutrition. It is not the ideal protein intake for optimal health. Thus, it should come as no surprise that recent researchers have determined that this volume is insufficient for many individuals.  Raising the RDA to 1.0 g of protein per kg of body weight is a more appropriate target for sedentary adults. This higher protein intake can help sedentary adults to lose weight, prevent muscle loss during aging, and improve bone health.

 

Lifestyle choices can also impact our dietary requirements. Protein needs increase with exercise, pregnancy, age, and illness.

 

Protein Intake for Athletes and Active Individuals 

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. 

 

Protein Intake to Maintain Strength

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.  Since athletes are inherently active individuals, we recommend shooting for the upper end of this range. Even though protein will add to a person’s caloric intake, it will also help to keep us feeling full for longer. Thus, active individuals are more likely to be able to put this protein to use to repair their working muscles, as opposed to adding undue pounds to the scale. This protein intake is typical for many sports while they are in season such as soccer, field hockey, pickleball, and tennis.

 

Protein Intake to Increase Muscle Mass 

A higher dietary protein intake (1.6-2 g/kg) is necessary for athletes seeking to increase muscle mass.  When we couple a high volume of resistance training with the food our body needs (protein), we provide our muscles with the ingredients they need to grow. A couple research studies have shown that even higher intakes (up to 3.3 g/kg) of protein can help to minimize increases in body fat that athletes would likely experience when they consume the higher volume of calories needed to build a substantial amount of muscle. However, this extremely high intake is likely unnecessary for the vast majority of athletes. Instead, the recommended intake of 1.6 to 2 g/kg is typical for many strength-focused sports and off-season athletes such as rugby, football, discus, javelin, baseball, shot put, and weightlifting.

 

Protein Intake for Endurance Athletes Performing Sport-Specific Exercise 

Given the high training volume and aerobic nature of many endurance sports, these athletes often seek to improve their strength outside of the weight room. Cyclists may perform over-geared efforts to increase on the bike resistance. Orienteers may choose to use challenging terrain to build strength. Like every athlete, endurance sportspeople want to maximize the adaptation that they earn from each workout that they perform. Thus, endurance athletes should shoot for consuming 1.2-1.6 g/kg.  Endurance activities can include road cycling, triathlons, marathon, OCR, cross-country skiing, and orienteering.

 

Protein Intake for Athletes in a Weight Control Sport 

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.  This range has been shown to allow for weight loss while preserving muscle mass. Examples of sports that might find this protein range optimal include: gymnastics, wrestling, boxing, MMA, and judo.

Flexing your Protein Intake

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.  In order to promote the appropriate growth of tissues and organs, pregnant women should consume at least 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.  When compared to their younger counterparts, older adults are less responsive to low doses of amino acid and protein intake.  The age-related decline in muscle mass (sarcopenia) further underscores the importance of protein intake later in life. The current rate of sarcopenia in adults over 60 years is between 5 to 13%. These number increase to between 11 and 50% of the population as age progresses past 80 years. Sarcopenia is particularly problematic because it increases the likelihood of falls and fractures in older adults. 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. 

 

Older individuals that have had a health setback have an even greater dietary protein need (1.5 g/kg). Muscle mass (as measured by grip strength) is highly correlated with longevity. Thus, consuming more protein and performing a consistent exercise routine can significantly impact our quality of life and life expectancy.

 

It is important to note that protein alone will not build muscle. Protein must be coupled with a consistent exercise or resistance training regime. While almost any exercise can be beneficial to health, programs that involve a strategic progression (or progressive overload) will yield the greatest results. Pairing protein with these workouts will further amplify your adaptations and give you the greatest muscle-building potential for your time.

 

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.  This meal frequency can be beneficial for populations other than athletes as well.

 

For individuals who are looking to lose weight, spreading our protein consumption throughout the day can help us to feel full for a longer period of time as well as stabilize blood sugar levels. When protein is paired with carbohydrates is reduces the post-meal increase in blood sugar, as compared to carbohydrates without protein. When we stabilize our blood sugar we feel full for longer, reduce food cravings, and sustain our energy levels.  All of these factors combine to help us achieve sustainable weight loss.

 

Dietary Protein Immediately Before Exercise

Immediately before exercise protein consumption is, frankly, not beneficial for the performance that immediately follows.  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 power your immediate needs.

 

Dietary Protein 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 concentration (IGF-1, a hormone that signals satellite cells to build skeletal muscle).  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.

 

Dietary Protein 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. 

 

Dietary Protein the 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.  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.  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.  Since proteins aid in our immune defense, an insufficient protein intake can suppress the immune system and open the body up to opportunistic infections.  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.  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 3.3 g/kg/day are not any more effective at building muscle.  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 1.4 billion 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 noticeable.

 

Animal protein sources are relatively easy to identify. Beef, chicken, fish, shrimp, turkey, and eggs are all fantastic sources of protein. Animal proteins are usually complete proteins, meaning that they contain all nine of the essential amino acids. This makes it a very easy way to consume a complete protein from one source. Plant proteins, on the contrary, are not usually complete proteins. This means that you will likely have to consume multiple different plant sources in order to assemble all of the essential amino acids that the body needs.

 

Animal proteins are a good source of vitamin B12 and heme iron. B12 is important for the formation of red blood cells, DNA, and nerve cells. Heme iron transports and stores oxygen. Approximately 10 million Americans are iron deficient and could benefit from adding iron (both heme and non-heme) to their diets.

 

The International Food Information Council’s survey reported 28% of people are eating an increased amount of protein from plant sources between 2019 hand 2020.  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.  This protection can lower the risk of cardiovascular disease, cancer, and other diseases.  Fruits, vegetables and whole grains are also typically high in fiber, lower in saturated fat and low in cholesterol.  The increased fiber aids in blood sugar control and weight control.  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).  High cholesterol levels increase the risk of cardiovascular diseases such as heart disease and stroke.  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.  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.

 

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.

 

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, fava beans, 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). 

 

The Important Take Aways about Protein Intake for Optimal Health and Fitness

•       Proteins do more than just muscle contractions. 
•       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, fall risk (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.
•       Proteins from animals are usually easy to identify and are commonly complete proteins.
•       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. 

 

 

Author: Dr. Colleen Gulick