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Debunking Protein Myths

The amount and type of dietary protein athletes need to eat is a controversial topic in sports nutrition.  Protein’s role is to support muscle tissue recovery in response to exercise training, but is also important to support general growth during adolescence and is an integral part of skin, hair, nails, hormones and cell structures. 


After eating a protein-rich food, your body breaks it down to amino acids to be used for various functions, such as building muscle, regulating your immune function, and a small amount is used for energy during exercise. Your body needs 20 different amino acids to function properly but only nine amino acids are essential, meaning you have to get them through your diet. 


Depending on your protein needs, eating protein from whole foods is more desired, but supplementation may be helpful for vegetarian/vegan athletes, masters athletes, and/or athletes requiring additional protein when training in higher volumes during a competitive season. If you decide to use protein powders occasionally, remember to use ones that are certified by either NSF Sport or Informed Choice.


Myth: Eating too much protein is harmful for your bones and kidneys

Concerns of eating too much protein has been disproven to be harmful to your bone health and   kidneys as previously thought, except if you have existing kidney function issues. The National Kidney Foundation’s protein recommendations are only below those for the overall population (0.6-0.75 grams (g) protein per kilogram (kg) of body weight/day), but protein does not impact kidney function in healthy individuals.


Eating enough protein, but not excessive amounts, is actually important for bone health, especially in growing adolescent athletes and masters athletes at risk for osteoporosis and to prevent hip fractures. Eating more protein (1.5 g/kg/d) increases calcium absorption in the gut since protein induces gastric acid which allows calcium to absorb better. 


Myth: Eating a high protein diet is better for muscle building

Defining a high protein diet varies in the literature from eating more than 3 g/kg per day to over 35% of your total calories. Eating enough protein is important for building muscle and maintaining muscle mass, but if your diet contains a majority of calories from protein, this displaces the energy you need from carbohydrates and fats which are essential for energy, vitamin absorption, and gut health.


Protein increases satiety, meaning it makes you feel full.  This is a great way to help you manage your weight while improving muscle recovery and growth if you are trying to lose fat weight, and not lose muscle. However, if you eat a high protein diet, this can interfere with your ability to eat enough calories to support the amount of exercise you are doing, increasing the risk of experiencing low energy availability (LEA) resulting in poor sports performance, poor growth, and reduced energy.


In addition, during peak growth in adolescence, increases in lean body weight can be threefold compared to growth before puberty; therefore, the eating enough calories is important than just protein alone. If you don’t eat enough calories overall, protein is then used as an energy source, reducing its ability to help with muscle recovery.


Recommendations regarding the optimal protein intake should be individualized and not a “one- size- fits all” approach.  General recommendations are to eat adequate amounts of protein throughout the day, every 3 to 4 hours, to maximize recovery and muscle protein building. The International Society of Sports Nutrition (ISSN) suggests for building muscle and maintaining muscle mass, an overall protein intake can range from 1.4 to 2.2 g/kg per day.  Higher protein intakes (2.3-3.1 grams per kg/d) may be warranted to maintain lean body weight if you focus more on strength training when not eating enough calories to manage weight.


This means if you are an endurance athlete weighing 150# (68.1 kg) you may need 95 to 149 g of protein daily (1.4-2.0 g/kg), but if you are trying to lose weight and focusing more on strength training your protein intake may be as high as 170 grams daily (2.5 g/kg).


In addition, master athletes lose muscle mass more quickly related to decreased training and related to an inability of muscle to respond to and use amino acids to build new muscle, therefore require more protein compared to younger athletes.


Myth: Your body can only absorb 20 grams of protein at one time

Controversy exists about the amount of protein your body can process in a single meal. There is a difference in how much your body can absorb versus how much your body can utilize to maximize protein growth. After eating a protein-rich meal, amino acids are transported through the intestines, enters the liver, and the amino acids not used by the liver, enter the bloodstream to be used by the tissues.


The ability to absorb whole protein is not the limiting factor, but it is the amino acids.  Leucine (essential branched-chain amino acid) is needed to turn on muscle protein growth via gene expression (mTOR).  Eating enough leucine, about 2.5 to 3 grams per meal, will turn on muscle growth.  This means the type of protein is just as important as how much protein you eat daily.


General recommendations from the ISSN include to eat 0.25-0.40 g of high-quality protein per kg of body weight or an absolute dose of 20-40 grams 4 to 5 times per day, throughout the day to maximize muscle protein synthesis (muscle building).  This often translates to a minimum of 1.6 g/kg per day. However, this does not mean your body can’t absorb more than this amount.  According to researchers, the dose ceiling may be as high as 0.60 g/kg for some older individuals to maximize muscle growth.


Your body can absorb the protein you eat, but the amount amino acids that can be used for muscle growth may be limited when eaten alone (not in mixed meal).  The amount you need also varies based on your age, body composition, and training load.  To promote muscle growth, it’s best to spread out protein rather than eating a larger amount only a few times a day; however, remember that each meal should contain at least 2.5 g of leucine. Any additional protein eaten beyond the amount your body needs to maximize muscle growth is used to sustain protein balance when eaten in a mixed meal and not just eating protein alone.


You are not wasting protein if you eat beyond a certain amount, but it’s important to look at the big picture, balancing your diet containing enough protein to maximize muscle growth, but still get enough energy from fiber-rich carbohydrates and healthy fats to maintain energy levels, improve gut and immune health, and to reduce inflammation.


Myth: Animal Protein is Better Absorbed than Plant Protein

Protein can be categorized based on its amino acid composition and digestibility. Whole foods should represent the base of where you get your protein from, which are more nutrient dense, meaning they provide more nutrition benefits than just protein alone. But a recent meta-analysis showed that the protein source did not change the way you can still gain muscle growth when comparing animal versus plant based proteins.


Plant based protein may have lower amounts of essential amino acids, but this often is not a concern when eating a varied diet. However, research does suggest that plant based proteins from whole foods are less digestible (approximately 10-20%), than animal protein since plant protein contains more dietary fiber which can impact absorption.  In addition, leucine is key to promote new muscle growth, which is lower in plant based foods compared to animal foods found in eggs, dairy, meat and fish. This just means you may need to eat a little more plant-based protein to get the 2.5-3.0 g of leucine at each meal or snack. 


It’s recommended to eat an additional 10% to 20% more protein when eating a plant protein to compensate for digestibility and the limiting essential amino acids compared to animal protein. For example, eating 3 large eggs contains approximately 3.3 g of leucine, whereas you would have to eat a meal containing ½ cup of black beans (0.7 g) with 1 cup of lentils (1.3 g) with 3 ounces of tofu (0.7 g) to get 2.7 g of leucine.  As you can see, you may need to eat more calories from plant-based foods to get the same amount of leucine from animal foods; however, the plant based food options may provide additional nutritional benefits from dietary fiber and phytochemicals improving gut, immune, and cardiovascular health.


Take Home Message

Eating enough dietary protein is important for muscle growth and recovery.  The amount you need is based on your age, type of sport and amount you train, and body composition goals. It should not be a “one-size-fits all” approach.  


It’s better to eat smaller amounts of protein throughout the day, containing 2.5-3 g of leucine at each meal or snack to maximize muscle growth, but if you eat beyond this amount your body can still use the extra protein eaten, it’s not wasted. However, if you are eating a majority of your energy from protein this may displace the energy from fiber-rich carbohydrates and healthy fats which are essential for energy, gut and immune health, and to reduce inflammation.  


Finally, it doesn’t matter whether you eat protein from animals or plants as long as you are eating enough leucine at each meal or snack. You may be eating a little less calories from animal proteins, but plant based proteins provide additional benefits from the additional fiber and phytochemicals.


Meeting with a certified sports dietitian (CSSD) can help you determine how much and when to eat protein to maximize your muscle growth and recovery.





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