The Importance of Protein
by Dr. Stéfane Dias, Professor of Exercise Science at KU Orlando
Since the Greek Olympians of ancient times, protein has had a special place in the athletes’ diet. Nowadays, much is said about protein and its effects on the human body. Because it is extremely abundant, the function of this macromolecule is directly proportional, playing key roles in cells, especially in muscle cells. Amino acids form the basic structure of proteins and contain carbon, hydrogen, oxygen, and nitrogen. Nitrogen is what distinguishes amino acids from the composition of carbohydrates, fats and alcohol.
There are a total of 20 amino acids that are used by the human body to form different proteins. Of these 20 amino acids required in healthy adults, nine are considered essential (indispensable) because the body cannot produce them. The remaining eleven are called nonessential (dispensable) because they are produced by the liver. Six of these eleven amino acids are also called conditionally indispensable, because during periods of stress, illness, prolonged or physiologically intense aerobic training the body cannot produce enough of them.
One controversial point is about the recommended daily intake (RDA) of protein. If we look at the American RDA for adults we can see that it is 0.8g/kg of body weight/day. For example, an 80-kg, sedentary adult male needs approximately 64g of protein per day. For a male with the same body weight who is an endurance athlete he will need 1.2-1.4g/kg of protein per day which is between 96-112g of protein per day (an increase of 32-48g daily). According to the table below we can see that athletes can and should ingest more protein than their sedentary counterparts, and strength athletes need to increase these doses even more.
Recommended Protein Intake
|Group||Recommended intake (g / kg body weight / day)|
|Majority of adults||0.8|
|Non-vegetarian endurance athletes||1.2-1.4|
|Non-vegetarian strength athletes||1.2-1.7|
|Vegetarian endurance athletes||1.3-1.5|
|Vegetarian strength athletes||1.3-1.8|
Data from the American Institute of Nutrition
Too often, it has been erroneously reported in the media that a chronic intake of high doses of protein is detrimental to health and may result in unnecessary metabolic stress to the kidneys leading to kidney failure. Another frequently cited concern is that diets high in protein increase calcium excretion thus increasing the risk of osteoporosis. Both concerns are unfounded, as there is no substantial evidence that protein intake at the recommended doses suggested above will have adverse effects on healthy individuals. This is not the case when the guidelines are exercised according to the position of the International Society of Sports Nutrition.
Note that vegetarian athletes should ingest a higher dose of protein per day. This is because plant proteins do not have all the essential amino acids and are therefore called incomplete proteins. The proteins of animal origin are called complete because they contain in large quantities all the essential amino acids.
Another key factor is the quality of the protein, which is determined based on the quantity and type of amino acid(s) and its ability to be absorbed by the human body. The new method used internationally to calculate the quality of the protein is: “Protein Digestibility Corrected Amino Acid Score” (PDCAAS). This method outperforms the biological value of the protein. On a scale of 0-1 where 1 represents the highest score in the PDCAAS method and we have information on protein absorption and utilization as well as amino acid content.
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
protein quality source
|Milk protein (casein + whey)||1|
|Beans and legumes||.60|
In the table above it is clear that casein, albumin and whey protein are better sources of protein than nuts, beans, legumes and wheat.
It is important to emphasize that nutritional monitoring and diets should be prescribed only by professionals in the field of nutrition and that our intention in this article was only to transmit information about recent research to our readers. Therefore, before practicing any type of training consult a certified personal trainer and a nutritionist so that the practice of exercise and nutrition are individualized.
Article written by: Dr. Stéfane Dias – Professor of Exercise Science at Keiser Orlando; Dr. Fabio Vieira – Professor of Exercise Science at University of Brazil and Rokaya Mikhailenko – Exercise Science student at Keiser Orlando.