Published: 05/12/2010 - Updated: 08/19/2016
To begin to develop the issue, it’s necessary we step into the world of aminoacids, peptides and proteins. Thus, amino acids are the basic units of proteins. There are twenty different amino acids that are classified into two groups: essential and nonessential. The first cannot be synthesized by the body and therefore must be supplied by diet, while non-essential are synthesized in our body.
The essential amino acids are eight and vital for the proper functioning of the body and must be provided daily in our diet, so that if there weren’t these amino acids, we would stop manufacturing body proteins.
Proteins are an essential component for the body, being formed by a highly variable number of units, specifically known by the name of amino acids. Proteins are the only macronutrient that provides nitrogen to the body.
The nutritional value of a protein depends therefore, in essential amino acid content it possesses and its balance with respect to the needs of the organism.
The reference protein is the egg, which has been given a biological value of 100. Other biological value proteins are compared to egg protein.
Thus, the biological value of protein depends on:
- The amount of essential amino acids that have
- The balance of essential amino acid composition
Proteins are the fundamental substance of the body's cells and can represent the 14-20% of body weight. Proteins lie in three major functions of living matter such as: nutrition, growth and reproduction.
Life is not possible without the proteins as they represent the basic substrate of every living organism, while involved in many biological functions.
The main functions of proteins are:
Supporting: Many proteins are part of body structures such as keratin which is a protein found in skin, hair and nails, the collagen that is the essential complement of bones, tendons, cartilage.
Regulatory: Some proteins collaborate in regulating the activity of the body, such as certain hormones as insulin or growth hormone. Enzymes facilitate all metabolic reactions and are also proteins.
Defensive: Certain proteins are tasked to defend the body against invasion by other organisms or foreign particles, as in the case of antibodies or immunoglobulins. Also, there are also proteins involved in the process of blood clotting.
Transportation: In the blood, they transport different types of molecules. For example, lipid apoproteins is transported to various organs, the hemoglobin in red blood cells carries oxygen from the lungs to different tissues.
Energy: When the supply of carbohydrates and fats is not enough to meet the energy needs, the amino acids of the protein ingested is used for energy.
The group of foods rich in protein consists mainly of meat and meat products, fish, eggs and dairy foods. On the other hand, fruits and vegetables are often very poor in protein.
The main groups of protein-rich foods are:
- Meat and derivatives
- Dairy Foods
Meat and meat products: Meat contains on average 15-20% protein with good nutritional quality. It is also rich in phosphorus, iron, B vitamins, especially vitamin B1.
With few exceptions, the meat does not contain carbohydrates and on the other hand, it contains fat but their number varies greatly depending on the species from which it comes, and quality.
On average, 100 grams of meat provide about 170 kcal. If we consider for example, 100 grams of pasta, bring something less than 400 kcal and 100 grams of rice 360 kcal, easily understood that the energy value of meat is quite low when compared to other foods.
Without doubt, the nutritional value of meat is the protein content. Solely on the quality of the protein they provide, there is no difference between red meat and white meat nor between well done or undercooked.
Veal is one of most commonly consumed by athletes. Contains about 15-20% fat.
The lamb meat often contains too much fat, so we recommend only the leg and ribs, and avoid those other parts with visible fat.
Pork has most abundant fat than beef, approximately 20-30%, so we can advise the athlete limit the frequency of use and then only use lean cuts.
Meat products: In general these products are quite high in fat and should not be included in the normal diet of the athlete, except the ham. Overall, have the same limitations as the pork.
Chicken and rabbit: the nutritional value of poultry meat on the quality of the protein is similar to that of beef, lamb or pork. The difference between them lies mainly in the fat content. The chicken, rabbit, turkey are the most desirable for athletes because of their low percentage of fat is usually between 6-12%.
By contrast the duck and geese are much richer in fat and should be excluded from sports nutrition.
Fish: In general, fish contains a protein values similar to those of meat, reaching on average 25%. The nutritional quality of fish protein is very good and generally similar to that of meat. In addition, fish is rich in phosphorus, sulfur, iron, copper, iodine, as well as B vitamins, blue fish contain very appreciable quantities of vitamins A and D.
As is known, the nutritional difference between the fish is its fat content, so it is classified as white and blue fish on the basis of the abundance of fat in them. However, it is important to note that unlike meat, oily fish contains omega 3 fatty acids with considerable benefits for the athlete's health.
Eggs: The chicken egg contains 14% protein whose nutritional quality is one of the highest currently known. Both the white and yolk have a similar percentage of protein and nutritional value is similar.
The egg should not be eaten raw as the proteins in egg whites cannot be used by the body, because it is unable to digest. On the contrary, properly cooked, eggs are an important nutritional source.
Dairy: Milk proteins, casein and whey protein, are one of the largest sources of protein nutritional value.
Dairy products are the main nutritional source of calcium, which is a very important nutrient for athletes. Without milk products, it is practically impossible to ensure a proper intake of calcium through diet, so in these cases, we recommend the athlete to take a supplement rich in calcium.
However, in terms of athlete's protein needs for we can say that this requirement is very different according to sex, age, type of sport, intensity, etc.
Overall, it is considered that a man of 70 kg weight should synthesize about 90 grams of protein. To calculate how much protein a person should consume, must be taken into account muscle mass of this individual: it is an error calculating the amount needed an individual based solely on a person's body weight. Thus, it makes sense that two individuals of the same weight but with different physical constitution should also have different daily protein needs. Thus, the more lean muscle mass of the individual the greater the demand for protein.
The protein intake of a sedentary man, who does not perform heavy physical exertion has been established on average around of 0.90 grams of protein per kg of body weight while for a woman about 0.75 grams of protein per kg of body weight.
Thus, for example, for a 70 kg man weight daily needs would be:
Sedentary men: 70 x 0.90 = 63 grams per day of protein
Sedentary women: 70 kg x 0.75 = 52.5 grams of protein daily.
On the contrary, an athlete's protein needs are generally higher than those of a sedentary person.
In general, we agree that during periods of training, athletes have the following protein needs:
Athlete of strength and power: 70 kg
3000 kcal balanced diet provides approximately 90 g of protein per day.
Real needs in season training: 126 g of protein per day.
Possible Nutritional deficit -36 g of protein per day.
Source: GSN Sports Nutrition