Protein is an essential macronutrient, but not all food sources of protein are created equal, and you may not need as much as you think. Learn the basics of protein and shape your diet with healthy protein foods. Not all protein sources have the equivalent amount of essential amino acids. As research shows, foods with complete proteins stimulate muscle protein synthesis better than incomplete proteins.
There is a group of amino acids known as BCAAs (branched chain amino acids) consisting of leucine, isoleucine and valine. These 3 amino acids constitute approximately 35% of all muscle tissue and are essential for stimulating protein synthesis and inhibiting the breakdown of muscle cells. Animal proteins, such as meat, eggs, and milk, are complete proteins, meaning that they provide all the essential amino acids our bodies need. Animal products provide the highest quality sources of protein.
Protein is available in a variety of dietary sources. These include animal and plant-based foods, as well as the highly commercialized sports supplement industry. In the next section, plant and animal proteins, such as whey, casein, and soy, will be explored. Determining the effectiveness of a protein is achieved by determining its quality and digestibility.
Quality refers to the availability of the amino acids it provides, and digestibility considers how the protein is best used. Generally, all animal protein sources in the diet are considered complete proteins. That is, a protein that contains all the essential amino acids. Plant-based proteins are incomplete, as they generally lack one or two essential amino acids.
So, someone who wants to get their protein from plant sources (i.e. Vegetarian) you will need to consume a variety of vegetables, fruits, cereals and legumes to ensure the consumption of all the essential amino acids. As such, people can achieve the necessary protein requirements without consuming beef, poultry, or dairy products. Protein digestibility ratings generally involve measuring how the body can efficiently use dietary sources of protein.
Plant protein sources generally do not score as high in biological value, net protein utilization, PDCAAS and protein efficiency ratio as animal proteins. Dawson-Hughes et al. (200), not only demonstrated that animal protein does not increase urinary calcium excretion, but it was also associated with higher levels of IGF-I and lower concentrations of the bone resorption marker N-telopeptide. Incomplete proteins are not inferior to complete proteins, but they must be combined with another protein source to contain sufficient amounts of essential amino acids.
They demonstrated that, after ingestion of whey protein, the plasma appearance of amino acids is rapid, high and transient. Tarnapolsky and colleagues (199) have demonstrated that, in order for strong-trained people to maintain a positive nitrogen balance, they need to consume a protein intake equivalent to 1.8 g·Kg-1·day. It is important to recognize and restrict or limit proteins that have a lower content and digestibility. Net protein utilization and biological value measure the same nitrogen retention parameter; however, the difference is that the biological value is calculated from the nitrogen absorbed, while the net protein utilization is calculated from the nitrogen ingested.
Therefore, the concern about the increased risk of cardiovascular disease due to protein-rich diets seems to be unfounded. An essential amino acid, leucine, has been shown to be the key activator of muscle protein synthesis in both sedentary people and people who exercise. In addition to the benefits of total protein consumption, elderly subjects have also benefited from consuming animal sources of protein. They reported that a low intake of dairy and meat proteins late in pregnancy was associated with low birth weight.
However, the potential health problems associated with a diet of proteins consumed primarily of animal origin should be recognized. In the same way, such knowledge will make it possible to identify the proteins that provide the greatest benefit and that should be consumed. However, thanks to better nutrition awareness and education, many of these athletes can obtain their proteins from sources that minimize the amount of fat consumed. These results suggest that whey protein stimulates rapid protein synthesis, but a large part of this protein is oxidized (used as fuel), while casein can cause greater protein accumulation over a longer period of time.