Why Do We Need It?
Second only to water, protein makes up the greatest proportion of our total body weight - roughly 20%. It is the main component of muscles (including the heart), hair, nails, skin, eyes, internal organs and the brain. We generally associate protein with growth and maintenance of body tissues, and that is indeed one of its main functions. It is also needed for a healthy immune system, used in the formation of antibodies. Hemoglobin, which carries oxygen in the blood, is a protein. Enzymes, required for all manner of chemical reactions in the body, are proteins. Many hormones are proteins, and proteins help normalize the acid-alkaline balance as well as the fluid (water) content of cells. And, in certain situations, such as when carbohydrates are in short supply, proteins can be a source of energy. Clearly, protein is critical to the healthy function of all body systems.
How Much Do We Need?
There are different ways to look at the calculations of how much protein an individual requires. Under one method, studies suggest that to maintain balance in a healthy individual, protein should make up roughly 15% of our daily caloric intake. This would change based on activity levels, if you are recovering from an illness or injury, when pregnant or lactating, or if you are trying to gain muscle weight.
Another way to look at it is in terms of grams of protein per kilogram of ideal body weight. In these terms, a healthy sedentary adult needs roughly 0.8g/kg to maintain normal body processes and weight. Again, this does not apply during pregnancy or breastfeeding. During growth (children, young adults), during illness and healing, or increased activity levels, protein requirements increase to 1.2g - 1.7g/kg. For athletes, the increased protein intake compensates for the increased muscle breakdown during and after exercise, and is used to build new muscle cells.
Studies have shown that strength training approximately doubles one's required protein intake compared to a sedentary individual, which would indicate a requirement of 1.6g/kg. The same studies have revealed that increasing protein intake beyond this amount does not enhance strength, mass or size in a linear fashion. In other words, once you have reached your optimal intake level, additional protein will not be converted into muscle. Athletes that are on a weight gain program may need an intake of up to 1.8g - 2.0g/kg.
Excess protein may be turned into body fat and stored as potential fuel, or as glycogen in the liver. Too much protein taxes the kidneys, leads to obesity, and high protein diets have been associated with liver disease, certain cancers, arteriosclerosis, osteoporosis, gout and kidney disease. So it is possible, and not healthy, to get too much protein.
Does It Matter When We Get It?
Research has shown that timing is crucial when it comes to promoting muscle repair and growth, and that it is best to distribute your protein intake over the course of the day rather than in 1 or 2 meals. Anywhere from 15g to 25g (depending on your individual weight) with each meal is advised, as well as immediately after exercise. Muscles are the most receptive to amino acid uptake in the 2 hour post-exercise period (however, this may extend to 24 hours, which is why it is important to eat your protein evenly throughout the day). This is when muscle synthesis takes place at the fastest rate.
Research also shows that combining high quality protein, such as whey, with carbohydrates in exercise recovery (within an hour after) enhances muscle protein synthesis following resistance training compared to carbohydrates alone.
Is All Protein Created Equal?
The quality of the protein your eat is just as important as the amount. One measure of protein quality is biological value (BV), which measures protein quality by the amount of nitrogen released from the protein and absorbed by the body. Mother's milk has a BV of 100%, whereas eggs are at 94%, fish are at 75%-90%, whole grain rice is at 86%, etc.
Proteins are complex molecules of combinations of amino acids. Of the 22 amino acids, our body requires 20 of them for healthy function. Many of them can be synthesized by our bodies, but 9 of them cannot, and are often therefore referred to as "essential". That means that we must get them through our diet. As well, just because 11 of "non-essential" amino acids CAN be synthesized by our bodies, doesn't mean they ARE being synthesized - something like a vitamin deficiency can interfere with that process, creating a deficiency in that amino acid as well.
Each food has a different mix of amino acids so it is important to know what makes a "complete" protein. For example, eggs are a complete protein, but though whole grain rice has a high BV, it is not a complete protein. This is why it is important for those on plant-based diets to ensure they are getting the right combination of foods to provide the complete protein they require. For example, eating legumes or nuts together with grains will supply a complete protein.
Am I Getting Enough?
Signs of protein deficiency can include unexplained weight loss, fluid retention, general weakness, dry hair or hair loss, poor healing of wounds, ridges on nails, nausea, dizziness, anemia, muscle wasting, low hormone levels, poor coordination, and poor resistance to infection or illness. There are two reasons you may have a protein deficiency - you may not be eating enough good quality complete protein in your diet OR you may not be properly absorbing the protein you eat.
Protein digestion begins in the stomach, requiring adequate stomach acid, pepsin and proteases to split the bonds between the amino acid protein chains, allowing enzymes to do their work. Beyond the stomach, proteins are further broken down by pancreatic and other enzymes all along the small intestine. Once they are individual molecules, the amino acids are absorbed into the bloodstream. Therefore, a lack of adequate acid secretion by the stomach can compromise the entire process. If the stomach can't do its job, digestion will fall to the pancreas, which soon gets overwhelmed and this compromises the entire digestive system, and can result in additional health issues. An underactive stomach (hypochlorhydria) is quite common and can be a result of many factors, including but not limited to frequent use of antacids, chronic stress, aging, inadequate chewing, and poor dietary choices.
So What Do I Recommend?
The question of adequate protein intake and absorption is fairly complex and highly personal. This article is really only hitting the generalities in terms of its importance, the amount you as an individual require and the varying sources and quality of protein available. Customized advice is the best advice, and can take into account your individual activity levels, weight goals, health concerns, medications, dietary preferences, lifestyle circumstances, etc. Contact us at M'agine Nutrition or M'agine Fitness for a consultation and we would be more than happy to help you!