Food Protein and Amino Acids Are Essential Components of Our Diet
How much protein should we eat daily?
The RDA for protein for adults is set at 0.8 g of protein per kg body weight. This works out to about 54 to 60 g for most men and about 44 to 50 g for most women. You can estimate basic protein needs based on % of total calories, where by 12-15% will give you approximately the same level. This level of protein merely compensates for normal daily body protein loss and prevent dysfunctions related to getting too little protein; however it is not an optimal level of protein in various situations such as weight loss, exercise, aging and illness. Said differently, it is a minimum amount that can prevent the development of the effects of a deficiency state and the RDA was never meant to be a target level to hit for diet planning. In many situations like these situations like exercise training, performance, healthier weight management, disease management and aging, a base protein intake level of 20-25% of calories will be more aligned to help achieve goals. In fact many sport nutritionists now recommend at least 1 g/lb body weight (fit or performance weight target) or 2.2g/kg. While this might seem like a lot, the increased caloric needs for people who workout hard result in this protein level in the percentage above (20-25%).
What are essential amino acids?
From a nutritional standpoint, only ten of the twenty amino acids found in protein are essential to the diet. These amino acids present us with the same situation as do the other essential nutrients. We simply cannot make them or at least not in the amounts necessary to promote growth, development, and health throughout the lifespan. As a result, these amino acids must be provided by our diet. As listed in the Amino Acid Table, arginine and histidine are noted as essential during periods of growth and maybe at an advanced age but not necessarily at other times. The easiest way to remember the essential amino acids is by the acronyms TV-TILL-PM-AH. These are the first letters of the essential amino acids tryptophan, valine, threonine, isoleucine, leucine, lysine, phenylalanine, methionine, and the two semi-essential amino acids arginine and histidine.
What are nonessential amino acids?
The non-essential amino acids are those can be made in our body by using essential amino acids and/or other molecules. It should be understood that dietary essentiality or nonessentiality by no means is meant to imply biological essentiality or nonessentiality. All building block amino acids must be present in cells to make proteins which support the health of those cells and our body in general. Further, if a problem exists in making a nonessential amino acid, as is the case in some genetic anomalies, then that amino acid would also become a dietary essential for that person as well. This is the case with some individuals who lack the ability to produce the appropriate enzyme to convert phenylalanine (essential amino acid) to tyrosine (nonessential amino acid). In these cases (i.e., phenylketonuria [PKU]), tyrosine becomes an essential amino acid.
What are “complete” proteins?
The goal of protein nutrition is fairly simple - to provide our body with food protein that closely resembles our own protein and in adequate amounts. Furthermore, since the nonessential amino acids can be made in our body, it is desirable for food protein to provide the essential amino acids, in proportion to human protein. Food sources with levels of essential amino acid content similar to our essential amino acid requirements are considered more “complete” and sometimes referred to as higher biological value. Those that don’t measure up to the standard are considered incomplete. Complete Protein Sources: Animal based protein sources from such as beef, pork, fish, poultry, eggs, milk, and milk products are among the more complete protein sources. In addition, soy, quinoa, amaranth, buckwheat and spirulina are complete or nearly complete plant based protein sources. Incomplete Protein Sources: Plant-based foods such as wheat, corn, fruits and vegetables are considered incomplete or lower biological value as the levels of essential amino acid within their protein does not match our essential amino acid needs as closely.
How can incomplete protein foods be combined to form a complete protein?
When we compare the essential amino acid composition an incomplete food, we find that one or more of these amino acids are in a limited quantity relative to our protein. These amino acids are referred to as “limiting amino acids” because our cells ability to make new protein will be limited to the level in that protein. This is analogous to building a brick wall with alternating rows of red, white and blue bricks. If there is only enough red bricks to build the wall 4 feet tall that is as tall as wall can be built even if there are abundances of blue and white bricks.
What does it mean to “complement protein”?
Because the limiting amino acids within plant foods varies, strategic combinations of different plant foods will provide adequate quantities of all the essential amino acids. This practice is called “complementing” proteins. For example, we could combine cereals (i.e., oats, wheat, rice, rye) or nuts and seeds (walnuts, cashews, almonds, pecans and sunflower, pumpkin and sesame seeds) which are low in lysine but a good source of methionine, with legumes (beans, peas, lentils, garbanzos (chick peas)) which are low in methionine but a good source of lysine. While considered a complete protein source, soy is limited in lysine as well and often used in a complementing scheme. The practice of complementing proteins may be best served within the same or adjacent meals for strict vegetarians with lower daily protein intakes (e.g. below RDA); however, for less restrictive vegetarians complementing within the same day is fine.
How important is complementing protein to vegetarians?
Vegetarians either partially or totally restrict animal based foods and those containing animal based ingredients from their diet. Vegetarians with more restrictive practices will have to be more conscious of complementing proteins, especially since their overall protein intake tends to be lower than non-vegetarians. Fruitarians: Level of fruitarianism vary. Diet tends to include what certain plants bear (i.e., fruits, nuts, some or all vegetables) but not the foundational plant tissue that would be harvested such as grains. Strict fruitarianism is meant to simulate the diet in the Garden of Eden, therefore cooked vegetables will not be included. Complementing protein sources is very important and can be challenging depending on diet criteria. Vegans: Vegans tend to restrict their dietary choices to what plants bear as well as food produced from harvested plants (e.g. cereal grain products, sprouts, etc). A vegan diet tends to include cooked foods such a oatmeal, breads and some vegetables to enhance their palatability (e.g. corn, potatoes, beans), Vegans have numerous options for complementing proteins and soy based foods provide a complete protein source as well. Lactovegetarians – Include milk and dairy products to a vegan diet. Since milk is a good source of complete protein, there is less concern for complementing proteins, especially if milk-based products are consumed at different meals or if soy foods are part of the daily intake. Ovovegetarians – Include eggs and foods containing eggs to a vegetarian diet. Like the vegan, there are multiple options for complementing proteins and there is less concern for complementing proteins, especially if eggs are consumed at throughout the day or the diet includes ample soy foods. Lactoovovegetarians Include dairy, eggs, and recipe foods that include eggs and dairy products as ingredients. Minimal concern exists for complementing protein if these foods are found in meals and snacks throughout the day or ample soy is part of the diet.
What is the difference between protein concentrates and isolates used as ingredients?
Proteins from commons foods like milk, eggs, wheat, pea, soy, potato and rice can be concentrated by reducing other nutrition components (e.g. carbohydrate, fat, cholesterol, etc) and then dried to a powder. Based on the degree of removal of "non-protein" parts these powders are typically referred to protein isolates or concentrates can be used in sport nutrition, weight management, baby formula and health products as well as ingredients used in recipe products. Usually protein powders are categorized by protein level on a dry weight basis (water removed). PROTEIN CONCENTRATES typically contain up to 80-85% percent protein on a dry basis (75-80% protein as is) with the remaining percent from carbohydrates, minerals, moisture (water) and fats. PROTEIN ISOLATES have had more of the non-protein parts removed and contain up to or above 90 percent protein on a dry weight basis. For instance whey protein isolate is usually about 85% protein “as is” with moisture accounted for. PROTEIN HYDROLYSATES: The term hydrolyzed protein, or hydrolysates, refers to the presence of partially digested proteins including polypeptides and peptides. "Partially digested" may sound undesirable, but it may actually be beneficial! In addition to providing amino acid building blocks, peptides might have additional actions in the body.
What is whey protein?
Whey is by far the most popular protein ingredient used by bodybuilders and fitness enthusiasts. That’s because, gram for gram, whey has been shown to promote muscle growth and maintenance more potently than other proteins when coupled with resistance training. Plus, whey is digested and absorbed faster than other proteins, making it the ideal choice to consume either immediately before or after a workout. Whey is approximately 20 percent of the protein in cow's milk and over 60% human milk and has the highest branched-chain amino acid (BCAA) content, including roughly 11 percent leucine and 9-10 percent combined isoleucine and valine, yielding a 2:1:1 relationship. This approximates the ratio found within skeletal muscle proteins involved in contraction.Leucine is a very desirable BCAA as it plays a direct role in optimizing muscle-protein manufacturing after strenuous training and in response to a protein meal by increasing the activation of the mTOR pathway. Moreover, whey is probably the most thermogenic protein, meaning that the increase in calories burned per calorie consumed is greater than other proteins. This is likely tied to a more acutely potent effect on muscle protein synthesis (MPS).
What is casein?
Casein, the main protein family in cow’s milk, contributing up to 80% of its protein (but less than 30% in human milk). Casein is a slow-digesting protein, especially when compared to whey. Depending on how much you consume, casein can take more than six hours to be fully digested and absorbed by the body, which makes this protein great for a sustained amino acid delivery to muscle. Like whey, casein is a good source of BCAAs as well as glutamine, which might help limit muscle protein breakdown (MPB). Net gains in muscle protein reflect the imbalance between muscle protein synthesis (anabolic) and breakdown (catabolic). Because of its slow-digesting properties, casein is often recommended before bed or in between meals, either by itself or in blends with other proteins.
What are milk proteins?
Milk protein contains all of the essential amino acids in a natural 80/20 ratio of casein-to-whey blend, which allows for the fast and sustained release of amino acids necessary for muscle growth. Milk protein isolates and concentrates are common in protein-powder blends, creamy protein RTDs (ready-to-drink), and protein bars.
What are egg proteins?
Eggs are very popular again as a morning protein source now that some of the long-held beliefs about their role in heart disease are being dismissed. The egg protein found in protein powders is mostly egg-white protein isolate and an alternative for people with milk allergies. Egg protein is also listed at the top of its class when it comes to quality. With a score of 100 on the biological value (BV) index, egg protein contains all the essential amino acids necessary for protein synthesis, and is easily digested by the body.
Perhaps not as well-known as its protein counterparts, pea protein is a great option for vegetarians and those with allergies to dairy and eggs. Not only is it hypoallergenic, it's high in BCAAs and is efficiently digested and absorbed, meaning the body is able to use and process the majority of amino acids per serving. This makes pea protein far superior to other plant-based protein powders, which can be difficult to digest and are not well-utilized by the body.
Are high protein diets dangerous?
At one time there was a belief that higher intakes of protein can be problematic to health. Today we know that for most people this isn’t the case. In fact, diets with a higher level of protein then the RDA are encouraged for athletes as well as people during weight loss. Two areas of health have are often the target for concern regarding higher protein intakes. The first is kidney health. It was long believed that since higher intakes of protein leads to the formation of more nitrogen-based compounds such as urea would be removed from the body by the kidneys in urine. However we now know that this isn’t the case unless a person has a special situation related to the kidneys and receiving guidance from his or her physician. The second area is in relation to bone. Some earlier research studies indicated that when diet protein levels increase, so too does the level of calcium in the urine. This led to the conclusion that high protein diets cause a loss of calcium from bones, rendering a person more prone to osteoporosis. However, follow up research has shown that the higher protein intake also increases calcium absorption, thus leading to a corresponding increase in calcium in the urine. So, like kidney dysfunction, the notion that a high protein intake, such as 25% of calories for weight loss or maintenance leads to osteoporosis has not been shown to be true..