How much protein a person needs daily is a matter of base requirements to maintain good status and allow for normal growth and development. Here the term need is aligned with requirement. Meanwhile additional protein, beyond a base requirement, might have additional benefits. When additional benefits from protein are accepted then a recommendation might be a better term to use. A requirement for protein is often altered by certain conditions, life stages and aspirations, but long ago the RDA (Recommended Dietary Allowance) for protein in the United States and Canada were set to cover basic requirements under somewhat normal conditions. The basic criterion for establishing the RDA is general and somewhat crude, based on old methodology and data sets. Many argue that they should not be used as a dietary planning tool for most people as addressed throughout. Meanwhile, organizations such as the International Protein Board (iPB) have attempted to break down protein recommendations based on various people buckets including exercise and fitness, sport performance, weight loss, healthier aging and more. 

Protein Recommendations of the International Protein Board (iPB) for Different Populations.

*g/kg = grams of protein per kilogram body weight.
Derived from the International Protein Board (www.InternationalProteinBoard.org). Protein recommendations are not intended to exceed 35% of calories.

The RDA for protein is expressed in two ways. First, from a general quantity standpoint the RDA is 46 and 54 grams for men and women, respectively. In addition, the RDA is also stated as 0.8 grams per kilogram body weight. The RDA was developed to apply to the general population based on general height and weight standards for lean adults of average height and otherwise healthy. Compared to Daily Values (2000 and 2400 Calories) applied to the Nutrition Facts panel on food, this is just under 10%, which appears minimal. In addition, the RDA would then put the level of protein just below the AMDR (Acceptable Macronutrient Distribution Range) which 10-35% of calories from protein, again suggesting the RDA is low.

One could argue that the RDA expressed as 0.8 grams per kilogram body weight would yield a higher gram level RDA for heavier people. However, this should only be true for taller people with relative leanness, based on the criteria for the development of the RDA. So, in this scenario the RDA would still be low in a relative sense as height would be driving the higher body weight, not merely increased body weight at the same height. The RDA for protein was not developed factoring overweight and obese individuals. Moreover, those individuals falling in that category attempts to lower body weight would increase the base requirement.

It is important to keep in mind that the RDA was developed as a minimum intake standard that could provide helpful information for most people avoid a situation of not getting enough protein and avoid reduced body protein status and the development of deficiency over time. The RDAs for protein are subcategorized based on gender and age groups as well as pregnancy and lactation. Said differently, the RDAs for protein were not developed to serve as a personal diet planning tool for optimal health or to achieve goals for changing body weight, fitness, athletic performance or to address injury, illness or healthy aging. 

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 been 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, this work become detrimental to the kidneys. 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 research efforts have determined 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. The purported mechanism often cited was that certain amino acids, particularly the sulfur-containing amino acids, could render the blood more acid, which in turn would erode the bones and allowing calcium to be lost in the urine. This notion has not been supported. Moreover, follow up research with higher protein diets suggested that as diet protein went up, so too did calcium absorption, and this accounted for any increases in calcium in the urine. Furthermore, the National Osteoporosis Foundation (NOF) performed an exhausted review of protein levels in the diet and impact on bone integrity. One of the key takeaways was that higher protein intakes had no major impact on bone density or in some parts of the skeleton there was potential benefit. 

From a nutritional standpoint, only ten of the twenty amino acids found in protein are dietary essential. These amino acids present us with the same situation as do the other essential nutrients. We simply cannot make them, either at all or in 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 Table 5.1, arginine and histidine are noted as semi-essential which can become essential during periods of growth and maybe during more advanced age but not 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, Methion¬ine, and the two semi-essential amino acids Arginine and Histidine. Other acronyms include PVT TIM HALL or VP MATT HILL where PVT is the abbreviation for the military rank of private.

The remaining amino acids used to make protein in our body are called non-essential. That’s because they can be made in our body by using other amino acids and/or other molecules. Dietary essentiality or non-essentiality by no means is meant to imply biological essentiality or non-essentiality. All 20 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.

The goal of protein nutrition is simple - to provide our body with food protein that 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 like 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.

When we examine the essential amino acid composition of 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 somewhat limited by the level of an amino acid in a protein. This is analogous to building a brick wall with alternating rows of red, white and blue bricks. If there are only enough red bricks to build the wall four feet tall that is as tall as wall can be built even if there are abundances of blue and white bricks. 

Example of limiting amino acids include:

• Methionine and Tryptophan – Legumes, lentils, peas, beans
• Lysine, Isoleucine, Threonine – Wheat, corn, rice, oats, barley, rye
• Lysine, Isoleucine – Nuts, seeds

One way to overcome limiting amino acids is to plan for a variety of protein sources. That way, lower levels of some essential amino acids in foods can be made up by higher levels in others. 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; however, for less restrictive vegetarians complementing within the same day is fine. Meanwhile, as protein intake is elevated in the diet the need for strategies to compensate for limiting amino acids is reduced in somewhat relative fashion.

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 protein, especially since their overall protein intake tends to be lower than non-vegetarians. (See Table 5.5).   

• Fruitarians: Fruitarian diets tend 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 fruitarian diets are meant to simulate the diet in the Garden of Eden, therefore cooked vegetables are often not 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 as 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.
• Lacto-vegetarians – 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 ample soy foods are part of the daily intake.
• Ovo-vegetarians – 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.
• Lacto-ovo-vegetarians 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 and/or ample soy is part of the diet. 
• Pesco-vegetarians Include fish and other seafood to an otherwise vegetarian diet. Fish and other seafood provide complete protein and many other important nutrients including vitamin B12 and omega 3 fatty acids, namely EPA, DHA and DPA.

Simply Solutions for Complementing Proteins