Content by: Erin Nugent, RD and Contributor for SoulFIRE Health
Taking a moment to review the Protein Basics! Bring facts to the hype about high protein diets. Are they safe? When should a person consume more than daily recommendations?
The amino acids needed to make body proteins are supplied by the protein food we eat AND through cell synthesis.
Nonessential Amino Acids do not need to be obtained from the diet because our bodies make them.
- There are 11 nonessential amino acids: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine.
Essential Amino Acids must be obtained from foods.
- There are 9: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
Recommended Dietary Allowance:
For most adults, the recommended dietary allowance (RDA) for protein is 0.8 g/kg body weight. This RDA does not account for additional protein needs during the recovery process from injury or illness. The typical North American diet exceeds the RDA for protein. However, excess protein cannot be stored, therefore the carbon skeletons are broken down and used for energy needs.
Complete & Incomplete Proteins:
Animal proteins are considered complete proteins because they contain sufficient amounts of essential amino acids. Plant protein, with the exception of soy and quinoa, are considered incomplete due to their limited amount of essential amino acids. However consuming a diet rich in plant proteins can still provide adequate amounts of essential amino acids with careful planning.
Protein digestion begins in the stomach where it is partially digested by the enzyme pepsin and hydrochloric acid. This breaks down protein into shorter polypeptide chains of amino acids. Then these polypeptide chains are digested into dipeptides and amino acids which are absorbed by the small intestine. Then amino acids are transported by the portal vein into the liver, and from there into the general bloodstream.
One primary function of protein is to provide structural support for body cells and tissues. During periods of growth new proteins are synthesized to support the development of tissues and structures. However, during periods of malnutrition or disease, body proteins are broken down to synthesize glucose for energy. Muscles, connective tissue, transport proteins, enzymes, hormones, and antibodies are all made of proteins.
There can be health concerns associated with high protein diets and protein supplementation. Kidneys are responsible for excreting excess nitrogen as urea. High protein diets may overwork the kidneys’ capacity to excrete nitrogenous wastes. Furthermore, since water is needed to dilute and excrete urea, inadequate fluid intake can increase the risk of dehydration as the kidneys use the body’s fluids to work to dispose of the urea.
There are also concerns for athletes who supplement amino acids. The body is designed to obtain amino acids from dietary sources. This allows for a supply of amino acids in proportions needed for bodily functions. When individual amino acid supplements are taken, this increases the risk for amino acid imbalances and toxicity risk.
Byrd-Bredbenner, C., Moe, G., Beshgetoor, D., & Berning, J. R. (2013). Wardlaw's perspectives in Nutrition. McGraw-Hill.