If you ensure you have a protein intake of about 1.2g – 2g protein per kg of body weight (closer to the 2g mark for athletes, vegans, and those trying to lose weight), your body should be getting enough essential amino acids to function well and rebuild bodily tissues. Athletes tend to require a higher level of protein as they have a higher level of muscle damage and thus needs more to be able to repair it all and build new tissue. Vegans also tend to require more protein because vegetable proteins are less digestible than animal proteins and are often low is some amino acids; as such in a vegan diet ensure your protein comes from a variety of sources.
Bones, skin, muscle, and organs are all constructed by your body with protein. Protein is created out of amino acids. When you consume food with protein your body breaks down the protein into amino acids and absorbs a portion of them which it then uses to construct new proteins for your body.
There are 21 proteinogenic (protein building) amino acids your body requires, some your body can create by itself. There are 9 you must consume as your body has no way to make them. Additionally, for children, arginine is also considered essential. The amino acids you can’t produce yourself are known as essential amino acids (EAA) consisting of histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine; they are what we need to ensure we are consuming enough of. There are situations where other amino acids can be considered essential but typically not in healthy adults.
Protein sources have been classified as complete or incomplete proteins based on if they have sufficient levels all essential amino acids. Meat, dairy, and soy are all great complete protein sources. However, they are not the only way to meet your amino acid requirements, if you ensure your diet contains a variety of protein sources, grains (rice, corn, wheat, barley), legumes (peas, beans, lentils, soybeans), seeds (sesame, sunflower, quinoa, chia, flax) are some examples.
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
To give you an idea about the protein in individual foods there is a scoring system which takes into account the limiting essential amino acid and the amount of protein absorbed this is the PDCAAS, the following table is a summary to help you understand where the food you eat may fall into it, 1.0 being the highest scoring.
Dairy and Eggs – 0.95 – 1.0
Meat and Soy 0.80 – 0.95
Legumes and Vegetables 0.70 – 0.80
Fresh Fruit – 0.60 – 0.70
Cerials and Grains 0.40 – 0.60
Based on the data available it appears in a healthy adult (without liver or kidney issues) it is safe to have high protein intake. It is recommended for the elderly to have a higher protein intake as their bodies are less efficient at using the protein they consume. There is also a belief that the recommended dietary intake (which are minimums and in no way optimal) may be low due to flaws in the testing methods used and that the recommendations should be closer to 1g – 1.2g per kg of body weight.
For weight loss purposes it is also beneficial to aim for higher protein intake as it will help with feeling full and maintaining lean body mass; by making more of the weight loss come from fat stores rather than muscle mass.
Most people do not require supplementation, you can get all the protein you require through dietary changes. However, if you are struggling to meet your protein targets, you can supplement with protein concentrates or isolates like whey protein, soy protein or a combination of rice and pea protein (combining them is required to get a good amino acid profile). For people who have super strict calorie requirements, and/or athletes, there are potential benefits to using EAA (Essential amino acid) blends. BCAA blends however are only 3 of the essential amino acids sometimes with other amino acids added. These have become popular with very little reason or science backing them.