Proteins

Protein is an essential part of the human diet, found in a variety of foods. It is broken down and reformed in our bodies to perform crucial functions from fighting infections to aiding cell division. Proteins are chains of amino acids linked by peptide bonds, which twist and fold into their final shapes.

When we consume protein, it is broken down into individual amino acids. Most amino acids have a central carbon atom bonded to an amino group, a carboxylic acid group, a hydrogen atom, and a unique sidechain. Humans utilize about 20 of the hundreds of amino acids found in nature to construct various proteins.

Amino acids are categorized based on whether our bodies can produce them. Non-essential amino acids (5) can be made by the body, while conditionally essential amino acids (6) can be made under normal circumstances but not in cases like starvation or metabolic errors. Essential amino acids (9) must be obtained from food.

Dietary protein provides essential amino acids for creating our own proteins, hormones, and other vital molecules. Digestion begins in the stomach with hydrochloric acid denaturing proteins, followed by pepsin breaking them into smaller chains. In the duodenum, pancreatic enzymes further break them into tripeptides, dipeptides, and individual amino acids, which are then absorbed into intestinal cells and the bloodstream.

Animal-based foods like eggs, dairy, seafood, and meat provide all nine essential amino acids. Soy foods are unique plant-based sources that also offer all nine. Most other plant foods have varying amounts of amino acids, but a diverse plant-based diet, such as combining rice and beans, can provide all essential amino acids. While plant-based foods may require larger volumes to match the protein and amino acid profile of animal sources, they can be equally effective.

Daily protein requirements vary by age, sex, and health status. For healthy adults, the recommendation is about 0.8 grams per kilogram of body weight. Children, pregnant/breastfeeding women, athletes, and older adults may have elevated needs. Examples of how to meet daily protein goals through both animal and plant-based diets are provided, demonstrating that about 64 grams of protein can be achieved with thoughtful meal planning.

The optimal amount of protein is still under research. Certain individuals, such as those with malnutrition, trauma, burn injuries, or conditions impacting nutrient absorption, are at risk for protein deficiency and may need more protein. Generally, there is no health risk associated with high protein intake, except in specific cases like kidney disease, as the body can process it effectively. Everyone can meet their protein needs through a varied diet, regardless of dietary preference.