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Protein (nutrient)

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**Protein Functions and Sources:**
Protein is essential for growth, maintenance, and structural components in the human body.
– Proteins play a role in immune response, cellular repair, and blood cell formation.
– Sources of protein include plant-based foods, animal-derived foods, insects, meat, dairy, eggs, soybeans, fish, grains, legumes, nuts, seeds, vegetables, and fruits.

**Protein Quality and Evaluation:**
Amino acid composition is crucial for protein nutrition.
– Systems like biological value, net protein utilization, and PDCAAS rate proteins based on amino acid percentage and digestibility.
– PDCAAS is the preferred method for determining protein quality.
– Other methods for evaluating protein quality are considered inferior by FDA and FAO/WHO.
– Recent developments in protein quality evaluation are ongoing.

**Amino Acids and Dietary Requirements:**
– There are nine essential amino acids that humans must obtain from their diet.
– The body can synthesize five amino acids, while the rest must be obtained from the diet.
Protein intake requirements are determined by factors like energy intake, nitrogen need, and body weight.
Protein needs increase with physical activity, growth, pregnancy, and recovery from illness.
– Dietary recommendations for protein intake vary based on age, gender, and activity level.

**Health Conditions and Protein Consumption:**
– Individuals with chronic kidney disease should reduce protein consumption.
– Individuals with Phenylketonuria must keep their phenylalanine intake extremely low.
– High protein intake may impact renal function and calcium excretion.
– Dietary protein influences bone health, metabolic complications, and immune function.
Protein plays a crucial role in enzyme and hormone production and supports healthy skin, hair, nails, and muscle development.

**Protein Intake and Specific Health Aspects:**
Protein intake recommendations vary for athletes, non-diabetic adults with chronic kidney disease, and individuals with Phenylketonuria.
– Studies analyze protein conversion, nitrogen utilization, amino acid requirements, and the impact of protein on health outcomes.
Protein digestion, absorption kinetics, and metabolic advantages are essential considerations.
– Balanced protein intake may have a positive impact on blood pressure levels and weight management.
– Further research is needed to explore the relationship between dietary protein intake and specific health conditions.

Protein (nutrient) (Wikipedia)

Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue and can also serve as a fuel source. As a fuel, proteins provide as much energy density as carbohydrates: 4 kcal (17 kJ) per gram; in contrast, lipids provide 9 kcal (37 kJ) per gram. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition.

Amino acids are the building blocks of protein.
Amino acids are necessary nutrients. Present in every cell, they are also precursors to nucleic acids, co-enzymes, hormones, immune response, repair and other molecules essential for life.

Proteins are polymer chains made of amino acids linked together by peptide bonds. During human digestion, proteins are broken down in the stomach to smaller polypeptide chains via hydrochloric acid and protease actions. This is crucial for the absorption of the essential amino acids that cannot be biosynthesized by the body.

There are nine essential amino acids which humans must obtain from their diet in order to prevent protein-energy malnutrition and resulting death. They are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. There has been debate as to whether there are 8 or 9 essential amino acids. The consensus seems to lean towards 9 since histidine is not synthesized in adults. There are five amino acids which humans are able to synthesize in the body. These five are alanine, aspartic acid, asparagine, glutamic acid and serine. There are six conditionally essential amino acids whose synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress. These six are arginine, cysteine, glycine, glutamine, proline and tyrosine. Dietary sources of protein include grains, legumes, nuts, seeds, meats, dairy products, fish, eggs, edible insects, and seaweeds.

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