Protein
Protein is a crucial dietary nutrient essential for numerous functions within the human body. Composed of amino acids linked by peptide bonds, proteins serve as the building blocks for tissues, muscles, and organs, playing a vital role in growth, maintenance, and cellular functions. There are twenty-two different amino acids, of which the body can synthesize fourteen, while the remaining eight must be obtained through dietary sources. Proteins are categorized as complete or incomplete based on their amino acid content; animal sources generally provide complete proteins, while many plant sources offer incomplete proteins.
A balanced diet, rich in diverse foods, can help individuals meet their protein needs—omnivores typically have an easier time achieving this compared to vegetarians, who can obtain sufficient essential amino acids by consuming various plant proteins. While protein deficiency is rare in developed nations, it can lead to serious health issues, especially in regions with limited access to food. Conversely, excessive protein intake may pose health risks, including impacts on cholesterol levels, kidney function, and bone health. Additionally, proteins can be linked to food allergies, affecting many individuals. Recent studies suggest a nuanced relationship between protein consumption and fertility, indicating that plant-based proteins may be more beneficial than those from animal sources.
Protein
- BIOLOGY
- ANATOMY OR SYSTEM AFFECTED: All
- DEFINITION: An important dietary nutrient with many essential functions in the body.
Structure and Functions
Proteins are composed of twenty-two different amino acids in various combinations, joined together in a chain. The human body can synthesize fourteen amino acids, known as inessential amino acids, whereas the other eight, known as essential amino acids, must be provided by the diet.
Proteins from dietary sources are considered complete or incomplete based on their amino acid content. Complete proteins provide all eight essential amino acids, whereas incomplete proteins have low amounts of, or are missing, at least one essential amino acid. Only fish, meat, poultry, eggs, cheese, and other foods from animal sources contain complete proteins. Peanuts, soy, nuts, seeds, green peas, legumes, and some grains provide the richest plant proteins. Omnivores typically eat a sufficient variety of foods to consume adequate essential amino acids. Vegetarians ensure sufficient amino acid intake by consuming a variety of plant proteins.
Every cell in the body contains protein. Proteins are essential for cell structure and function and comprise major components of skin, tissues, muscles, and internal organs. Dietary protein, one of three types of nutrients used for energy, is required for the building, maintenance, and repair of body tissue. Growth and development during childhood, adolescence, and pregnancy depend on proteins. Proteins participate in all cellular functions, such as acting as enzyme catalysts and transport and storage molecules. They also provide mechanical support and immune protection, generate movement, transmit nerve impulses, and control growth and differentiation. Important classes of proteins include enzymes, hormones, and antibodies.
Disorders and Diseases
Protein deficiency is relatively rare in developed countries, although poverty can prevent adequate protein consumption. Protein deficiency can result from stringent weight loss diets or in older adults. Severe protein deficiency is fatal. In developing countries, protein deficiency causes the disease known as kwashiorkor, which includes symptoms such as apathy, diarrhea, inactivity, failure to grow, fatty liver, and edema. Since the body cannot store protein, too much protein can also be harmful, with a high-protein diet potentially leading to high cholesterol or other diseases and possible effects on kidney function. Excess protein may also result in immune system hyperactivity, liver dysfunction, bone loss, and obesity. As high-protein, low-carbohydrate diets became increasingly popular in the twenty-first century, these issues came to the forefront of public discourse. Proteins contribute to food allergies, with many people allergic to proteins in milk (casein), wheat (gluten), or proteins found in peanuts, shellfish, or other seafood.
Perspective and Prospects
A nutritionally balanced diet provides adequate protein. The average diet in the United States includes nearly twice the amount of protein required to maintain a healthy body. Although it was once believed that vegetarians needed to combine proteins by consuming all amino acids in the same meal, it is realized that the benefits of protein combining can be achieved over a longer period of time. In May 2013, the New York University Fertility Center published a study showing that women undergoing fertility treatment increased their chances of conception by increasing the amount of protein in their diets. However, a 2019 study by the Harvard School of Public Health found that excess animal protein could interfere with ovulation, affecting fertility. Women who ate a diet rich in plant proteins, however, had increased fertility.
Bibliography
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"High Protein Foods Boost Cardiovascular Health, as Much as Quitting Smoking or Getting Exercise." ScienceDaily, 17 Aug. 2015, www.sciencedaily.com/releases/2015/08/150827083651.htm. Accessed 17 Oct. 2024.
Łakoma, Klaudia, et al. "The Influence of Metabolic Factors and Diet on Fertility." Nutrients, vol. 15, no. 5, p. 1180, doi:10.3390/nu15051180. Accessed 17 Oct. 2024.
Manetti, Stefania. "Protein in Diet." MedlinePlus, NIH National Library of Medicine, 13 Apr. 2023, medlineplus.gov/ency/article/002467.htm. Accessed 17 Oct. 2024.
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