Protein for human being

Protein

Proteins are complex, organic compounds composed of many amino acids linked together through peptide bonds and cross-linked between chains by sulfhydryl bonds, hydrogen bonds and van der Waals forces. There is a greater diversity of chemical composition in proteins than in any other group of biologically active compounds.

There are nine essential amino acids which humans must obtain from their diet in order to prevent protein-energy malnutrition. They are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.[2][4] There are five dispensable amino acids which humans are able to synthesize in the body. These five are alanine, aspartic acid, asparagine, glutamic acid and serine.[2] 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.[2]These six are arginine, cysteine, glycine, glutamine, proline and tyrosine.[2]

Proteins functionality in human body

Proteins are essential nutrients for the human body.[1] They are one of the building blocks of body tissue, and can also serve as a fuel source. As a fuel, proteins contain 4 kcal per gram, just like carbohydrates and unlike lipids, which contain 9 kcal per gram. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition.[2]

Protein is a nutrient needed by the human body for growth and maintenance.[1] Aside from water, proteins are the most abundant kind of molecules in the body. Protein can be found in all cells of the body and is the major structural component of all cells in the body, especially muscle.[1][6] This also includes body organs, hair and skin. Proteins are also used in membranes, such as glycoproteins. When broken down into amino acids, they are used as precursors to nucleic acid, co-enzymes, hormones, immune response, cellular repair, and other molecules essential for life.[6]Additionally, protein is needed to form blood cells.[1][7]

Humans need the essential amino acids in certain ratios. Some protein sources contain amino acids in a more or less 'complete' sense. This has given rise to various ranking systems for protein sources, as described in the article.

Protein digestion and metabolism

Ingested proteins are first split into smaller fragments by pepsin in the stomach or by trypsin or chymotrypsin from the pancreas. These peptides are then further reduced by the action of carboxypeptidase which hydrolyzes off one amino acid at a time beginning at the free carboxyl end of the molecule or by aminopeptidase which splits off one amino acid at a time beginning at the free amino end of the polypeptide chain. The free amino acids released into the digestive system are then absorbed through the walls of the gastro intestinal tract into the blood stream where they are then resynthesized into new tissue proteins or are catabolyzed for energy or for fragments for further tissue metabolism.

Newborns of mammals(including human baby) are exceptional in protein digestion and assimilation in that they can absorb intact proteins at the small intestine.

Protein Quality

The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition.[2] There are multiple systems which rate proteins by their usefulness to an organism based on their relative percentage of amino acids and, in some systems, the digestibility of the protein source. They include biological value, net protein utilization, and PDCAAS (Protein Digestibility Corrected Amino Acids Score). Also see complete protein, nitrogen balance and protein combining. The PDCAAS was developed by the FDA as an improvement over the Protein efficiency ratio (PER) method. The PDCAAS rating is a fairly recent evaluation method; it was adopted by the US Food and Drug Administration (FDA) and the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO) in 1993 as "the preferred 'best'" method to determine protein quality. These organizations have suggested that other methods for evaluating the quality of protein are inferior.[13]

Dietary requirement

The amount of protein required in a person's diet is determined in large part by overall energy intake, the body's need for nitrogen and essential amino acids, body weight and composition, rate of growth in the individual, physical activity level, individual's energy and carbohydrate intake, as well as the presence of illness or injury.[3][12][20] Physical activity and exertion as well as enhanced muscular mass increase the need for protein. Requirements are also greater during childhood for growth and development, during pregnancy or when breast-feeding in order to nourish a baby, or when the body needs to recover from malnutrition or trauma or after an operation.[21]

According to US & Canadian Dietary Reference Intake guidelines, women aged 19–70 need to consume 46 grams of protein per day, while men aged 19–70 need to consume 56 grams of protein per day to avoid a deficiency.[22] The generally accepted daily protein dietary allowance, measured as intake per kilogram of body weight, is 0.8 g/kg.[18]. This requirement is for a normal sedentary person.[20]

active people and athletes may require elevated protein intake (compared to 0.8 g/kg) due to increase in muscle mass and sweat losses, as well as need for body repair and energy source.[18][19][20]

Protein deficiency

If not enough energy is taken in through diet, as in the process of starvation, the body will use protein from the muscle mass to meet its energy needs, leading to muscle wasting over time. If the individual does not consume adequate protein in nutrition, then muscle will also waste as more vital cellular processes (e.g. respiration enzymes, blood cells) recycle muscle protein for their own requirements.

Although protein energy malnutrition is more common in low-income countries, children from higher-income countries are also affected, including children from large urban areas in low socioeconomic neighbourhoods. This may also occur in children with chronic diseases, and children who are institutionalized or hospitalised for a different diagnosis. Risk factors include a primary diagnosis of intellectual disability, cystic fibrosis, malignancy, cardiovascular disease, end stage renal disease, oncologic disease, genetic disease, neurological disease, multiple diagnoses, or prolonged hospitalization. In these conditions, the challenging nutritional management may get overlooked and underestimated, resulting in an impairment of the chances for recovery and the worsening of the situation.[16]

PEM(Protein Energy Malnutrition) is fairly common worldwide in both children and adults and accounts for 6 million deaths annually.[2] In the industrialised world, PEM is predominantly seen in hospitals, is associated with disease, or is often found in the elderly.[2]

Excess consumption

The body is unable to store excess protein.[20][25] Protein is digested into amino acids, which enter the bloodstream. Excess amino acids are converted to other usable molecules by the liver in a process called deamination. Deamination converts nitrogen from the amino acid into ammonia, which is converted by the liver into urea in the urea cycle. Excretion of urea is performed by the kidneys. These organs can normally cope with any extra workload, but, if kidney disease occurs, a decrease in protein will often be prescribed.[26] When there is excess protein intake, amino acids can be converted to glucose or ketones, in addition to being oxidized for fuel.[27]

Sources

Animal sources of protein include meats, dairy products, fish and eggs. Vegan sources of protein include whole grains, pulses, legumes, soy, and nuts. Vegetarians and vegans can get enough essential amino acids by eating a variety of plant proteins.[5]

Meat, products from milk, eggs, soy, and fish are sources of complete protein

A good source of protein is often a combination of various foods, because different foods are rich in different amino acids.

Healthy people eating a balanced diet rarely need protein supplements.[5][8] Except for a few amino acids, most are readily available in human diet. The limiting amino acids are lysine, threonine, tryptophan and sulfur-containing amino acids.[10]

Comparative study of Protein supplements available in market

Nutrilite protein supplement

This all-vegetarian base, derived from soy, wheat, and yellow peas, provides balanced amounts of the nine essential amino acids. So, It provides complete protein. Moreover, With Protein Digestibility Corrected Amino Acids Score (PDCAAS) of 1, 100% absorption, it can help the cell metabolisms and repairment.

Complete Protein

Each scoop of Nutrilite Protein Powder contains 25 to 26 grams of protein, or around 67 percent of every serving's 150 calories. The mix obtains its protein from whey protein isolate and whey protein concentrate and is considered a complete protein source because it supplies all of the amino acids required by the body. People who are lactose-intolerant may experience side effects due to the lactose in the milk-based whey.

Red Orange Complex

Nutrilite Protein Powder has 50 milligrams of Red Orange Complex per scoop. Developed by Bionap, Red Orange Complex consists of the powdered extract of three varieties of Italian blood oranges, Moro, Sanguinello and Tarocco. The compound is rich in phytochemicals such as flavanones, anthocyanins and hydroxycinnamic acids that may inhibit the activity of free radicals naturally produced during exercise. A study published in Nutrition Research in 2009 demonstrated that athletes experienced less free radical damage when taking Red Orange Complex.

Appendix

Net Protein Utilisation

The net protein utilization, or NPU, is the ratio of amino acid converted to proteins to the ratio of amino acids supplied.

Experimentally, this value can be determined by determining dietary protein intake and then measuring nitrogen excretion. One formula for NPU is:NPU = ((0.16 × (24 hour protein intake in grams)) - ((24 hour urinary urea nitrogen) + 2) - (0.1 × (ideal body weight in kilograms))) / (0.16 × (24 hour protein intake in grams))

As a value, NPU can range from 1 to 0, with a value of 1 indicating 100% utilization of dietary nitrogen as protein and a value of 0 an indication that none of the nitrogen supplied was converted to protein.

Certain foodstuffs, such as eggs or milk, rate as 1 on an NPU chart.

Complete protein

A complete protein (or whole protein) is a source of protein that contains an adequate proportion of all nine of the essential amino acids necessary for the dietary needs of humans or other animals.[1]

Generally, proteins derived from animal foods (meats, fish, poultry, milk, eggs) are complete.[1] Proteins derived from plant foods (legumes, seeds, grains, and vegetables) can be complete as well (examples include chickpeas,[10] black beans,[11] pumpkin seeds,[12] cashews,[13] cauliflower,[14] quinoa,[15] pistachios,[16] turnip greens,[17] black-eyed peas,[18] Kasha, and soy[19]).

Protein Digestibility Corrected Amino Acid Score

Protein digestibility-corrected amino acid score (PDCAAS) is a method of evaluating the protein quality based on both the amino acid requirements of humans and their ability to digest it. The PDCAAS rating was adopted by the US Food and Drug Administration (FDA) and the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO) in 1993 as "the preferred 'best'" method to determine protein quality. A PDCAAS value of 1 is the highest, and 0 the lowest.

The table shows the ratings of selected foods.[2][3][4][5]

1.00 casein (milk protein)

1.00 egg white

1.00 soy protein

1.00 whey (milk protein)

0.99 mycoprotein

0.92 beef

0.78 chickpeas

0.76 fruits

0.75 black beans

0.73 vegetables

0.70 Other legumes/daal