Protein Type, Source, Function and Health Effect Short Notes

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. 

Proteins contain 4 kcal per gram, just like carbohydrates and unlike lipids, which contain 9 kcal per gram. 

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 synthesis of the essential amino acids that cannot be biosynthesized by the body.

There are three type of amino acid-

1- Essential Amino Acid

2- Dispensable Amino Acid

3- Conditionally Essential Amino Acids 

Essential Amino Acid 

Essential amino acids are amino acid which humans must obtain from their diet in order to prevent protein-energy malnutrition. 

There are 9 type of essential amino acid such as phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.  

Dispensable Amino Acid are amino acid which humans are able to synthesize in the body. 

There are five dispensable amino acids, such as alanine, aspartic acid, asparagine, glutamic acid andserine.

Conditionally Essential Amino Acids 

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. 

There are six conditionally essential amino acids These six are arginine, cysteine, glycine, glutamine, proline and tyrosine. 

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.

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. 

It is commonly believed that athletes should consume a higher-than-normal protein intake to maintain optimal physical performance. 

Protein is a nutrient needed by the human body for growth and maintenance.  

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. 

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. 

Additionally, protein is needed to form blood cells. 

Protein can be found in a wide range of food.

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

Whole grains and cereals are another source of proteins. 

However, these tend to be limiting in the amino acid lysine or threonine, which are available in other vegetarian sources and meats. 

Vegetarian sources of proteins include legumes, nuts, seeds and fruits. 

Legumes, some of which are called pulses in certain parts of the world, have higher concentrations of amino acids and are more complete sources of protein than whole grains and cereals.

Examples of vegetarian foods with protein concentrations greater than 7 percent include soybeans, lentils, kidney beans, white beans, mung beans, chickpeas, cowpeas, lima beans, pigeon peas, lupines, wing beans, almonds,

Whey protein is a mixture of globular proteins isolated from whey, the liquid material created as a by-product of cheese production.

Whey protein is commonly marketed and ingested as a dietary supplement, and various health claims have been attributed to it in the alternative medicine community.  

Although whey proteins are responsible for some milk allergies, the major allergens in milk are the caseins. 

Whey is left over when milk is coagulated during the process of cheese production, and contains everything that is soluble from milk after the pH is dropped to 4.6 during the coagulation process. 

 It is a 5% solution of lactose in water, with some minerals and lactalbumin.  

The fat is removed and then processed for human foods.

Processing can be done by simple drying, or the protein content can be increased by removing lipids and other non-protein materials. 

Whey protein is the collection of globular proteins isolated from whey. 

The protein in cow’s milk is 20% whey protein and 80% casein protein, whereas the protein in human milk is 60% whey and 40% casein.

The protein fraction in whey constitutes approximately 10% of the total dry solids in whey. 

This protein is typically a mixture of beta-lactoglobulin (~65%), alpha-lactalbumin (~25%), bovine serum albumin (~8%), and immunoglobulins.

These are soluble in their native forms, independent of pH.

The amino acid cysteine in whey protein is a substrate for the synthesis of glutathione in the body which is an ubiquitous cellular antioxidant; laboratory experiments have suggested that whey protein and its components might reduce the risk of cancer in animals, suggesting an avenue for future medical research. 

Whey protein typically comes in four major forms:   

• Concentrate (WPC)

• Isolate (WPI), 

• Hydrolysate (WPH)

• Native Whey.

Concentrates have typically a low level of fat and cholesterol but, in general, compared to the other forms of whey protein, have higher levels of bioactive compounds, and carbohydrates in the form of lactose — they are 29%–89% protein by weight.

Isolates are processed to remove the fat, and lactose, but are usually lower in bio activated compounds as well — they are 90%+ protein by weight. 

Like whey protein concentrates, whey protein isolates are mild to slightly milky in taste.

Hydrolysates are whey proteins that are predigested and partially hydrolyzed for the purpose of easier metabolizing, but their cost is generally higher. 

Highly hydrolysed whey may be less allergenic than other forms of whey. 

Native whey protein the purest form of whey protein which has been extracted from skim milk and not a byproduct of cheese production, produced as a concentrate and isolate.

The use of whey protein as a source of amino acids and its effect on reducing the risks of diseases such as heart disease, cancer and diabetes. 

Whey is an abundant source of branched-chain amino acids (BCAAs), which are used to stimulate protein synthesis. 

When leucine is ingested in high amounts, such as with whey protein supplementation, there is greater stimulation of protein synthesis, which may speed recovery and adaptation to stress. 

Consumption of whey protein shortly after vigorous exercise can boost muscle hypertrophy.

Proteins high in essential amino acids (EAA), branched chain amino acids (BCAA), and particularly leucine (Leu) are associated with increased muscle protein synthesis, weight loss, body fat loss, and decreased plasma insulin and triglyceride profile.  

Whey has approximately three grams of leucine per serving and the threshold for optimal protein synthesis is three grams.