Proteins and their value in human nutrition The

Proteins and their value in human nutrition. The role of essential amino acids in human body Performed by: Imangali Maira

Content: 1. Proteins: • a)Etymology • b)Classification by: • Biological functions, and Nutritional Basis. • c)Sources • d)Importance 2. Amino Acids classified as:

Proteins: • Proteins are large, complex molecules that have many critical roles in the body. They are composed of amino acids and bound together by peptide bonds • • • It’s name was derived from the Greek word “Proteios” which means “Primary” or “Holding the First Place”. Proteins are used in many different ways throughout the body: part of DNA part of haemoglobin creating neurotransmitters creating antibodies in blood part of keratin in hair and nails creating enzymes throughout the body In the gastrointestinal tract proteins undergo hydrolysis via proteolytic enzymes resulting in amino acids.

Amino acids • • Amino acids are classified as: Essential: cannot be made by the body, and must be supplied by the diet. Non-essential: are made by the body from essential amino acids or in the normal breakdown of proteins. Complete proteins: usually of animal origin, contain all essential amino acids (which the body cannot synthesise itself). • Incomplete proteins: mostly of plant origin, they are deficient in one or more of the essential amino acids. The capacity of proteins is called their supplementary value. • Food sources from animals (meat, fish, eggs, dairy) usually score highly on the amino acid profile and are subsequently regarded as “high-quality proteins”. Some vegetables are good sources of protein, such as beans, peas, lentils, and seaweed. For vegetarians and vegans, the most complete protein comes from soya beans.

The body needs eight "essential" different amino acids throughout all stages of life. They are: • • Two of the essential amino Tryptophan acids, lysine and tryptophan, Methionine are poorly represented in most plant proteins. Thus Valine strict vegetarians should take Threonine special pains to ensure that their diet contains sufficient Phenylalanine amounts of these two amino Leucine acids. For infants, a ninth "essential" amino acid is also needed: histidine. Isoleucine Essential amino acids cannot be stored in the body so they must be supplied in the diet. These are "essential" amino acid Lysine requirements. Recommended amino acid requirements will include a lot more than the essential 8 or 9 compounds (up to around 20).

Classification of proteins Proteins are used as plastic material For the construction of different Tissues and cells.

Protein Composition • Protein Composition - basically, all proteins contain carbon, hydrogen, oxygen, and nitrogen. • • • Carbon: 48. 2% Hydrogen: 7. 8% Oxygen: 24% Nitrogen: 16% Sulfur: 4%

Proteins are needed in the body for: • 1. Body growth and repair: building and maintenance muscles and other soft tissues 2. Regulation: proteins and amino acids are or are part of compounds that regulate or modulate the processes in the body, such as enzymes, hormones, antibodies and neurotransmitters. 3. Energy: to burn as fuel (i. e. to provide a source of energy). Proteins are found in all active tissues of the body (e. g. muscle cells, the liver, glands, etc). Though one gram of protein can yield 4 calories, the most important functions of the protein are tissue building, and repair and provision of the ingredients for the formation of enzymes, hormones and antibodies.

Protein use depends on the following: • The all or none rule An appropriate amount of all necessary amino acids must be present to make a particular protein, or the protein will not be made. Any essential amino acids not used to make proteins will soon be oxidised for energy, or converted to produce carbohydrates or fats.

• Calorie intake adequacy If a diet doesn't contain adequate carbohydrates or fats for calories in energy production as ATP, tissue proteins are then used for energy. (NB: ATP is a chemical involved in the process of storage and release of energy, allowing work and movement to occur in the body).

• Body nitrogen balance In healthy adults, the rate at which proteins are synthesised should be the same as the rate at which they are being broken down in the body. This balance is reflected by the nitrogen balance in the body based on the fact that all protein average approximately 16% nitrogen. The body is considered in balance when the amount of nitrogen ingested in protein is equal to the amount excreted in urine. Under physical or emotional stress, the protein breakdown can be affected and exceed by the amount of protein being synthesised: this is called a "negative nitrogen balance".

• Hormone activity Anabolic hormones can cause acceleration of protein synthesis and growth. The effect of these hormones may continuously change (affected by things such as age, stress, growth rate etc), hence growth rates and protein synthesis rates can be continuously changing.

RECOMMENDED PROTEIN INTAKE • As a general guide: approximately 0. 8 -1 g per kilogram of body weight per day. • Typically a small serve of fish and an egg would be adequate for an average person, per day. • Protein needs vary much among different people, depending on their metabolism, physical activity and health conditions. • A sports person will need to rebuild muscles more often that a sedentary one. They will also have higher metabolic rates. So their protein consumption will need to adapt to higher requirements, and can be as high as 1. 2 -1. 4 g of protein per kg of body weight. • People with kidney stones will have to be careful about their nitrogen intake, as in concentrated proteins sources, as a high intake will tend to stress the kidney in an attempt to increase urea elimination. According to theories behind Metabolic Typing, some people may require more proteins in their diet, as much as 55%, and others may require less protein and more carbohydrates, as much as 70%. This is due to genetic differences in the way biochemistry cycles occur in our bodies, if people are fast or slow oxidisers.

• Proteins sources are very varied, they can be supplied with plant or animal sources, and both of them lead to good health provided the essential amino acids are supplied an adequate total quantity of protein is ingested. Too much protein is as bad too little. Moderation is the key. Too many proteins can lead to blood p. H unbalances, which will put stress on other bodily systems in order to equilibrate the p. H. Also, protein degradation will produce residues that will need to be eliminated from the body. Animal sources of proteins are animal meats, poultry, fish, dairy and eggs. Plant sources of proteins include seeds, nuts and beans, grains, leafy greens, other vegetables and fruits.

• GRAIN Grains are a good source of protein, complex carbohydrates, fibre and many different minerals and vitamins. Different grains have different food values. Typically they consist of 65 -75% carbohydrates (sugars and starches), 7 to 12 % proteins, 2 to 6% lipids and the rest is water. Whole grains are generally better nutritionally than processed grains, particularly with respect to dietary fibre, minerals and vitamins. Grains are a staple component of many diets in many cultures around the world, including Western countries. They are a basic component of daily protein intake in Western and Asian vegetarian and vegan diets, together with beans, nuts and seeds.

Requirement • • The recommended daily allowance of protein for: Adult females is 46 g/day (more in children, pregnant and lactating women) Adult males is 56 g/day Approximately 10 -35% of daily caloric intake should be protein.

Excess • The human body is unable to store extra protein. An upper limit of safe protein intake has not yet been established but an intake of more than 2 g/kg body weight leads to increased levels of nitrogenous substances, increased glomerular filtration and changes in liver function.

Deficiency Protein deficiency is a state of malnutrition in which an insufficient amount of protein is taken in for the body to utilize in order to produce energy. This condition is largely responsible for the high incidence of starvation and disease in many developing countries. However, protein deficiency also occurs in developed countries, primarily due to poverty. Certain individuals may also become prone to protein deficiency, such as crash dieters and vegetarians who neglect to properly balance their diet. Symptoms of protein deficiency include: • weight loss • diarrhoea • oedema • hair loss, scaly skin, and lethargy

Conclusion • Protein deficiency in the diet reduces the body's resistance to infections, so it reduces the level of antibody formation. Disturbed synthesis and other protective factors - lysozyme and interferon. • Reduction of protein intake, or increase its flow in the body (with heavy physical work or due to illness) is a protein deficiency. Severe form of protein deficiency called kwashiorkor. This disease often occurs in children. In Russia, kwashiorkor is not observed, but the disease often occurs in developing countries in Asia, Africa, Central and South America. • Uncompensated protein in the body adversely affects the cardiovascular, respiratory and other systems. Lack of protein affects the appetite, which in turn reduces the influx of protein intake - a vicious circle.

Mnemonics • Using the one-letter designation shown above, mnemonic devices have been developed for use in memorizing the essential amino acids. Previous devices have utilized the first letter of the amino acids' names, and in general did not include arginine which is not always essential. Mnemonic devices in common use are PVT TIM Ha. LL[12] and TT HALL V(ery) IMP(ortant). [13] • Alternative mnemonics based on the amino acids' assigned single letters include LIFT HIM KIW(V)I and TV FILM HW(R)K. • Another method uses the first letter of each essential amino acid to begin each word in a phrase, such as: "Any Help In Learning These Little Molecules Proves Truly Valuable. "[14] This method begins with the two amino acids that need some qualifications as to their requirements.

Bibliography • Ballentine, R. (2010). Diet & Nutrition: A Holistic Approach. New Delhi: Himalayan Institute Press. • Insel, P. (2013). Discovering Nutrition. United States of America: Jones & Bartlett Publishers. • Nicoteri, L. (2013). Nutrition. United States of America: Jones & Bartlett Learning. • Shike, M. (2009). Modern Nutrition in Health and Disease. Canada: Lippincott Williams & Wilkins. • BENCKO, Vladimir, et al. Hygiene and epidemiology : selected chapters. 2. edition. Prague