Wednesday, April 16, 2014

Therapeutic food proteins

Proteins are most abundant nitrogen containing organic substances of living organisms. They form enzymes, hormones, antibodies, transport and informational biological molecules. They are the principal structural (“brick and mortar” roles) and metabolically active compounds (“working horse” roles) found in the human body. They are the “beginners and builders of biochemical reactions.”  If carbohydrates and lipids are considered as the fuels of metabolic furnace, proteins can be regarded as forming not only the structural framework but also the gears and levers of the operating machinery.  Proteins constitute 50% of the cellular dry weight and some 17% by weight of the total lean body tissue.  The Food and Nutrition Board allows up to 35% of total calorie intake to be supplied by dietary proteins.The protein requirement of an individual is based on age, size and activity level.   Each gram of protein and carbohydrate provides 4 calories.Proteins not only provide energy but also build muscles and repair body tissues. The body stores leftover proteins as body fat.
 Five of the elements, carbon, hydrogen, oxygen, nitrogen and sulphur are found in all naturally occurring proteins. Other elements such as phosphorus, iron, iodine and magnesium are essential constituents of certain special proteins. Proteins are biopolymers made up of 20 different amino acids, and these 20 amino acids are the building blocks of different protein molecules. Nine of the amino acids are called essential because human bodies cannot synthesize them. The essential amino acids must be obtained only through diet. Amino acids are considered as the “currency” of protein nutrition and metabolism (Young, 2001). Often 300 or more amino acids found per protein molecule.

 Human protein nutrition

Proteins in human diet are derived from two main sources, namely animal proteins (e.g., egg, milk, meat and fish) and plant proteins (e.g., pulses, cereals, nuts, beans and soy products. Foods that provide all the essential amino acids are biologically complete proteins or high quality proteins. The high quality proteins can be obtained from meat, fish, poultry, eggs and dairy products. Foods that do not provide a good balance of all the essential amino acids are called biologically incomplete proteins or lower quality proteins. Plant foods contain incomplete proteins with regards to their amino acid composition. Most fruits and vegetables are poor sources of proteins. Some plant foods like beans, peas, and lentils, peanuts and other nuts, seeds and grains like wheat are better protein sources. A diet with incomplete proteins can be converted in to a complete protein diet, if two incomplete proteins (e.g., grains or legumes and nuts mixed together) are added together to produce what is called “complementarity of proteins.”

Protein - energy malnutrition (PEM)

The term Protein – energy malnutrition (PEM) is referred to as protein – calorie malnutrition and a fatal body – depletion disorder.  It develops in children and adults whose consumption of protein and energy is insufficient to satisfy the body’s nutritional needs. PEM applies to a group of related disorders that include marasmus (sickness of withering or wasting), kwashiorkor (protein malnutrition) and intermediate states of marasmus-kwashiorkor (protein deficiency). The effects of PEM leads to tissue damage, growth arrest and brain damage. Protein – energy malnutrition (PEM) is common on a worldwide basis in both children and adults (Stephenson et al 2000) causing the death of 6 million children a year (FAO 2000). In 2000, the WHO estimated that malnourished children numbered 181.9 million (32%) in developing countries. In India 70-80 million children under 5 years suffer from PEM and 4 million from severe forms of PEM. Protein deficiency affects all organs including the developing brain (Pollitt 2000), as well as the immune system (Bistrian1990) and gut mucosal function (Reynolds et al 1996). A serious depletion in the body mass protein can be life threatening with muscle loss, including loss of heart muscle (Hansen et al 2000).

Plant food proteins

Grain legume proteins
The seeds of legumes are rich in high quality protein and highly nutritious food resource.  Proteins in legume seeds represent from about 20% (dry weight) in peas and beans up to 38 – 40% in soybean and lupin.  Lupins are non-starch leguminous seeds with similar protein content to soybean at about 40% and high fibre content. The most abundant class of storage proteins in grain legumes are the globulins. The major staple foods such as beans, soybean, lentils, peas and chickpeas are all legumes. Legume seeds contain a number of antinutritional compounds (ANCs) which can be proteinous. The frequent intake of legumes can help control the lipid homeostasis and reduce the risk of cardiovascular disease (CVD). High fibre content, low glycaemic index and the presence of minor components such as Phytosterols, saponins, and oligosaccharides are claimed to control type II diabetes and digestive tract diseases.
Soybean proteins –Dry soybean contains approximately 35% protein, most of which is globulin, a storage protein. The major components of soy-globulin are glycinin and β glycinin both of which constitute about 80% of the storage protein. The nutritional value of soybean protein is one of the highest of vegetable proteins. The β glycinin has shown to lower serum triglyceride levels in human beings. Soybean also contains the biologically active protein components hemagglutinin, trypsin inhibitors, α amylase and lipoxygenase. A number of  studies indicate  the antidiabetic and antiobesity activities of soybean proteins. Soybean lectins have anticarcinogenic activity.
Cereal proteins
Wheat is the single most important food crop in the world. Wheat contains 8 – 15% protein depending on grain variety. The main storage proteins in wheat grains are the gluten proteins.  The protein content of maize is between 9 – 12%. Barley is the fourth most important cereal crop in the world after wheat, rice and corn. Barley constitutes 10 – 17% protein, slightly higher than other cereal grains such as wheat and rice. Rice is the second largest cereal crop in the world. Rice has the lowest protein content of all major cereals at 7 – 9% by weight. Sorghum is the fifth most widely grown cereal crop in the total world production (FAO 2009). Sorghum contains about 9 – 17% protein and is an underutilized food resource for human consumption.
Proteins from tuber and nuts
Potato is a versatile carbohydrate – rich food with a low overall protein content of 1 – 1.5% of tuber fresh weight. The potatoes provide complex carbohydrates, fibres, proteins, vitamins A, C and B complex and minerals such as copper, iron, magnesium and potassium. The juice of potatoes is excellent to cure gastritis and stomach ulcers.
Nuts are rich in energy and nutrients. They contain proteins, omega 3- fatty acids and dietary fibres. They also contain monounsaturated fatty acids (MUFA) such as oleic and palmitoleic acids which help to lower LDL or ‘bad cholesterol’ and increase HDL or ‘good cholesterol’. Nuts are the important sources of polyphenolic flavonoids antioxidants such as carotenes, resveratrol, lutein, cryptoxanthin etc. These compounds have been found to offer protection against cancers, heart diseases, degenerative nerve diseases and viral/ fungal diseases.

Animal  food proteins

Milk proteins
Milk is made of two proteins, casein and whey. Casein protein constitutes 80% and whey protein 20% of milk protein. Human breast milk is 80% whey protein. Milk for human consumption can generally be obtained from a number of domesticated animals such as sheep, goat, buffalo and cow. Fresh cow milk contains approximately 3.5 % protein, 80% casein, 15% whey protein as well as vitamins and lipids, all of which provide necessary ingredients of growth. Casein protein is recognized for its excellent amino acid content, slow digestion and anti-catabolic effect.
Bovine Whey   proteins
 Whey protein can be separated from the casein in milk or formed as a by-product of cheese making. There are 3 primary types of whey proteins: whey protein concentrate (WPC), whey protein isolate (WPI) and whey protein hydrolysate (WPH). Whey protein is considered as a nutritionally perfect protein with high biological value (BV), high protein efficiency ratio (PER) and high net protein utilization (NPV).Whey protein includes a mixture of globular proteins (lactoferrin, beta-lactoglobulin, alpha lactalbumin, bovine serum albumin and immunoglobulins), all essential amino acids and low lactose content. Whey protein has the ability to act as an antioxidant, antihypertensive, antitumor, hypolepidemic, antimicrobial and chelating agent. A number of clinical trials successfully revealed the therapeutic effects in cancer, HIV, hepatitis B, cardiovascular disease and osteoporosis. The higher glutathione levels in whey proteins have important immune, antioxidant and detoxification benefits (Report of International Whey Conference, Oct 1997).
Bovine colostrum
Colostrum is nature’s most nutrient dense zoonutrient. A mother animal produces true colostrum for only the 24 hours after giving birth. It is a non-milk immune supporting fluid. It is rich in highly bioavailable vitamins and minerals. Colostrum yield as high 40% immunoglobulins and immuno-modulatory  proline – rich polypeptides (PRPs).  It can help preventing anaemia, arthritis, multiple sclerosis and Alzheimer’s disease.Colostrum has growth factors that promote healing and anti-aging reponses.
Egg proteins
Eggs generally weigh about 57 grams.  The yolk proteins of an egg makes up about 34% of the liquid weight and the albumen accounts for about 66% of the egg’s liquid weight. A large  egg provides a total of 6.29 grams of high quality complete protein. The yolk portion provides 55 calories and the egg white contributes 17 calories. About 9% of the egg content is fat and is found in yolk.  Egg yolk carries the cholesterol, the fat and the saturated fat. The egg white contains bulk of proteins, folic acid, choline and minerals. The egg protein is a rich source of the essential amino acid leucine, which is important in modulating the use of glucose by the skeletal muscles. The egg is an excellent source of iodine for thyroid hormone synthesis, phosphorus for bone health, zinc for growth and wound healing and selenium for anti-cancer activity. The egg cholesterol is useful for the production of sex hormones, cortisol, vitamin D and bile salts.
Fish proteins
Fish is low in total fat, high in protein and rich in vitamins and minerals.  The protein content of most fish averages 15 to 20%. In addition to proteins and essential amino acids, fish contains significant amounts of lipids, vitamins and minerals.   Fish meat is a valuable source of calcium and phosphorus as well as iron, copper and selenium. Salt water fish have a high content of iodine. Both  fresh water fish of cold waters and  salt water fish contain significant levels of two  omega-3 fatty acids (N-3 fatty acids) such as EPA (eicosapentaenic acid) and DHA (docosahexaenoic acid). Some good choices of fish include salmon, trout, sardines, herring, mackerel, tuna and oysters. Fish oil is the best source of N-3 fatty acids which help reduce platelet activity (blood clotting) and plaque formation (atheroscelerosis) leads to heart attacks. The fish nutrients keep our heart and brain healthy. The USDA’s My Plate says that eating seafood (fish and shellfish) twice a week is good for our heart, brain and entire body.
Meat proteins

Foods in the meat, poultry and fish group are diverse, but all of them are rich in proteins. The amount and quality of protein in the foods varies. Animal meats like beef, pork and ham contain high quality proteins with all the amino acids. Besides proteins, these animal foods contain varying amounts of minerals such as iron, zinc and magnesium and vitamins E and B (thiamine, niacin, vitamins B6 and B12). The bad aspect of these foods is having substantial amounts of fat, saturated fat and cholesterol. Eating lean cuts of protein rich meats can help reduce the risk of cardiovascular disease and diabetes. Vitamins B6 and B12 help improve memory. Both niacin and zinc help protect against vision problems.

Food for thought

The American Health Association (AHA) strongly advised the people to follow a diet that contain a variety of foods from all the food categories and emphasized the consumption of fruits and vegetables, fat – free and low fat dairy products, cereal and grain products, legumes and nuts, fish, poultry and lean meats. Choose healthier sources of dietary proteins.

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