Last Updated : 07 July 2008
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The word protein comes from the Greek word “protos”, meaning first element. Proteins are essential elements for growth and repair, good functioning and structure of all living cells. Hormones, such as insulin, control blood sugar levels; enzymes, such as amylases, lipases, proteases are crucial for digestion of foods; antibodies help us fight infections; muscle proteins allow contraction, etc. So, indeed proteins are essential to life.
Proteins are made up of amino acids, the building blocks, linked together. There are about twenty different amino acids commonly found in plants and animals. A typical protein may contain 300 or more amino acids. Each protein has its own specific number and sequence of amino acids. Rather like the alphabet, the amino acid 'letters' can be arranged in millions of different ways to create 'words' and an entire protein 'language'. Depending on the sequence in which they are combined, the resulting protein carries out specific functions in the body. The shape of the molecule is important as it often determines the function of the protein. Each species, including humans, has its own characteristic proteins – the proteins of human muscle, for instance, are different from those of beef muscle.
Amino acids can be classified as either essential (indispensable amino acids that cannot be produced during metabolism by the body and therefore must be provided by our diet) or non-essential (dispensable amino acids that can be produced endogenously in the body from other proteins). Eight amino acids (Leucine, Isoleucine, Valine, Threonine, Methionine, Phenylalanine, Tryptophan and Lysine) are considered essential for adults and nine (those mentioned above plus Histidine) for children.
When a protein contains the essential amino acids in the right proportion required by humans, we say that it has high biological value. When the presence of one essential amino acid is insufficient, the protein is said to have low biological value. The amino acid that is in shortest supply in relation to need is termed the limiting amino acid.
The protein cycle
Proteins in our body are constantly being built and disposed of. After we eat, proteins are broken down by digestion into amino acids. Amino acids are then absorbed and used to make other proteins in the body. Adequate protein and energy intake, on a daily basis, ensures the cycle continues.
Proteins are found in different foods. All animal and plant cells contain some protein but the amount of protein present in food varies widely. It is not just the amount of protein that needs to be considered – the quality of the protein is also important and that depends on the amino acids that are present. In general, proteins from animal sources have a higher biological value than proteins from plant sources. Animal sources of protein are meat, poultry, fish, eggs, milk, cheese and yogurt, and they provide high biological value proteins. Plants, legumes, grains, nuts, seeds and vegetables provide low biological value proteins.
However, as the limiting amino acid tends to be different in different vegetable proteins, combination of vegetable sources of proteins in the same meal (e.g. legumes or pulses with cereals), can result in a mix of higher biological value. These combinations are generally found in traditional culinary recipes from the different continents (e.g. beans with rice/pasta/manioc, chick-peas with bread, lentils with potatoes, etc).
Omnivorous diets (containing foods derived from animals and plants) in the developed world provide adequate amounts of protein. However, subgroups of the population who avoid all foods of animal origin may have difficulties in meeting their protein requirements.
Protein content of a selected number of foods (g/100 g food)
Amount of protein (g per 100 g of food)
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White rice, cooked
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Rump steak, grilled
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Vegetarian diets and dietary protein supply
Vegetarian diets are based on grains, vegetables, fruits, legumes, seeds and nuts, with the elimination of meat, fish or poultry from the diet. Variations exist within vegetarian diets, where some include dairy products and eggs (e.g. lacto- ovo vegetarian diets), others include only dairy products but not eggs (e.g. lacto-vegetarian diets), while the strictest vegetarian diets include no products produced by animals (e.g. vegan diets). Vegan diets in particular, may lack the main sources of high biological value proteins and people following these diets may have difficulty meeting their protein requirements especially to support extra needs due to growth (e.g. children and pregnant women). Therefore in the case of vegetarians, vegans in particular, the combination of proteins from different vegetable sources and a balanced food choice are very important to ensure that required levels of essential amino acids are attained.
Protein energy malnutrition
Protein energy malnutrition (PEM) describes a range of disorders occurring mainly in developing countries. It mainly affects young children and is the result of both too little energy and too little protein in the diet. The two most common forms of PEM are Marasmus and Kwashiorkor.
Marasmus is a chronic condition that occurs in young children who have been weaned off breast milk on to a diet containing too little energy and protein and is characterised by muscle wasting and an absence of subcutaneous fat. Inadequate hygiene often leads to contamination of foods which causes infections, particularly gastro-intestinal infections, and a further increase in energy requirements. The parent may treat the infection by fasting the child, giving only water or other fluids of little nutritional value. As a result, the child becomes severely underweight and very weak and lethargic.
Kwashiorkor tends to occur in slightly older children who, after an extended period of breast feeding, have been weaned onto a diet mainly comprising starchy foods, which is low in energy and protein. Kwashiorkor often follows an acute infection. A child with kwashiorkor is severely underweight but this is often masked by oedema (water retention) which makes the face moon-shaped, and the arms and legs look plump. The hair is thin and discoloured, and the skin may show patches of scaliness and variable pigmentation. Medical treatment and an adequate diet, combined with good hygiene practices, are vital if children with PEM are to recover and grow properly.
Protein and chronic diseases
Scientific studies have suggested that mortality rates from cancer and cardiovascular disease (CVD) are lower in those who avoid eating meat. Results from these studies are often confounded, however, by factors such as smoking, social class and body mass index (BMI). Although a vegetarian (and in particular a vegan) diet may be higher in fibre, fruit and vegetables than an omnivorous diet, at present there is no scientific justification for eliminating lean meat from the diet. It would, however, be prudent to advise that, whether an omnivorous or vegetarian diet is chosen, the diet should be well balanced, provide a variety of different foods, and include plenty of fruit and vegetables. For those adults who eat red meat (i.e. beef, lamb and pork) and processed meat, moderate consumption is recommended. Advice on improving morbidity and mortality should focus on diet and lifestyle factors for which there is clear evidence of a beneficial effect. For example, people should be encouraged to stop smoking, to take more exercise and to maintain a healthy body weight.
In order to be able to maintain the normal protein turnover, necessary for proper growth and repair of body tissues, 10-15% of our total energy intake should come from proteins. This is about 0.75 grams of protein per kilogram of body weight per day. Two or three servings of animal protein foods or four servings of mixed vegetable-protein sources, such as whole grain cereals, vegetables, legumes, nuts and seeds can easily provide the needed protein.
Pay attention to the food labels. You rarely eat straight protein. Some protein comes packaged with saturated fat. If you eat meat, steer yourself toward the leanest cuts. If you like dairy products, skim or low-fat versions are healthier choices. Beans, soy, nuts, and whole grains offer protein without much saturated fat and with plenty of dietary fibre and micronutrients.
What are low biological protein foods? ›
LBV foods: peas, beans, nuts, lentils, cereals (rice, oats, barley, rye, millet, sorghum) and cereal products (bread, pasta), seeds and gelatine. Protein alternatives are manufactured food products, with a high protein content, e.g. mycoprotein (Quorn), tofu, TVP and tempeh. They are used instead of meat in meals.Which food has the highest biological value protein? ›
Animal Protein. Proteins from animal sources (i.e. eggs, milk, meat, fish and poultry) provide the highest quality rating of food sources. This is primarily due to the 'completeness' of proteins from these sources.What are HBV and LBV proteins? ›
(HBV) protein: protein that contains all ten essential amino acids. (LBV) protein: a protein that lacks one or more essential amino acids. complementation: combining LBV protein foods to form a HBV protein meal. Different foods contain different amounts of amino acids.What are LBV proteins and give examples? ›
Low biological value proteins are missing one or more essential amino acids. The foods that provide these are mainly foods from plants, such as peas, beans, lentils, nuts, seeds and cereals. The exception is gelatine, which is an animal-based product, and is a LBV protein.What are high biological proteins? ›
In general, animal sources, such as meat, poultry, fish, eggs, milk, cheese and yogurt, have higher biological value proteins, while plants, such as legumes, grains, nuts, seeds and vegetables, provide low biological value proteins.Are eggs HBV or LBV? ›
High Biological Value (HBV) protein: Meat, fish, poultry, eggs, Quorn, milk, soya, Quinoa Low Biological Value (LBV) protein: Tofu, beans, nuts, seeds, grains eg wheat It is needed for growth and repair, the production of body chemicals eg enzymes and hormones Is also a source of secondary energy 1g protein = 4Kcal ...What are low quality proteins? ›
A protein usually of plant origin that lacks one or more essential amino acids—e.g., corn (which is low in lysine) or beans (which are low in tryptophan).What is biological value of egg? ›
Biological Value of eggs
One large egg contains 6.3 grams of protein. The protein is almost equally split between the egg white and the egg yolk. The white contains 3.5 grams of protein while the yolk contains 2.8 grams. The protein in an egg contains all the essential amino acids used for growth and development.
Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism.What is the difference between LBV and HBV? ›
If a food is missing one or more of the indispensable amino acids, it has a low biological value (LBV). For example, baked beans have an LBV. If a food has all the indispensable amino acids, it has a high biological value (HBV).
Are kidney beans HBV? ›
Have a high biological value (HBV). Beans, peas, lentils, nuts, seeds •Lack one or more of the 8 ESSENTIAL AMINO ACIDS.
When a protein contains the essential amino acids in the right proportion required by humans, we say that it has high biological value. When the presence of one essential amino acid is insufficient, the protein is said to have low biological value.Why is gelatine low in biological value? ›
Answer: Gelatin is classified as an incomplete protein, that is, it is incapable of replacing or building new tissue and hence cannot support life.Do soybeans have a high biological value? ›
The quality of soybean protein can be compared to proteins of meat, milk, and eggs. Of the plant-based protein sources, the soybean protein is considered to have the highest biological value .What is the biological value of milk? ›
Milk is an excellent source of vitamins and minerals, including “nutrients of concern,” which are under-consumed by many populations ( 3 ). It provides potassium, B12, calcium and vitamin D, which are lacking in many diets ( 4 ). Milk is also a good source of vitamin A, magnesium, zinc and thiamine (B1).Is soy a high quality protein? ›
Soybeans are an excellent source of high quality protein, which most other legumes lack, making the soybean and its food products a superior protein source for people following a strict vegetarian diet.What are the best source of protein? ›
Animal-based foods (meat, poultry, fish, eggs, and dairy foods) tend to be good sources of complete protein, while plant-based foods (fruits, vegetables, grains, nuts, and seeds) often lack one or more essential amino acid.Are lentils a HBV protein? ›
1) Vegetarians don't eat meat, so they need to get their protein from elsewhere. 2) Beans, lentils and nuts are all good sources of protein, as are eggs. There are also alternative proteins: Soya beans are one of the few plant-based HBV protein sources.Which one is a HBV source of protein? ›
Guidelines state that half of your protein should come from “high biological value” (HBV) sources, which are almost entirely animal sources (meat, fish, poultry, egg whites, dairy).Which two plant foods are the exception to the rule and are HBV? ›
Proteins from animal sources have a higher biological value than proteins from plant sources. The exceptions to this rule are gelatine, an animal protein with low biological value (LBV), and soya, a plant protein with high biological value (HBV).
What are high and low quality proteins? ›
Complete protein sources contain all EAAs and are therefore considered 'high quality', whereas 'low quality' protein sources are incomplete proteins as they do not contain all EAAs.Is milk a high quality protein? ›
Milk proteins, such as whey and casein are considered high quality proteins and help provide a convenient source of protein. Studies using dairy protein supplements have shown greater increases in strength and lean body mass compared to all other protein sources.Is rice a high quality protein? ›
Rice has the highest protein digestibility among the staples (Table 27). Potato protein had a higher biological value than cereal proteins, consistent with its high amino acid score, but its net protein utilization (NPU) was lower than that of rice.What are the 3 types of protein? ›
Proteins are the basic component of living cells. They are made of carbon, hydrogen, oxygen, nitrogen, and one or more chains of amino acids. The three structures of proteins are fibrous, globular and membrane, which can also be broken down by each protein's function.Is 3 eggs a lot of protein? ›
They're the perfect little package. Not only are they protein-rich (about 7 grams each), but eggs — specifically the yolks — contain inflammation-fighting omega-3s; vitamins D, E, and B12; and minerals like selenium.What are 5 proteins in your body? ›
There are seven types of proteins: antibodies, contractile proteins, enzymes, hormonal proteins, structural proteins, storage proteins, and transport proteins.What is the bioavailability of chicken? ›
The unit for measuring how much protein a certain source of food can provide is called biological value, or BV. For instance, the protein in chicken has a BV of 79.How many amino acids are in HBV protein? ›
Hemoglobin subunit beta (beta globin, β-globin, haemoglobin beta, hemoglobin beta) is a globin protein, coded for by the HBB gene, which along with alpha globin (HBA), makes up the most common form of haemoglobin in adult humans, hemoglobin A (HbA). It is 147 amino acids long and has a molecular weight of 15,867 Da.How can a vegan get high biological value protein in their diet? ›
- Quinoa. ...
- Pulses. ...
- Tofu. ...
- Nuts and seeds. ...
- Chia seeds. ...
- Buckwheat. ...
- Oats. ...
- Brown and wild rice.
Fish – Salmon, tuna, halibut, and whitefish are all considered lean, complete protein. Meat – Most animal proteins are considered complete and high-quality. This includes red meat, poultry, and dairy products. Eggs – An average egg is a high-quality protein with approximately 6 or 7 grams of protein.
Which beans are good for kidneys? ›
|Legume||Serving size (cooked)||Estimated Phosphorus (mg) available for absorption|
|Kidney beans||1/2 cup||61|
|Pinto beans||1/2 cup||63|
|Navy beans||1/2 cup||66|
|Blacked eyed peas||1/2 cup||67|
Toxicity occurs when you eat raw, soaked kidney beans either alone or in salads or casseroles. There have also been reports of toxicity when cooking raw, dried kidney beans in a slow-cooker. Just four or five raw kidney beans can trigger the symptoms of toxicity.Is corn good for hepatitis B patient? ›
Most countries, including the U.S., allow low amounts of aflatoxin in corn and peanuts. However, some researchers suggest even these low levels can lead to liver damage in people infected with hepatitis B who rely on diets rich in corn, nuts and grains.Is whey protein A complete protein? ›
Whey protein is a complete protein, containing all nine essential amino acids. “Amino acids are important for many functions in the body, from building muscle to creating new immune cells,” says Smith. Your body makes many amino acids on its own, but not essential amino acids.Is gelatin high protein? ›
Gelatin is a high protein product. For example, 100 grams (g) of dry gelatin powder contain more than 85 g of protein .Is soy milk a complete protein? ›
Soy is a complete plant protein, meaning that it contains all the essential amino acids in adequate proportions. Silk soymilk is also a good source of calcium and vitamin D—two nutrients especially important for growing kids.What type of protein is gelatin? ›
Gelatin is a protein derived from collagen by controlled hydrolysis. Depending on the method of gelatin processing from native collagen, either using acidic or alkaline pretreatments, two types of gelatin can be formed: type A and type B.
Tofu is an exception. It is complete, though it's not considered as high-quality as animal sources. (Quality is judged by the proportion of amino acids in the food.) Oddly enough, soybeans, from which tofu is made, are considered very high-quality protein; tofu, however, is made from only the curds of soybeans.Is soy a low quality protein? ›
Soy protein is a high-quality protein with a protein digestibility-corrected amino acid score (PDCAAS) of 1.00, which is close to some of the proteins from animal sources, such as meat and dairy. Soy proteins contain well-balanced essential amino acids except for sulfur-containing ones like methionine.Is soy or pea protein better? ›
Soy protein is a superior protein source than pea according to its bioavailability and amino acid score which is similar to casein or egg protein.
Which vegetable is low in protein? ›
Although the protein content of vegetables varies by type, most vegetables are considered low in protein. Green vegetables, such as lettuce, cabbage, bell pepper and asparagus provide only 1 to 2g of protein per serving. Broccoli and spinach are exceptions, providing 4 and 5g per serving, respectively.What meat is low in protein? ›
sausage. low-salt ham or cold cuts. hot dogs, chicken dogs. turkey ham, turkey bologna.How do you treat protein in urine naturally? ›
- Eat plenty of fruits and vegetables, grains, and legumes.
- Lean meats are better than red meat, as the latter is harder to break down.
- Consume more fish.
- Restrict salt intake.
- Drink plenty of water and avoid soda.
- Exercise regularly.
If a food is missing one or more of the indispensable amino acids, it has a low biological value (LBV). For example, baked beans have an LBV. If a food has all the indispensable amino acids, it has a high biological value (HBV).Are Bananas high in protein? ›
High protein fruits include guavas, avocados, apricots, kiwifruit, blackberries, oranges, bananas, cantaloupe, raspberries, and peaches.Is milk high in protein? ›
Milk is a rich source of protein — providing approximately 1 gram of this nutrient in each fluid ounce (30 mL), or 8.14 grams in each cup (249 grams) ( 1 ).Are carrots low in protein? ›
Carrots are about 10% carbs, consisting of starch, fiber, and simple sugars. They are extremely low in fat and protein.Is oatmeal high protein? ›
You're eating it plain
On its own, oatmeal is relatively low-calorie, high in fiber, and high in protein. A serving of ½ cup dry oatmeal made with water sets you back 150 calories, 3 grams of fat, 27 grams of carbs, 4 grams of fiber, 1 gram of sugar, and 5 grams of protein.
- Skinless, white-meat poultry.
- Lean beef (including tenderloin, sirloin, eye of round)
- Skim or low-fat milk.
- Skim or low-fat yogurt.
- Fat-free or low-fat cheese.
- Cranberries keep the urinary tract free from infection (UTI)
- Red grapes reduce inflammation and help protect against diabetes.
- Apples help to prevent constipation and reduce cholesterol.
How do I remove protein from my body? ›
Drinking water is a good way to help get rid of high protein in your body. Your body is a fascinating, well-oiled machine that's extremely effective at balancing the amount of protein in your blood and urine when everything is working as it should.What does LBV mean in food? ›
Low biological value (LBV) proteins. are missing one or more of the. essential amino acids we need. They're only found in plant sources.Are kidney beans HBV? ›
Have a high biological value (HBV). Beans, peas, lentils, nuts, seeds •Lack one or more of the 8 ESSENTIAL AMINO ACIDS.
Animal sources of protein are meat, poultry, fish, eggs, milk, cheese and yogurt, and they provide high biological value proteins. Plants, legumes, grains, nuts, seeds and vegetables provide low biological value proteins.