PROTEIN 

Protein

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.Protein is a nutrient your body needs to grow and repair cells, and to work properly. Protein is found in a wide range of food and it's important that you get enough protein in your diet every day. How much protein you need from your diet varies depending on your weight, gender, age and health. Protein is a part of every cell in the body. It helps the body to build and repair cells and tissues. so we can say it is a major component of the skin, muscle, bone, organs, hair, and nails. Protein is considered the building block of life and is found in every cell of the body, according to MedlinePlus.There are 20 different kinds of amino acids, and the sequence in which the different amino acids are arranged helps determine the role of that particular protein, per MedlinePlus.

 

Proteins  perform a vast array of functions within organisms, including catalysing metabolic reaction, DNA replications,responding to stimuli,Providing to cells and Organisms and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding  into a specific 3D structure  that determines its activity.

Protein

Protein is an essential macronutrient, but not all food sources of protein are created equal, and you may not need as much as you think. Learn the basics about protein and shaping your diet with healthy protein foods.

Protein is found throughout the body—in muscle, bone, skin, hair, and virtually every other body part or tissue. It makes up the enzymes that power many chemical reactions and the hemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.

Protein is made from twenty-plus basic building blocks called amino acids. Because we don’t store amino acids, our bodies make them in two different ways: either from scratch, or by modifying others. Nine amino acids—histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine—known as the essential amino acids, must come from food.

Sources of protein

According to the Dietary Guidelines for Americans 2015–2020Trusted Source, a healthful eating pattern includes a variety of foods containing protein. Both animal and plant foods can be excellent sources of protein.The guidelines classify the following foods as protein foods:-

seafood

lean meats and poultry

eggs

legumes, which include beans and peas

nuts

seeds

soy products

Dairy products, such as milk, cheese, and yogurt, also contain protein. 

Whole grains and vegetables contain some protein, but generally less than other sources. 

What does the body need protein for? 

Your body uses protein for energy, among other functions. This mainly happens when there is a deficit in other sources of energy, such as carbohydrates. There are 4 (kilo)calories in each gram of protein. They mainly provide our bodies with important amino acids, however, of which there are 21 altogether. Our bodies need them to build their own proteins for muscle mass, hormones or enzymes. There are nine essential amino acids. They are essential precisely because your body cannot produce them itself, whereas your body can produce non-essential amino acids on its own. We thus don’t need nearly as many of these from food.

What do proteins do for the body?

Our bodies are made up of thousands of different proteins, each with a specific function. They make up the structural components of our cells and tissues as well as many enzymes, hormones and the active proteins secreted from immune cells.

These body proteins are continually being repaired and replaced throughout our lives. This process (known as ‘protein synthesis’) requires a continuous supply of amino acids. Although some amino acids can be recycled from the breakdown of old body proteins, this process is imperfect. This means we must eat dietary protein to keep up with our body’s amino acid demand.

As protein is essential for cell and tissue growth, adequate intake of protein is particularly important during periods of rapid growth or increased demand, such as childhood, adolescence, pregnancy,  and breastfeeding

What are proteins made of?

Proteins are made up of many different amino acids linked together. There are twenty different of these amino acid building blocks commonly found in plants and animals. A typical protein is made up of 300 or more amino acids and the specific number and sequence of amino acids are unique to each protein. 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 number and sequence of amino acids, the resulting protein will fold into a specific shape. This shape is very important as it will determine the protein’s function (e.g. muscle or enzyme). Every species, including humans, has its own characteristic proteins.

Protein evolution

A key question in molecular biology is how proteins evolve, i.e. how can mutations  (or rather changes in amino acid  sequence) lead to new structures and functions? Most amino acids in a protein can be changed without disrupting activity or function, as can be seen from numerous homologous  proteins across species (as collected in specialized databases for protein families, e.g.  In order to prevent dramatic consequences of mutations, a gene may be dublicated before it can mutate freely. However, this can also lead to complete loss of gene function and thus pseudo-genes. More commonly, single amino acid changes have limited consequences although some can change protein function substantially, especially in enzymes. For instance, many enzymes can change their substrate specificity, by one or a few mutations.

Method of study

The activities and structures of proteins may be examined in vitro, in vivo and in silico. In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function: for example, Enzyme kinetics studies explore the chemical mechanism  of an enzyme's catalytic activity and its relative affinity for various possible substrate molecules. By contrast, in vivo experiments can provide information about the physiological role of a protein in the context of a cell  or even a whole organism. In silico studies use computational methods to study proteins.

Is there a difference between animal and plant-based proteins?

The quality of a protein can be defined in many ways; however, all definitions relate to the distribution and proportion of essential and non-essential amino acids they contain. In general, animal-based proteins are of higher quality as they contain higher proportions of essential amino acids compared to plant-based proteins. 

There is a common misconception that plant-based proteins completely lack certain essential amino acids. In fact, most plant-based proteins will contain all 20 amino acids but tend to have a limited amount of certain essential amino acids, known as their limiting amino acid(s). This means, if a small number of plant foods are consumed as the only protein sources, they are unlikely to supply enough essential amino acids to meet our requirements.  For people who consume little to no animal-based foods, such as vegans or vegetarians,  it is important that they consume protein from sources with complementary limiting amino acids. For example, consuming rice (limited in lysine and thiamine but high in methionine) and beans (limited in methionine, but high in lysine and thiamine) will provide complementary amino acids that can help meet essential amino acid requirements.

Animal and plant-based proteins also differ in their bioavailability and digestibility. The digestible indispensable amino acid score (DIAAS) is the recommended method for determining dietary protein digestibility and is expressed in values below or sometimes even above 100.

A DIAAS of over 100 indicates that the protein has very high digestibility and quality and is a good complement protein to those that have lower qualities. Animal-based proteins tend to have higher DIAAS scores compared to plant-based proteins. As most people consume protein from a variety of sources the quality and digestibility of protein is not usually a concern.

How much protein should we eat every day?

EFSA has developed dietary reference value (DRVs) for protein. The DRVs for protein at different life stages are summarised in table 3. For an average adult, the recommendation is to consume at least 0.83 g of protein for every kilogram of body weight per day. In other words, a 70 kg adult should aim to eat at least 58 g of protein everyday day. This is the equivalent to the protein found in around 200 g of chicken breast or 240 grams of mixed nuts.

During periods of growth, such as childhood, pregnancy, and breastfeeding, protein requirements are relatively high. In addition, during old age, our protein to energy ratio begins to increase. This means we require the same amount of protein but less energy (or calories) due to a decrease in metabolic rate and a more sedentary lifestyle.

What happens if you eat too much protein?

There is insufficient evidence to establish a threshold for protein intake and EFSA have stated that a protein intake of twice the DRV (1.7 g/kg per day, or 119 g per day for a 70 kg adult) is still considered safe under normal conditions.  For individuals with kidney disease excessive protein can be an issue and these individuals should consult a registered dietitian or general practitioner before increasing protein levels.

Red and Processed Meat and Cancer Risk

Protein is essential for good health, but some high protein foods may be better for our health than others. In particular, consuming high amounts of red and processed meat has been associated with an increased risk of certain cancers. Red meat is a good source of protein as well as many other essential nutrients such as iron, vitamin B₁₂, and zinc, and does not necessarily need to be avoided altogether to reduce risk. The World Cancer Research Fund recommends we try to consume no more than three portions (around 350-500g cooked weight) of red meat per week and very little, if any, processed meat

                                      

What are the health benefits of protein?

Eating enough protein to meet our bodies’ requirements is important for many body functions. However, there is evidence to suggest that in certain situations increasing protein intake above required levels could provide additional health benefits.

Research on Protein and Health

Available evidence indicates that it’s the source of protein (or, the protein “package”), rather than the amount of protein, that likely makes a difference for our health. You can explore the research related to each disease in the tabs below, but here’s the evidence-based takeaway: eating healthy protein sources like beans, nuts, fish, or poultry in place of red meat and processed meat can lower the risk of several diseases and premature death.

Protein and Weight Control

Eating protein-rich foods has been shown to increase our feeling of fullness (also known as satiety) more than foods high in fat or carbohydrate. There is good evidence from short term studies that diets high in protein (i.e. 1.2 – 1.6 g/kg per day; 84 – 112 g per day for a 70 kg adult) can help reduce overall calorie intake and prompt weight loss. However, the evidence for long-term weight maintenance is less clear. Like all diets, a high protein diet is only effective if it is stuck to, which can be difficult for some people and low adherence may partly explain the limited benefit observed for long term weight maintenance.

Protein and athletic performance

Protein has long been associated with athletic performance. Protein plays a key role in helping to repair and strengthen muscle tissue after exercise. Although protein is critical for building muscle, to maximise the benefits it should be considered in the context of the whole diet, which includes the right amount of carbohydrates, fats, vitamins and minerals. Optimum protein intake will depend on the type (e.g. endurance or resistance training), duration and intensity of exercise, with more not always being better. Athletes should aim to achieve protein intakes through consuming a balanced diet, with protein supplements being used for individuals who need to keep protein high but limit total calorie intake.

Protein and sarcopenia

Sarcopenia is a disorder characterised by the progressive loss of muscle mass and physical function that is commonly associated with older adults. Sarcopenia is associated with increased frailty, risk of falls, functional decline and even early death. As protein is essential for the repair and maintenance of muscle mass, it is no surprise that low intake of protein is associated with an increased risk of developing sarcopenia. Similarly, increasing protein intake, as well as increasing physical activity, can help  maintain muscle mass and strength as we age, decreasing our risk of sarcopenia and skeletal disorders. 

What are the health benefits of protein?

Eating enough protein to meet our bodies’ requirements is important for many body functions. However, there is evidence to suggest that in certain situations increasing protein intake above required levels could provide additional health benefits. Eating protein-rich foods has been shown to increase our feeling of fullness (also known as satiety) more than foods high in fat or carbohydrate. There is good evidence from short term studies that diets high in protein (i.e. 1.2 – 1.6 g/kg per day; 84 – 112 g per day for a 70 kg adult) can help reduce overall calorie intake and prompt weight loss.  However, the evidence for long-term weight maintenance is less clear. Like all diets, a high protein diet is only effective if it is stuck to, which can be difficult for some people and low adherence may partly explain the limited benefit observed for long term weight maintenance.

Weight Gain

There is a common misconception that you can’t gain weight from eating protein. This is not true, just like carbohydrates and fats, when consumed during a calorie surplus, excess protein can be converted to body fat, leading to weight gain. When it comes to weight maintenance, the most important thing is to stay in enery balance.

Protein sustainability

The food choices we make not only affect our health they also affect the environment.In general, animal-based proteins such as beef, dairy, and lamb have a higher environmental impact (i.e. uses more resources and produces more greenhouse gases) compared to plant-based sources such as soy, peas and lentils. While it is not necessary or recommended to completely avoid animal-based foods, shifting dietary patterns to include more plant-based protein sources, can benefit our health and the planet.Sustainable eating is more than just choosing sustainable protein-rich foods, for more tips on how you can live a more sustainable life see tips to eat a healthy and sustainable diet and tips to reduce food waste. 

Conclusion

Protein is essential for life; it supplies the essential amino acids needed for the growth and maintenance of our cells and tissues. Our requirement for protein depends on our stage of life and most Europeans consume enough to meet their requirements. As most people consume a varied diet, the quality and digestibility of the proteins they eat should not be a concern as long as the total amount of protein meets their daily needs. As we eat foods and not nutrients, we should choose protein-rich foods that not only provide essential amino acids but also support a healthy and sustainable diet.