Protein - an introduction to protein in the diet.
What is protein?
Protein is found in every cell, muscle and tissue of our body and is also present in many of the foods that we eat. The protein in our body is essentially the same as the protein in our food, except that it is structured differently.
Basically proteins are made up of long chains of amino acids. There are 22 different types of amino acid and the body needs all of them to function properly.
Amino acids are chemical compounds containing carbon, hydrogen, oxygen and nitrogen, which combine together into different structures to form the various types of protein that the body requires.
There are many forms of protein, which all play an important role in the function of the body. For example, collagen is a protein and is vital for the strength, elasticity and composition of our hair and skin.
Essential and non-essential amino acids
When the proteins that we consume in our food are broken down through digestion into individual amino acids, these amino acids are then absorbed and reform in order to create new proteins that are then used by the body.
The 22 types of amino acid are divided into two groups: essential and non-essential amino acids.
There are 14 non-essential amino acids. They are termed non-essential as they can be manufactured by the body and do not have to be derived from food.
The body, on the other hand, cannot produce the remaining 8 essential amino acids itself, and therefore they must be derived from the food that we eat.
Non-essential amino acids are just as important as essential amino acids, as without the other, new proteins that are needed by the body cannot be properly formed. It is therefore vital that a variety of foods are eaten in order to provide the body with all of the amino acids required.
Complete and incomplete proteins
There are some foods that contain all of the 8 essential amino acids required to form the new proteins together with the non-essential amino acids. These foods are called "complete" proteins and tend to come from animal sources of protein such as meat, dairy products, eggs, fish, shellfish and poultry.
The proteins that are termed "incomplete" proteins are usually lacking in one or more of the essential amino acids. They are generally found in vegetable products like fruits, vegetables, pulses, grains and nuts.
However, by combining two or more of the "incomplete" proteins, a complete supply of essential amino acids is available. For example, baked beans on toast or rice and beans will form a complete protein and give the body all the essential amino acids.
What is the exact role of protein in our body?
Protein is required by the body for the growth, maintenance and repair of all cells.
Protein is a major component of all muscles, tissues and organs and is vital for practically every process that occurs within the body such as metabolism, digestion and the transportation of nutrients and oxygen in the blood.
It is also necessary for the production of antibodies, which fight against infection and illness, and is the main nutrient that keeps our hair shiny and healthy, our nails strong, our skin fresh and glowing and our bones strong and healthy.
Which foods are good sources of protein?
The best sources of complete protein are found in animal foods such as meat, fish, shellfish, poultry and dairy produce.
Eggs are the best source of protein as they contain the highest amount of essential amino acids. Fish is the next best source and is then followed by meat, milk, cereal eaten with pulses, soya beans, oatmeal, rice, peas, lentils, kidney beans and then wholemeal bread.
Try to consume a variety of protein-rich foods, including pulses, fish, vegetables, shellfish and lean meat, rather than just red meat or only dairy products, as some foods that contain high amounts of protein also contain high levels of saturated fat, which is extremely bad for the body.
It is also advisable to swap full-fat foods or foods that are high in saturated fats, for a low-fat version, for example change cheddar cheese to cottage cheese and full-fat milk to semi-skimmed or skimmed milk.
How much protein should we eat each day?
Protein is an important part of our daily diet and it should be consumed every day, although our body does not need as much protein as it does other types of food such as carbohydrates, fruit and vegetables.
Expert nutritionists recommend that we eat 2 - 3 servings of dairy produce per day and 2 - 3 servings of meat, poultry, fish, shellfish or pulses a day. They also advise us that 10 - 15% of our calorie intake should be made up of protein.
As some protein-rich foods, especially animal produce, are high in calories and bad fat, they should be eaten in moderation and prepared in a healthy way. For example, use grilling and roasting as cooking methods rather than frying or deep fat frying.
Eating plenty of fresh fruit and vegetables can lower the risk of developing any illnesses that may be caused by eating a diet that consists of mainly meat and if possible try to eat fish, particularly oily fish, at least three times a week.
Is too much protein bad for you?
Although the body needs a certain amount of protein, too much can be harmful for a person's health.
There is a significant risk of high cholesterol, due to the high amount of saturated fats in certain foods, which could in turn lead to heart disease and stroke.
Too much protein also puts a strain on the liver and kidneys. Foods that contain protein have high levels of nitrogen, which are harmful to the body and must be eliminated. The role of the kidneys is to filter out waste products and therefore an excess of protein will force the kidneys to work harder to remove the nitrogen waste from the body. This stress could ultimately lead to kidney disorders or damage to the body's filtering capacities.
Due to the inability of the body to store excess protein, any surplus protein that is consumed is then converted into glucose in the liver and either used up as energy or stored as fat.
Some protein-rich foods are high in nucleic acids, which when broken down, are converted into uric acid. Consequently, too much uric acid in the blood can lead to gout, an extremely uncomfortable condition that causes a person's joints to become inflamed, tender and agonizingly painful to move.
Finally, too much protein in the diet could also lead to osteoporosis (thinning of the bones), as an excess of protein promotes the loss of calcium in the bones through urine.
Can too little protein affect our health?
Just as too much protein is detrimental to our health, too little protein can also affect the body negatively.
Many foods containing protein are also good sources of iron amongst other minerals and vitamins. A lack of iron can result in tiredness and fatigue, leaving the body weak and with little energy.
Protein in the body is lost daily and therefore must be replenished daily through the diet. Too little protein can cause skin problems and generally give us an unhealthy and tired appearance.
Protein is needed to repair and create new cells, tissues, hormones, enzymes and muscles and a lack of protein can prevent these processes from being carried out correctly.
In children, who need a lot of protein to help them grow and develop, not enough protein can lead to a stunted growth and even poor mental development.