All cells contain thousands of different kinds of proteins that perform a myriad of functions. For example, proteins provide structural integrity to cells, organ systems; they are important components in blood, the immune system, cell signalling, and chemical reactions as enzymes. Furthermore, protein can supply energy for the body if required. Proteins are formed by the bonding together of the building blocks; these building blocks are called amino acids. Amino acids are found in the protein-containing foods we eat as well as being made by the cells in the body.
There are 20 amino acids in total and the body needs all 20 to function. Of the 20 amino acids, 9 amino acids are essential, that is we need to get these from the foods we consume. The remaining 11 are considered nonessential, that is the body is able to make them. Some of the non essential amino acids are considered semi-essential. What that means is the body still makes them but it requires an adequate supply of essential amino acids in order to do so.
Every single cell in the body contains protein. Protein is a major component of muscle tissue, connective tissue, and transport proteins in the blood circulation, enzymes, some hormones, visual pigments, and the supportive structure inside bones. Half of the protein in the human body is made up of collagen, actin, and myosin as well as the oxygentransport protein, haemoglobin.
Proteins function in many crucial ways in human metabolism and the formation of body structures. We rely on foods to supply the amino acids needed to form these proteins. Note: only when we consume adequate amounts of carbohydrates and fats can the proteins in our body perform efficiently.
In the absence of a sufficient amount of dietary fats and carbohydrates, protein is broken down to supply the amino acids to produce energy and therefore they are unavailable to build body proteins. So to help maintain our lean muscle mass we need to consume adequate amounts of protein throughout the day, especially necessary when dietary carbohydrate consumption is low.
The blood proteins, albumin and globulin maintain body fluid balance. In the arteries, normal blood pressure forces blood fluid into the capillary beds. The blood fluid then moves from the capillary beds into the spaces between adjacent cells to provide nutrients to those cells. Proteins in the bloodstream such as albumin are too large to move out of the capillary beds into the tissues. The albumins in the capillary beds therefore attract fluid back to the blood and partially counteract the force of blood pressure.
Most hormones require amino acids for their synthesis. Hormones are our body’s internal messengers that provide communication between adjacent cells, cells in the vicinity, and cells that are far away (distal). For example, insulin which is produced by the beta cells of the pancreas, enters the bloodstream to act on distal tissue such as skeletal muscle, fat and the liver. Enzymes are also proteins and are involved in facilitating biochemical reactions.
Proteins are key components of the immune system. For example, antibodies are produced by immune cells (β-lymphocytes) and act to bind to foreign particles in the body; they are an important immune defence protein. In the absence of sufficient dietary protein, the immune system becomes compromised.
Those who are looking to lose weight should aim to increase the protein in their diet. This serves a number of purposes. Protein is a high satiety macronutrient; that is, it helps keep the feeling of fullness after consuming it. This is because protein takes longer to digest than carbohydrates, helping you feel fuller for longer. So from a weight loss perspective, increasing protein will help reduce hunger and cravings and reduce the urge to grab a carbohydrate rich snack.
For the general population a good rule of thumb for ensuring you have enough protein is to consume approximately 1 gram of protein per kilogram of body weight. So for someone who weighs 70kg and is moderately actively, eating 70 grams a day of protein will easily meet their daily requirement. If you include flesh foods, like meat, chicken or fish on a daily basis then you will almost certainly meet your daily requirements. Those who are vegetarian or vegan need to be a little more conscious around selecting plant based foods that are high in protein to ensure they get adequate supplies. A quick google search for ‘high protein plant based foods’ will provide plenty of rich sources to choose from. Those following a low carbohydrate eating plan, ensure you consume between 15-30% of your daily energy requirements from protein sources.