Edouard Manet: still life with salmon
Macronutrients
Recent research into the role of the role of macronutrients within nutrition has shown that they have a more complex relationships than was first thought. What is important is that a healthy meal would have a balance of all three.
Carbohydrates
Carbohydrates are often seen as the initial form of energy that keeps the body active: that is ,of providing glucose. However carbohydrates play an important regulatory role within the body. This is particularly the case within the digestive system, where they have a beneficial effect on intestinal flora. Also fibre aids in regulating the absorption of nutrients, facilitating elimination of waste, and increasing the satiety value of a meal. Carbohydrates are the principle metabolic fuel providing 4Kcal/g of energy, and glucose is the only fuel that can be used by the brain and erythrocytes. It is shored in the form of Glycogen in the liver and muscles (however the store of glycogen in the muscle, and its release for use as glucose, is only for its own needs, while glycogen stored in the liver is more systemic). In addition to their role as fuel they also have additional roles. Combined to proteins in the form of glycoproteins and fats in the form of glycolipids. Glycoproteins have numerous functions including; structural in the form of collagen, lubricant and protective as in mucin, the transport molecule transferrin, immunoglobulins within the immune system, and the hormones; Human chorionic gonadotropin (HCG), and thyroid-stimulating hormone (TSH). Glycolipids are an essential part of the cell membrane and play an important role in intercellular signalling.
Protein
Proteins are responsible for most of the catalytic and regulatory activities in the body. What is important is not just the quantity eaten but its quality. Protein is made up of amino acids, which are easily assimilated. Each food will have a different combination of amino acids. Some foods are considered complete proteins in that they contain all the essential amino acids required. Many amino acids are considered non-essential because the body is able to synthesise them as quickly as they are utilised. Foods that are considered complete proteins are: eggs, dairy, organ meats, red meat, fish, poultry and soya.
Protein has a number of regulatory functions, as in: Growth, hormones, enzymes, cytokines, neurotransmitters, and transcription factors. Protein is also required for the immune system, and can act as transport carriers in the blood. Protein is also involved in fluid balance, PH levels, detoxification and energy. Some protein enzymes, such as kinases and phosphatases, act in a regulatory manner controlling the action of other enzymes. There is no specific storage of protein in the body but the breakdown of muscle will serve as a fuel reserve in times of energy needs.
The amount of daily protein required is usually calculated as 0.8 - 1.0 g per Kg. of body weight.
During protein metabolism the amino acids which make up the protein are broken down and nitrogen content, which is toxic to the body, needs to be eliminated through the urine.
An important distinction needs to be made between two aspects of protein, that is, protein quantity and protein quality. Protein is broken down through digestion into its constituent amino acids and then absorbed. The amino acids have been traditionally divided into essential and nonessential. The essential amino acids are; histidine, leucine, isoleucine, valine, lysine, phenylalanine, tryptophan, threonine, and methionine. The identified non essential amino acids are; alanine, arginine, aspartic acid, cysteine, citrulline, glutamic acid, glutamine, glycine, ornithine, proline, serene, tyrosine, asparagine, taurine, selenocysteine. Many of these nonessential amino acids can be further differentiated as conditionally essential, in that, it is possible to be deficient if the body is unable to synthesise them. This may be due to the body's need being greater than its ability to synthesise the relevant amino acid. For example cystine plays an important anti-inflammatory and antioxidant role. Increased exposure to toxins may increase the body's needs to utilise more cystine than it is able to produce. A number of nonessential amino acids are involved in detoxification. The branched chained amino acids: leucine, isoleucine and valine are able to be oxidised completely in the mitochondria to provide energy. Creatine and carnitine also play key roles within energy production. Creatine is stored in muscles as phosphocreatine and helps in the regeneration of ATP (adenosine triphosphate). Carnitine helps to transport fatty acids and pyruvate into the mitochondria to be used for energy production.
Sometimes a protein or a peptide can cause an allergic reaction, or the person may be intolerant due to not having the requisite enzyme to break it down. For example lactose found in milk and dairy products. Without the enzyme lactase (a protein) the lactose is not broken down and ferments in the stomach causing bloating, flatulence, and diarrhoea. An elimination diet can be beneficial in identifying the underlying cause and relieving the symptoms of foods that initiate an allergic response.
Fats/Lipids
Lipids have an important function to play within the body. As well as being a long term energy store, they help to maintain body temperature, and insulate and protect internal vital organs. They are stored principally within adipose tissue in the form of triglycerides, and can be used as a form of energy when required, providing 9kcal/g of energy, They are contained in cell membranes in the form of phospholipds and sphingolipids, the latter being found in nerve cells and brain tissue. The myelin sheath which insulates nerve cells is almost 80% fat.
The two main types of fats are saturated, which is solid at room temperature, and unsaturated, which is liquid. Unsaturated fats can be further divided into Monounsaturated and Polyunsaturated (PUFAs) differentiated as regard to the number of hydrogen atoms missing. Most vegetable oils are high in PUFAs. Fats are obtained mainly from meat, dairy food, nuts and seeds, but most foods contain some fat. Saturated and unsaturated fats can be further sub-divided into, long, medium, and short chained fatty acids, which will have different properties, and differing functions within the body. Generally the more saturated tend to have structural properties within the body, while the unsaturated are have more of an interactive role. (see also inflammation section). Two polyunsaturated fatty acids, linoleic (omega6) and linolenic (omega3) cannot be synthesised in the body and need to be obtained through the diet.
Lipids are also involved in metabolic regulation, for example, steroid hormones, and are also required for the uptake of certain nutrients within the body.
Energy
The body is an equi-dynamic system and therefore requires a constant supply of energy to carry out its various metabolic processes. Digested carbohydrates are converted to glucose, which are then absorbed and transported via the portal circulation to the liver where it is utilised to provide energy. Erythrocytes and neurones can only use glucose for fuel and therefore maintenance of blood glucose levels is needed to provide a constant energy source for these cells. However too much glucose in the blood can be very damaging, interfering with blood circulation, and causing oxidative stress. Excess glucose above immediate requirements is converted to an insoluble form glycogen and stored in the liver and skeletal muscles. There is a limit to the amount of glycogen that can be stored and therefore any excess is covered into fats and stored within adipose tissue as triglycerides. When blood glucose levels drops the stored glycogen is broken down into glucose, once depleted the body will draw on other forms of energy supply.
ATP (adenosine triphosphate) is the energy currency utilised by the body. The body creates this energy supply through a number of processes, Initially through the breakdown of Glucose. The initial stage, glycolysis, requires no oxygen for the process to take place and is therefore termed anaerobic (without oxygen). During this process the glucose is converted to Pyruvic acid and a limited amount of energy is created. If sufficient oxygen is present the pyruvate will enter the mitochondria of the cell and is converted to acetyl CoA. When no oxygen is present the pyruvate is then broken down to form lactic acid. The lactic acid can be reconverted back into pyruvate. During strenuous exercise oxygen supply is unable to keep up with demand and there is a build up of lactic acid which limits the functioning of the muscles, thereby helping to prevent damage to the muscles through overwork. If oxygen is present then the pyruvate which has been converted into Acetyl CoA enters the Krebs cycle. During these two stages of glycolysis and the Krebs cycle the body requires; magnesium, vitamins B1,B2,B3,B5 and lipoic acid. The final process in the production of energy involves the electron transport chain. During this process a high amount of energy in the form of ATP is created. Elements required during this stage are :Iron, Copper, Sulphur and Co enzyme Q10 (CoQ10).
When glucose is unavailable, the body can utilise its storage of fats to produce energy. Fats are broken down and converted into acetyl CoA and enters the krebs cycle, The glycerol component of fats can also be used for energy and enters the glycolysis pathway. Because glucose is unavailable, the brain is able to use Ketone bodies which are also produced from the breakdown of fats. However these Ketone bodies in excess can be harmful. Proteins in the form of amino acids are also a potential energy source, but they are used only when other energy sources are low, as in starvation. The amino acids enter the energy production system at different stages. Some amino acids can be converted to glucose and enter glycolysis. Others enter the process at different stages; some are converted to pyruvic acid, Acetyl CoA, or oxaloacetic acid. During the breakdown of the amino acids nitrogen is released which then has to be excreted by the body.
Recent research into the role of the role of macronutrients within nutrition has shown that they have a more complex relationships than was first thought. What is important is that a healthy meal would have a balance of all three.
Carbohydrates
Carbohydrates are often seen as the initial form of energy that keeps the body active: that is ,of providing glucose. However carbohydrates play an important regulatory role within the body. This is particularly the case within the digestive system, where they have a beneficial effect on intestinal flora. Also fibre aids in regulating the absorption of nutrients, facilitating elimination of waste, and increasing the satiety value of a meal. Carbohydrates are the principle metabolic fuel providing 4Kcal/g of energy, and glucose is the only fuel that can be used by the brain and erythrocytes. It is shored in the form of Glycogen in the liver and muscles (however the store of glycogen in the muscle, and its release for use as glucose, is only for its own needs, while glycogen stored in the liver is more systemic). In addition to their role as fuel they also have additional roles. Combined to proteins in the form of glycoproteins and fats in the form of glycolipids. Glycoproteins have numerous functions including; structural in the form of collagen, lubricant and protective as in mucin, the transport molecule transferrin, immunoglobulins within the immune system, and the hormones; Human chorionic gonadotropin (HCG), and thyroid-stimulating hormone (TSH). Glycolipids are an essential part of the cell membrane and play an important role in intercellular signalling.
Protein
Proteins are responsible for most of the catalytic and regulatory activities in the body. What is important is not just the quantity eaten but its quality. Protein is made up of amino acids, which are easily assimilated. Each food will have a different combination of amino acids. Some foods are considered complete proteins in that they contain all the essential amino acids required. Many amino acids are considered non-essential because the body is able to synthesise them as quickly as they are utilised. Foods that are considered complete proteins are: eggs, dairy, organ meats, red meat, fish, poultry and soya.
Protein has a number of regulatory functions, as in: Growth, hormones, enzymes, cytokines, neurotransmitters, and transcription factors. Protein is also required for the immune system, and can act as transport carriers in the blood. Protein is also involved in fluid balance, PH levels, detoxification and energy. Some protein enzymes, such as kinases and phosphatases, act in a regulatory manner controlling the action of other enzymes. There is no specific storage of protein in the body but the breakdown of muscle will serve as a fuel reserve in times of energy needs.
The amount of daily protein required is usually calculated as 0.8 - 1.0 g per Kg. of body weight.
During protein metabolism the amino acids which make up the protein are broken down and nitrogen content, which is toxic to the body, needs to be eliminated through the urine.
An important distinction needs to be made between two aspects of protein, that is, protein quantity and protein quality. Protein is broken down through digestion into its constituent amino acids and then absorbed. The amino acids have been traditionally divided into essential and nonessential. The essential amino acids are; histidine, leucine, isoleucine, valine, lysine, phenylalanine, tryptophan, threonine, and methionine. The identified non essential amino acids are; alanine, arginine, aspartic acid, cysteine, citrulline, glutamic acid, glutamine, glycine, ornithine, proline, serene, tyrosine, asparagine, taurine, selenocysteine. Many of these nonessential amino acids can be further differentiated as conditionally essential, in that, it is possible to be deficient if the body is unable to synthesise them. This may be due to the body's need being greater than its ability to synthesise the relevant amino acid. For example cystine plays an important anti-inflammatory and antioxidant role. Increased exposure to toxins may increase the body's needs to utilise more cystine than it is able to produce. A number of nonessential amino acids are involved in detoxification. The branched chained amino acids: leucine, isoleucine and valine are able to be oxidised completely in the mitochondria to provide energy. Creatine and carnitine also play key roles within energy production. Creatine is stored in muscles as phosphocreatine and helps in the regeneration of ATP (adenosine triphosphate). Carnitine helps to transport fatty acids and pyruvate into the mitochondria to be used for energy production.
Sometimes a protein or a peptide can cause an allergic reaction, or the person may be intolerant due to not having the requisite enzyme to break it down. For example lactose found in milk and dairy products. Without the enzyme lactase (a protein) the lactose is not broken down and ferments in the stomach causing bloating, flatulence, and diarrhoea. An elimination diet can be beneficial in identifying the underlying cause and relieving the symptoms of foods that initiate an allergic response.
Fats/Lipids
Lipids have an important function to play within the body. As well as being a long term energy store, they help to maintain body temperature, and insulate and protect internal vital organs. They are stored principally within adipose tissue in the form of triglycerides, and can be used as a form of energy when required, providing 9kcal/g of energy, They are contained in cell membranes in the form of phospholipds and sphingolipids, the latter being found in nerve cells and brain tissue. The myelin sheath which insulates nerve cells is almost 80% fat.
The two main types of fats are saturated, which is solid at room temperature, and unsaturated, which is liquid. Unsaturated fats can be further divided into Monounsaturated and Polyunsaturated (PUFAs) differentiated as regard to the number of hydrogen atoms missing. Most vegetable oils are high in PUFAs. Fats are obtained mainly from meat, dairy food, nuts and seeds, but most foods contain some fat. Saturated and unsaturated fats can be further sub-divided into, long, medium, and short chained fatty acids, which will have different properties, and differing functions within the body. Generally the more saturated tend to have structural properties within the body, while the unsaturated are have more of an interactive role. (see also inflammation section). Two polyunsaturated fatty acids, linoleic (omega6) and linolenic (omega3) cannot be synthesised in the body and need to be obtained through the diet.
Lipids are also involved in metabolic regulation, for example, steroid hormones, and are also required for the uptake of certain nutrients within the body.
Energy
The body is an equi-dynamic system and therefore requires a constant supply of energy to carry out its various metabolic processes. Digested carbohydrates are converted to glucose, which are then absorbed and transported via the portal circulation to the liver where it is utilised to provide energy. Erythrocytes and neurones can only use glucose for fuel and therefore maintenance of blood glucose levels is needed to provide a constant energy source for these cells. However too much glucose in the blood can be very damaging, interfering with blood circulation, and causing oxidative stress. Excess glucose above immediate requirements is converted to an insoluble form glycogen and stored in the liver and skeletal muscles. There is a limit to the amount of glycogen that can be stored and therefore any excess is covered into fats and stored within adipose tissue as triglycerides. When blood glucose levels drops the stored glycogen is broken down into glucose, once depleted the body will draw on other forms of energy supply.
ATP (adenosine triphosphate) is the energy currency utilised by the body. The body creates this energy supply through a number of processes, Initially through the breakdown of Glucose. The initial stage, glycolysis, requires no oxygen for the process to take place and is therefore termed anaerobic (without oxygen). During this process the glucose is converted to Pyruvic acid and a limited amount of energy is created. If sufficient oxygen is present the pyruvate will enter the mitochondria of the cell and is converted to acetyl CoA. When no oxygen is present the pyruvate is then broken down to form lactic acid. The lactic acid can be reconverted back into pyruvate. During strenuous exercise oxygen supply is unable to keep up with demand and there is a build up of lactic acid which limits the functioning of the muscles, thereby helping to prevent damage to the muscles through overwork. If oxygen is present then the pyruvate which has been converted into Acetyl CoA enters the Krebs cycle. During these two stages of glycolysis and the Krebs cycle the body requires; magnesium, vitamins B1,B2,B3,B5 and lipoic acid. The final process in the production of energy involves the electron transport chain. During this process a high amount of energy in the form of ATP is created. Elements required during this stage are :Iron, Copper, Sulphur and Co enzyme Q10 (CoQ10).
When glucose is unavailable, the body can utilise its storage of fats to produce energy. Fats are broken down and converted into acetyl CoA and enters the krebs cycle, The glycerol component of fats can also be used for energy and enters the glycolysis pathway. Because glucose is unavailable, the brain is able to use Ketone bodies which are also produced from the breakdown of fats. However these Ketone bodies in excess can be harmful. Proteins in the form of amino acids are also a potential energy source, but they are used only when other energy sources are low, as in starvation. The amino acids enter the energy production system at different stages. Some amino acids can be converted to glucose and enter glycolysis. Others enter the process at different stages; some are converted to pyruvic acid, Acetyl CoA, or oxaloacetic acid. During the breakdown of the amino acids nitrogen is released which then has to be excreted by the body.
