Nutrients are an essential compound which organisms need to survive and thrive. Macronutrients are the nutrients that provide energy for your body to perform. There are 6 nutrients key to a healthy diet, of which three are macronutrients:
Macronutrients are required in large amounts for your body to be able to perform physically and cognitively. Each one offers unique qualities that facilitate different functions and keep you healthy. To help you understand the importance of macronutrients and how they work within the body, we’ve explored each of them in detail below.
Carbohydrates
Generally, it is accepted that, of the three macronutrients (macros from hereon in), carbohydrates are the one we require in the most significant quantities and the government’s healthy eating advice recommends that over half of your caloric intake for the day should come from carbohydrates.
What are carbohydrates?
Carbohydrates are made up of carbon, oxygen and hydrogen atoms, and there are two main types of carbohydrate:
Simple
Simple carbohydrates are broken down quickly by the body and made available as energy soon after consumption. Carbohydrates are made of sugar molecules, and a simple carbohydrate is made up of single sugar molecules. There are two types of simple sugar:
- Monosaccharides – The most simple form of sugar, your body cannot break them down any further and are therefore the most easily absorbed. There are three types of monosaccharides – glucose, fructose & galactose.
- Disaccharides – Disaccharides are composed of two sugar molecules which must be broken apart before the body can absorb them. There are three types of Disaccharides – Sucrose (glucose + fructose), Lactose (glucose and galactose) and Maltose (glucose and glucose)
All sugar molecules are converted into glucose for your body to be able to use them. Simple carbohydrates are often called ‘empty calories’ because they have little to no nutritional value beyond energy production.
Complex
Complex carbohydrates take more time to digest and, as a result, the energy output occurs over a more extended period. Known as starches, complex carbs are composed of long chains of sugar molecules. These chains must be broken down into individual molecules and then converted into glucose.
How are carbohydrates useful?
Carbohydrates are used as fuel that allows your body to perform physically. The carbs you eat are digested and broken down into glucose. Then the glucose enters the bloodstream and is transported to your body’s cells where it is used to produce a fuel molecule called ATP. The breakdown of ATP releases energy for use by the bodies tissues, including your muscles.
Energy
Your body needs a certain amount of glucose which is dependent on your physical activity level. Any excess is converted to glycogen which is then stored as adipose tissue (body fat for example) or within cells of the liver and muscle. The glycogen stored in the liver and muscle is made immediately available to the body when glucose levels are depleted during activity.
As simple carbohydrates release energy more immediately, the process of converting them to glucose, which is then burned or stored as adipose tissue or muscle glycogen, also occurs more immediately unless the energy is burned immediately. With complex carbohydrates releasing energy over a more sustained period, there are fewer carbohydrates available at any one time to be converted to glucose. The body can store up to 2,000 calories of glycogen in skeletal muscle and the liver. Once these stores are full, the remainder is stored as body fat.
Protects Muscle
Carbohydrates are also crucial in that when they’re used as the primary fuel source, they allow the other macronutrients to be put to other uses such as tissue growth and repair. When your body can’t draw upon glycogen for energy, it begins to convert protein into sugars for fuel. It will draw the protein from wherever it is available, including muscle tissue. This process is called gluconeogenesis and is your body’s survival response.
Your brain is also reliant on glucose as an energy source and needs approximately 130g per day to cover its needs. As your brain is full of neurons controlling and messaging all other parts of your body, it is the most energy-demanding organ in your body using over half of all its sugar energy. Without the glucose that it needs to perform, the neurons cannot communicate with one another efficiently meaning your body cannot perform the tasks it needs to.
Fibre
Fibre is an essential form of carbohydrate. It is indigestible and, therefore, it passes straight through your digestive system whole and takes other waste products with it. There are three types of fibre:
- Soluble Fibre – This fibre slows the emptying process of the stomach, which helps you feel fuller for longer and gives your body the time it needs to absorb nutrients from the foods you have eaten.
- Insoluble Fibre – Insoluble fibre draws water into the digestive process, which softens stool and helps keep movements regular.
- Resistant Starch – Making its way to the large intestine without being digested in the small intestine, resistant starch helps produce good bacteria which promotes a healthy gut flora.
Consuming Carbohydrates
Carbohydrates have been somewhat demonised in some circles in recent years. With diets such as the Keto Diet and the Carnivore Diet gaining popularity, carbs have become associated with obesity and fat gain in the eyes of devotees. However, carbohydrates are an essential macronutrient that is difficult to remove entirely from your diet and should not be removed entirely from your diet.
There is a train of thought that there are ‘good carbs’ and ‘bad carbs’, some which should be avoided and some which should be prioritised.
Traditionally, complex carbohydrates have been considered ‘good carbs’ due to the slow release of energy and nutritional density, whereas simple carbohydrates have been demonised as ‘bad carbs’ due to the swift release of energy or ‘energy dump’ and lack of nutritional value.
Simple carbs have their place, namely the immediate restoration of glycogen levels within the liver and skeletal muscle after intense physical activity. However, simple carbs should be consumed in moderation, especially for those with a sedentary lifestyle.
Complex carbs have a range of health benefits:
Reduced Risk of Chronic Diseases
Complex carbs have been shown in some studies to reduce your risk of diabetes and heart disease. The dietary fibre, antioxidants and vitamins found in complex carbs play a significant role in disease prevention.
Gut Flora
The billions of “good” bacteria in your intestines feed off soluble fibres found in complex carbohydrates. This helps them multiply and positively balance your gut flora. They also help contribute to better overall digestive health.
Inflammation
In response to infection or injury, your body inflames tissue. Whole grains, fruits and vegetables contain plant compounds which help reduce inflammation.
Dietary Considerations
There are other essential considerations to make when choosing your carbohydrates;
Whole grains
Whole grains are foods that contain the endosperm, germ and bran of the grain. They’re a rich source of b vitamins, antioxidants, fibre and minerals. They also contribute to the efficiency of a healthy digestive process.
Whole fruits & veg
Whole fruits & veg should always be prioritised over smoothies & fruit juices. When you blend or juice a fruit or vegetable, you don’t get the entirety of the fibre content of the fruit or vegetable. Fruit juices lose the fibre entirely, whereas smoothies don’t contain the insoluble fibre. The soluble fibre left alone is dependent on that insoluble version to form the intestinal barrier, which prevents your body absorbing the entirety of the sugar content of the fruit or vegetable. A healthy diet should consist of at least 5 whole fruit and vegetables.
Summary
Carbohydrates are an essential macronutrient. They’re your body’s preferred source of energy, and insufficient carbohydrate intake can lead your body to convert muscle mass to glycogen for energy. Carbohydrates also contribute to digestive process efficiency by reducing inflammation and promoting a positive gut flora. Complex carbohydrates should be considered a priority due to the slow, sustained release of energy and nutrient density. Simple carbohydrate consumption should be restricted depending on activity levels. Whole grains and whole fruits should be a part of a healthy, balanced diet due to their benefits.
Protein
Best known as the muscle-building macronutrient, proteins are an essential part of every cell within the body. They contribute to the efficiency of almost every chemical process your body relies on to function. Guidelines suggest you should be getting anywhere from 10-30% of your daily caloric intake from proteins in order to be eating a healthy diet.
What are proteins?
Protein is composed of amino acids which are organic compounds. These amino acids consist of carbon, hydrogen, nitrogen, oxygen and sulfur; elements which are essential to life. Proteins are made up of hundreds and thousands of amino acids.
Amino Acids
Amino acids are the building blocks of protein. There are 20 different types of amino acid, nine of which are considered essential:
Non-Essential
- Alanine – encourages the consumption of carbohydrates for energy.
- Arginine – deficiency can lead to weakened muscles, hair loss and inefficient healing of wounds.
- Asparagine – Aids ammonia synthesis and the nervous system health.
- Aspartic Acid – Responsible for a contribution to the enzyme activity.
- Cysteine – Cysteine plays an essential role in the structure of a protein
- Glutamic Acid – Glutamic acid is a chemical that helps brain cells send and receive signals.
- Glutamine – Glutamine helps optimise the efficiency of the immune system and eliminates excess ammonia from the body,
- Glycine – Transforms toxic substances into safer, non-toxic substances
- Proline – Proline is a precursor to hydroxyproline which the body uses to make connective tissue.
- Serine – An essential ingredient of brain proteins, serine contributes to several bodily functions, including fat metabolism and tissue growth.
- Tyrosine – helps make dopamine and adrenaline. Has also been shown in studies to improve performance under stress.
Essential
- Histidine – Important in infant development, histidine deficiency can cause speech disorders and cognitive disabilities in children.
- Isoleucine – Contributes to brain stimulation, producing mental clarity and alertness.
- Leucine – Effective in producing chemicals that provide energy and promotes mental alertness.
- Lysine – Application or consumption of lysine helps fight herpes
- Methionine – helps prevent liver damage and treats liver disorders
- Phenylalanine – Used to make essential molecules responsible for the transmission of signals around the body
- Threonine – Used in the treatment of multiple sclerosis, spinal spasticity and other nervous system disorders.
- Tryptophan – Creates Niacin which is essential in the production of serotonin and also helps with nitrogen balance.
- Valine – Enhances energy and endurance as well as contributing to tissue growth
While the body needs all of the above amino acids, 9 are considered essential. Essential, in this instance, means that they must be consumed as part of your diet as your body is unable to produce them itself.
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How are proteins useful?
Protein’s are inextricably linked with muscle growth and repair. This is for a reason. When your muscles are put under stress, they are stretched, and a certain amount of stretching causes microtears. Your body’s response to this damage is to repair the muscles. Your muscles contact the brain to ask for the appropriate amino acids to be directed to the torn tissues so that they can repair the tear by filling the newly formed gap.
Muscle growth is stimulated by overload, where a muscle is worked beyond its current capacity and requires growth (hypertrophy) to continue to perform. Two types of stress trigger hypertrophy:
Metabolic Stress
Metabolic stress involves depleting energy levels to a low level, increasing the amount of blood, lactate and other metabolites into the muscles. This is believed to cause cellular swelling leading to muscular microtears.
Mechanical Tension
Mechanical tension is the amount of force applied to a material. In this instance, the material is skeletal muscle and the force applied is resistance in the form of weight pulling the muscular fibres apart.
The muscle damage caused by these two stressors depends on proteins to recover, repair and to grow. Protein is the primary structural component of cells, and its prior function is to build and repair damage within cells, and this includes the cells within the muscle.
Beyond muscle repair, protein also acts as a non-primary fuel source. When your body’s glycogen levels are depleted, and it isn’t receiving any carbohydrates or fat from your diet, it turns to protein as a fuel source. It converts proteins to glucose to fuel physical exertion. This can involve your body converting proteins within muscle mass into glucose which induces atrophy.
Storage
Unlike with carbs, your body has no storage system for protein. Instead, your body separates the amino acids from the nitrogen, and excrete the nitrogen via urination. This leaves behind something called alpha keto-acids, which are then converted to triglycerides and stored in adipose tissue or body fat. Alpha-keto acids can be converted to glucose, but this only occurs in the absence of its preferred fuel sources.
Every cell in the body relies on protein for structure which makes protein essential to every process and function within the body.
Consuming protein
Eating protein-rich foods is the only way to ensure you’re getting a full profile of amino acids from your diet. The only way to get the 9 essential amino acids is through diet.
The amount of protein a person needs to eat is dictated by many different factors including gender, body composition, age and activity level. It has been suggested that anywhere between 10 and 30% of your caloric intake is a healthy amount of protein. Weightlifters and bodybuilders are believed to need more protein than the general population due to the stress they put on their muscles to grow. However, many overconsume protein in the misguided belief that the more protein they eat, the more muscle they build.
Protein Foods
When looking for foods to include in your dieet to meet your protein requirements, you should prioritise foods that are classed as complete proteins. These are foods that supply a considerable amount of each of the nine essential amino acids. Complete, healthy protein sources include:
- Red meats
- Eggs
- Quinoa
- Soy
- Fish
- Cheese
- Poultry
You may also consider amino acid supplementation. The amino acids can be supplemented individually, or you can buy essential amino acid tablets. You should always prioritise foods when it comes to meeting your protein and amino acid requirements. Protein foods are essential to a healthy diet.
Summary
Protein is integral to the structure of every cell in the body. Without protein, the cells would not be able to form, and your body would atrophy. To optimise a range of health markers, you should aim to meet your daily requirements for the 9 essential amino acids that your body can’t produce itself. It is essential to consider some different things when determining your protein intake levels. If you’re very physically active, you may want to consider an increased amount of dietary protein to ensure proper muscle repair and growth. If you’re unable to meet your amino acid requirements through whole foods, you may want to consider supplementation. Your body can use proteins as fuel, but it prefers to use carbohydrates and fats first. When using protein for fuel, your body may break down muscle.
Fats
The last of the three macronutrients may well be the least understood because of the dual use of the word ‘fat’ leads many to think that eating fat makes you fat. This is, basically, false. Dietary fat and body fat are entirely different things. Your body’s relationship with dietary fat is far more complicated than this and fat is incredibly important to a healthy diet.
What are fats?
Fats are a compound, composed of chains of carbon atoms bonded to hydrogen atoms. What differentiates the different fats from one another is the length of the chains of carbon atoms and to how many hydrogen atoms they’re bonded. Marginal differences in structure result in significant differences in form and associated functions.
There are four types of dietary fat:
Saturated Fats
Traditionally the villain of the piece, our understanding of saturated fats’ role in health has evolved. Named ‘saturated’ because they’re saturated with hydrogen molecules. For 
decades we were told that saturated fats clogged our arteries and increased the risk of heart disease and should be restricted. Despite the general population adhering mostly to this advice, obesity has continued to soar.
Monounsaturated Fats
Unsaturated fats are fats that, in their chemical structure have a double bond (a bond is an attachment between molecules), so a monounsaturated fat is fat with only one (mono) double bond. Historically, monounsaturated fats have been known as ‘Healthy Fats’ due to their health benefits, such as their ability to lower harmful cholesterol levels.
Polyunsaturated Fats
In tandem with monounsaturated fats, polyunsaturated fats have been considered good fats (at the expense of their saturated cousins). Well known polyunsaturated fats include omega-3 and omega-6 fatty acids. They’re known for their promotion of healthy brain function, lower blood pressure and cell growth.
Trans Fats
Counter to the injustice of the demonisation of saturated fats, trans fats are linked with an increased risk of heart disease and raising bad cholesterol. They’re traditionally found in fried foods and processed foods. Your body has no need whatsoever for trans fats and guidance suggests you should restrict your consumption of trans fats to no more than ONE PERCENT of your total calories.
How are fats useful?
Fats are the most calorie-dense macronutrient. There are nine calories per gram of fat, regardless of type, this in comparison to four calories per gram of carbohydrate or protein. Fat is also your body’s second preferred energy source after carbohydrates. Unlike carbohydrates and proteins, fat is not stored as glycogen.
Energy
Fat molecules are large and need breaking down in the intestines using bile salts from the gall bladder. Once broken down into smaller pieces of fat, enzymes break them down into their base parts; glycerol and fatty acids. The two are then absorbed into the cells lining the intestine where they’re put back together as into protein-coated packages called chylomicrons. They are then passed into the lymphatic system where they eventually join up with the bloodstream. Once in the bloodstream, they’re broken down again by enzymes into fatty acids. These fatty acids are then absorbed into fat, muscle and liver cells. Here they are made into fat molecules by insulin and stored as fat droplets. Once your body has drawn on its carbohydrate reserves, it turns to fats to fuel physical exertion. It can use fat in one of two ways:
Dietary fat
Where carbohydrates and glycogen are not available, your body burns dietary fat for fuel. This involves a process called lipolysis. During lipolysis, the fat droplets are broken down into glycerol and fatty acids. The fatty acids can then be used by the body directly as energy, or they undergo gluconeogenesis, where the body turns them into glucose. Consumption of fats protects against catabolysis which is where your body breaks down muscle tissue to stay alive.
Stored fat
The fat that is stored in cells are broken down by different enzymes into glycerol and fatty acids which are then released into the bloodstream and make their way to the liver. Here they’re either broken down further or used in the production of glucose.
As well as being a rich fuel source, fats are essential to the absorption of certain types of vitamins called fat-soluble vitamins don’t dissolve in water and need to be taken with higher-fat foods for your body to be able to absorb them.
Cholesterol
Fats are also essential to the maintenance of a healthy cholesterol balance. But, to understand fats job in cholesterol, we must first define cholesterol, its role in the body and the two types. Cholesterol is a waxy substance found in every cell of the body which is vital in the production of hormones, vitamins and bile acids which are used aid digestion. There are two types of cholesterol:
- LDL (bad) cholesterol – High levels of LDL cholesterol in the body results in fatty build-ups which narrow the arteries and this, in turn, increases your risk of heart attacks and strokes.
- HDL (good) cholesterol – HDL cholesterol is the anti-LDL cholesterol. It is believed that HDL cholesterol acts as a removal van for LDL in that it carries it away from the arteries, to the liver where it is broken down and removed.
Eating mono or polyunsaturated fats helps increase your bodies production of HDL cholesterol which lowers your levels of LDL cholesterol.
Brain Function
Fatty acids have also been shown to have a positive impact on brain health because omega-3 fatty acids EPA & DHA are essential components of all cells in the body & have powerful anti-inflammatory properties. Sustained inflammation of the brain is believed to contribute to conditions such as Alzheimer’s & Parkinson’s. Also, low levels of blood DHA have also been linked to smaller brain size, a sign of brain ageing. A study which supplemented older adults with 900 mg of DHA a day saw a better performance on memory and learning tests than their placebo counterparts.
Consuming Fats
As discussed previously, it is important to prioritise mono and polyunsaturated fats in your diet when looking to achieve a complete, healthy diet with the benefits of fats. Sources of polyunsaturated fats include:
- Fish
- Sunflower Oil
- Walnuts
- Flax seed
- Soybean Oil
It is also important to include monounsaturated fats in your diet too. Rich sources include:
- Avocado
- Olive Oil
- Peanuts
- Cashews
- Almonds
Summary
Fats are the most complicated macronutrient due to the dual use of the word ‘fat’. Including monounsaturated and polyunsaturated fats in your diet has been shown to have significant positive health impacts. Understanding of the role of saturated fats in a healthy diet is still evolving and, while you should undoubtedly restrict your consumption of saturated fats, the link between them and heart disease is being challenged. As your body’s second choice fuel source, dietary fat protects against catabolysis, where the body converts muscle tissue to energy. Also, fatty acids have been shown in numerous studies to contribute to good brain health. As with the other two macronutrients, fats are an essential part of a healthy diet.
