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The foods that we consume play more of a role in our health than perhaps anything else.  It may be a cliché, but the saying, “you are what you eat”, rings with truth and good nutrition leads to a healthy body and a sound mind.  Read on to learn more about the science of nutrition.

What is Nutrition?

Nutrition is the science that establishes the relationship between a person’s diet and their levels of health.  People that specialise in this are called nutritionists or dietitians.  In Australia, there are no rules governing the use of the terms 'Dietitian' and 'Nutritionist'. They may be used by Dietitians, nutrition scientists and nutrition graduates, or people with very limited nutrition qualifications. To make sure you are receiving expert nutrition advice, always enquire about the qualifications of a dietitian or nutritionist.  

The body requires six main things in order to function correctly:  carbohydrates, protein, fat, vitamins, minerals, and water.  These all need to be consumed on a daily basis.  If one of these becomes low or deficient, a negative impact occurs on the body and illness or a general feeling of being unwell may result.


Carbohydrates are the body’s main source of energy.  They used to be classified as being either simple or complex but now they are classified according to their glycaemic index.  The glycaemic index scales carbohydrates according to how long they take to absorb and how quickly they raise blood sugar levels.  Foods may be low, medium or high on this index.

Examples of foods that are rich in carbohydrates include breads, cereals, rice, pasta, legumes, fruits, milk, yoghurt, sugar, potatoes, corn, and many processed foods.  All foods that contain carbohydrates are converted into simple sugars, mainly glucose, by the body’s digestive system.  This glucose is then transported to cells via the blood stream.  Insulin is released by the pancreas to help the glucose move from the blood into the cells.  Once inside the cell, the glucose is burned along with oxygen in order to produce energy.  Any excess glucose in the body is converted into glycogen which is stored inside the muscle tissue and the liver.  This glycogen is ready for use if blood sugar levels should drop.

Fats and Energy

Fats have often been maligned as being bad for you and something that you need to avoid as much as possible, but the truth is that fat is important in the body and we do need some fat for optimal health and energy.  The key is to choose the fats that are good for you and avoid the bad fats.

Fat plays a role in many bodily processes.  It forms a protective layer around the organs, helps to keep the body warm, assists in the transportation and absorption of nutrients, and helps in the production of hormones.

The key with fats is to choose the healthy fats such as mono-unsaturated fats and poly-unsaturated fats.  Including these in your diet can help to lower the levels of blood cholesterol.  Fatty acids are also an important component of your diet as your body is unable to manufacture them itself – it needs them to come from the diet.  There are two main types of fatty acids – omega 3 and omega 6.  Omega 3 is found in plant and marine foods, while omega 6 is found mainly in nuts, seeds, and plant oils.  Fatty acids are important for reducing the risk of heart disease, for brain function and can even help to treat depression.

Saturated fats are fats that are found in animal foods, dairy, fast foods, and processed foods.  These fats increase the level of cholesterol in the body and therefore should be avoided wherever possible.  The best way to do this is to choose lean cuts of meat, reduced-fat dairy products, and to eat a diet that is low in processed or refined foods.

Trans-fatty acids are a type of fat that are rare in nature but are found in many processed foods thanks to a process that turns liquid vegetable oil into a partial or full solid.  Trans-fatty acids are dangerous because they increase the levels of bad cholesterol in the blood as well as reducing the levels of good cholesterol.  They also increase the risk of heart disease.

All foods contain energy but fats are considered to be energy dense as they contain twice as many kilojoules per gram than say carbohydrates or protein.  For this reason, it is important to be aware that foods that are high in fats are also high in kilojoules, and this needs to be taken into account when planning your diet.


Fibre should be a large component in all diets.  It is found in all plant foods, such as cereals, fruits and vegetables, legumes and nuts.  It is not found in animal products.  Fibre is important because it:

  • prevents and relieves problems in the bowel and digestive system
  • helps to improve blood cholesterol levels
  • reduces the risk of heart disease and diabetes
  • reduces the risk of some forms of cancer

There are two types of fibre – soluble and insoluble.  Soluble fibre is fibre that dissolves in water and it is excellent for controlling cholesterol and blood sugar levels.  Insoluble fibre is referred to as “roughage” and it is best for increasing stool volume and relieving problems in the digestive system.  Both types of fibre need to be included in the diet but fibre intake needs to be paired with adequate water intake.  If there is not enough water in the diet, increased amounts of fibre can actually cause constipation.

If you want to control your weight, or lose weight, including more fibre in your diet can be very beneficial.  This is because foods that are high in fibre are digested more slowly, leaving you feeling fuller for longer.  They are also low in fat.  Fibre also delays the absorption of sugar in the intestines, meaning that blood sugars levels do not “spike”.  Spikes in blood sugar levels have been linked with obesity and diabetes.

Easy ways to increase your fibre intake include eating whole grain foods, adding a few extra vegetables to your dinner or eating an additional piece of fruit every day, and snacking on things such as dried fruit, nuts, or wholegrain crackers.

Protein and Amino Acids

Protein makes up an enormous part of the human body with the hair, skin, nails, muscles, and brain cells being just some of the things that are based on protein.  Protein is found in animal foods such as chicken, red meat, and fish, soy products, dairy products, and also in legumes (which is the group name for things such as beans and lentils), nuts and seeds, and grains.  Proteins are converted into amino acids in the body.

People should eat one gram of protein for every kilogram of bodyweight – but many Australians actually eat more protein than they need so deficiencies are rare. 

Proteins are made up of smaller chemicals called amino acids and a protein can contain anywhere from fifty to tens of thousands of amino acids that are held together by peptide bonds.  Non-essential amino acids are amino acids that can be made by the body while essential amino acids are amino acids that can only be obtained from the diet.  Broadly speaking, animal products will contain all of the essential amino acids and are thus called complete proteins, while plant products are usually missing at least one of the essential amino acids, thus are non-complete proteins.  The notable exceptions to this are soy products and amaranth, the only complete vegetable proteins.

Amino acids are used for three main things in the body – protein synthesis, as precursors to other compounds and for energy.


Water is absolutely vital to the human body.  The body is made up of as much as 75 percent water and it can last for a matter of only days without it.  Water is the basis of the blood, the digestive juices, urine, and sweat, and is contained in muscles, fat and bone.  Water cannot be stored by the body and thus needs to be replaced every day.

Water is essential for:

  • maintaining the health of the cells
  • keeping the blood liquid and flowing correctly throughout the body
  • eliminating waste products
  • regulating body temperature
  • keeping the mucous membranes moist
  • lubricating and cushioning joints
  • the digestive process
  • moisturising the skin
  • transporting nutrients and oxygen
  • acting as a shock absorber in the body

Dehydration occurs when the body does not have enough water, and it can be acute or chronic.  Acute dehydration occurs when the body is depleted of water due to things such as heavy exercise or hot water and it can be easily fixed by increasing fluid intake.  Chronic dehydration is more serious and it occurs when the body does not have enough water over a prolonged period of time.  Some symptoms of dehydration include: headaches, lethargy, changes in mood, dry nasal passage and dry or cracked lips, urine that is dark in colour, weakness, tiredness, confusion, and even hallucinations.

Some people will need more water in their diet than others.  These include those that are on a high protein or high fibre diet, children, those that are physically active, those living or working in hot conditions, and people suffering illnesses that cause vomiting or diarrhea. 

On the opposite end of the scale, drinking too much water can result in a condition called water intoxication, or hyponatremia.  This occurs when there is too much water in the body, causing the levels of sodium to drop to dangerously low levels. Sodium is necessary in the body for muscle contraction and for sending nerve impulses and, if water consumption is too high, the kidneys actually cannot get rid of enough water.

Six to eight glasses of fluid should be consumed each day as a general guideline.  More may be required for some people.  Sources of water include fluids such as water, coffee, tea, milk, juice, soft drinks and soup.  Water can also be found in most foods.

Vitamins and Minerals

Vitamins and minerals are another essential part of our diet.  Vitamins are natural, chemical substances that are used by the body in many daily functions such as growth and cell reproduction.  There are two types of vitamins – fat soluble and water soluble.  Fat soluble vitamins include vitamin A or retinol, vitamin D, vitamin E, and vitamin K.  These are vitamins that can be stored within the body in the liver and within the body’s fat.  Water soluble vitamins include the B group of vitamins, folic acid or folate, and vitamin C.  While these are also able to be stored within the body, they are stored for shorter periods of time.

Vitamin deficiencies occur over a period of weeks or months.  However, for optimum health and bodily function, it is important to include a wide range of fresh foods in the diet.  Organic foods are ideal.  Supplements are usually not necessary when the dietary intake of vitamins and minerals is adequate.  However, they may be useful for vegans, pregnant women, people on very low fat diets, people on restrictive diets, people recovering from serious illnesses or surgery, or people that have problems with absorption.

Minerals are inorganic elements that are necessary for the body to function correctly and they serve two major purposes.  They build the skeletal and the soft tissues of the body and they also regulate bodily processes such as the heartbeat, blood clotting, internal fluid pressure, nerve response and oxygen transport.  Minerals may be classed in two categories – “major” minerals, and trace minerals.  Major minerals include calcium, phosphorus, sodium, potassium, chlorine, sulfur and magnesium, and the body needs relatively large amounts of these.  Trace minerals are so called because the body requires less than 100mg a day of these, and these include iron, copper, zinc, cobalt, manganese, fluorine, molybdenum, and selenium.   Silica is also an important mineral in the body and it is necessary for the bones, skin, tendons, blood vessels, and the blood itself.


Antioxidants are substances that occur in nature that are very good for our health.  The purpose of antioxidants is to neutralise free radicals in the body. While some free radicals are necessary, too many can contribute to diseases such as heart disease, liver disease, and even some cancers.  Free radicals have also been attributed to premature ageing.  Excessive amounts of free radicals can be caused by things such as smoking, pollution, drinking alcohol, high-fat diets, and exposure to the sun.

There are literally thousands of antioxidants in the diet, with some of the better known ones including vitamin C, vitamin E, beta-carotene, selenium and copper.  Eating a diet that is full of fresh fruits and vegetables, as well as wholegrains (link to wholegrains article) and other unprocessed foods is the best way to gain these antioxidants.  This is because it is thought that antioxidants work most effectively in combination.  They do not work as well on their own.

Some foods that are extremely high in antioxidants and in vitamins in general are Goji berries, spirulina, and green tea.

Salt and Sodium

Salt and sodium are necessary in the human body but many people eat twice as much salt as they actually need.  The recommended dietary intake is between 920 grams and 2,300 grams.  Salt is obtained primarily through processed foods, but it also obtained through use at the table and during cooking, and through fruits, vegetables and meat (however, only about 10 percent of salt is obtained from the latter).

Sodium is responsible for maintaining the correct volume of circulating blood and tissue fluids.  Salt is loss through bodily processes such as sweating, vomiting, diarrhea and urine.  If too much salt is lost, the level of fluid in the blood will decrease and cause such things as dizziness, muscle cramps and nausea.  It can occur as a result of heavy sweating, acute gastroenteritis, and water intoxication.  However, because most people get more than adequate salt intake, sodium depletion is rare. 

Problems that are caused by ingesting too much salt include:

  • high blood pressure
  • heart failure
  • kidney problems
  • edema
  • stroke
  • osteoporosis
  • left ventricular hypertrophy
  • gastric cancer

Many people believe that muscle cramps are caused by losing salt during hot weather or through exercise, and thus the salt needs to be replaced.  The cramps are actually caused by a lack of water.

It is interesting to note that the human body is designed for a high potassium diet and not a high sodium diet.  What is happening in many diets is that the levels of sodium are increasing while the levels of potassium are decreasing.  Potassium is very protective and actually lowers the body’s blood pressure.  Therefore, salt should be reduced in the diet wherever possible, and people should try to eat unprocessed, natural foods where practical.  An alternative to traditional table salt or rock salt, is Himalayan crystal rock salt, which contains all of the elements necessary to the human body, and is actually very beneficial.

Food Intolerances

A food intolerance is when a person has a reaction to a food or ingredient every time it is eaten.  The reaction occurs when the nerve endings in various parts of the body are irritated.  Symptoms are varied but some of the more common ones include nausea, bloating, diarrhea, abdominal pain, and bowel irritation.

It is important to note that food intolerances are not the same as food allergies.  Food allergies involve an immune reaction and are therefore much more serious.

One common food intolerance is to gluten.  Gluten is a protein that is found in many different grains such as wheat, barley, oats, and rye, and foods that contain these grains.  People that are intolerant to gluten have a condition called celiac disease.  People with this condition are permanently intolerant and have to avoid gluten for the rest of their life.

Moderation is the Name of the Game

In the modern diet, it is important to practice moderation as too much of any food can be bad for you.  One group of foods that should definitely be eaten occasionally is the processed foods such as biscuits, potato chips, cakes, pastries, fast food, and so forth.  This is because these are high in saturated fats and do not provide much nutritional value for the amount of kilojoules that they contain.  Processed foods are high in fat, salt, and sugar.    However, there is no need to completely cut them out of your diet.  As long as you eat fresh, healthy foods the majority of the time, it is perfectly fine to have the occasional treat.


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