What is diabetes? | Viva!

What is diabetes?

What is diabetes?

Diabetes mellitus (the full medical name) is a condition characterised by high levels of glucose (sugar) in the blood which the body cannot properly use and which is eventually excreted in the urine, along with a good deal of water. As glucose passes through the kidneys, it attracts water which results in frequent trips to the toilet to urinate and a feeling of thirst caused by fluid loss. Diabetes is caused either by the pancreas entirely failing to produce the hormone insulin or producing insufficient quantities; or by the body cells’ inability to react to insulin.

Insulin is produced by the pancreas and acts as a key, allowing glucose into the body’s cells. Glucose is a vital source of energy for cells and is the main fuel for the body’s processes. It comes from digesting carbohydrates but is also partially produced by the liver. Carbohydrates are the main nutrients in healthy foods such as wholegrain or rye bread, wholegrain pasta, oats, brown rice, pulses (beans, peas and lentils) and sweet potatoes. They are also in not-sohealthy foods such as white bread, white pasta, cakes, sweets and other sugary foods.

If the body cannot use glucose as a source of energy it uses fat instead, but this inevitably disturbs the biochemical balance of the body and can lead to further health complications. When glucose is prevented from entering the body’s cells, they are denied their basic and most important fuel. This can result in tiredness, which is one of the symptoms of diabetes. Other symptoms are irritability, nausea, hunger, thirst, weight loss, blurred vision, tingling sensations in the hands and feet and dry, itchy skin.

In 1985, about 30 million people worldwide had diabetes of both types; a decade later this figure had increased to 135 million and by 2000 an estimated 171 million people had the disease. It is predicted that at least 366 million people will have diabetes by 2030 (Wild et al., 2004). This increase is attributed to a range of factors, including population growth, ageing, unhealthy diets high in saturated fat and cholesterol, obesity and lack of physical exercise.

In the UK alone, 2.8 million people have been diagnosed with diabetes (Diabetes UK, 2010a), while an estimated half a million more have it but have not been diagnosed yet (Diabetes UK, 2010b).


Type 1 diabetes

Type 1 diabetes typically develops early in life when the immune system attacks the insulin-producing cells in the pancreas and destroys them. It results in the body being unable to produce any insulin. Because insulin is a vital medium through which glucose is able to enter the body’s cells, when it is absent glucose simply builds up in the blood.

Type 1 diabetes accounts for 10 per cent of all people (15 per cent of adults) with diabetes (Diabetes UK, 2010b). The incidence is increasing in all age groups but the rise is particularly steep among children under five years old (NHS, 2008).

Evidence is mounting up that a combination of susceptible genes combined with early exposure to cow’s milk are responsible for this self-harming reaction of the body (see page 10 for more information). It might be also triggered by a virus or other infection.


Type 2 diabetes

In type 2 diabetes, the body can still make some, but not enough, insulin or it fails to react to insulin as it should (insulin resistance). Again glucose builds up in the blood. This condition accounts for approximately 90 per cent of all cases (85 per cent of adults). (Diabetes UK, 2010b).

Type 2 diabetes usually develops in people over the age of 40, although South Asian and Afro-Caribbean populations are at greater risk and tend to become diabetic relatively early in life – at around the age of 25 (Diabetes UK, 2010b). However, type 2 diabetes is rapidly becoming more common in children, adolescents and young people of all ethnicities. It is predominantly ascribed to the increase in childhood obesity (NHS, 2008).


Gestational diabetes

This type of diabetes appears in women during pregnancy, usually after the first trimester, but mostly disappears when the pregnancy terminates. In most cases, it arises because the body cannot produce enough insulin for both mother and baby. However, if diabetes occurs during the first trimester, the condition is likely to have existed already before the pregnancy and
may continue after it.

Being overweight or obese is a critical factor in contracting type 2 diabetes and puts people at higher risk, so it follows that the same principle applies to pregnant women.

Gestational diabetes affects up to five per cent of all pregnancies (Lancet, 2008). Those women who developed gestational diabetes which subsequently disappeared, are at an increased risk (about 30 per cent) of the disease reappearing later in life (Girling and Dornhorst, 2004).


Metabolic syndrome

Metabolic syndrome, or Syndrome X, is a condition characterised by central obesity (most weight accumulated around the waist), raised blood pressure, raised triglycerides (fats in the blood), low HDL cholesterol (the ‘good’ type that helps to clear cholesterol from the bloodstream) and impaired glucose metabolism. Impaired glucose metabolism means that the body is not using glucose properly and the level in the blood is elevated but has not yet reached diabetic levels.

All these symptoms significantly increase the risk of diabetes and cardiovascular disease.



Individuals with impaired glucose metabolism (elevated blood glucose) which has not yet reached diabetic levels are diagnosed with pre-diabetes. This condition is also associated with insulin resistance. The main risk factor for pre-diabetes is obesity and related risk factors include high blood pressure, low HDL cholesterol and high triglycerides (fats in the blood).

Pre-diabetes almost always precedes type 2 diabetes but many people don’t know they have the condition until diabetes has developed. However, pre-diabetes, as well as metabolic syndrome, is reversible with the D-Diet (see page 16).

Diabetes is not usually diagnosed immediately after its onset and by the time the diagnosis is made, many people will have already developed some health complications. However, even people who are aware of their condition and have adjusted their lifestyle accordingly, are still at considerable risk of heart disease, stroke, eye problems, kidney disease, nerve damage and amputations.


Common health complications

Cardiovascular disease

Cardiovascular disease (CVD) is a broad term and includes heart disease, stroke and other diseases of the heart and circulation – for example hardening and narrowing of the arteries supplying blood to the legs (peripheral vascular disease). CVD is more common in people with diabetes because high glucose levels in the blood enable fatty deposits to build up more easily on the inner walls of arteries. CVD is also the leading cause of death and disability in people with diabetes.

Because of prolonged periods of poorly controlled blood glucose levels, patients with diabetes also tend to have raised cholesterol and triglyceride levels and higher blood pressure. High blood glucose levels actually cause an increase in the blood lipids (fats) and make cholesterol more likely to stick to the walls of blood vessels. All these complications contribute to worsening CVD but can also cause further complications such as eye and kidney disease (see below).

Kidney disease

High blood glucose levels and high blood pressure can cause damage to small blood vessels, particularly in the kidneys. Kidneys clean blood by filtering out waste products and excess compounds but are extremely sensitive to damage. Once the damage reaches a certain point, they start to fail. The sign of kidney damage is when protein albumin begins to appear in the urine. The level of damage is measured by the amount of this protein present in the urine.

Almost one in three people with type 2 diabetes develops kidney disease (Department of Health, 2006) and one in five with type 1 diabetes dies of kidney failure (Morrish et al., 2001).


Blood vessels in the eye are just as sensitive to high blood glucose and cholesterol levels and high blood pressure as those in the kidneys. Blood vessels supplying the retina – the seeing part of the eye – can become blocked, damaged, leaky or grow unpredictably. Any such damage or abnormal growth affects the vision and can ultimately lead to blindness. The condition where the retina is damaged is called retinopathy and it is estimated that 4,200 people in England are blind due to diabetic retinopathy (Scanlon, 2008). Almost all people with type 1 diabetes develop some degree of retinopathy within 20 years of diagnosis and almost two thirds of people with type 2 diabetes have retinopathy (Scanlon, 2008).


Any type of diabetes, especially when poorly controlled, can lead to nerve, muscle and sweat gland damage, which can seriously affect circulation and sensitivity in feet and legs and can result in injuries or infections. It can progress to a point where amputation is necessary.


Diabetes and the complications that can spring from it, the side effects of medication or daily diabetes management itself can affect the emotional well being of anyone. As a result, depression, eating disorders, anxiety and various phobias can develop.


Changing levels of blood glucose can damage nerves which transmit impulses to and from the brain and spinal cord, to muscles, blood vessels, skin and other organs.

The nerve damage can cause pain and may also lead to other problems, such as poor sensitivity in the feet making any minor injuries more likely to go unnoticed, which makes the damage more serious. Neuropathy can also lead to erectile dysfunction or impotence.

Neuropathy affects up to 50 per cent of people with diabetes (Boulton, 2005) whilst chronic painful neuropathy affects about one in six – compared to one in 20 non-diabetic people of the same age (Daousi et al., 2004).