What is glucose intolerance?
Glucose intolerance is a term used to describe conditions associated with abnormally high levels of glucose in the blood, including ‘impaired fasting glucose (IFG)’ and ‘impaired glucose tolerance (IGT)’. In IFG, glucose levels are raised following a period of fasting and in IGT, glucose levels remain high hours after the ingestion of glucose. These conditions are also called ‘pre-diabetes’, because blood glucose levels are below the cut off points for diagnosing type 2 diabetes (T2D), although risk of progression to T2D is high.
What is type 2 diabetes (T2D)?
T2D is a chronic disorder characterised by raised blood glucose levels (hyperglycaemia) because the body has become inefficient at responding to the hormone insulin, a condition known as insulin resistance. Insulin production can also become insufficient in people with T2D as the disease progresses. Insulin enables the body to process glucose to make energy in the cells. Insulin keeps blood glucose within a safe range by latching on to a cell and signalling the cell to take in glucose.
How common is T2D?
T2D is estimated to affect around 6% of the population in the UK, however occurrence is higher in certain ethic groups, including people of South Asian and African Caribbean origin.
What are the symptoms of glucose intolerance and T2D?
In the pre-diabetic stage symptoms can be absent or go unnoticed. Symptoms of glucose intolerance can overlap with those of T2D and can include:
- Frequent urination
- Excessive thirst
- Light-headedness
- Tiredness
- Blurred vision
- Frequent illness
- Cravings and hunger
What are the health risks associated with glucose intolerance and T2D?
People with glucose intolerance and T2D often have other health conditions such as obesity, high blood pressure and high cholesterol levels. Chronically high blood glucose levels lead to many serious health conditions and premature deaths. These are largely attributed to the damage chronically high blood glucose levels cause to the body’s large and small blood vessels, which leads on to conditions such as heart disease, stroke, poor circulation, damage to the kidneys, retina of the eyes and nerves.
What causes of glucose intolerance and T2D?
Factors thought to be involved in the development of glucose intolerance and T2D include:
Food intake patterns: dietary trends indicative of a nutritionally poor diet high in processed foods, such as a high intake of sugary drinks, fat and saturated fat and low in dietary fibre, increase the risk of being overweight or obese and either independently of, or as a consequence of obesity, development of T2D.
Overweight and obesity: obesity can impair the body’s metabolism and increase insulin resistance, which is why weight loss is an important strategy in preventing and supporting T2D.
Inflammation: obesity is associated with a chronic low-level of inflammation, originating from excess fat tissue stores which produce inflammatory messengers. Inflammation is thought to interfere with insulin’s communication with cells and therefore is an important factor in the development of insulin resistance.
Genetics: genes have been identified which play a role in T2D development.
Inactivity and sedentary lifestyle: sedentary behaviour and low physical activity levels contribute to weight gain and further increase the health risks associated with being overweight.
Age: risk of T2D increases with age.
Smoking: smoking increases the risk of T2D.
What is the treatment for glucose intolerance and T2D?
Glucose intolerance disorders and diabetes can frequently be managed by dietary and lifestyle advice alone or in combination with drugs to control blood glucose. Some patients require multiple drugs in combination with insulin.
What diets are used to support glucose intolerance and T2D?
Controlling blood glucose levels is crucial in both diabetes prevention and delaying the advancement of associated blood vessel damage. Dietary strategies can stop the progression of pre-diabetes to T2D in some individuals. As with any serious health condition, it is important that people with T2D consult a doctor before starting a new diet. Diets to support glucose intolerance and T2D may include:
- Very low or low calorie diet
- Low carbohydrate diet
- Low glycaemic index diet
- Low sugar diet
- Intermittent fasting diet
Some simple strategies to support glucose intolerance and T2D are:
- Lose weight: overweight and obese people could achieve a reduction in many risk factors by loosing 5-10% of their current body weight, regardless of how much they weigh to begin with.
- Eat a balanced meal: include foods from mixed food groups (proteins, fats and oils, low glycaemic index and high fibre carbohydrates, vegetables and fruit), because well-balanced meals may promote a slower and more sustained release of sugar into the blood.
- Eat low GI and wholegrain and wholemeal carbohydrates: replace refined and processed carbohydrates (e.g. white bread, white rice and pasta) with wholegrain and lower glycaemic index carbohydrates (e.g. porridge, brown rice, rye bread, sweet potato, wholemeal bread, beans and lentils), which offer higher nutritional value and may support better blood sugar balance.
- Meal patterns: have a regular pattern of meals and snacks throughout the day to supply regular fuel to the body.
- Eat the right fats: omega 3 fats found in oily fish (sardines, mackerel, salmon, anchovy, herring and tuna), nuts and seeds, can alter the body’s inflammatory response and could improve insulin resistance.
- Eat plenty of rainbow coloured fruit and vegetables: these are a good source of antioxidants, which the body uses to prevent injury to cells and therefore may attenuate damage to blood vessels associated with T2D.
- Exercise regularly: exercise can improve the body’s response to insulin. Physical activity also can also alter the body’s ratio of muscle to fat, which could reduce inflammation.
- Limit alcohol consumption: alcohol can raise blood sugar levels therefore consumption should be occasional and in moderation.
- Regularly monitoring of blood glucose: monitoring of blood glucose levels through regular blood tests (including HbA1C) and also using self-monitoring blood glucose devices at home can help people keep track of their progress.