6. Food for life

Before the 1980s, dietary advice centred on carbohydrate restriction as the only means of controlling blood glucose levels. People were advised to limit their intake of carbohydrate foods such as bread, potatoes, rice, pasta and cereals and to fill up on foods such as meat, cheese, eggs, cream and butter. This resulted in a diet low in carbohydrate but high in fat. Research in the 1970s (Brunzell et al 1974, Simpson et al 1979) showed that high-carbohydrate diets could actually improve diabetic control, providing the carbohydrate was in a complex, high-fibre form. Studies were also beginning to show that reducing fat intake in non-diabetic people resulted in reduced morbidity from cardiovascular disease (Miettinen et al 1977). This led researchers to ask whether the high-fat diet could be contributing to the increased risk of heart disease in people with diabetes.

As a result of this research, guidelines were published in both the USA (American Diabetes Association 1979) and the UK (British Diabetic Association Nutrition Subgroup 1982). These overturned decades of teaching by recommending that people with diabetes should consume a diet high in carbohydrate and low in fat. These were considered to be radical documents, but they were followed by the introduction of almost identical policies by diabetes associations in many other countries. These were also very similar to nutritional guidelines published for the general population in the UK (Department of Health and Social Security (DHSS) 1984) and by the World Health Organization (James et al, WHO 1988) for Europe. This had positive implications in that people with diabetes were no longer being advised to follow a ‘special diabetic diet’.

These guidelines have now become established practice throughout Europe and North America, although there have been some shifts in emphasis in the light of new knowledge and clinical experience (American Diabetes Association 2003, Diabetes UK Nutrition Subcommittee 2003, European Association for the Study of Diabetes 2000).

The current recommendations on the composition of the diet for diabetes are summarised in Table 6.1 and Table 6.2.

The main differences in emphasis from previous recommendations (British Diabetic Association Nutrition Subgroup 1992) are:

The scientific evidence for the effect of diet on diabetes management needs to be translated into practical and realistic advice for the individual. Because the nutritional objectives for those with diabetes are very similar to those advocated for the entire population, dietary guidance should be based on a framework of healthy eating principles such as the Balance of good health (Health Education Authority (HEA) 1994) shown in Fig. 6.1. More information on this is given in Box 6.3.

This does not mean, however, that dietary advice is simply a matter of healthy eating guidance; many other issues have to be borne in mind and specific aspects relevant to diabetes will need to be superimposed on this. Table 6.4 shows how it can be adapted for diabetes.

Approximately 80% of people with type 2 diabetes, and many with type 1 diabetes, are overweight and hence weight loss and stabilisation will be a major priority in their management.

Moderate weight loss of 5–10 kg can help to improve blood glucose and lipid levels, reduce insulin resistance and improve hypertension. It has also been shown that losing weight can improve life expectancy in overweight people with type 2 diabetes by an average of 3–4 months for each 1 kg (2.2 lb) of weight lost (Lean et al 1990). The largest published study to date into weight loss in overweight people with diabetes (Williamson et al 2000) showed that a weight loss of 11% of initial body weight was associated with a reduction in mortality of 25% and in heart disease of 28%. However, losing even small amounts of weight has health benefits. It is therefore worth stressing the benefits of any weight loss and maintenance of this loss for the overweight person with type 2 diabetes.

For most people, carbohydrate intake should be fairly evenly distributed throughout the day. Those who have erratic eating habits should be encouraged to adopt a more regular meal pattern to ensure a better and more constant balance between supply and usage of glucose. This can have added benefits in aiding weight loss in those who are overweight. For many, a meal pattern of three evenly sized meals and three snacks is ideal, but this will vary between individuals. Lifestyle might dictate the meal pattern for some and, for people with type 2 diabetes who are overweight, between-meal snacks might need to be discouraged. No matter what, the most important aspect is that the individual’s meal pattern stays relatively constant from day to day. Those who are treated with oral hypoglycaemic agentsor insulin should also be able to adapt their diet for different circumstances, e.g. exercise or illness.

Advice is essential so that an adequate carbohydrate intake can be achieved from day to day, especially for those on sulphonylureas or insulin. Traditionally, the amount of carbohydrate was regulated by various different systems, where foods containing a defined amount of carbohydrate were substituted for one another. This allowed individuals to calculate and usually restrict their intake of carbohydrate. Following the realisation in the 1980s that carbohydrate restriction was both unnecessary and counterproductive, simpler methods of meal planning were introduced:

It is worth remembering that different approaches will be required for different people in different circumstances and from different cultures. People who have had diabetes for many years might have been taught, and still use, the 10-g carbohydrate exchange system. Although it would be reasonable to encourage them to have a better composition of diet, it can be very disturbing for some to be told to abandon a system that they have used with confidence for many years to manage their diabetes. They should not therefore be forced to change the way in which they do manage the dietary aspects of their diabetes if they do not wish to do so, although many will welcome a more liberal approach.

Some people will feel more comfortable with two fixed daily injections of insulin and a regular meal pattern. Others, by contrast, who are knowledgeable and motivated can, in conjunction with frequent blood glucose monitoring, vary the amount of carbohydrate consumed, or the time at which it is eaten, by adjusting their insulin doses or physical activity or both. In the UK, the results of a trial (DAFNE Study Group 2002) into this liberal approach have been published. This is a 5-day outpatient programme that teaches individuals to adjust their insulin doses to carbohydrate portions by way of carbohydrate to insulin ratio. People are taught to make adjustments on their blood glucose trends associated with food, exercise, alcohol and illness. Although this intensive insulin therapy and carbohydrate counting is time intensive, this style of education helps people understand more about the effects of food on blood glucose levels and be empowered in their self-management (see Chapter 11).

It used to be thought that if you ate the same amount of carbohydrate – whatever it was – it would have the same effect on your blood glucose levels. It is now known that different carbohydrate-containing foods have different glycaemic responses (Jenkins et al 1984). This means that they have different effects on blood glucose levels, so 10 g of carbohydrate as bread does not have exactly the same effect as 10 g of carbohydrate as fruit or as pasta. Attempts have been made to quantify this effect and to classify foods according to their glycaemic index (GI). This is defined as the glycaemic response to individual foods in relation to that of glucose, i.e. the GI is a measure of how quickly foods containing carbohydrate raise blood glucose levels. Thus choosing slowly absorbed carbohydrates 1can help even-out the blood glucose levels. The glycaemic effect of a carbohydrate food is determined not only by its sugar and fibre content, but also by many physical and chemical characteristics; the way in which an individual food is cooked or processed, or its degree of ripeness, will also affect its GI. The glycaemic response to a single food will also change when it is eaten in combination with other foods, e.g. fat content will delay gastric emptying and therefore delay absorption of carbohydrate; the soluble fibre content of one carbohydrate food will affect the absorption of another. The concept of GI is useful as a pointer to food choice. Foods with consistently low glycaemic effect can be promoted as particularly good choices in preference to those with higher glycaemic potential (Box 6.6). It should be remembered, however, that GI should not be emphasised to such an extent that other important messages concerning meal pattern and overall dietary balance are lost.

Drugs will be required in the treatment of type 2 diabetes if diet alone fails to control diabetes adequately. Drugs should not, however, be used as an alternative to diet. There are different types of oral hypoglycaemic agents; the modes of action of these are discussed in more detail in Chapter 4.

Glucose (10–20 g) is the preferred sugar for the immediate treatment of acute hypoglycaemia because it does not require digestion or metabolism. This could be given in the form of 50–100 mL Lucozade or between three and six glucose tablets. After recovery from hypoglycaemia, a further 10–20 g of slower-acting carbohydrate (e.g. two digestive biscuits) should be given, unless the next meal or snack is due, in which case it should be eaten straight away. See Chapter 11 for further explanation on the treatment of hypoglycaemia.

Regular exercise has positive benefits in that it can lower blood pressure and blood lipids. It can also reduce insulin requirements and improve overall blood glucose control. For overweight individuals with type 2 diabetes, exercise will have the added benefit of increasing energy expenditure, which, when combined with a healthy diet, should assist weight loss. Regular exercise also helps to maintain lean body mass. This prevents the lowering of metabolic rate, which can be a danger with prolonged dieting.

There is no need for the person with diabetes to avoid alcohol completely, but it can create additional hazards. Alcohol consumption should be restricted to 3–4 units per day in men and 2–3 units per day in women, as in the general population (SIGN 2001). Alcohol can act as a very potent hypoglycaemic agent because it inhibits the formation of glucose by the liver. Glucose-lowering agents (e.g. sulphonylureas or insulin) together with alcohol can have a very serious effect if inadequate carbohydrate is eaten. Delayed hypoglycaemia can occur up to 16 hours after alcohol consumption – a fact that must be emphasised. People should avoid drinking alcohol on an empty stomach and ensure that they have extra carbohydrate to make up for the added hypoglycaemic effect of the alcohol. It is especially important to have a bedtime snack, as alcohol can continue to lower the blood glucose for several hours after alcohol consumption has stopped. Signs of hypoglycaemia can resemble signs of drunkenness; so that alcohol can mask the symptoms, which can therefore go unnoticed. Hence it is also vital that individuals carry identification that they have diabetes.

Any illness can affect diabetic control. Individuals taking insulin or tablets must continue with these when ill (see Chapter 11). If people are vomiting they should contact their GP, but insulin must never be stopped. The body’s natural response to illness is to utilise more glucose. Insulin requirements rise and there is an increased risk of diabetic ketoacidosis. This means that increased doses of insulin or oral hypoglycaemics might be required. Carbohydrate must also be taken in some form and meals can be replaced with liquid, semi-solid or solid foods containing carbohydrate depending on the person’s appetite. As a guide, 10 g of carbohydrate should be taken every hour until the person feels better. Regular blood testing is essential in times of illness. Table 6.7 suggests some sources of carbohydrate during illness.

During the month of Ramadan, practising Muslims abstain from food and liquids between dawn and sunset, commonly eating one large evening meal after sunset and a light meal before dawn. Fasting is obligatory for all healthy adult Muslims, although people with diabetes are exempt from fasting. Despite this, many choose to observe this religious obligation. Fasting can last up to 18 hours a day during the summer months and large quantities of sugary fluids, such as canned juices and fizzy drinks, together with fried foods and carbohydrate-rich meals are taken during the non-fasting hours. Sweet foods may also be specially prepared for Ramadan. Longer gaps between meals and greater amounts of foods (in particular foods high in sugar and starch) mean that people with diabetes can experience large swings in blood glucose levels during Ramadan.

With the appropriate advice, Amina should be able to undertake the fast safely. Ideally, discussions should take place well in advance of Ramadan as clinic attendance often drops at this time because people avoid exercise to conserve energy. Amina should be encouraged to attend the clinic to discuss monitoring her diabetes with the healthcare team and to be given advice about any changes to her insulin regime. Appointments should not be scheduled for days that she wishes to visit the mosque. Amina should be encouraged to take her blood glucose regularly because she will be at risk of hypoglycaemia. Some Muslims consider blood glucose testing as breaking a fast; however, an educational class designed specifically for self-management during Ramadan explains that this is a myth (Chowdhury et al 2003). Meal times should be discussed to ascertain the exact changes from Amina’s current meal pattern and some general dietary guidelines given:

Amina will also require advice about insulin. The most important message is for her not to stop taking insulin during Ramadan. She would need guidance on how to make appropriate adjustments to her insulin dosage and to negotiate for how long she can safely fast. There are some general guidelines regarding insulin:

With the appropriate support and guidance, the period of Ramadan should not pose a risk to the person with diabetes (www.diabetes/org.uk/healthcare).

Altered lipid metabolism occurs in people with both type 1 and type 2 diabetes but the pattern of dyslipidaemia is different. It is often present in people newly diagnosed with diabetes or those with poor glycaemic control. People’s lipid profiles should be reassessed after there has been control of hyperglycaemia. In people with type 1 diabetes with adequate control, lipid profiles tend to be similar to those of the non-diabetic population [elevated total and low-density lipoprotein (LDL) cholesterol; see Chapter 8]. As the risk of cardiovascular disease is higher in the population of people with diabetes, it is more important that these elevated levels are detected and corrected, ideally by means of dietary adjustment.

Most people with type 2 diabetes, and some overweight people with type 1 diabetes, have a dyslipidaemia associated with insulin resistance. This is characterised by an increase in triglyceride and harmful LDL cholesterol and a reduction in protective high-density lipoprotein (HDL) cholesterol. This often persists after glycaemic control has been achieved. Lifestyle interventions include weight loss, particularly by reduction of saturated fat (which reduces concentrations of triglyceride, LDL cholesterol and may increase HDL cholesterol). If weight loss is not required, energy from saturated fat can be replaced by carbohydrate or cis-monounsaturated fat. Regular physical exercise will help to reduce triglyceride concentrations and to improve insulin sensitivity. Sterols and stanols of plant origin have been shown to lower LDL cholesterol. These are now being incorporated into spreads and other fat-derived products such as yoghurts, semi-skimmed milk, etc., and are marketed as adjuncts to other dietary methods of reducing LDL cholesterol. However, they are very expensive (two to four times more than conventional) and their long-term effects on morbidity and mortality due to coronary heart disease are unknown. Hypertriglyceridaemia is sometimes associated with alcohol consumption and this possibility should always be considered. Fish oil supplements should not be recommended because of potential deleterious effects on LDL cholesterol and glycaemic control (Franz et al 2002).

People with type 1 diabetes have a greater risk of developing coeliac disease than the general population, possibly as a result of the presence of HLA-related autoimmune factors common to both conditions (Cronin & Shanahan 1997). Because of this, coeliac disease should be suspected in anyone with diabetes with gastrointestinal symptoms or unexplained anaemia. Coeliac disease is characterised by intolerance to gluten, a protein found in wheat and rye and to similar proteins found in barley and possibly oats. The reaction to gluten damages the mucosal lining of the small intestine, flattening the villi and reducing the ability to absorb nutrients. As a result, symptoms of malabsorption commonly occur, although these can vary in nature and severity. The intolerance is permanent and requires complete and life-long exclusion of gluten from the diet. This not only corrects the histological and clinical consequences but also reduces the risk of long-term detrimental effects on health.

Belinda will need to be referred to a dietician for detailed advice about commencing on a strict gluten-free diet. This is a major undertaking in itself, as it will place a double dietary burden on someone who already has diabetes and it is vital that she receives good dietetic support. There will be additional constraints on food choices many of which are key dietary sources of carbohydrate, such as bread, pasta, breakfast cereals, biscuits and many other manufactured foods. When coeliac disease is untreated, there is an increased risk of hypoglycaemia, and the introduction of a gluten-free diet results in an increase in insulin requirement (Iafusco et al 1998). There should be good liaison within the diabetes team to ensure that the appropriate support and advice is given. Dietetic guidance will be essential to ensure that Belinda’s carbohydrate intake is not compromised and that she has appropriate information on avoiding gluten, how to make alternative food choices (such as rice and potatoes) or how to make substitutes in foods (such as specially manufactured gluten-free breads, flours and pasta). It will also be necessary to ensure that Belinda has a balanced diet to maintain health and protect against disease, particularly osteoporosis. She should have regular dietetic follow-up to encourage adherence with thegluten-free diet. The difficulties in following a gluten-free diet, both in terms of family meals and eating away from home, should not be underestimated.