Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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more difficult delivery, it is now less certain that this

is a consequence of the hyperglycemia per se. Mater-

nal obesity may be the more relevant factor since this

tends to worsen the glucose intolerance of pregnancy

(thus taking some women into the ‘gestational dia-

betes’ range) and is also the main factor associated

with macrosomia in the normal obstetric population.

0012 The benefits of intervention have also been ques-

tioned for a number of reasons:

0013 By the time gestational diabetes is identified, the

pregnancy will have advanced beyond the stage of

embryogenesis when any risk to the fetus in terms

of hyperglycemia-induced malformations can be

prevented.

0014 Since the condition is symptomless, there is no need

for symptom relief.

0015 While gestational diabetes may in some cases pro-

gress to frank diabetes necessitating insulin treat-

ment, this cannot be predicted or prevented during

the pregnancy itself.

0016 Weight loss in those who are obese is the only

intervention which can improve glucose tolerance

and lessen the risk of macrosomia, but active slim-

ming is always contraindicated during pregnancy

itself because of the risk of fetal undernutrition. At

most, dietary measures to prevent excessive weight

gain can be instituted (via adjustments in food

choice which preserve high nutrient quality while

lessening energy density) and these should be

encouraged in all pregnant women, not just those

with gestational diabetes.

0017 A formal diagnosis of gestational diabetes has a

number of implications in terms of patient anxiety,

acquisition of disease status, and perhaps unneces-

sary obstetric interventions such as Caesareian

section. If little can be done about the condition

during pregnancy itself, the justification for making

such a diagnosis requires careful consideration.

It now seems more likely that the main significance of

impaired glucose intolerance in pregnancy is that it is

a strong marker for the development of maternal

diabetes in later life, particularly if that person

remains or becomes obese. The time for intervention

is therefore postpregnancy when women should be

encouraged to make diet and lifestyle changes which

will help them achieve and maintain a healthy body

weight. Such people should be considered ‘at risk’ for

development of diabetes and regularly screened for

signs of its development.

Diabetes in Children

0018 The diagnosis of diabetes in a child is a traumatic

event for the entire family, and parents usually take

far longer than the child to adapt to the situation.

Insulin injections, diet, and hypoglycemia are the

major worries and a high level of support and reassur-

ance from professional advisers will be required in the

early stages.

0019Fortunately, modern management of diabetes

means that the dietary constraints are no longer as

disruptive to family life as used to be the case. Chil-

dren with diabetes are no longer prescribed a diet

restricted in carbohydrate, virtually devoid of sugar,

controlled by means of complicated exchange lists,

and necessitating different meals to those of the rest

of the family. Instead they are encouraged to consume

a diet based on healthy eating principles, regulated

via appropriate meal pattern and food choice, and

which is also suitable for the entire family.

0020The aims of dietary management in diabetic chil-

dren can be summarized as follows:

0021To achieve good glycemic control without an

unacceptable frequency of hypoglycemia.

0022To insure the diet is sufficient to meet the demands

for growth.

0023To establish eating habits which will provide pro-

tection against complications in later life.

0024To achieve these in a way which causes the min-

imal amount of psychological and social disrup-

tion for the child (and family).

Specialist pediatric dietetic care is essential in order to

achieve these aims.

Diet and Glycemia

0025Most children with diabetes will have the type 1 form

of the disease and require insulin. It is therefore essen-

tial that there is a balance between dietary carbohy-

drate consumption and insulin action in order to

maintain good blood glucose control and prevent

extreme glycemic swings. Most insulin-treated

patients experience a mismatch in this balance from

time to time and suffer the unpleasant consequences

of hypoglycaemia (low blood sugar) but this is

particularly likely to occur in diabetic children

because both dietary habits and activity levels

tend to be more erratic. Children’s food likes and

dislikes may change rapidly, appetite may be highly

variable and, particularly in younger age groups,

food refusal may be used as a way of seeking attention

or asserting independence. Physical activity levels are

also less predictable in children; school breaktime

may be spent sitting chatting to friends or running

round the playground; at home a child may decide

to ride a bike or just watch TV. It is therefore much

more difficult to maintain a balance between food

intake and the dual hypoglycemic effects of insulin

and exercise.

1796 DIABETES MELLITUS/Problems in Treatment

0026 In order to minimize the problem, the child needs

to consume fairly constant amounts of starchy carbo-

hydrate at frequent intervals. Dietetic expertise is

needed to determine the timing and composition of

daily meals and snacks which are most compatible

with both the family’s eating habits and the child’s

medication, and this pattern should form the frame-

work of food intake. Parents and carers then need to

be taught how dietary adjustments may need to be

made to this pattern in the light of blood glucose

monitoring results, changes in the child’s food intake

(e.g., due to illness), activity level, and other circum-

stances.

0027 Hypoglycemia will still almost inevitably occur

from time to time and everyone who has responsi-

bility of care for the child will need to be aware of this

and know how to deal with it. This may include

considerable numbers of people – not just parents,

carers, and school or preschool staff, but other adults

such as grandparents, parents of the child’s friends,

leaders of youth organizations, ballet teachers, baby-

sitters, and others.

Diet and growth

0028 In this age group, the dietary needs for growth must

not be overlooked. Dietary energy content is particu-

larly important. In the days when diabetes was con-

trolled by highly regulated and restrictive diets, energy

intake was often inadequate and growth stunting a

fairly common occurrence.

0029 Energy needs of children vary widely and cannot be

assessed accurately from tables of average needs. The

best guide to individual dietary energy needs is habit-

ual dietary energy intake. If a child is a healthy weight

and growing normally, the usual dietary energy intake

should remain unaltered. The underweight child will

require dietary measures to boost the energy content

of the diet, usually by increasing its energy density

rather than the total amount of food consumed. The

overweight child will require some curtailment of

energy intake, usually by decreasing dietary energy

density, in order to achieve weight stabilization.

0030 It is also important that the energy and nutrient

content of diabetic children’s diets are reviewed at

regular intervals. It is sometimes forgotten that diet-

ary needs will change as the child grows. An energy

intake which is appropriate at the time of diagnosis

may be totally inadequate a year later.

Diet and the Prevention of Complications

0031 Tight glycemic control is imperative for the long-term

prevention of complications and this is primarily

achieved by maintaining a day-to-day balance be-

tween carbohydrate intake and insulin activity. In

addition to this, the overall composition of the diet

also needs to be one which provides protection against

the increased risk of developing cardiovascular

disease in later life.

0032As with diabetic adults, starchy carbohydrate

should comprise the greatest proportion of dietary

energy intake. Suitable food choices which are popu-

lar with children include bread, breakfast cereals,

pasta, rice, and potatoes. Wholemeal or fiber-rich

varieties can be encouraged for their general health

benefits, although have no particular advantages in

terms of diabetic control. Cereal fiber intake should

not be excessively high in very young children or those

with small appetites because such foods are bulky and

can compromise the intake of other foods needed to

meet energy and nutrient needs. Conversely, high-

fiber foods can be encouraged in the diets of children

with healthy appetites who are becoming overweight.

0033There is no need for the diabetic child to eat a

sugar-free diet. Sugar-rich foods or drinks should not

normally be consumed as isolated snacks, although

may at times be necessary to prevent or alleviate

hypoglycemia. Candy (sweets) and chocolate can, if

desired, be included in the diet as planned carbo-

hydrate top-ups prior to exercise. Modest amounts

of sugar-containing foods can be consumed as part of

main meals. There are no benefits from substituting

fructose or sorbitol for sucrose, nor from the use of

specialist foods such as ‘diabetic’ chocolate; all these

products are unnecessary and may cause diarrhea in

children. However sugar-free ‘diet’ drinks sweetened

with artificial sweeteners such as saccharine, aspar-

tame, and acesulfame-K are useful alternatives to

sugar-containing soft drinks.

0034Excessive fat intake, especially of saturated fat,

should be avoided and healthy eating measures to

achieve this are suitable for the entire family. Visible

meat fat and poultry skin should be discarded,

minimum amounts of fats or oils used in cooking or

added to foods, and fat-rich foods and snacks such as

pastry, pies, crisps, biscuits, and fried foods regarded

as occasional treats rather than regular dietary fea-

tures. However other fat restriction measures should

not be overzealous in very young children or energy

and nutrient intake may be compromised. For this

reason, reduced-fat milks and dairy products are not

suitable for children below the age of 2 years.

0035Protein intake should be sufficient but also not

excessive. Small portions of lean meat, fish fingers,

cheese, eggs, and pulse foods such as baked beans are

good choices for children. Convenience foods such as

burgers, sausages, and other meat products are popu-

lar but also have a high fat content so should only be

provided occasionally and, where possible, reduced-

fat varieties should be chosen.

DIABETES MELLITUS/Problems in Treatment 1797

Minimizing Social and Psychological Disruption

0036 Children hate to feel different from their peers, and

while the presence of diabetes inevitably imposes some

constraints, every effort should be made to keep these

to a minimum. Dietary management therefore has to

find the best compromise between maintaining good

control while keeping life as normal as possible.

0037 The key to achieving this is individualized rather

than standardized guidance. Dietary changes neces-

sary to maintain good diabetic control and long-term

health should be made by modifying existing family

meal patterns and food choices as much as possible,

taking account of individual food preferences, appe-

tite, activity level, and lifestyle, rather than by impos-

ing dietary rules which are alien to the child and

disruptive to the family.

0038 Advice should be as positive as possible, with dia-

betes presented as a condition which presents chal-

lenges to be overcome rather than one which precludes

normal life. Diabetic children have to learn to under-

stand that because they take insulin, they have to be

more careful than other children in terms of what

they eat, and when they eat. However diabetes will

not stop them from eating foods which other children

eat or from doing the activities which others do; it is

simply that some advance planning may be needed to

incorporate these things into daily life. Most children

accept and adapt to this with surprising speed.

Diabetes in Teenagers

0039 A number of factors, particularly dietary ones, can

affect diabetic control during the teenage years. An

increasingly independent lifestyle means that eating

habits often change markedly, with trends towards

consumption of snacks and fast foods rather than

formal meals, a greater proportion of food consumed

outside the home away from adult supervision, and

alteration in food choice which may either be widened

as new foods are encountered, or sometimes narrowed

by the constraints of vegetarianism or slimming.

0040 Energy and nutrient requirements will also change

during these years. Sudden growth spurts, especially

in boys, can result in a dramatic increase in the need

for dietary energy and carbohydrate. The body’s

demands for micronutrients such as calcium and iron

are also high. Activity levels may also alter, and in

either direction; some teenagers may take up physic-

ally demanding new sports such as squash or jogging

while others may give up formal sports altogether and

spend increasing amounts of time sitting at a com-

puter.

0041 It is also likely that alcohol will be consumed and

this is of major significance for people on insulin.

Alcohol potentiates the effect of insulin and, if con-

sumed on an empty stomach, can cause severe, poten-

tially fatal, hypoglycemia. It is therefore imperative

that alcohol is not consumed in excessive quantities

and always in conjunction with sufficient carbohy-

drate. This is perhaps the most important dietary

message to get across to diabetic teenagers. They do

need to be aware of the risks and should be offered

written guidance on safe drinking limits, how to use

the alcohol unit labeling system, and how much add-

itional carbohydrate is needed when alcohol is

consumed. They should also know that many of the

beers and lagers popular with this age group have an

extremely high alcohol content.

0042Most diabetic teenagers will require modifications

to their diet and insulin regimen in order to cope with

the changes associated with adolescence. At the same

time, many will tend to become less receptive to the

advice of health professionals and begin to resent

what they perceive as perpetual nagging about diet,

control, and the risk of complications. Some will bend

the rules as much as they can. With greater maturity, a

more responsible attitude will return and the young

adult will become more receptive to health guidance.

In the meantime, health professionals should aim

to keep the channels of communication open and

encourage their clients to regard them not as people

telling them ‘what to do’ but ‘how to do it.’

Diabetes in Older Adults

0043The risk of developing type 2 diabetes increases with

age, and increasing longevity now means an increas-

ing prevalence of diabetes in people over the age of 65

years. In the past there has been a tendency to regard

diabetes in this age group as a ‘mild’ form of diabetes

and its management confined to mere symptom relief.

It is now known that this is not the case; the risk of

complications such as blindness, gangrene, renal

failure, stroke, and coronary heart disease is greatly

increased if the condition is not diagnosed promptly

and managed effectively.

0044In this age group, as in any other, tight glycemic

control is important. In most patients who develop

type 2 diabetes in later life, this can be achieved by a

combination of dietary measures and oral hypogly-

cemic drugs. However, if these prove inadequate

for optimum control, some type 2 patients will be

managed on insulin.

0045Although the objectives of diabetes care are no

different in older adults, some specific aspects of care

need to be borne in mind:

0046Treatment with insulin or sulfonylurea hypogly-

cemic drugs always poses a risk of hypoglycemia

1798 DIABETES MELLITUS/Problems in Treatment

and in older adults this may have serious conse-

quences in terms of falls and fractures. If patients

are frail or unsteady on their feet, a balance has to

be found between keeping preprandial blood glu-

cose levels low enough to minimize complications

but high enough to prevent the hazards from hypo-

glycemia.

0047 The physical effects of aging in older adults tend to

impair self-management of diabetes. Poor eyesight

may make it difficult to draw up the correct dose of

insulin or read a blood glucose monitor; short-term

memory loss may mean that a dose of an oral

hypoglycemic drug may be forgotten or perhaps

taken twice. Physical infirmity may make it diffi-

cult to shop, cook, or eat. Psychosocial factors such

as loneliness, depression, or bereavement may

result in loss of interest in food and self-care.

0048 Older adults are also more likely to have other

diseases associated with aging such as stroke,

cancer, or dementia as well as diabetes. The effects

of these illnesses, and of the drugs or other therap-

ies used to treat them, on appetite, mobility, or

memory can have a profound impact on food

intake and hence the maintenance of diabetic

control.

Recent surveys have highlighted many inadequacies

in the care of older adults with diabetes, both those

living in the community and people in residential

homes. It is now recognized that better and more

individualized care and support could do much to

reduce the unnecessary morbidity and mortality asso-

ciated with the disease, and improve the quality of life

in the later years.

Diabetes in People from Ethnic Minority

Groups

0049 The prevalence of diabetes is particularly high among

some ethnic minority groups. People of South Asian

origin living in the UK are four times more likely to

develop the disease than the indigenous Caucasian

population. In African-Caribbean people, the risk of

diabetes is twice as high. Both these groups are also

more likely to die from long-term complications of

diabetes such as cardiovascular disease and renal

disease.

0050 Diagnosis and management of the disease are often

hampered by the fact that access to, or uptake of,

health care services by this sector of the population

is often poor and language barriers can further

hamper communication. In order to provide effective

care, health professionals need to be sensitive to

the cultural beliefs and customs of each individual

and understand the practical implications of these,

particularly in terms of dietary management. Dietetic

expertise is vital to insure that the guidance given is

both appropriate and culturally acceptable.

See also: Adolescents; Alcohol: Alcohol Consumption;

Children: Nutritional Requirements; Nutritional

Problems; Pregnancy: Nutrition in Diabetic Pregnancy

Further Reading

Ales KL and Santini DL (1989) Should all pregnant women

be screened for gestational glucose intolerance? Lancet i:

1187–1191.

Benbow SJ, Walsh A and Gill GV (1997) Diabetes in insti-

tutionalised elderly people: a forgotten population?.

British Medical Journal 314: 1868–1869.

British Diabetic Association, Nutrition Sub-Committee

(1989) Dietary recommendations for children and ado-

lescents with diabetes. Diabetic Medicine 6: 537–547.

British Diabetic Association, Nutrition Sub-Committee

(1993) Dietary recommendations for children and ado-

lescents: an implementation paper. Diabetic Medicine

10: 874–885.

British Diabetic Association (1997) Recommendations for

the Management of Diabetes in Primary Care. London:

BDA.

British Diabetic Association (1999a) Guidelines of Practice

for Residents with Diabetes in Care Homes. London:

BDA.

British Diabetic Association (1999b) Recommendations for

the Structure of Specialist Diabetes Care. London: BDA.

Dornhorst A, Bailey PC, Anyaoku V, Elkeles RS, Johnston

DB and Geard RW (1990) Abnormalities of glucose

tolerance following gestational diabetes. Quarterly

Journal of Medicine 284: 1219–1228.

Goldenburg RL and Tamura TT (1996)) Pre-pregnancy

weight and pregnancy outcome. Journal of the American

Medical Association 275: 1127–1128.

Haines LC and Swift PGF (1997) Report of the 1994 British

Paediatric Association/British Diabetic Association

survey of services for children with diabetes: changing

patterns of care. Diabetic Medicine 145: 693–697.

ISPAD/IDF/WHO (International Society for Paediatric and

Adolescent Diabetes; International Diabetes Federation,

World Health Organization) (2000) Consensus Guide-

lines for the Management of Insulin Dependent (Type 1)

Diabetes Mellitus in Childhood and Adolescence. Zeist,

The Netherlands: Medical Forum International.

Jardine Brown C, Dawson A, Dodds R et al. (1996) Saint

Vincent and improving diabetes care. Report of the

pregnancy and neonatal care group. Diabetic Medicine

13(suppl. 4): S43–S53.

Jarrett RJ (1997) Should we screen for gestational diabetes?

‘The concept of gestational diabetes was popularised

before considerations of evidence based medicine came

on the scene’. British Medical Journal 315: 736–737.

Walkinshaw SA (1999). Dietary regulation for ‘gestational

diabetes’ (Cochrane review). In: The Cochrane Library,

issue 2. Oxford: Update Software.

DIABETES MELLITUS/Problems in Treatment 1799

Secondary Complications

B Thomas, Dorking, Surrey, UK

Types of Complications

0001 As the life expectancy of people with diabetes has

increased, the long-term consequences of the disease

have become more apparent. The treatment object-

ives of diabetes are therefore not confined to the

short-term relief of its symptoms but also aim to

prevent or minimize its long-term effects.

0002 Complications of diabetes can be divided into two

main categories:

0003 Arterial disease of large or medium-sized blood

vessels (macrovascular disease)

0004 Damage to the microvascular circulation of the

retina and kidneys and to peripheral nerves

(microvascular disease).

There are several differences in the pathogenesis of

these two types of complications. Microvascular

complications are unique to diabetes, and their devel-

opment is associated with prolonged exposure to

hyperglycemia. In contrast, arterial disease affects

both diabetic and nondiabetic populations alike,

although the prevalence of the disease is greatly

increased in people with diabetes. However, there

are some links between diabetic complications:

retinopathy and nephropathy often develop together,

and patients with diabetic nephropathy have a greatly

increased risk of cardiovascular mortality.

0005 The recent findings from two major prospective

studies – the Diabetes Control and Complications

Trial and the UK Prospective Diabetes Study – have

greatly clarified the role of different risk factors in the

development of diabetic complications.

Macrovascular Disease

0006 Macrovascular disease results from atheromatous

changes in large and medium-sized blood vessels that

may become partly or totally blocked. The resulting

impairment can affect the cardiovascular system

(causing angina and coronary thrombosis), the

cerebrovascular system (causing stroke), and the

peripheral blood supply to the lower limbs (causing

claudication and tissue damage).

0007 The susceptibility to cardiovascular disease is of

particular concern. People with diabetes are at least

twice as likely to develop heart disease as the non-

diabetic population. Furthermore, the disease tends

to strike at a younger age and in both sexes; diabetic

women appear to lose much of their premenopausal

protection against heart disease and are at a much

greater risk than their nondiabetic counterparts.

People with diabetes also have a two- to threefold

increase in the risk of stroke.

0008The reason why diabetes enhances the atherogenic

process has not been fully explained, but it is un-

doubtedly due to a combination of factors. Hyper-

glycemia almost certainly plays a role, probably as a

result of the metabolic disturbances associated with

it, in particular, disordered lipid metabolism. Abnor-

mal blood lipid profiles are a common feature of both

types of diabetes, although the pattern of dyslipid-

emia is usually different. Type 1 patients tend to

have elevated levels of total and low-density lipopro-

tein (LDL) cholesterol and reduced high-density lipo-

protein (HDL) cholesterol, a combination known to

enhance atherogenic risk. Type 2 patients commonly

have elevated very-low-density lipoprotein (VLDL)

triglyceride levels, particularly if they are obese,

together with increases in the highly atherogenic

small dense LDL subclass. All these lipid profiles are

exacerbated by poor glycemic control.

0009Thrombogenic factors, such as the fibrinogen level

or degree of platelet stickiness, may also be adversely

affected by diabetes, leading to an increased likeli-

hood of thrombosis and blood vessel occlusion.

0010The presence or absence of other cardiovascular

risk factors also plays a key role. Hypertension is

particularly strongly associated with cardiovascular

risk in diabetic subjects, and long-term tight blood

pressure control in hypertensive Type 2 patients

has been shown to result in a significant fall in the

incidence of coronary heart disease and stroke. Other

known contributors such as cigarette smoking,

obesity, and physical inactivity are also particularly

detrimental to people at such high risk of cardio-

vascular disease. Prevention of diabetic macrovascu-

lar complications therefore requires multiple risk

factor reduction from all these influences, in addition

to the maintenance of good diabetic control.

0011Diet plays an important part in cardiovascular dis-

ease prevention. The modern diabetic diet, based on

healthy eating principles, confers a much greater

atherogenic protection than its low-carbohydrate,

high-fat predecessor. Like the rest of the population,

people with diabetes are advised to obtain at least

50% of their dietary energy from starchy carbohy-

drate foods such as bread, cereals and potatoes.

Carbohydrate food choices with a low glycemic

index (such as oat-based breakfast cereals, pasta,

and rice) should be encouraged in order to minimize

postprandial glycemia. Dietary fat intake should be

reduced to 30–35% of dietary energy, with particular

emphasis on avoidance of saturated fat. Use of

spreading and cooking fats and oils should be kept

1800 DIABETES MELLITUS/Secondary Complications

to a minimum and should be mainly derived from

monounsaturated sources; excessive intake of poly-

unsaturated fat is no longer encouraged because of

the risk of lipid peroxidation. Adequate consumption

of fruit and vegetables (at least five servings a day) is a

particularly important dietary measure, since there is

growing evidence that these foods confer significant

antioxidant protection. In addition, the soluble fiber

content of fruit and vegetables, together with that

found in oats and pulses, may have beneficial effects

on both glycemic control and blood lipids. Foods

with a high content of cereal fiber (e.g., wholemeal

bread) are encouraged for their high satiety value and

gastrointestinal benefits but are no longer thought to

offer any particular advantage in terms of glycemic

control.

0012 High sodium intakes may exacerbate or contribute

to hypertension, and, along with the rest of the popu-

lation, people with diabetes should be encouraged to

reduce their sodium intake by about one-third (from

the typical average of 9 g per day to 6 g per day). This

can be achieved quite easily by not adding salt to

foods, avoiding highly salted foods and making sure

the diet is not over-reliant on processed manufactured

foods (the major contributors to the sodium content

of the UK diet) such as canned foods, ready meals, or

convenience foods.

0013 For those who are overweight, weight loss is an

over-riding priority. Even modest weight loss (5–

10 kg) will have marked benefits in terms of glycemic

control, blood pressure, and lipid profile. In Type 2

diabetic patients, weight loss is the treatment out-

come most closely related to improved life expect-

ancy. In general, a low-energy diet relatively high in

starchy carbohydrate, fiber, and low in fat is the most

suitable for weight loss because of its high satiety

value. Increasing the daily level of physical activity

is also important.

Microvascular Disease

Nephropathy

0014 Diabetic nephropathy results from damage to the

microvascular circulation of the kidney. It is charac-

terized by persistent proteinuria, rising blood pres-

sure, and a progressive decline in renal function,

which eventually may result in renal failure. The

risk of premature death from either uraemia or

cardiovascular disease is greatly increased.

0015 Nephropathy affects about 30% of people with

Type 1 diabetes, typically appearing about 10–20

years after diagnosis. In those with Type 2 diabetes,

it tends to be appear after a shorter time scale, and its

incidence varies with ethnic origin, ranging from

about 25% in Europeans to as much as 50% in

people of African-Caribbean and Asian origin.

0016Prior to the development of overt diabetic nephro-

pathy, damage to the glomerular capillaries results in

leakage of albumin into the urine. These losses are

small and symptomless but appear to be an important

predictor of the subsequent development of clinical

nephropathy. Identification of patients with microal-

buminuria (urinary albumin excretion in the range of

30–300 mg per day) is now regarded as an important

way of ensuring that preventive measures are applied

at an early stage to those at greatest risk.

0017It is now established beyond doubt that diabetic

nephropathy is related to both hyperglycemia and

hypertension. Prevention therefore requires tight

control of each of these parameters.

0018In the early stages of the disease, strict glycemic

control and effective antihypertensive treatment can

reduce microalbuminuria and restore the glomerular

filtration rate (GFR) to the normal range. There is

evidence that the progression to clinical nephropathy

can be slowed and associated mortality reduced if

these measures are started early enough.

0019The role of protein restriction in the prevention of

nephropathy remains equivocal. Dietary protein

intake is known to influence renal function, and a

low-protein diet can retard the progression of chronic

renal failure. There is some evidence that a diet that

includes moderate dietary protein restriction (to

about 45 g per day or 0.6–0.7 g per kilogram of

ideal body weight) may also reduce the rate of decline

in GFR and reduce urinary protein excretion in some

patients, particularly if started before renal impair-

ment becomes too advanced. Further research is

required to determine precisely which dietary com-

ponents are important, at what stage protein restric-

tion should be introduced, and at what level. Current

recommendations in the USA are that diabetic

patients with overt nephropathy should not exceed

a protein intake of 0.8–0.9 g per kilogram of body

weight per day. Once GFR begins to fall, a further

restriction to 0.6 g per kilogram per day may be

advisable.

0020What does seem clear is that all diabetic patients

should be discouraged from consuming excessive pro-

tein intakes. In the now outmoded era of carbo-

hydrate restriction, people were often encouraged to

satisfy their hunger with protein-rich foods such as

meat, cheese, and eggs. As well as being unwise in

respect of atherogenesis, such a measure may well

have been detrimental to renal function.

0021Excessive protein intake can be avoided by insuring

that foods such as meat, poultry, fish, and cheese are

not the largest component of a meal, and that a

greater proportion of food intake comprises starchy

DIABETES MELLITUS/Secondary Complications 1801

foods and vegetables (as recommended in The Bal-

ance of Good Health healthy eating plate model).

Such a measure also will help decrease the consump-

tion of saturated fat and hence improve the lipid

profile. This may be particularly important in pa-

tients with diabetic nephropathy, most of whom

have a disordered lipid pattern and eventually die

from cardiovascular disease. Other dietary aspects

that also minimize this risk, such as weight reduction

and salt restriction, are also high priorities in these

patients.

Retinopathy

0022 Diabetic retinopathy is the most common cause of

blindness in the UK. Damage to retinal capillaries

causes microinfarcts, hemorrhages, and retinal

deposits, which, if unchecked, can result in visual

impairment. The risk of cataracts is also increased.

0023 Retinal changes usually remain mild and asymp-

tomatic for many years, so-called ‘background retino-

pathy.’ However, in time, ‘proliferative retinopathy’

may develop; new blood vessels appear, and progres-

sive damage eventually leads to retinal detachment or

vitreous hemorrhage and loss of sight.

0024 The development of background retinopathy is

closely associated with the duration and degree of

exposure to hyperglycemia. After 20 years of dia-

betes, most Type 1 diabetic patients and well over

half of those with Type 2 will have some degree of

retinopathy. However, not all will develop the sight-

threatening proliferative changes, the peak incidence

of which occurs after about 15 years of diabetes and

remains constant at about 3% per annum thereafter.

It is unclear which factors trigger this effect. Poor

control is a contributory factor (although, paradoxic-

ally, a sudden improvement in diabetic control often

leads to an abrupt deterioration in retinopathy for a

period).

0025 Prospective studies have now established that long-

term tight glycemic control is of primary importance

in minimizing the development of retinopathy. For

this reason, it is also vital that Type 2 diabetes (which

can remain undetected for considerable periods of

time in older adults) is diagnosed at any early stage;

about 20% of these patients already have significant

retinopathy at the time of diagnosis as a result of

prolonged untreated hyperglycemia.

0026 If retinopathy does occur, much can now be done

to halt its progression. Laser photocoagulation can

be used to prevent new retinal blood vessels

from proliferating and threatening sight, and new

surgical techniques may be able to improve vision

or prevent further deterioration. However, these

damage-limitation measures need to applied at the

earliest possible stage in order to protect sight. Since

retinopathy is usually asymptomatic until serious

damage has occurred, regular screening of the retina

is important. All diabetic patients should have annual

ophthalmological examinations.

Neuropathy

0027Diabetes may result in damage to nerves, causing

disordered motor, sensory, and autonomic function.

Much less is known about the incidence and preva-

lence of this complication, because its effects are so

diverse and difficult to classify.

0028About 10–20% of insulin-dependent patients may

have evidence of peripheral neuropathy. Peripheral

nerve damage is characterized by ‘pins and needles,’

numbness, or pain in the lower limbs, and is particu-

larly likely to contribute to problems in the diabetic

foot. Loss of sensitivity to pain can result in unfelt

injuries, which, if associated with poor control or

peripheral vascular disease, may become infected,

leading to ulcers and, possibly, gangrene.

0029Symptomatic autonomic neuropathy is more rare,

but when it does occur, it may cause severe problems,

including postural hypotension, incontinence, and

impotence. Neuropathy affecting the gastrointestinal

tract can cause diarrhea or constipation. Gastric neur-

opathy may reduce gastric secretion and delay gastric

emptying, causing unpleasant sensations of bloating

and resulting in anorexia, or even nausea and

vomiting. These problems can seriously affect dietary

management. As with other microvascular complica-

tions, hyperglycemia promotes neuropathy, and its

development is related to the duration of diabetes.

There is some evidence that improved glycemic con-

trol may benefit nerve function.

Prevention of Diabetic Complications

0030The factors with the greatest influence on the devel-

opment of each type of diabetic complication, and

hence of most relevance to its prevention, have been

outlined above. However, since all patients are poten-

tially at risk from all complications, preventative

measures have to be global in nature so that protec-

tion from all types is maximized.

Treatment Objectives to Prevent Complications

0031Central to the prevention of every complication is

tight glycemic control. Maintaining preprandial

blood glucose level between 4 and 7 mmol l

1

and

glycosylated hemoglobin (HbA

) at 7.0% or below

are the most important treatment objectives.

0032Correction of hypertension and maintenance of

blood pressure at 140/80 mmHg or below may be

equally critical, particularly in respect of nephropathy

and cardiovascular disease.

1802 DIABETES MELLITUS/Secondary Complications

0033 Correction of disordered blood lipids is important.

Sometimes, this will necessitate drug therapy but

often can be achieved by more effective management

of obesity or by tightening glycemic control.

0034 People also need to minimize the influence of other

known cardiovascular risk factors, particularly those

from cigarette smoking, obesity, physical inactivity,

and an atherogenic diet.

0035 These treatment objectives must be pursued with

equal vigor in both Type 1 and Type 2 patients. In the

past, the latter form of the disease has often been

regarded as a ‘mild’ form of diabetes, but it is now

clear that it is anything but mild in its effects.

Role of Diet in the Prevention of Complications

0036 Effective dietary management is crucial if these object-

ives are to be achieved. Diet is central to the mainten-

ance of tight glycemic control, by ensuring there is a

balance between glucose entering the blood following

the ingestion of food and the amount of insulin (either

exogenous or endogenous) available to deal with it.

This is primarily achieved by the maintenance of a

stable day-to-day pattern of eating in terms of meal

timing and carbohydrate consumption, to which

minor adjustments are made as needed to meet fluctu-

ations in activity level or other circumstances.

0037 Considerable dietetic skill is needed to help people

make the necessary adjustments to their normal eating

habits so that carbohydrate intake is compatible with

hypoglycemic medication, and also in a way that is

acceptable to the individual and hence sustainable in

the long term. Patients also have to be taught how to

use their blood glucose monitoring results to assess

whether the balance between diet and glycemia is ap-

propriate, whether further dietary adjustments need to

be made, and, if so, what form these should take.

0038 The dietitian also has to insure that the diet is

balanced in terms of energy and nutrient content

and of optimal composition for the prevention of

cardiovascular disease. The healthy eating guidelines

detailed in the UK national food guide (The Balance

of Good Health) are a good basis for achieving this.

This model recommends that starchy cereal foods

should be the main part of each meal, that at least

five portions of fruit/vegetables should be consumed

every day, and that the daily diet should also contain

two or three servings of low-fat dairy products and up

to two modest servings of meat or alternatives. The

consumption of fat-rich and sugar-rich foods should

be avoided as much as possible. If these guidelines are

adopted, the resultant dietary composition will meet

all the diabetic dietary objectives, i.e., contain a rela-

tively high proportion of energy from starchy carbo-

hydrate, a low proportion of energy from saturated

fat, a high content of antioxidants and soluble fiber, a

lower-than-average sodium content, and not exces-

sive protein content.

0039In those who are overweight, effective weight man-

agement is imperative, because obesity has detrimen-

tal effects on glycemia, blood pressure, and blood

lipids, and hence impacts on all types of complica-

tions. Achieving permanent weight reduction is a

notoriously difficult task, but the potential health

benefits of even modest weight loss justify the efforts

involved. This requires far more than just providing

dietary guidance; behavioral strategies and consider-

able support measures will be necessary to effect per-

manent lifestyle change

0040Along with other aspects of diabetes care, dietary

management has changed considerably in recent

years. Treatment is much more patient-centered,

with the individual being encouraged to take greater

responsibility for their own self-care in partnership

with health professionals. The role of the dietitian is

no longer to dispense standard advice to all-comers,

often in the form of complicated exchange lists or

restrictive diet sheets, but to assess the unique dietary

and clinical circumstances of each patient, identify

the nutritional priorities and help that individual

make appropriate dietary changes. Dietetic expertise

is an essential component of the skill mix of the

diabetes care team.

Quality of Care Necessary to Prevent

Complications

0041Prevention of diabetic complications depends, firstly,

on achieving the best possible control of the diabetes

and, secondly, on early diagnosis of any problems that

do arise. Diabetes care that consists solely of brief

routine visits to an overworked GP or busy outpatient

clinic may be sufficient to maintain short-term con-

trol of diabetes, but will not provide the quality of

care necessary to prevent minor problems becoming

major and possibly life-threatening.

0042Effective diabetes management requires multidisci-

plinary care from a team that incorporates the skills

of a number of health professionals such as dietitians,

ophthalmologists, and chiropodists as well as those of

clinicians and nurses. Regular monitoring and follow-

up are vital; all diabetic patients should have an

annual clinical and dietetic review to assess the effect-

iveness of current treatment, identify any emerging

problems, and implement any necessary action. Care

provision in the primary and secondary sectors needs

to be closely integrated so that all patients have access

to expert services as a matter of routine.

0043There is evidence that the care of many people with

diabetes has been substandard, particularly that of

Type 2 patients, whose susceptibility to complications

has often been underestimated. It is also clear that

DIABETES MELLITUS/Secondary Complications 1803

better care could significantly reduce much of the

morbidity and premature mortality associated with

the disease. In the UK, high priority is currently being

given to implementing national standards of diabetes

care in order to reduce the high economic and human

cost of diabetic complications.

See also: Coronary Heart Disease: Etiology and Risk

Factor; Diabetes Mellitus: Treatment and Management;

Hyperlipidemia (Hyperlipidaemia); Hypertension:

Physiology; Obesity: Etiology and Diagnosis