LIFESTYLE

Published on 03/04/2015 by admin

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CHAPTER 2 LIFESTYLE

DIET OR MEDICAL NUTRITIONAL THERAPY

Medical nutritional therapy (MNT) is an essential component of diabetes management, not only in optimising glycaemic control, but also in reducing cardiovascular risk.

Diabetics no longer require a separate diet with special food products: a “healthy” diabetic diet suits most of the general population, particularly when the modification of cardiovascular risk is a priority. MNT involves balancing complex issues and needs, tailored to the lifestyle, cultural and religious customs, and to the patient’s overall diabetes management.

BASIC DIETARY RECOMMENDATIONS

In 2003 Diabetes UK issued a comprehensive list of consensus-based recommendations for diabetics that drew upon many sources to provide detailed practical advice for professionals to implement (Connor et al 2003). These are summarised in Table 2.1. The American Diabetes Association has also published its recommendations in its annually updated guidance.

TABLE 2.1 Summary of recommendations for a diabetes diet–based upon Diabetes UK 2003 (Connor et al 2003) and ADA position statement (ADA 2007)

Component Comments
Protein Not > 1 g per kg body weight (different for nephropathy and children)
Total fat < 35% of energy intake
Saturated + transunsaturated fat < 7% of energy intake with trans fat intake minimised
n-6 polyunsaturated fat < 10% of energy intake
n-3 polyunsaturated fat Eat fish, especially oily fish, 1–2 times weekly
  Fish oil supplements not recommended
cis-monounsaturated fat* 10–20%
Total carbohydrate* 45–60%
Sucrose Up to 10% of daily energy, eaten within the context of a healthy diet
Consider using non-nutritive sweeteners where appropriate if overweight and/or hypertriglyceridaemic
Fibre No quantitative recommendation
Soluble fibre has beneficial effects on glycaemic and lipid metabolism
“Insoluble” fibre has no direct effects on glycaemic and lipid metabolism, but its high satiety content may help weight loss and is advantageous to gastrointestinal health
Vitamins and antioxidants Encourage foods naturally rich in vitamins and antioxidants
Supplements are usually not recommended (except in special circumstances) and some may be harmful
Salt < 6 g sodium chloride per day

* combined should total 60–70% of energy intake

Central to MNT must be changes in the patient’s behaviour. Crucial to helping to bring about change is an understanding of various aspects of health education, discussed in detail later in this section.

MODELS OF DIETARY ADVICE

Appropriate dietary advice should follow practical models that reflect current dietetic thinking. The two following models may provide a useful basis for dietary advice:

Diabetes dietetic advice should emphasise the need to space regular meals and snacks appropriately throughout the day. This will spread nutrient intake and avoid hypoglycaemia. If the daily energy intake is appropriate, the frequency of meals is not critical; however, dieticians advise eating at regular intervals and not undergoing prolonged spells without food: avoiding a “feast or famine” eating pattern. By making the mealtime an occasion to enjoy and savour food, patients may avoid abstractly consuming (possibly excess quantities of) food while focused upon another activity. Patients should be warned to avoid special diabetic products, which are often expensive and with a high fat content.

Due to recent concerns about the accuracy of food labelling in the UK, shoppers do need to pay close attention to the information provided on labels and to not accept blindly adjectives such as “healthy”, “low”, “high” or “restricted”.

DIETARY CARBOHYDRATE

The glycaemic response to foods can be affected by several factors:

Dietary carbohydrate is a source not only of energy, but also of water-soluble vitamins and minerals.

Quantity of carbohydrate

The carbohydrate intake should comprise 45–60% of total calories, but the proportion may vary according to individual factors, such as age, activity levels and weight. The total carbohydrate consumed should not normally be less than 130 g per day, since the brain and central nervous system have a minimum requirement for glucose as an energy source.

Glycaemic control can be optimised by controlling the quantity, timing and distribution of carbohydrate consumed. Educating diabetics about this can involve different approaches:

www.leedsth.nhs.uk/sites/diabetes/food/CarbohydrateCountingRef.php

Reducing the total quantity of carbohydrate consumed is the basis of producing an energy deficit of between 500 and 1000 kcal/day. Very low calorie diets (VLCD) are defined as containing less than 800 kcal/day and are designed to produce more rapid weight loss in very obese individuals (BMI greater than 35 kg/m2). However, there is no evidence that they produce better long-term results and should only be used under careful specialist supervision with close attention paid to glycaemic control and nutritional maintenance.

DIETARY FAT

Both Diabetes UK (Connor et al 2003) and the National Cholesterol Education Program (Expert Panel 2001) recommend that the total fat should not exceed 35% of the total energy intake. The most important dietary modification is to reduce the intake of saturated fat, the principal dietary determinant of serum LDL-cholesterol levels; saturated and transunsaturated fat should provide less than 7% (ADA 2007) or 10% (Connor et al 2003) of energy. Unfortunately, in most European countries, current intake of saturated fat is above the recommended maximum 10% of total energy intake.

The main advice should be:

Sterols and stanols of plant origin have been shown to reduce serum LDL-C levels, and are now incorporated into spreads and other fat-derived products, such as yoghurts, semi-skimmed milk, cereal bars and soft cheeses. These are marketed as adjuncts to other methods of lowering LDL-cholesterol. However, the spreads are markedly more expensive than conventional margarines, their effect on long-term cardiovascular morbidity and mortality is unknown, and their benefits may be offset by reductions in fat-soluble vitamin absorption and in plasma concentrations of the antioxidants β- and α-carotene and vitamin E. Furthermore, they may not reduce total energy intake or weight.

OTHER CIRCUMSTANCES

Hypertension

There are a number of dietary modifications that can contribute to lowering blood pressure:

Salt restriction. The ADA’s Expert Consensus recommends that the maximum daily intake of sodium should be 2400 mg (100 mmol), or 6000 mg of salt (sodium chloride) (ADA 2003). Reducing the daily intake from 12 g to 6 g can produce a fall in blood pressure of 5/2–3 mmHg. Salt restriction can potentiate the blood pressure-lowering effect of some agents in type 2 diabetics. However, since most commercial cereal and bread products contain 1% salt by weight, consuming these products increases the intake of both starchy carbohydrate and salt. It may be preferable to eat unsalted cereals and to replace some cereal foods with fruit and vegetables.

The American Dietary Approaches to Stop Hypertension (DASH) is an eating plan that advises hypertensive individuals to consume a diet rich in fruit, vegetables and low-fat dairy products with a reduced content of saturated and total fat. Those who follow this diet combined with sodium restriction can expect to their lower systolic blood pressure by 8 to 14 mmHg (Sacks et al 2001). The eating plan can be downloaded off the internet.

Although there appears to be an inverse relationship between blood pressure levels and the consumption of potassium (found in fruit and vegetables), magnesium and calcium, the 2004 BHS guidelines do not recommend supplementation of these minerals.

PHYSICAL ACTIVITY AND EXERCISE

RATIONALE

A sedentary lifestyle is associated with an increased risk of coronary heart disease (CHD). Sedentary individuals are more likely to be obese and have adverse lipid profiles. In one study that recruited diabetic women, those undertaking less than 1 hour per week or no physical activity doubled their risk of having a cardiovascular event, compared to those undertaking at least 7 hours per week of physical activity (Hu et al 2001). Another study that recruited diabetic men found that “low” baseline cardio-respiratory fitness nearly trebled overall mortality compared with “moderate” or “high” fitness, and overall mortality nearly doubled in those reporting no recreational exercise in the previous 3 months, compared to those reporting any recreational physical activity in the same period (Wei et al 2000).

There is no current evidence to demonstrate a direct relationship between levels of physical activity and the development of the macrovascular and microvascular complications of diabetes. The arguments in favour of increased physical activity are based upon extrapolation from the effect of exercise on glycaemia. A recent report by the Chief Medical Officer distinguishes between the preventive effects (which appear to be strong) and the therapeutic effects of physical activity in type 2 diabetics (Department of Health 2004). The key message is that “the correct type of exercise is good”.

Exercise has both short- and long-term benefits in type 2 patients (see Table 2.2). Exercise can be an effective way to reduce the risk of cardiovascular disease (CVD) (Pierce 1999): an appropriate level of physical activity, particularly in conjunction with diet, can improve cardiovascular risk factors, such as blood pressure, weight and lipids. A Cochrane meta-analysis of 14 RCTs “showed that exercise … improves glycaemic control and reduces visceral adipose tissue and plasma triglycerides, but not plasma cholesterol, … even without weight loss” (Thomas et al 2006).

TABLE 2.2 The benefits of exercise for type 2 patients (ADA 1995, Buckley et al 1999)

Metabolic:
Reduced short-term insulin resistance; long-term effect has yet to be established
Increased peripheral glucose uptake
Less atherogenic profile (decreased triglycerides and LDL cholesterol with a beneficial increase in HDL cholesterol)
There is still no clear consensus on whether physical training results in improved fibrinolytic activity, which is impaired in type 2 diabetics
Reduces hypertension, particularly when hyperinsulinaemia is present
Helps to maintain muscle mass and promote preferentially the loss of adipose tissue, which may reduce the fall in metabolic rate during slimming and accelerate long-term weight loss
Favours weight loss by increasing energy expenditure (although an ageing overweight type 2 diabetic will be hard pressed to maintain the necessary daily level of exercise), in combination with a “slimming” diet

Prevention: physical activity undertaken in early adult life protects against the subsequent development of type 2 diabetes in middle-aged men and women (Ha & Lean 1997) and in patients with impaired glucose tolerance (Tuomilehto et al 2001)