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Fresh approach to diet advice for diabetics

Natasha Ede takes a look at new guidance on nutrition in diabetes, including diets for ethnic minority patients

The newly issued guidelines for the nutritional management of diabetes emphasise the practical implementation of nutritional advice for people with diabetes1. GPs need to be aware of the important differences from the previous UK recommendations regarding diet.

 · Flexibility There is now greater flexibility in the proportions of energy derived from starchy carbohydrate foods and from monounsaturated fat.

Meals should include starchy carbohydrate foods though the proportion of energy from carbohydrate is more flexible.

The amount of carbohydrate in meals or snacks has much greater influence on blood glucose than the source or type, and although carbohydrate restriction is no longer part of diabetes management, for most patients total carbohydrate intake remains an important consideration in order to optimise glycaemic control.

Different approaches are required for different patients. People on two fixed daily insulin injections have better glycaemic control if they achieve day-to-day consistency in the amount and source of the carbohydrate of their diets.

However, the newer insulin regimes, when combined with more frequent blood glucose monitoring, have enabled more knowledgeable and motivated patients to vary their carbohydrate

intake at meal times by adjusting their insulin doses or physical activity or both.

 · South Asian diet Traditionally the distribution of starchy carbohydrate in the south Asian diet tends to be uneven with very little eaten during the day and a carbohydrate-rich meal in the evening.

But there is enormous variety ­ many south Asians consume a diet that is no different from that of their indigenous peers while others may retain their traditional eating practices. Religious festivals with fasting are common among the south Asian population.

Approximately 2.5 million Muslims live in the UK, so most GP practices will have some Muslim patients on their list. Ramadan is the holy month for Muslims and the timing of this varies.

Despite being exempt, people with diabetes often wish to fast because of the status of Ramadan. Those whose diabetes is treated with insulin or sulphonylurea should be advised not to fast because of the risk of hypoglycaemia. People whose control is poor should be advised likewise due to the risk of ketoacidosis.

During Ramadan there is a major change in the dietary pattern, with only two meals a day at sehri (early-morning meal) and iftar (break of fast at sunset). During non-fasting hours large quantities of sugary fluids together with fried foods and carbohydrate-rich meals can be taken. Meal times should be defined before further advice is given. The dietary advice below should help control blood glucose levels:

 · Limit amount of foods taken at iftar such as ladoo, jelebi or burfi

 · Fill up on starchy foods such as basmati rice and chapatis

 · Include fruit, vegetables, dhal and yoghurt in meals at iftar and sehri

 · Try to have the meal at sehri just before sunrise, not at midnight, so spreading out energy intake more evenly

 · Drinks should be sugar free and fried food should be limited.

It is counterproductive to advise people to avoid totally the traditional rich foods that mark the end of a fast. By allowing a small amount compliance will be improved.

Changes to diabetes medication will depend on the quantity of food consumed at sehri and iftar, the length of fast and medication taken2.

 · Sugar Sucrose can now provide up to 10 per cent of daily energy provided it is eaten in the context of healthy diet and distributed throughout the day. Those who are overweight should avoid sucrose where this is practical.

Sugar in liquid form and sweets will affect blood glucose levels rapidly. Sources of sugar in the south Asian diet include sweets such as jalebi and burfi, and desserts such as keer, halva and kulfi. Traditional sweet foods in the African-Caribbean diet include sugar cake, dukono, condensed milk, malted and nourishment drinks.

 · Glycaemic index The glycaemic index (GI) is a ranking of foods based on their overall effect on blood glucose levels. Slowly-absorbed foods have low GI

rating whereas foods that are absorbed more quickly will have a higher GI

rating.

Including foods with a low GI in meals will help even out blood glucose levels. Low GI foods can help people control their appetite by making them feel fuller for longer.

The use of carbohydrate foods with low glycaemic index, such as beans and pulses, commonly eaten by south Asians, and sweet potato by African-Caribbean patients should be encouraged. Other low-GI foods include noodles, pasta and porridge.

 · Fat Total fat intake should be less than 35 per cent of energy intake.

Monounsaturated fats are now promoted as the main source because of their lower susceptibility to lipid peroxidation and lower atherogenic potential and should provide 10-20 per cent of energy intake.

Dyslipidaemia is often present in the newly diagnosed or those with poor glycaemic control and should be reassessed after control of hyperglycaemia. Many patients with type 2 diabetes and some overweight patients with type 1 have dyslipidaemia associated with insulin resistance.

Saturated and transunsaturated fats (manufactured foods containing hydrogenated vegetable oils such as cakes and biscuits) should provide less than 10 per cent of energy intake. If weight loss is not required, saturated fat can be replaced by carbohydrate or

cis-monounsaturated fats.

Sterols and plant stanols have been shown to lower LDL cholesterol concentrations, with an intake of 2g a day producing an average reduction of 10-15 per cent in LDL cholesterol. See products for guidance on servings. Pregnant women or children should not use these products as there is insufficient data in these groups.

N-3 polyunsaturated fat should be encouraged. Oily fish such as salmon, mackerel and pilchards are key. It is unlikely that many south Asians in the UK will eat oily fish, but fish oil supplements are not recommended

due to their potentially deleterious effects on LDL cholesterol and glycaemic control.

 · Salt Reduction to 6g per day is recommended. Three-quarters of salt consumed by individuals comes from processed foods and foods prepared outside the home.

A salt reduction of more than 20 per cent is generally detectable, although individuals do adapt to taste and it takes only three weeks to get used to a lower salt diet.

Restricting salt intake from 12g to 6g per day leads to a drop in systolic/ diastolic pressure of 5/2-3mmHg.

Adequate intake of calcium and potassium should be encouraged (fruit, vegetables and low-fat dairy foods) although in many south Asians calcium intake can be low.

Salt substitutes can be beneficial in selected patients but due to their potassium content are not appropriate for all patients.

 · Weight and exercise Weight management is a key factor in good diabetes management, particularly in type 2 diabetes, and it plays an important role in prevention.

Moderate weight loss (5-10 per cent of body weight) reduces insulin resistance, improves blood glucose, blood lipid and blood pressure levels and improves life expectancy. There is also a need for increased monitoring of blood glucose and adjustment of diabetes medication should be advised where appropriate.

Most people with diabetes should be urged to take 30 minutes of physical activity daily, according to age and fitness level. Physical activity helps with weight loss and helps to reduce triglycerides and insulin resistance. Those at risk of hypoglycaemia should be given advice on managing blood glucose levels.

Assessment using both BMI and waist circumference is recommended as the BMI takes no account of distribution of body fat. People of south Asian origin generally have an increased amount of intra-abdominal fat (apple shape as opposed to pear shape) even though, according to their BMI, they are not obese. In Caucasian populations a waist greater than or equal to 102cm in men and 88cm in women predicts risk of disease associated with obesity whereas in south Asian populations the figures are 90cm and 80cm respectively.

 · Other advice To get enough vitamins and antioxidants a healthy, balanced diet including plenty of fruit and vegetables is recommended. The supplement Karella (taken by many south Asian patients) can lower blood glucose levels although, like all supplements, it is not recommended.

With the exception of certain groups, for example pregnant women, there is no evidence for the use of supplements and there is some evidence that they may be harmful.

References

1 National Subcommittee of the Diabetes Care Committee of Diabetes UK. The implementation of nutritional advice for people with diabetes. Diabet Med 2003;20:786-807

2 Diabetes In Practice. Fact Sheet 30. Fasting During Ramadan. Autumn 2003

Sources of fat in typical traditional ethnic diets

Saturated

 · Ghee (clarified butter), commonly used in south Asian curries and

puddings such as halva

 · Butter and lard

 · Coconut and coconut cream, commonly used in African-Caribbean cooking

Trans-unsaturated

 · Hydrogenated vegetable oils (hard margarine)

 · Manufactured foods containing hydrogenated vegetable oils

(pastries and pies)

Polyunsaturated

ln-6 (sunflower oil)

ln-3 (oily fish and

marine oils)

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