Nutritional Guidelines:
Diabetes UK’s new guidelines for the nutritional management of diabetes emphasise the practical implementation of nutritional advice for people with diabetes.
Nutritional advice should be tailored to patients, relatives and carers, and should take account of other lifestyle factors.
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Carbohydrate:
Why low carb?
The chief symptom of diabetes is an elevated blood glucose level. While some medications can help to reduce blood glucose, a reduction of foods in the diet which significantly raise levels in the first place can itself be sufficient to normalise them.
Medications can therefore often be reduced (in consultation with healthcare professionals) and in some cases (type 2 diabetics only) eliminated altogether.
Which foods are restricted?
Lowering the intake of obvious sugars is clearly beneficial in controlling blood glucose. However, starchy carbohydrates such as bread, pasta, rice and potatoes and foods containing processed flours are also metabolised by the body to produce large amounts of glucose. As they contain very few micronutrients (vitamins and minerals) low carb diets often reduce or eliminate only these foods.
Which foods are included?
A low carb diet is not necessarily low in all carbohydrate foods, simply those which disrupt blood glucose and insulin levels.
Many contain large quantities of vegetables, with the exception of some starchy root vegetables. Typically, they also include nuts and some fruits. Generally, they include the healthy natural and unprocessed foods similar to those eaten in populations where diabetes and heart disease are rarely found.
In this category comes meat, fish, eggs and dairy foods including butter and cream. Vegetarian protein sources such as tofu, quorn and TVP can also be included .
The impact of particular foods on blood glucose can vary greatly between individuals and testing after meals is recommended to figure out which foods to safely include in your diet.
In broad terms, carbohydrates have a large impact on blood glucose levels, protein much less, and fats have little if any effect.
How low is low?
An effective low carb diet is one which maintains, most of the time, a healthy blood glucose level. The amount of carbs it contains will vary between individuals. The consensus is that the following applies:
Low carb (ketogenic) 0-50g carbohydrate per day
Typical low carb 50-90g
Liberal low carb 90-130g
Moderate carbs 130-170g
High carb 170g plus a day
What is a healthy blood glucose level?
A healthy non-diabetic will typically have a blood glucose level within a tightly controlled range, usually below 5mmol/l for the majority of the time. This equates to a glycated haemoglobin (HbA1c) of below 5%. The current health service ‘target’ HbA1c of 7% is roughly equivalent to an average blood glucose approximately 50% higher than that of a non-diabetic.
What about cholesterol?
Diabetics are right to be fearful of the risks of heart disease, since rates are many times higher than those of non-diabetics.
Since around 80% of the cholesterol in the body is actually manufactured by the liver and the cells, relatively little comes directly from the diet. Total cholesterol is however now widely recognised as a very poor indicator of heart disease risk.
Far more meaningful are the individual components of total cholesterol, known as high density lipoprotein (HDL) and triglycerides. Trig. / HDL ratio is perhaps the single most significant measure of heart disease risk.
The lower the triglycerides and the higher the HDL, the better.
Insulin and glucose combine to raise triglycerides and lower HDL, which is why a low fat, high carbohydrate diet may actually increase heart disease risk. It’s commonly reported that those on low carb diets have lower cholesterol levels and certainly much improved trig. / HDL ratios.
What are the best fats to eat?
Monounsaturated fats are now promoted as the main source of dietary fat because of their lower atherogenic potential.
- Total fat intake should be less than 35 per cent of energy intake. Saturated and transunsaturated fats (found in hydrogenated vegetable oils, hard margarines, and manufactured cakes, biscuits and pastries) should provide less than 10 per cent of energy intake.
- Monounsaturated fat should provide 10-20 per cent of energy intake. Encourage use of oils and spreads made from olive, rapeseed or groundnut oils.
- N-6 polyunsaturated fat should be less than 10 per cent of energy intake. N-3 polyunsaturated fat (omega 3) lowers the risk of heart disease and helps reduce triglyceride levels. Encourage intake of oily fish twice a week. Fish oil supplements are not generally recommended.
Dietary cholesterol (eg offal, shellfish, and eggs) has less impact than saturated fat, but check that consumption is not excessive.
Used daily, if sufficient quantities are eaten, food products containing plant stanols and sterols can reduce low-density lipoprotein (LDL) cholesterol by 10-15 per cent. See products for guidance on servings. These products should not be used by pregnant women or children, due to insufficient data in these groups. Price may exclude this option for some people.
Protein:
In general for adults without nephropathy, protein intake should not be greater than 1gm per kg bodyweight. This equates to between 10-20 per cent total energy intake. There may be benefits to restricting protein further in those with nephropathy, but this should be done under specialist dietetic supervision.
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Fibre:
There is no quantative recommendation for fibre intake. Diets high in fruit and vegetables, including beans and pulses and a variety of grains and cereal products, are likely to contain adequate amounts of fibre. 'Soluble' fibre (ie fruit and veg, beans and pulses, oats) has beneficial effects on glycaemic and lipid control. 'Insoluble' fibre (ie wholemeal breads, cereals, rice, pasta) has no direct effects on glycaemic and lipid metabolism but, by promoting a feeling of fullness, may be helpful to those trying to lose weight. It is also beneficial to gastro-intestinal health.
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Vitamins and anti-oxidants:
Promote foods naturally rich in vitamins and anti-oxidants. With the exception of people in certain groups or particular clinical need, there is no evidence to support the use of supplements; there is evidence that some of these are harmful.
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Salt:
Limit sodium chloride intake to 6 grams or less per day. Reducing salt intake from 12g-6g per day leads to a drop in systolic/diastolic pressure of 5/2- 3mmHg. Adequate calcium and potassium intake should also be encouraged. Salt substitutes, where some of the sodium is replaced by potassium and magnesium, may be beneficial.
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Alcohol:
Alcohol intake should be limited to 14 units per week for women and 21 units per week for men. This moderate amount has the same cardio-protective effect in those with and without diabetes.
The main concern is the potential to increase hypoglycaemia and hypoglycaemia unawareness. Alcohol should be restricted by those trying to lose weight and those with hypertrigylceridaemia.
People with diabetes should consider using low calorie mixers and limiting sweet liqueurs/wines to reduce risk of reactive hypoglycaemia, and shouldn't drink on an empty stomach. People who treat their diabetes with insulin should be aware that hypoglycaemia may occur up to 16 hours after drinking.