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.
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 NICE ‘target’ HbA1c of 7.5 % 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 about weight loss?
Insulin is often referred to by biochemists as the fat building hormone. In fact, the body cannot make body fat without insulin. It is very unusual to find an overweight individual who doesn’t also have elevated insulin levels. Type 2 diabetics, at diagnosis, will often be overproducing insulin.
Insulin also inhibits the body’s use of stored fat as a source of fuel. Lowering insulin levels is extremely important, perhaps essential, for weight loss to succeed. This is one reason why low carb diets are particularly successful in weight loss since the fewer the carbs, the less insulin is required. Some may also find that they consume fewer calories without feeling hungry because their fat metabolism begins to work properly once more, allowing the body access to energy reserves in fat stores which were previously inaccessible.
Diabetics, and even some health professionals, often confuse two quite distinct metabolic processes - ketosis and ketoacidosis. Ketosis is a perfectly natural and healthy state during which the body uses stored or dietary fat for fuel. In order to enter this state, carbohydrate intake needs to fall below a certain level. Ideally, a healthy metabolism should regularly use ketosis, while fasting overnight for example, to fuel the body's processes and utilise stored fat reserves. Most of the body's organs, the heart for example, in fact run very efficiently on ketones.
Ketoacidosis is quite different and is typically the result of a chronic lack of insulin, not a lack of carbohydrate. With insufficient insulin, the body attempts to fuel itself by breaking down fat and protein stores in an uncontrolled way, a process which results in the blood becoming dangerously acidic. In short, ketosis usually occurs when blood sugars are at the lower end of the normal range, and ketoacidosis occurs when blood sugars are dangerously elevated. Ketosis is a result of low carbohydrate intake, ketoacidosis is a result of inaquate insulin levels.
What about physical energy?
Strictly speaking, we burn neither glucose nor fat for physical energy. Energy within our cells actually comes from a molecule called adenosine triphosphate, or ATP. When its molecular bonds are broken, energy is released in the mitochondria, the power plants of our cells. A glucose molecule will generate 36 ATP molecules. A 6 carbon fatty acid molecule will generate 48 ATP molecules. Therefore, when insulin levels are low and the body can access fatty acids as a fuel source, physical energy levels can actually increase on a low carb diet.
Anecdotally, many on low carb diets often report feeling considerably more energetic, without the peaks and troughs of energy which appear to come with a diet high in carbohydrates.
Is it suitable for type 1 diabetics?
The benefits of reduced insulin levels also apply to type 1’s. Insulin has a measureable impact on blood vessels by narrowing them, with increased cardiovascular risks. Smaller doses can also make blood glucose fluctuations far more predictable, resulting in fewer highs and lows. It is not true to say that type 1’s need carbohydrates to feed their insulin. They may simply need less insulin.
Why doesn’t the NHS recommend low-carb diets?
Great question. Largely because it was once thought that dietary fat caused heart disease and dietary protein caused kidney damage, so without carbs there’d be nothing left to eat. Subsequent research has revealed that neither of these hypotheses was correct and that the finger of suspicion ought to be pointed at glucose, but changes to established mindsets are very slow to happen.
Isn’t low carb just another diet fad?
Since the emergence of the human species in the Rift Valley around 3-4 million years ago, we have been meat eaters. Fruit and vegetables were a rare treat during their short growing seasons. We only began cultivating crops during the agricultural revolution 10,000 years ago. Refined sugars and starches became our staples around 200 years ago.
In the context of our evolutionary history, perhaps it’s the ‘healthy balanced diet’ which is the real diet fad?