Diabetes is a condition in which blood sugar levels are hard to control. Blood sugar is glucose, whose level can be controlled by the hormone insulin, which is released from beta cells in our pancreas.
Normal levels of blood glucose range between 4.0-5.5 mmol/L (72-99 mg/dl), with higher values soon after meals. If our levels go above 7.8 mmol/L (140 mg/dl) for extended durations, then damage can occur in various parts of our body. Levels above 10 mmol/L (180 mg/dl) lead to excessive thirst (polydipsia).
Rates of diabetes are increasing, and in 2012 it was reported that 9.3% of people in the US were affected(1), of whom around 90% had type 2 diabetes. Figures in other countries are catching the US figure all the time. This represents a huge and growing burden on our health services.
In type 2 diabetes two problems occur.
- Our tissues become resistant to insulin. Insulin works by opening up the channels in our cells that allow glucose in, and so with unresponsive insulin receptors the glucose in our blood is left to accumulate.
- The beta cells in our pancreas become less effective at secreting insulin.
The causes of diabetes
Two questions now arise. How do we become resistant to insulin and what causes our beta cells to fail?
- Insulin resistance can develop as a result of fat cells releasing more pro-inflammatory chemicals such as IL-6, and fewer anti-inflammatory chemicals such as adiponectin. The fatter you are the more this will happen. It can also occur due to lack of activity, which helps cells respond to insulin.
- Beta cell dysfunction is thought to result from high levels of glucose and free fatty acids in the blood. These high levels occur in diabetics, and are associated with increased levels of reactive molecules that can damage beta cells(2). The damage builds up over time and normally this insulin insufficiency due to beta cell destruction occurs years after the first appearance of insulin resistance.
While some people are more prone to type 2 diabetes than others, the genetic link is very weak. That is not what some of my textbooks say, which claim that type 2 diabetes has a stronger genetic component than type 1 diabetes. Unfortunately their authors have been lazy and taken the fact that type 2 diabetes runs in families as evidence of a genetic link. It is all to do with the fact that people in the same family follow a similar dietary pattern, and often a similar exercise pattern as well. In fact type 1 diabetes has a much stronger genetic component with a few genes on chromosome 6 being responsible for much of the susceptability. In type 2 diabetes a large number of genes are associated with risk and none particularly strongly.
What happens in the diabetic
There are some tissues in our body that let glucose in without insulin. To enter cells glucose passes through cross membrane transporters called GLUT. Fat and muscle cells contain GLUT-4 transporters, which don't allow much glucose in without insulin being present. The brain on the other hand has a lot of GLUT-3 transporters, which allow appreciable amounts of glucose in without insulin being present.
Tissues which let in glucose without insulin are found in the eye, kidneys, peripheral nervous system as well as the liver, ovaries and seminal vesicles. However, there are not enough of them to lower raised blood glucose levels. The unfortunate result for these cells is that they can accumulate too much glucose over time. The excess of glucose is turned into sorbitol. The cells in the liver, ovaries and seminal vesicles can turn the sorbitol into fructose. However, those cells in the eyes, kidneys and in our peripheral circulation accumulate sorbitol, which causes swelling of the cells due to osmotic pressure. This swelling is responsible for some of the nastier complications of diabetes.
Symptoms of diabetes
Diabetes is the leading cause of blindness and amputation in the Western world, and a major contributor to heart attack, stroke and kidney failure.
Diabetic kidney, blindness and amputation
Severe long term complications of diabetes often involve the kidneys, eyes and legs. Most of these complications result from raised levels of glucose in cells which do not rely on insulin to obtain it. In particular some cells lining capillaries and nerves in the kidneys, eyes and limbs are vulnerable. There are four examples of this.
- The lens of the eye forms cataracts more easily when sorbitol levels are higher(3).
- A second example, involving the retina of the eye, is the damage resulting from destruction of tiny capillaries that proliferate over the eye and then bleed, clouding the vision(4). This is known as diabetic retinopathy.
- A third example involves the kidney. The glomeruli, capillary beds in the kidneys, filter blood. In diabetes these become damaged and leaky. As a result they leak proteins which ultimately result in constriction of the blood vessels supplying the kidney. The kidney itself then gradually gets damaged as it receives insufficient nutrients from the blood.
- A final example involves the deterioration of feet and legs as nerves are damaged.
If insulin is lacking, our tissues and especially our brain can't get enough energy. Since the brain uses sugar as its main energy source it goes to plan B which is creating ketones, which can provide energy also. Too many ketones acidify our blood and cause excess urination, thirst, vomiting and tummy pain. Ultimately severe dehydration, swelling of the brain and coma can occur, which is why hospitalisation is often needed. This is a serious complication of type 1 diabetes. However, it is uncommon with type 2 as some insulin is normally available.
Curing diabetes naturally
Exercising more and consuming foods that do not raise blood sugar levels is the key to reversing diabetes. While it becomes harder to regain full health the longer you have had diabetes, when first diagnosed, the vast majority of people have the potential to completely cure themselves of the condition.
The correct diet
The modern western diet is the main cause of diabetes. The key is to reduce the blood sugar raising effect of the foods you eat.
Low GI diet
The blood sugar raising effect is commonly known as the glycaemic index or GI. A GI of 100 is the benchmark level for pure glucose on blood sugar. Other foods can have greater or lesser effects than this. For instance on one of my GI lists I have a baked potato with a GI of 111, greater than pure glucose while peanuts are listed with a GI of just 7, which implies that foods containing the East Asian sauce, satay would be very low GI. Remember however that these effects vary between people and over time. So in other words the GI is not an absolute value, but just a guideline.
Sometimes it is more realistic to consider the glycaemic load or GL of a food, which takes account of the amount of a food you eat. Obviously one Cornflake (GI=93) is not going to raise blood sugar as much as a whole can of baked beans (GI=40), but a small bowl of them probably will.
Foods that are normally low GI can be eaten as the main part of a diet for someone with diabetes. These include meat, fish, eggs, dairy as well as nuts, seeds, most vegetables and some fruits. The one vegetable that has a high GI is the potato (this includes the sweet potato), and the fruits with a high GI include ripe bananas, dates and raisins. Generally speaking fruits from warm climates have a higher GI than those from more temperate climates. So apples, pears, plums and berries are all relatively low GI.
A high GI food need not be off limits however. You can do a number of things that reduce its effect. For instance if you exercise soon after consuming the food then some of the blood sugar it creates will be taken up by your muscle cells. If you combine it with other foods of much lower GI or eat a small portion of it you will also find your blood sugar does not rise as far.
In general if you exercise then you will reduce your blood sugar level. A 30 minute exercise stint before food will allow you to get away with a higher overall glycaemic load. Equally if you do some light exercise soon after a large meal you can lower the peak which your blood sugar will reach.
In general it is best to leave some time between any meal and completely sedentary activity such as bed or watching the TV. Kids get it about right when they automatically rush about after a meal, often to the frustration of their bloated parents. A bit of housework, gardening or short walk are often quite effective at making a real dent in your blood sugar readings.
Treating diabetes with drugs
It really is best to avoid the need for drugs. I would always advise making concerted efforts to control blood sugar levels with increases in exercise and changes to the diet. Many people find they can come off drugs completely when they do this properly.
For those who cannot control their blood sugar levels without drugs then it is sensible to take them. The cumulative effect over time of high blood sugar levels is extremely damaging, and this is why so many diabetics suffer from amputations, blindness, heart attacks and strokes.
Blood sugar lowering agents
The main one is perhaps Metformin which lowers the amount of sugar your liver produces. Another class of drugs called sulfonylureas increase insulin secretion e.g. Chlorpropamide and Glipizide. Thiazilienediones such as Rosiglitazone increase insulin sensitivity of the tissues and glucosidase inhibitors such as Acarbose reduce absorption of glucose from the gut. All these drugs will be more or less effective in different people depending on how their diabetes is affecting them.
Measuring blood sugar levels
Diabetes is diagnosed using criteria that are arbitrary. There are several ways that are used to measure blood sugar problems:
Fasted blood sugar level - FBG
This measures blood sugar levels after not eating anything for at least 8 hours. A healthy figure is between 4.0-4.6 mmol/L (72-83 mg/dl). However, this value will vary depending on factors such as stress, recent exercise and illness. One reading is not enough to draw any conclusions. In fact fasted values greater than 4.6 may be perfectly OK so long as blood sugar spikes are avoided.
For instance very low carbohydrate diets raise the FBG figure for a number of reasons. Firstly less insulin is produced in people who don't consume many carbohydrates. Secondly their muscles get used to using fat as a fuel place of glucose and so more glucose is left in the blood. If you come into this category the measure below could be more useful to you.
Long term blood sugar control
To assess this we measure the amount of glycosylated haemoglobin - HbA1c, in your red blood cells. Haemoglobin - Hb, is the protein found in red blood cells that is responsible for carrying oxygen to your tissues. Glycosylated haemoglobin has sugar stuck to it. In good health somewhere between 3-5% of our haemoglobin is in the HbA1c form.
Red blood cells live for an average of 120 days. More become glycosylated towards the end of their life (90-150 days). There are a number of factors that can skew the measurement:
- People with healthy low blood sugar have longer lived red blood cells that may survive for an average of 150 days. In this case a high end reading for HbA1c does not imply bad blood sugar control.
- Diabetics with high blood sugar levels have red blood cells that live shorter lives than average, typically around 90days. They may present with surprisingly low HbA1c readings.
- People who suffer blood loss, are dehydrated, have anaemia or destroy blood cells through activity, such as distance running, will have shorter lived red blood cells and should also present with lower HbA1c readings.
So when HbA1c is measured take these factors into account before assuming that your number is telling you your blood sugar control is either rubbish, or perfect!
There are alternatives to HbA1c which include measuring amounts of a substance called fructosamine. It may be a better measure than HbA1c, and gives an indication of blood sugar levels over the previous 2-3 weeks(5).
Glucose challenge or OGTT
The oral glucose tolerance test - OGTT is a measure of our response to consuming 75g of glucose in one hit. Blood glucose is then measured at intervals over the following 2 hours. It is unrealistic as most people never consume such a large and purified amount of glucose. However, this general approach is useful.
If you have a glucometer and measure your blood sugar 1 and 2 hours after your typical meals, you will get a measure of how well you control your blood sugar. After one hour, good blood sugar handling should lead to a blood glucose figure below 7.0 mmol/L (125 mg/dl). After 2 hours you should have a figure below 5.5 mmol/L (100mg/dl). If your figures are above this it is sensible to alter your diet to achieve this, which normally involves eating less starchy foods such as bread, pasta, rice and potato and more meat, fish, dairy or vegetables (except potatoes).
When it comes to measuring blood sugar level the best way by far is to use a glucometer after meals. Nevertheless, make sure you take into account factors such as exercise, illness and stress. Ideal levels are <4.8 for fasting glucose, <6.8 for post meal glucose at 2hrs and <5.3 for HbA1c remembering all the caveats in the article above.
The key changes to make are to eat lower GI meals and introduce some light activity into the first few hours post meal. For most people achieving the low GI meal involves limiting the amount of starchy carbohydrates they eat. This is where the main UK diabetes charity is sorely deficient as they do not highlight the major role played in diabetes by over consumption of bread, rice, pasta and potatoes.
2) http://www.sciencedirect.com/science/article/pii/S1550413113001046 how nutrient excess may damage beta cell mitochondria.
3) http://www.fasebj.org/content/13/1/23.full how sorbitol can cause cataracts in diabetic patients.
4) http://www.ncbi.nlm.nih.gov/pubmed/19881493 diabetic retinopathy caused by vascular cell destruction
5) http://www.ncbi.nlm.nih.gov/pubmed/25249070 fructosamine measurement of blood sugar over previous weeks
Conversion between US and UK units for blood sugar measurement