Simply put, the glycemic index measures how quickly and how high a food raises your blood sugar once it is eaten. The foods that do this are carbohydrates, as neither protein nor fats have the ability to raise blood sugar. Typically, it is the highly refined carbohydrate grains and other starches which cause the greatest and most rapid rises. Some examples are most boxed breakfast cereals, white flour, pretzels, rice cakes, white bread, white potatoes, and parsnips.
High Blood Sugar is Damaging
These kinds of foods which dominate the Western diet can be damaging to your health for numerous reasons when they cause an excessive rise in blood sugar:
- Excess blood sugar is converted into fat and stored in your fat cells, causing immediate weight gain
- High blood sugar is highly inflammatory, and linked to artery wall damage and heart disease (1)
- High blood sugar increases the risk of colorectal and endometrial cancer (2)
- A rapid rise in insulin to lower this inflammatory level of blood glucose quickly returns blood sugar to starvation levels, triggering a craving for more sweet and/or starchy food
- High blood sugar after eating greatly increases your risk of insulin resistance and type 2 diabetes
The reason that high blood sugar is damaging is because it is inflammatory. That is, it causes inflammation of the blood vessels it comes into contact with. In fact, in the literature, having excessively high blood sugar is referred to as "glucotoxicity," or glucose poisoning. The longer and more intense the rise in blood sugar level, the greater the organ damage done.
Some of the causes of organ damage are the increased oxidative stress due to higher free radical production, oxidation of LDL cholesterol, an increase in arterial plaque build-up, and decreased arterial wall flexibility. In some instances, high blood sugar might induce heart arrhythmia, perhaps enough to be fatal. (3)
Blood Sugar and Insulin are Inflammatory
These reactions, as well as others happen not only among prediabetics and diabetics, but also among those who still have the ability to adequately control their blood sugar. However, once you become insulin resistant, due mainly to weight gain and lack of exercise, and you have persistently high blood sugar levels, then you are in a persistently inflammatory condition, and the damage is ongoing.
Furthermore, the insulin your pancreas produces to lower blood sugar is also inflammatory when present in excess. The only mechanism your body has to lower blood sugar is to increase insulin production. When blood sugar remains high because of insulin resistance, your pancreas just keeps making more and more insulin. This excess insulin adds further to the inflammatory condition.
The best way to avoid this highly damaging situation is to avoid the high glycemic index foods that cause it.
References
1. R Peter, A Rees. Postprandial Glycaemia and Cardiovascular Risk. Br J Diabetes Vasc Dis. 2008;8(1):8-14.
2. P Gnagnarella et al. Glycemic index, glycemic load, and cancer risk: a metabolic analysis. Am J Clin Nutr. 2008;87:17931801.
3. Antonio Ceriello. Postprandial hyperglycemia and diabetes complications. Diabetes 2005;54(1):1-7
