Carbohydrates and Insulin Resistance

January 19, 2013
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So we already know how our bodies work to maintain blood sugar balance. But how is our blood sugar affected by what we eat?

Carbohydrates—alongside fat and protein—are one of the major nutrients the body requires in large, balanced quantities. All consumed carbohydrates manifest as blood sugar, but how they affect blood sugar balance depends on whether they are simple or complex.

Simple carbs are those that are made of one or two simple sugars, like fructose or glucose. Examples of simple carbs include white flour, white rice, pasta and sweeteners, which have been processed to remove everything—such as the bran and germ—except the quickly digestible carb. This process gives the grain a finer texture and prolongs shelf life, but removes key nutrients such as B vitamins, fiber and iron.

Complex carbs, on the other hand, are chains of simple sugars bonded into larger structures; examples include whole grain breads, bran, beans, lentils and peas. They contain fiber and other nutrients along with the carbohydrate, and therefore take longer to digest, allowing for slower absorption of the glucose and consequently a slower rise in blood sugar. (Read more about a recent study showing how legumes can help stabilize blood sugar among diabetics.)

The Glycemic Index (GI) is a useful tool that ranks how quickly different foods will increase blood sugar after ingestion. Foods are indexed based on their relativity to glucose (which rapidly raises blood sugar and has a GI score of 100, the highest). Yogurt and whole barley come in around 20; a baked potato ranks 98 on the scale. Whole grain foods are often the best option because they are typically lower on the glycemic index. Refined carbohydrates, on the other hand, tend to have the highest GI scores. (See examples of GI scores of many common foods from Harvard Medical School.) High glucose-rich foods, when combined with fiber, protein or fat will lower the GI of that food.

Because of the differences in GI scores, choosing carbohydrates wisely is vital for good blood sugar regulation and nutritional health. When we consume too many simple carbs (and don’t exercise enough), a detrimental cycle develops: blood sugar spikes from refined carbohydrate intake, insulin is released, glucose is stored in the cells, blood sugar drops, the body thinks you’re hungry, and you crave carbs…and the process starts all over again.

The problem is that the cycle wears down over time and the body’s cells begin to lose sensitivity to insulin. The body compensates for this by pumping out more and more insulin in an effort to get the sugar out of the bloodstream and into the cells. Lack of fiber, high sugar intake, too much iron (e.g. high red meat consumption), free radicals and a sedentary lifestyle all contribute to insulin resistance.

In addition, insulin resistance can cause excessive weight gain even without overeating because excess glucose in the blood is eventually stored as fat. There is also a relationship that exists between stress and elevated cortisol which drives insulin resistance and stores fat in the belly. Belly fat then perpetuates insulin resistance because it acts as a hormone disruptor (insulin in particular), and the unhealthy cycle continues.

Insulin resistance is also associated with high blood pressure, high triglycerides, plaque buildup in the arteries and low levels of HDL (good cholesterol). Together, this is called Metabolic Syndrome, a pre-diabetic state. Insulin resistance is a serious condition that, left untreated, is a strong risk factor for heart disease and type 2 diabetes.

Next we’ll talk about simple strategies for regulating blood sugar and preventing insulin resistance.