Control Your Blood Sugar: Glycemic Index vs. Glycemic Load

It's hard to argue there is a metabolic condition wreaking more havoc in the United States today than diabetes.  In particular, the incidence rate of adult onset diabetes, better known as type 2, continues to skyrocket.  At its core, type 2 diabetes is a condition brought on by poor blood sugar regulation, which eventually leads to impaired insulin function.  Unfortunately, that is truly just the tip of the iceberg when it comes to the potential health hazards of diabetes.

Hyperglycemia, aka chronically high blood sugar, can severely damage blood vessels throughout the body, leading to increased risk of:

-Cardiovascular disease

-Obesity

-Kidney disease

-Nerve damage

-Eye disease

-Skin disease

-Gum disease

If left uncontrolled, diabetes greatly increases the risk of all-cause mortality.  The good news is, type 2 diabetes is largely the result of lifestyle factors and can not only be managed, but actually reversed with the proper interventions.  However, when an individual sees their doctor and is diagnosed as diabetic or pre-diabetic (which may include up to 40% of the U.S. population at this point), the vastly oversimplified recommendation they often receive is "cut back on sugar".

Ok, so don't slam cake, candy, soda and ice cream on a daily basis and I'll keep my kidney function, eyesight, and both of my feet, right?  Sounds easy enough!

In reality, while reducing the consumption of refined sugar is a good place to start, it's more like the bare minimum intervention to get your blood glucose levels and hemoglobin A1C in check.  While exercise certainly plays a role as well, understanding how foods of all types affect blood sugar levels is crucial to managing and reversing type 2 diabetes (and is certainly helpful for managing type 1 as well).

The glycemic index and glycemic load scales are helpful tools for understanding this connection, and for informing your food choices.  So what exactly do these scales measure?

The glycemic index is a measurement of how much a particular food raises blood sugar.  It is a 0-100 scale, and compares a food's effect on blood sugar as a percentage against pure glucose, which is rated 100.  For example, if a food has a 36 glycemic index score, it may raise blood sugar about 36% as much as pure glucose.  Several factors influence a food's G.I. score, including the amount of protein, fat, and fiber it contains in conjunction with its carbohydrate content.  The glycemic index is broken down into three scoring categories:

-Low: 55 or less

-Medium: 56-69

-High: 70+

The idea of course, is to primarily consume foods that fall into the "medium" or preferably "low" end of the scale.  In theory, these foods will have less effect on blood sugar, and will help maintain healthy blood glucose levels.  There are however, several limitations to the glycemic index scale that could prove misleading.

To begin, G.I. score applies only to a food's effect when eaten on an empty stomach, without any other food involved.  It goes without saying that this is not how we typically eat in the real world.  In addition, a food's G.I. score may change based on its ripeness (ex. Unripe bananas have a much lower score than ripe ones) or how the food is prepared.

The consideration above is usually based on the amount of resistant starch a food contains.  Resistant starch is a form of carbohydrate that slows digestion speed and therefore decreases glycemic index.  Starch content may decrease or fluctuate based on the ripeness of fruit, or based on the cooking method, temperature, or time that certain foods are prepared.  All of these variables can alter G.I. score, creating inconsistency and confusion. 

Lastly, and perhaps most important of all, the glycemic index scale doesn't take into account how MUCH of a food you're actually eating in a real world setting.  G.I. score is based on a serving size that contains a standard 50g of carbohydrates.  This becomes an issue when we take into account the carbohydrate density of a food.  One cup of rice does not contain the same amount of carbs as one cup of beets.  It's likely an average real world serving of rice may contain 50g of carbs, while it is highly unlikely someone would be consuming enough beets to hit 50g of carbs.

Enter glycemic load, the measurement tool that solves this issue.  Glycemic load, or G.L., takes into account the carbohydrate density of a food, and is calculated by the following:

Carbs per serving x Glycemic Index/100

G.L. tells us not only how quickly a food makes glucose enter the blood, it also tells us how much glucose per serving that food delivers.  The glycemic load scale is also broken down into three scoring categories:

-Low: <10

-Medium: 11-19

-High: 20+

For example, this is very helpful for determining the glycemic effect of a food like watermelon.  While watermelon has a high glycemic index score (approx. 75), a typical serving of watermelon is actually quite low in carbohydrates, so its  glycemic load is low (approx. 5).  Essentially, someone would need to be consuming a huge amount of watermelon in order to have a drastic effect on their blood sugar levels.

Confused yet?  Ultimately, neither glycemic index or glycemic load are perfect measurements, and should always be taken with a grain of salt.  That said, they can serve as helpful guidelines to making informed food choices that will have less negative impact on blood sugar levels.