The glycemic index (GI) is a measure used to express the effect of glucose on one’s blood sugar. If you read that and actually understood it, congrats! You already have some sort of strong nutritional knowledge base! So, let’s break that down a bit. Glucose is the scientific name for the main sugar your body uses for energy. Glucose comes from carbohydrates, which include fruits, veggies, beans, grains, crackers, cereals, sweets, and even dairy products. Once you eat one of these items, they are broken down into their most basic components, i.e. sugar, and…sugar = glucose.
Great, now that we’ve established what glucose is (sugar from the breakdown of carbohydrates), let’s talk about what glucose does in the body. Carbs can get a bad rap. But, here’s the thing, your body NEEDS carbs. Glucose is the body’s preferred choice of energy. While it can use fat and even protein, it doesn’t like to. And your brain? Well, your brain is VERY picky – it only wants glucose. The way your body makes sure it can properly fuel itself is by sending hormonal signals to maintain your blood sugar levels (or blood glucose levels) at the necessary amount so you can function at your best at all times. Sometimes the glucose comes from stores in your body, sometimes it comes from the food you’re eating. In either case, your blood begins circulating the necessary glucose fuel around your body and then your body release insulin so that the tissues which need this energy, can pull the glucose (fuel) out of the blood and in for its own use.
Whew. That’s a lot, huh? So, this whole glycemic index thing…this is a measure of how your blood glucose level responds to a particular food. It’s expressed as some number from 0 to 100, 100 being if you ate pure glucose. The higher this number, the faster/more dramatic the blood glucose response. In order to make sure the body doesn’t have too much sugar floating around in its blood stream, that lovely insulin is secreted to get the sugar out of the blood and into the needy tissues. But, when the blood sugar level shoots up rapidly, the insulin response is just as dramatic. Why does this matter? Well, studies have shown again and again that these massive spikes and then dips in blood sugar levels (and consequently insulin levels) are very hard on the body. It can actually affect the body’s ability to continue properly utilizing and secreting insulin, leading to type 2 diabetes in some cases, or less obviously, headaches, energy crashes, weight gain, sugar cravings, and poor sleep.
The goal? Keep those blood sugar levels at a consistent level, no peaks and valleys. So, does that mean you should watch the glycemic index of all foods and never eat the ones with a higher (close to 100) number? Not exactly. For example, bananas rate at a 62, while watermelon is a whopping 72! However, bananas are an amazing source of potassium, healthy fiber, and many b vitamins. And watermelon is majorly hydrating, contains a plethora of nutrients, is low calorie, and has lycopene, a compound that is a crazy good antioxidant, helping fight cancer and bodily stress! I would never tell you to avoid these foods, or even really limit them. In contrast, a Snicker’s bar has a GI of 51, and peanut M&Ms a GI of 33. Whoa! Should you make either of these a dietary staple? Definitely not!
Glycemic index is only one aspect of food and its affect on the body. Yes, some foods definitely spike your blood sugar (pure sugar, sugary candy, processed & refined bread products like white bread, white rice), but so do some really healthy foods like those bananas and sweet potatoes. While GI can be informative, there are other ways to moderate that blood sugar spike than merely avoiding high GI foods. Avoiding eating any carb in isolation (without fat or protein) can help moderate the blood sugar rise, no matter what that food’s GI (hence why the glycemic index of that Snicker’s bar and those peanut M&Ms are lower, as they have fat and protein too!). Take away message? The glycemic index can be an interesting way to look at foods and learn more about what you’re putting into your body and it’s effects. However, the glycemic index doesn’t tell the whole story and following a merely “low glycemic index” diet doesn’t mean a magical recipe for weight loss or health. Maintaining a stable blood sugar level is the most important aspect for good health and disease prevention. To find out how you’re doing tackling this task and strategies for improving your blood sugar control and health, come on in for a visit!
Aubrey Phelps MS RDN